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cecilia abrahamSSonmaSticatory function and temporomandibular diSorderS in patientS with dentofacial deformitieSStudies before and after orthodontic and orthognathic treatment

isbn 978-91-7104-395-5

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Swedish Dental Journal, Supplement 231, 2013

m a s t i c a t o r y f u n c t i o n a n d t e m p o r o m a n d i b u l a r d i s o r d e r s i n pa t i e n t s w i t h d e n t o f a c i a l d e f o r m i t i e s

Swedish Dental Journal, Supplement 231, 2013

© Copyright Cecilia Abrahamsson, 2013

Illustrations: Eva Lilja-Karlander

ISBN 978-91-7104-395-5

ISSN 0348-6672

Holmbergs i Malmö AB, 2013

cecilia abrahamssonmasticatory function and temporomandibular disorders in patients with dentofacial deformities

Studies before and after orthodontic and orthognathic treatment

Malmö högskola, 2013Faculty of Odontology

Department of OrthodonticsDepartment of Orofacial Pain and Jaw Function

Publikationen finns även elektroniskt,se www.mah.se/muep

innehåll

PREFACE ....................................................................... 9

ABSTRACT .................................................................. 10Key conclusions and clinical implications: ................................12

POPuläRvETEnSKAPlig SAMMAnFATTning .................. 13Klinisk betydelse: ..................................................................15

ABBREviATiOnS AnD DEFiniTiOnS ............................... 16

inTRODuCTiOn .......................................................... 18Dentofacial deformities ..........................................................18

Definition ........................................................................18Prevalence ......................................................................19Aetiology .......................................................................19Treatment strategies .........................................................20

Temporomandibular disorders ................................................21Definition ........................................................................21Prevalence ......................................................................22Aetiology ........................................................................23Research Diagnostic Criteria for TMD (RDC/TMD) ..............24

Malocclusion and TMD .........................................................25Orthognathic treatment and TMD ...........................................25Dentofacial deformities and mastication ..................................26

SigniFiCAnCE ............................................................ 28

AiMS ......................................................................... 29Paper i ................................................................................29Paper ii ...............................................................................29

Paper iii ..............................................................................29Paper iv ..............................................................................29

HYPOTHESES .............................................................. 30Paper i ................................................................................30Paper ii ...............................................................................30Paper iii ..............................................................................30Paper iv ..............................................................................30

MATERiAlS AnD METHODS ........................................... 31SuBJECTS ............................................................................31

Ethical considerations .......................................................32METHODS ...........................................................................33

Paper i ...........................................................................33Paper ii-iv .......................................................................36Paper iii-iv ......................................................................38Paper iv .........................................................................39

Statistical analyses ...............................................................40

RESulTS ..................................................................... 43Systematic review – Paper i ...................................................43

Dentofacial deformities and frequency of TMD ....................43The effect of orthognathic surgery on TMD ..........................43Quality analysis ...............................................................44new literature search .......................................................44

Paper ii ...............................................................................47Anamnestic findings .........................................................47TMD diagnoses ...............................................................47

Paper iii ..............................................................................48TMD diagnoses ...............................................................48TMD diagnoses in relation to different kinds of dentofacial deformities .....................................................49Symptoms of TMD ............................................................50Mandibular movement capacity .........................................51Occlusal interferences ......................................................52Patients’ satisfaction with treatment.....................................52level of anxiety ................................................................52

Paper iv ..............................................................................52Self estimated masticatory ability .......................................52Factors influencing the self estimated masticatory ability .......52

Masticatory performance ..................................................53Factors influencing MPi ....................................................53Correlations ....................................................................54Occlusion ......................................................................55

DiSCuSSiOn ............................................................... 58Systematic review .................................................................59Methodological aspects.........................................................60

Paper ii-iii ........................................................................60Paper iv .........................................................................63

Anamnestic findings ..............................................................64Frequency of TMD ................................................................64Masticatory ability and performance ......................................66Future research.....................................................................67

COnCluSiOnS ........................................................... 69Key conclusions and clinical implications: ................................70

ACKnOwlEDgEMEnTS ............................................... 71

REFEREnCES ............................................................... 75

PAPERS i – iv ............................................................... 87

To Jonas, Klara, Alva and Henrik

9

preface

This thesis is based on the following papers, which are referred to in the text by their Roman numerals.

I. Abrahamsson C, Ekberg EC, Henrikson T, Bondemark L. Alterations of temporomandibular disorders before and after orthognathic surgery – a systematic review. Angle Orthod 2007;77:729-734.

II. Abrahamsson C, Ekberg EC, Henrikson T, Nilner M, Sunzel B, Bondemark L. TMD in consecutive patients referred for orthognathic surgery. Angle Orthod 2009;79:621-627.

III. Abrahamsson C, Henrikson T, Nilner M, Sunzel B, Bondemark L, Ekberg EC. TMD before and after correction of dentofacial deformities by orthodontic and orthognathic treatment. Int J Oral Maxillofac Surg 2013; 42: 752–758.

IV. Abrahamsson C, Henrikson T, Bondemark L, Ekberg EC. Masticatory function in patients with dentofacial deformities before and after orthognathic treatment. Submitted.

The papers are reprinted with kind permission from the copyright holders.

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abstract

About 30 % of individuals in the Swedish population will at some stage during life have treatment with orthodontic appliances. In more severe cases, when orthodontic treatment is not considered sufficient enough to correct the malocclusion, the orthodontic treatment is combined with orthognathic surgery. For these cases, a satisfying jaw relation is achieved by surgically moving the maxilla and/or the mandible into a pre-planned position.

Patients due to be treated with orthognathic surgery often suffer from an impaired masticatory function, symptoms from the masti-catory muscles or temporomandibular joints (tempo romandibular disorders), headaches as well as dissatisfaction with their facial aesthetics.

Since orthognathic treatment is expensive, in many cases arduous to the patient and not without complications, it is important to assess the treatment outcome and if this is satisfying for the patients. Previous studies that have examined the outcome after ortho-gnathic treatment have had diverging study designs and have come to different conclusions with regard to both tempo romandibular disorders and masticatory function.

The overall aim of this thesis was to assess and compare the frequencies of temporomandibular disorders and the masticatory function in patients with dentofacial deformities before and after orthognathic treatment.

The thesis is based on the following studies:paper i is a systematic literature review aiming to, in an evidence-based approach, answer the question whether orthognathic treat-

11

ment affects the prevalence of signs and symptoms of temporoman-dibular disorders. The review encompasses the period from January 1966 to April 2006 and was further extended to May 2013 in the frame story of this thesis.

Conclusions in Paper I and the complementary survey• There is insufficient scientific evidence for a decrease of sub

diagnoses of temporomandibular disorders after orthognathic treatment.

• There is limited scientific evidence for a reduction of masti-catory muscle pain on palpation after orthognathic treatment.

• There is insufficient scientific evidence for an effect on tempo-romandibular joint pain on palpation and temporomandibular joint sounds from orthognathic surgery.

• Further controlled, well-designed studies assessing tempo-romandibular disorders before and after orthognathic treat-ment are needed to consolidate strong evidence considering treatment outcomes.

papers ii and iii are studies comparing frequencies of temporo-mandibular disorders in patients with dentofacial deformities with a control group. The patients were referred for a combined orthodon-tic and orthognathic treatment to correct their malocclusion. The control group comprised individuals with normal occlusion or minor malocclusion traits not in need of orthodontic treatment. In Paper III, temporomandibular disorders were longitudinally analysed by assessing and comparing frequencies before and after orthognathic treatment. All individuals in the studies were diagnosed according to the research diagnostic criteria for temporomandibular disorders.

Conclusions in Papers II and III• Patients due to be treated with orthognathic surgery had more

signs and symptoms of temporomandibular disorders and a higher frequency of diagnosed temporomandibular disorders compared with the age- and gender matched control group.

• Patients with dentofacial deformities, corrected by ortho dontic treatment in conjunction with orthognathic surgery, had a positive treatment outcome in respect of myofascial pain and arthralgia.

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• After treatment the frequency of temporomandibular disorders in the treatment group was low and at an equivalent level of that in the control group.

paper iV evaluates the self-estimated masticatory ability and the masticatory performance before and after orthognathic treatment in the same individuals as in Paper II and III.

Conclusions in Paper IV• Masticatory ability and performance increased after orthogna-

thic treatment.• The number of occlusal contacts and severity of overall symp-

toms of TMD influenced both the masticatory ability and performance.

• Open bite had a negative effect on masticatory performance.

Key conclusions and clinical implications:Patients with dentofacial deformities diagnosed with temporo-mandibular disorders do in most cases benefit from orthogna-thic treatment. In addition, masticatory ability and performance, which is impaired in patients with dentofacial deformities, improve after treatment. Thus, patients with dentofacial deformi-ties that are to be treated with orthodontics in combination with orthognathic surgery can be recommended the treatment in order to relieve symptoms of TMD and impaired mastication.

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populärVetensKaplig sammanfattning

Ca 30 % av Sveriges befolkning genomgår någon gång i livet behandling med tandreglering. I de fall där bettavvikelsen är mer omfattande är enbart tandreglering inte tillräckligt för att uppnå ett bra bett. Istället kombinerar man tandregleringen med en kirurgisk förflyttning av käkarna s.k. ortognat kirurgi. Dessa patienter besväras ofta, före behandling, av smärta och funktionsstörningar i käkar och tuggmuskler och är dessutom ofta missnöjda med sitt utseende. Då denna behandling är omfattande, kostsam och inte helt utan komp-likationer är det av stort intresse att undersöka utfallet av behandlin-gen och om denna motsvarar förväntningarna hos patienterna.

Tidigare studier som har utvärderat utfallet av tandreglering i kombi-nation med ortognat kirurgi har kommit fram till mot sägelsefulla slutsatser vad gäller hur behandlingen har påverkat före komsten av smärta och funktionsstörningar i käkar och tuggmuskulatur.

Det övergripande syftet med denna avhandling är att i en serie studier, före och efter ortognat kirurgi, utvärdera och jämföra före-komsten av smärta och käkfunktionsstörningar hos patienter med stora bettavvikelser.

Avhandlingen är baserad på följande studier: delarbete i är en systematisk litteraturöversikt med följande frågeställning:

Påverkar ortognat kirurgi förekomsten av smärta och funktions-störningar i käkleder och tuggmuskulatur?

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I studien utvärderas den tillgängliga vetenskapliga litteraturen ur ett evidensbaserat perspektiv. Översikten omfattade tidsperioden januari 1966 till april 2006 och utökades senare till maj 2013.

Slutsatser i delarbete I• Det finns ett otillräckligt vetenskapligt underlag för om

före komsten av diagnostiserad smärta och funktionsstörning i käkleder och tuggmuskler minskar efter ortognat kirurgi.

• Det vetenskapliga underlaget är begränsat när det gäller en minskning av palpationsömhet i tuggmuskler efter ortognat kirurgi.

• Det finns ett otillräckligt vetenskapligt underlag för om förekomsten av käkledsljud påverkas av ortognat kirurgi.

• Det behövs ytterligare studier som är av hög eller medel-hög kvalitet för att på ett evidensbaserat sätt kunna styrka behandlings utfallet av ortognat kirurgi när det gäller smärta och funktionsstörningar i käkleder och tuggmuskler.

delarbetena ii och iii är kontrollerade studier som undersöker förekomsten av smärta och funktionsstörningar i käkleder och tugg-muskler hos patienter med stora bettavvikelser, i jämförelse med personer med eller utan små bettavvikelser (ej i behov av tandreg-lering). Patienterna var remitterade för behandling med ortognat kirurgi. I delarbete III, som är en longitudinell uppföljningsstudie, analyseras hur förekomsten av smärta och funktionsstörningar i käkleder och tuggmuskler påverkas av behandlingen.

Slutsatser i delarbete II och III• Patienter som ska behandlas med ortognat kirurgi har mer

smärta och funktionsstörningar i käkleder och tuggmuskler jämfört med kontrollgruppen.

• Patienter som genomgått ortognat kirurgi har ett positivt behand lingsutfall avseende smärta från käkleder och tugg-muskler.

• Efter behandling är förekomsten av smärta och funktions- störningar i käkleder och tuggmuskler låg och i nivå med den i kontrollgruppen.

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delarbete iV utvärderar den självupplevda tuggförmågan och den testade tuggprestationen före och efter ortognat kirurgi hos samma individer som i studie II och III.

Slutsatser i delarbete IV• Patienter med stora bettavvikelser har innan ortognat

kirurgi en sämre självupplevd tuggförmåga och testad tuggprestation jämfört med kontrollgruppen.

• Efter behandling förbättras både den självupplevda tuggförmågan och tuggprestationen.

Klinisk betydelse:Patienter som har stora bettavvikelser och dessutom smärta och funktionsstörningar i käkleder och tuggmuskler har oftast ett positivt behandlingsutfall efter ortognat kirurgi. Dessutom förbättras den självupplevda tuggförmågan och den testade tuggprestationen efter behandlingen. Patienter med stora bett-av vikelser som ska behandlas med tandreglering i kombination med ortognat kirurgi kan därför rekommenderas behandlingen för möjlighet till minskade besvär från tuggmuskler och käkleder samt förbättrad tuggförmåga.

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abbreViations and definitions

ANB The angle between point A in the maxilla and point B in the mandible in relation to nasion - describing the sagittal relation between the jaws

BSSO Bilateral Sagittal Split OsteotomyCI Confidence IntervalDC/TMD Diagnostic Criteria for TMDEMG ElectromyographyIVRO Intraoral Vertical Ramus OsteotomyICP Intercuspation positionRCP Retruded contact positionMasticatory ability Self evaluated masticatory functionMasticatory performance Tested masticatory functionML Mandibular plane (extending from gnathion to

gonion)ML/NSL The angle between ML and NSLMPI Masticatory Performance IndexMeSH Medical Subject HeadingNIH National Institutes of HealthNSL Nasion-Sella line (extending from Nasion to Sella)Orthognathic Treatment Orthodontic treatment in conjunction with

orthognathic surgery

17

Q PercentilesRDC/TMD Research Diagnostic Criteria for TMDRCT Randomized Controlled TrialSBU The Swedish Council on Health Technology

AssessmentTMD Temporomandibular DisordersTMJ Temporomandibular JointVAS Visual Analogue Scale

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introduction

dentofacial deformitiesDefinitionMalocclusion has been defined as a deviation in intramaxillary and/or intermaxillary relations of teeth that presents a hazard to the individual’s well being. (1)

More severe forms of malocclusion have been termed dentofacial deformities (Figure 1). The suggested definition of dentofacial defor-mities is a malformation of the dentofacial complex with resulting disabling disharmony in size and/or form (1) or as clearly described in PubMed (2); An abnormality of the jaws or teeth affecting the contour of the face.

Figure 1. Different kinds of dentofacial deformities a) Open bite b) Deep bite c) Class II d) Class III

1a

1c

1b

1d

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PrevalenceDeviations from a normal occlusion are common and it has been estimated that about 74 % of Swedish schoolchildren have some form of malocclusion. (3)

The most prevalent malocclusions, according to Thilander and Myrberg 1974(3), are:• Postnormal occlusion (14 percent)• Prenormal occlusion (4 percent)• Open bite (4 percent)• Deep bite (8 percent)• Cross-bite: uni- and bilateral (11 percent)• Anterior Cross bite (11 percent)• Overjet ≥ 6 mm (8 percent)

These prevalence figures for malocclusions include the pre valence figures for dentofacial deformities. Assessing the prevalence of severe skeletal malocclusions requiring orthognathic surgery is diffi-cult (4) since dentofacial deformities can merely be regarded as a more severe form of malocclusion. (4) It has been estimated that 5 % of all Class II, 33 % of Class III and 25 % of all open bites needs orthognathic treatment. (5)

Aetiology Malocclusion and dental deformities are in most cases caused by moderate distortions from normal development. They are the result from a complex interaction among multiple factors and it is in most cases not possible to describe a specific factor. In a population it has been reported that, about one third has a normal occlusion, 60 % has a malocclusion with unknown cause and 5 % has a malocclu-sion with a known cause. (6)

Skeletal growth disturbances such as Pierre Robin sequence and hemifacial microsomia are known to cause mandibular deficiencies. (6) Another factor known to affect craniofacial growth is muscle dysfunction. Muscular dystrophy, one kind of muscle dysfunction, leads to a decrease in muscle tonus allowing the mandible to drop downward, resulting in an increased facial height and development of an open bite. (7)

20

Other more well-known and common causes of malocclusion are oral habits such as sucking on fingers or pacifiers. (8)

Genetics has a strong influence on facial appearance and certain types of malocclusion like a Class III malocclusion runs in families e.g. the Habsburg jaw. (6) The relative influence of environment and heritability in the development of malocclusions with both skeletal and dental components is unclear. (6) However, it has been suggested that the heritability is high for craniofacial characteristics but low for dental characteristics. (9) So, it is therefore likely that a hereditary component is present in the aetiology of dentofacial deformities.

Treatment strategies In Sweden, the reported need for orthodontic treatment in indi-viduals between 8 and 20 years of age varies between 24 and 46 %. (10-12) In cases, when there is a good skeletal jaw relationship, the malocclusion can be corrected by orthodontic treatment using orthodontic appliances. In more severe cases, when a skeletal jaw discrepancy is involved, there are three treatment possibilities; a) growth modification, i.e. dentofacial orthopaedics that is appli-cable on growing individuals; b) camouflage treatment (orthodon-tic positioning of the teeth to compensate for the jaw discrepancy), not always resulting in an acceptable dental occlusion or satisfying facial aesthetics; c) orthodontic treatment in conjunction with ortho-gnathic surgery in order to reposition the jaws, or the dentoalveolar segments, or both.(4)

Orthognathic surgery can be done either in the maxilla or in the mandible separately, or as bimaxillary surgery involving both jaws. Maxillary osteotomies are primarily performed as a LeFort I osteotomy, which allows the maxilla to be moved in both vertical and sagittal directions (Figure 2).

Bilateral sagittal split osteotomy is used for mandibular advance-ment in Class II cases or for setback in both Class II and Class III cases. The vertical ramus osteotomy is an alternative to sagittal split osteotomy when treating Class III deformities. A lower incidence of neural damage and fewer complaints of TMD are mentioned as some of the advantages with the vertical ramus osteotomy.(4, 13, 14)

21

The indications for treatment of dentofacial deformities by orthog-nathic surgery are mainly facial aesthetics, functional problems and temporomandibular disorders (TMD). The importance of the various individual indications varies between genders and between different parts of the world due to cultural differences and econom-ical aspects. (15, 16) During 2012, 97 patients underwent orthog-nathic surgery in Lund University hospital. Unfortunately, there is a lack of data regarding the total number of orthognathic treatments performed per year in Sweden, which makes it impossible to validate the impact in oral health care.

Figure 2. A patient, diagnosed with an open bite, before and after orthognathic treatment.

temporomandibular disordersDefinitionTMD is a collective term describing musculoskeletal disorders arising from the masticatory structures (Figure 3), (17) and has been identified as “a major cause of nondental pain in the orofacial region and are a sub-classification of musculoskeletal disorders”. (17)

The most important feature of TMD is chronic musculoskeletal pain. Palpation tenderness of the muscles of mastication and the temporomandibular joints is also frequently reported. Impaired range of motion (leading to difficulties when eating, e.g. apples or hamburgers) and various joint sounds elicited by mandibular excursions are associated with certain types of TMD. (19) Patients with TMD often also describe a feeling of fatigue of the jaws and symptoms of pain and dysfunction affecting ears, eyes and/or throat and headaches. (20)

22

PrevalenceThe prevalence of TMD has been found to be high, albeit of a mild character, already in childhood. (21, 22) It then seems to increase, in a fluctuating pattern, from adolescence(23) to middle age and then to decrease in old age. (24) TMD is therefore primarily seen as a condition of young and middle-aged adults. (25)

TMD pain is common, occurring in about 10-14 % of the popula-tion over the age of 18 (25, 26) and is about twice as common in women as in men. (25)

TMJ clicking is even more prevalent and is found in 20-30 % of the adult population. (17, 25, 27, 28) There is evidence that TMJ sounds alone are frequent and a natural phenomenon in the general popula-tion and that they fluctuate longitudinally, but they are also recognized as a sub diagnosis of TMD. (19) Disc displacement with reduction diagnosed according to Research Diagnostic Criteria for TMD (RDC/TMD) (19) is present in 12-18 % of the adult population.(26)

Figure 3. Schematic picture of the masticatory structures. (18)

23

In a meta-analysis by Al-Jundi et al(29) it was estimated that the treatment need for TMD in adults, is in the region of 16 %, which indicates that TMD can be considered as a major health problem.

AetiologyThere is uncertainty as to the actual underlying aetiology of TMD. (25) Even if there are similarities with musculoskeletal disorders and pain disorders in general, the stomatognathic system is also unique with the upper and lower jaw, and occluding teeth, between bilate-rally functioning temporomandibular joints, which has led to a need for a multifactorial etiologic approach. (30)

Contributing factors are often discussed in respect of the aetiology of TMD. These factors are divided as predisposing, initiating and perpetuating. Predisposing factors can increase the risk of devel-oping a condition, initiating factors can cause the onset of the condition and perpetuating factors contribute to the maintenance or persistency of the condition.(30)

Psychosocial and biomedical factorsEvery time a pain signal reaches the central nervous system the infor-mation in the impulse is processed and influenced by different areas of the brain, for example the limbic system, thalamus and cortex. (30) Beside age and gender, psychosocial factors like stress, depres-sion and the presence of multiple somatic symptoms are therefore seen as possible risk factors in the development of TMD. (25, 31) Actually, psychological disorders have been shown to be a major contributing factor in chronic TMD. (30)

It has also been argued that biomechanical factors such as func-tional impairments of the TMJ´s, muscles and occlusion are involved in the aetiology of TMD. (20) Also behavioural factors such as tooth clenching or grinding have been discussed, (23) together with the possible influence from occlusion, (31-33) external trauma including whiplash injury(34) and micro-trauma due to overloading of the masticatory system.(30)

The various factors involved have led to a multidimensional perspective regarding TMD with an appreciation that a combination of physical, psychological and social factors can contribute to the overall presentation of this disorder. According to NIH Consensus

24

Conference (1997) it is hypothesized that the two cardinal features of TMD are pain and dysfunction, incorporating individual vari-ability (Figure 4).

Figure 4. Aetiological factors in TMD. The cardinal features of temporomandibular pain and dysfunction. (20)

Dysfunctional central pain modulationIt has been emphasized that the development of chronic musculo-skeletal pain in the case of the TMD diagnoses myofascial pain and arthralgia starts with peripheral trigeminal pain and inflammation, which has been proceeded by long-standing, repetitive muscular load. (35) This pain and inflammation in turn leads to a periphe-ral nociceptive hyper-excitability in the dorsal horn neurons in the spinal cord, i.e. primary hyperalgesia. This condition is normally reversible but in some individuals a central sensitization may develop due to functional (neurochemical) and structural (neuroanatomical) changes in the dorsal horn neurons and in other parts of the central nervous system as a consequence of the repeated and/or continuing peripheral noxious output. The condition can then result in a long-standing and refractory pain disorder, i.e. secondary hyperalgesia. (35) The structural changes can include development of dendrites and activation of latent synapses, which may cause spread, and referral of pain often seen in patients with TMD. (35)

Research Diagnostic Criteria for TMD (RDC/TMD) The RDC/TMD were introduced in 1992 and was primarily developed for research purposes. There was a need for standard-ized research methods to enable comparisons of findings between different clinical investigators. The RDC/TMD has, since then, been

25

used in a large number of studies and it is now a well-accepted dia gnostic tool. The diagnostic system in RDC/TMD is non-hierar-chical and allows for the possibility of multiple diagnoses for a given subject. (19)

malocclusion and tmdAn association with TMD and certain malocclusions has been reported. In a case-control study Henrikson et al(33) found more TMD among girls with a Class II malocclusion compared with controls with a normal occlusion. (33) This finding was confirmed in a study by Miller et al(36) who concluded that severe retrognathia was a risk factor for TMJ pain disorders in women.

Other malocclusions that have been suggested to be of impor-tance in the development of TMD in some individuals, are unilateral cross-bite (32, 37) and crowding(38). There is however a general consensus that occlusal variables alone are not considered etiologic factors of TMD and that their role should not be overstated. (20, 30, 39, 40) In a systematic review by The Swedish Council on Health Technology Assessment (SBU) it was concluded that there is insuf-ficient scientific evidence for an association between specific maloc-clusions and TMD. (12, 41)

orthognathic treatment and tmdEven though the occlusion does not seem to have a major role in the TMD aetiology, TMD are one of the main complaints among patients that are referred for orthognathic treatment. (15, 42) Can it be that individuals with dentofacial deformities are more susceptible to TMD than the population in general?

The frequency of TMD in patients with dentofacial deformi-ties referred for orthognathic surgery, have been reported to vary between 43 and 73 %. (13, 43-45) These existing studies are not population based and therefore, sound epidemiologic data on the prevalence of TMD in individuals with dentofacial deformities is limited.

It has been agreed that orthodontic treatment does not seem to have a negative impact on the frequency of TMD. (12, 33, 38, 46)

Several studies have investigated whether orthodontic treatment in combination with orthognathic surgery has an influence on TMD.

26

Some of these studies indicated that orthognathic treatment does not affect frequencies of TMD at all. (45, 47, 48) On the other hand, Pahkala et al (49) concluded that patients diagnosed with TMD of myogenous origin benefited more from treatment compared with those diagnosed with TMD of arthrogenous origin. This conclusion was based on the findings that TMJ clicking decreased whereas crep-itations were found to increase. These findings were confirmed by Rodrigues-Garcia et al(50) who in Class II patients found a decrease in TMD pain and TMJ clicking, but an increase in TMJ crepitus after treatment. The finding of decreased TMD pain after treatment, especially when of myogenous origin, has been confirmed in other studies.(43, 44)There are also reports indicating an overall decrease in TMD after treatment. (13, 42, 51)

Taken together, the cited articles above show a broad spectrum of different study designs and results, reflecting the divergence of the available literature. Therefore no consensus can be reached at this point in time with regard to treatment outcomes of TMD after combined orthodontic and orthognathic treatment.

dentofacial deformities and masticationMastication is one of the most important functions of the digestion process. During mastication the food particles are reduced in size, thereby increasing the surface area and facilitating enzymatic processing. Saliva is produced to moisten and lubricate the food for swallowing.

Mastication can be assessed as masticatory ability - an indi-vidual’s self-estimated masticatory capacity or as masticatory per formance – the tested defragmentation of food after a certain number of chewing strokes.

The number of chewing cycles before swallowing depends on the volume(52, 53) and the characteristics of the food, such as consistency and the percentage content of water and fat. (54, 55) Swallowing thresholds for hard food products, like carrots, are further affected by the masticatory performance and maximum bite force. (54)

The number and size of the occlusal contacts have been proposed as one determinant of self estimated masticatory ability(56) and masticatory performance since the contacts between occluding

27

pair of teeth determine the area available for shearing and grinding the food. (57) Compared to individuals with a closer to “ideal” bite, individuals with malocclusions have fewer occlusal contacts. Malocclusions have also been found to negatively affect an indi-vidual’s masticatory performance and self estimated masticatory ability. (57, 58)

Masticatory performance has also been reported to be affected by the maximum bite force(54) Individuals with an open bite or a Class III occlusion have demonstrated less maximum isometric bite force compared with controls. (53, 59) One explanation for this, at least in patients with open bite, can be that they exhibit thinner mastica-tory muscles. (53)

It has also been shown that there are gender differences in both thickness and activities of the masticatory muscles, with men having thicker masseter muscles (60) and higher EMG activity (61)compared with women.

Masticatory ability, an individual’s own assessment of their masti-cation, is an important factor in oral-health related quality of life and general health. It may therefore possibly reflect the impact of mastication on food choice and enjoyment of meals.(56)

28

significance

Orthognathic surgery and its effect on TMD and mastication have been examined in several studies. However, most of the existing studies were designed as case-series and diverging in both study-design and results. This means that based on previous literature it is difficult to evaluate and comprehend the treatment effects of orthognathic surgery. Therefore, a systematic literature review in an evidence-based manner could increase the understanding in this field of research.

The consequences for patients with impaired masticatory function and pain from the masticatory muscles or joints often include difficulties in speaking, chewing and swallowing. These types of problems can probably affect the individual in daily activities such as in the choice of food and even in the everyday social intercourse.

The indications for orthognathic treatment typically reflect the patient complaints. Besides symptoms of TMD and dissatisfaction with facial aesthetics, treatment is therefore primarily performed due to the need to correct functional problems like mastication. The available literature unfortunately does not bring clarity, neither to whether patients with TMD benefit from orthognathic treatment, nor if their mastication is improved. Since orthognathic treatment is arduous for the patient, not without complications, time consuming and expensive for the society and sometimes also for the individual, it is of outmost importance to evaluate if the treatment meets the expectations from the patients, the profession and the society.

This thesis is based on a series of studies, unique in the way that they in a prospective longitudinal design assess TMD and mastica-tory function, in patients with dentofacial deformities, before and after orthognathic treatment in comparison with a control group.

29

aims

paper i• To accomplish a systematic review of the present literature

in order to evaluate whether orthognathic surgery affects the prevalence of signs and symptoms of TMD.

paper ii• To evaluate whether TMD are more common in individuals

referred for orthognathic surgery than in a control group.

paper iii• To investigate whether correction of dentofacial deformities by

orthognathic treatment alters the frequency of TMD.• To compare and monitor the frequency of TMD in an untrea-

ted normal group over the same period of time.

paper iV• To evaluate the self estimated masticatory ability and masti-

catory performance in patients with dentofacial deformities before and after orthognathic treatment; in comparison to an age- and gender matched control group.

• To investigate possible factors that can have an impact on self estimated masticatory ability and masticatory performance.

30

hypotheses

paper i• The scientific evidence based on currently available literature

is insufficient to clarify if orthognathic treatment can affect the frequency of TMD.

paper ii• Neither frequency of signs and symptoms of TMD or diagno-

sed TMD according to Research Diagnostic Criteria for Tem-poromandibular Disorders (RDC/TMD) would differ between the patient and control group.

paper iii• Patients with dentofacial deformities benefit from treatment, in

respect of TMD. • Post-treatment, the frequency of TMD is similar to that in the

control group.

paper iV• Patients with dentofacial deformities have impaired self-

estimated masticatory ability and masticatory performance compared to a control group.

• For patients with dentofacial deformities the self estimated masticatory ability and masticatory performance is improved by orthognathic treatment.

31

materials and methods

subJectsPaper II-IVThe treatment group comprised 121 consecutive patients (51 males and 70 females) with dentofacial deformities, referred to the Depart-ment of Oral Maxillofacial Surgery, Malmö University Hospital, Sweden for orthognathic treatment. The mean age at the start of the trial was 22.5±7.4 years. All patients with Class II, Class III, open bite or deep bite diagnoses were included and recruited during two periods, between 1992–1995 and 2000–2002. Patients with such severe dentofacial deformities are entitled to subsidized treatment under the Swedish National Health Service. The exclusion criteria were craniofacial syndromes, systemic arthritic and muscular diseases, and a dentition of fewer than 24 teeth. There were 98 patients that completed the follow-up examination (Paper III and IV, Figure 5); 38 males and 60 females, mean age 22.4 ± 7.5 years.

The control group comprised 56 subjects, 23 males and 33 females, mean age 23.4 ±7.4 years, age and gender matched with the subjects in the treatment group. They were recruited from general dental patients at the Faculty of Odontology, Malmö University, Sweden, and the Public Dental Health Clinic in Oxie, County Skane, Sweden. The inclusion criteria for the controls were normal occlusion, or minor malocclusions for which neither orthodontic treatment nor orthognathic surgery was indicated.

The same exclusion criteria applied to the control group as to the treatment group. Three years after the initial examination a follow-up questionnaire was sent to the individuals in the control group. They were contacted by telephone 2 to 3 weeks later, and asked to participate in the follow-up examination. Thirty-eight

32

of the 56 individuals (68 %) in the control group underwent the clinical follow-up examination in Paper III (Figure 5).

Analysis of those who withdrew from the treatment and control groups, (n = 23, 19 %, and n = 18, 32 %, respectively) showed no significant differences compared with the final samples with respect to age, gender, self-rated level of anxiety, pain in the jaws and related muscles, diagnosed TMD, self-estimated masticatory ability or performance reported at baseline. Thus, the participants who completed the study were considered to be representative of the initial study sample.

Ethical considerationsThe study was approved by the Ethics Committee of Lund Univer-sity, Sweden (Ref. No. LU-241-01), which follows the guidelines of the declaration of Helsinki.

Figure 5. Flow chart showing the participants in Paper III.

33

methodsPaper iSearch strategyTo identify all studies that examined orthognathic surgery and its effect on TMD in patients with severe malocclusions, a literature survey was performed using the PubMed (www.ncbi.nlm.nih.gov) and the Cochrane Library electronic databases (www.cochrane.org). The search covered the period from January 1966 to April 2006.

The terms used in the search were malocclusion (MeSH-term), retrognathia (MeSH-term), prognathia, open bite (MeSH term), and deep bite in various combinations with craniomandibular disorders (MeSH-term), temporomandibular disorders, temporomandi bular dysfunction, temporomandibular joint dysfunction, temporo-mandibular joint pain, and orthognathic surgery (MeSH-term), sur gical-orthodontic treatment, and surgery (MeSH-term).

Selection criteriaControlled human studies published as full-length articles, com-paring symptoms and signs of TMD before and after ortho gnathic surgery in patients with malocclusion, were included. Articles con-cerning treatment of syndromes, e.g. cleft lip and palate were not considered. Three reviewers independently assessed all the article abstracts that appeared to meet the inclusion criteria. The article abstracts were collected irrespectively of the language in which they were published, after that the retrieved articles were read in their entirety and independently by the three reviewers. The reference lists of the retrieved articles were also hand- searched for relevant studies not found in the database search. Any inter-examiner conflicts were resolved by discussion to reach a consensus.

Data collection and analysisData were extracted on the following items: author, year of publi-cation, study design, sample size, gender and age, surgical treatment methods, follow-up time, methods to determine TMD, outcomes, and authors’ conclusions. In addition, to document the methodo-logical soundness of each article, a quality evaluation modified by the methods described by Antczak et al (62) and Jadad et al (63) was performed with respect to pre-established characteristics. The following variables were evaluated:

34

1. Study design; RCT = 3 points, prospective study = 2 points, retrospective study = 1 point

2. Adequate sample size = 1 point, 3. Adequate selection description = 1 point4. Valid measurement methods = 1 point5. Use of method error analysis = 1 point6. Adequate statistics provided = 1 point7. Consequences of confounders discussed in analysis = 1 point

By summarizing the scores for these seven variables, a study could achieve a quality score ranging from zero to a maximum of 9. A study’s quality was then categorized as low (0 to 4 points), medium (5 to 7 points), or high (8 or 9 points). To increase the objectivity of the analysis, four evaluators independently assessed the data extrac-tion and quality scoring from each article. For each article, any inter-examiner disagreements were resolved by discussion to reach a consensus.

Supplemental searchPaper I was supplemented with a new literature search extending from April 2006 to May 2013 in the PubMed database and the Cochrane Collaboration Library for reviews and clinical trials. The same search terms as previously were used, and with the addition of the MeSH term ”dentofacial deformities” in combination with the original terms. The same selection criteria, data collection and analysis as described in Paper I were used, the only exception being that only three evaluators assessed the quality of the retrieved articles.

The grading and the final level evidence, based on the evaluated studies, were estimated according to the SBU (Tables 1 and 2). (38, 64-66)

35

Table 1. Criteria for grading of assessed studies.(66)

Grade A – High value of evidenceAll criteria should be met:• Randomized clinical study or a prospective study with a well-

defined control group• Defined diagnosis and endpoints• Diagnostic reliability test and reproducibility tests described• Blinded outcome assessment

Grade B – Moderate value of evidenceAll criteria should be met:• Prospective or retrospective study with defined controlled or

reference group• Defined diagnosis and endpoints• Diagnostic reliability tests and reproducibility tests described

Grade C – Low value of evidenceOne or more of the conditions below:• Large attrition• Unclear diagnosis and endpoints• Poorly defined patient material

Table 2. Definitions of the evidence levels.(66)

level Evidence Definitions

1 Strong At least two studies assessed as grade A.

2 Moderate One grade “A” study and at least two grade “B” studies.

3 limited At least two grade “B” studies.

4 insufficient Fewer that two grade “B” studies

36

Paper ii-ivQuestionnaireIn the questionnaire, the individuals reported:• Reasons for seeking treatment (impaired chewing capacity,

symptoms from the masticatory muscles, TMJs, headaches, and aesthetic reasons)

• State of general health • Use of painkillers for headaches and TMD (yes/no)• Awareness of oral parafunctions as tooth grinding (yes/no), or

tooth clenching (yes/no) • Frequency of TMD pain, jaw fatigue, TMJ clicking, and hea-

dache (never/once or twice a month/once a week/once or twice a week/daily)

• Pain at rest (yes/no) and during mandibular movements (yes/no) and reported TMJ clicking (yes/no)

• Ability to masticate different kinds of food; meat (yes/no), car-rots (yes/no), toffee (yes/no), French loaf (yes/no) or cold cuts of ham, cheese and cucumber (yes/no).

A visual analogue scale (VAS) (67) 0-100 mm, was used to register severity of overall symptoms of TMD (Paper II) with the endpoints none = 0 and severe = 100 and on a verbal scale as follows: 0 = no or minimal discomfort, 1 = slight discomfort, 2 = moderate discomfort, 3 = severe discomfort, 4 = very severe discomfort (Paper III, IV). The VAS was also used for registration of the individuals self-estimated ability to masticate food with the end points “good” = 0 mm and “bad” =100 mm and the level of anxiousness with the endpoints “calm” = 0 and “nervous/anxious” = 100.

The follow-up questionnaire in Paper III included questions about treatment satisfaction, including whether the pre treatment informa-tion had been adequate (yes/no), whether treatment met expectations (yes/no) and whether, post-treatment, the subjects had perceived any alterations in masticatory capacity, aesthetics and TMD symptoms (better, unchanged, worse).

Clinical examinationBefore the orthognathic treatment was started, two calibrated specialists in stomatognathic physiology conducted the clinical

37

examination at the Department of Stomatognathic Physiology at Malmö University. The extraoral examination preceded the intraoral examination.

The examination included measurement of mandibular move-ments, pain during non-guided mandibular movements, registration of TMJ sounds (clicking and crepitation), and tenderness of the TMJs and related muscles. The clinical registrations were improved by calibrating the examination techniques of the two examiners before the start of the study. The calibration was performed by examining 8 patients, not included in the study, and was achieved after discus-sion. The 8 subjects were also examined regarding occlusal inter-ferences with an observer error that was found to be acceptable. (33) The specialists conducting the examinations were not informed whether the subject belonged to the treatment or control group at the follow-up.

The functional occlusion was assessed by methods previously described and investigated for observer error. (68) Mediotrusion interferences within a lateral excursion of 3 mm, laterotrusion inter-ferences, protrusion interferences, and the distance and the direction of the slide between retruded contact position (RCP) and the inter-cuspal contact position (ICP) were registered.

Sub-diagnoses of TMDDiagnoses according to RDC/TMD (19) are divided into three groups (Paper II):• Muscle disorders: (a) myofascial pain, (b) myofascial pain with

limited opening • Disc displacements: (a) disc displacement with reduction; (b)

disc displacement without reduction, with limited opening; (c) disc displacement without reduction, without limited opening

• Arthralgia, arthritis, arthrosis: (a) arthralgia, (b) osteo-arthritis of the TMJ, (c) osteoarthrosis of the TMJ

In Paper III the criteria for diagnosis of disc displacement were modified:

Disc displacement was diagnosed if, upon opening and closing from maximum intercuspation, a click was noted audible or by palpation. Osteoarthrosis was diagnosed as registered crepitations by palpation of the TMJ.

38

Sub-diagnoses of dentofacial deformitiesMorphologic occlusion according to Björk et al (69) was registered by intraoral examination. For the patient group, further data were obtained from dental study casts, lateral cephalograms, and a ceph-alometric analysis. (70) An open bite was classified as an NSL/ML angle of ≥40° and a deep bite as an NSL/ML angle of ≤26°. A Class II skeletal relationship between the dental arches was classified as an ANB angle of ≥6° and a Class III skeletal relationship as an ANB angle of ≤0°. Consequently, the diagnoses in the treatment group were separated into sagittal and vertical discrepancies (Table 4).

Paper iii-ivIn the treatment group, TMD and masticatory function was assessed by means of a questionnaire and a clinical examination before (baseline) and 18 months after surgery. The interval between the two examinations was approximately 3 years depending on the length of the orthodontic treatment. The questionnaire and the clinical examination were performed after treatment planning. The control group was similarly assessed, on two occasions, at an interval of at least 3 years.

Treatment methods All subjects in the treatment group underwent pre- and postsurgi-cal orthodontic treatment with fixed orthodontic appliances in both arches. Ten specialists carried out the orthodontic treatment; the duration varied between 18 and 24 months.

Four maxillofacial surgeons at the Department of Oral Maxillo-facial Surgery, Malmö University Hospital, Sweden, performed the orthognathic surgery. Vertical deformities was corrected in the maxilla with a one piece Le Fort I osteotomy or a segmental maxillary osteotomy (Table 4). (71) Sagittal adjustments were made either by sagittal split osteotomy, to advance the mandible (72) or by intraoral vertical ramus osteotomy, to correct mandibular prog-nathism (Table 4). (71) When bimaxillary surgery was indicated, maxillary osteotomies were combined with either sagittal split or vertical ramus osteotomies (Table 4). Maxillo-mandibular fixation was used for 4 weeks after intraoral vertical ramus osteotomies. In all other cases, rigid intra jaw fixation was used.

39

Paper ivSelf-estimated masticatory abilityAssessed by a questionnaire, as described previously (p. 42).

Masticatory performance testFor assessment of the masticatory performance (73), the individuals were instructed to chew round tablets of silicon impression material (Optosil®, Bayer, Germany) with a standardized weight (Figure 6). The test involves chewing of 5 separate tablets for 20 strokes. The chewed sample was expectorated into a plastic cup. The mouth was then rinsed with water until all particles were removed from the mouth. The rinse water was also collected in the cup and then filtered. The chewed material from each of the tablets was frac-tionated in a system of sieves with coarse, medium and fine meshes (Figure 6). Essentially, the more efficient the mastication was, the greater the quantity of material that passed through the finest sieve. The quantity of material was estimated by weight.

A masticatory performance value, by proportion of weight, was calculated for each test portion, and the mean of the best four values out of five was used as the masticatory performance index (MPI). (73) The index ranges from 0 to 100 - the highest number corre-sponds to the highest performance value. Data of the MPI test was lost from 1 patient at baseline and another 6 patients at follow-up in the treatment group. In the control group the MPI test was only performed at baseline.

Figure 6. Showing the Optosil®

tablett and the sievesystem.

40

Tooth contactsThe number of tooth contacts was recorded in habitual intercuspal position during maximal isometric biting force. The indication of contacts was registered in the maxilla by means of a thin double folded plastic-foil (GHM occlusion foil® 8 μm, Hanel –Ghm Dental, Germany). The markings by the foil were registered as follows: single dot = one contact; line = two contacts; region of several small markings = three contacts (Figure 7). The evaluation of the meth-odological error for measuring the number of occlusal contacts has been described earlier and was found to be low. (58)

Figure 7. Registration of tooth contacts. 1) Single dot – one con-tact, 2) Line – two contacts, 3) Region of several small markings – three contacts.

statistical analyses All statistical analyses were performed using the Statistical Package for the Social Scenes (SPSS) versions 13-20 for Windows (IBM). The criterion for significance (alpha) was set at .05. The tests were 2-tailed, which means that an effect in either direction was recog-nized. When necessary, statistical consultations were made with a statistician at the Department of statistics, Lund University, Sweden.

41

Sample size calculation (Paper II-IV)With the proposed sample size of 35 in the treatment and control groups, the study had a power of 89.8% to yield a statistically significant result. This computation assumed that the difference in proportions was 0.30 (specifically, 0.05 versus 0.35) in the preva-lence of TMD pain. This difference was selected as the smallest effect that would be important to detect, in that any smaller effect would not be of clinical or substantive significance.

Descriptives Mean and standard deviations were calculated for all continuous, numerical variables (Paper II-IV) and medians and percentiles (Q) for continuous, ordinal variables (Paper II-IV).

Differences between groups Pearson’s chi-square test with Yate’s correction for continuity was used when 2 x 2 cross tabulations were applicable. When the expected cell value was less than 5, Fisher’s exact test was used (Paper II-IV).

Mann-Whitney rank sum test was used to compute the difference between ranks and groups with ordinal data (Paper II-IV).

Two-sample t-statistics was used when comparing means of numerical variables (Paper II-IV).

Analysis of variances (ANOVA) was used when comparing means between sub groups of sagittal and vertical discrepancies (Paper IV).

Differences within groups (Paper III-IV) McNemar exact test was used to analyse dichotomous data before and after treatment.

Wilcoxon signed ranks test was used to analyse ordinal data before and after treatment.

Paired t-test was used to compare the means of maximum mandi-bular opening capacity.

42

Multivariate analysisLinear regression analysis, with the enter method, adjusted for age and group belonging, was used for multivariate analysis of masti-catory ability and MPI (Paper IV).

Bivariate analysisBivariate correlation with Pearson correlation coefficient was performed on numerical variables (thesis).

43

results

systematic review – paper iThe search strategy resulted in 467 articles. After analysis according to the inclusion/exclusion criteria, three articles (43-45) were included for further analysis. All of the included studies were controlled, prospective and longitudinal.

An agreement of more than 90 % was found between the reviewers in assessing the data extraction and decisions of quality scores of the included articles.

Dentofacial deformities and frequency of TMDWhen comparing signs and symptoms of TMD before treatment, none of the included studies (43-45) found any significant differ-ences between patients and control groups or between different kinds of malocclusion.

The effect of orthognathic surgery on TMDThe reported findings after orthognathic treatment were contra-dictory. Two of the studies(43, 44) found a statistically significant decrease in muscle palpation tenderness after surgery, whereas in one study, (45) no such change was found. (Table 3) One study(43) also reported a significant decrease in TMJ palpation tenderness (Table 3). Consequently the authors’ conclusions for the studies also diverged with two of the studies(43, 44) declaring that both signs and symptoms related to TMD had improved significantly, whereas one study, (45) reported that TMD symptoms did not always show improvement after surgical correction, and for some patients, the symptoms even changed for the worse.

44

Quality analysisAccording to the quality assessment of the included articles there were two studies (44, 45) of medium and one(43) of low quality. All of the studies used valid and well-known methods for measure-ments and provided adequate statistics. The general shortcomings were inadequate selection description, no method error analysis and no discussion of consequences of confounders. One study was also found to have an inadequately small control sample. (43) It is also notable that no study (43-45) reported a prior estimate of the sample size.

new literature searchThe complementary literature search of studies published April 2006-May 2013 resulted in 234 articles. Only one study met the inclusion criteria. (74) The reasons for exclusion and number of excluded articles were;

• Studies not concerning the objectives of this • review (analysis of surgery technique, • treatment of arthritis and osteoarthrosis, • treatment of syndromes as cleft lip or • palate treatment) 218• Case reports, case series 10• Review articles 5––––––––––––––––––––––––––––––––––––––––––––––––––––––––––Total 233

Treatment effects The only included study in the new search was a prospective, longitudinal and controlled trial (Paper III in this thesis). (74) The findings revealed a decrease of both myofascial pain, arthralgia and disc displacements. The results also indicated an increase in osteo-arthrosis (Table 3). The conclusions from the study were that for patients with dentofacial deformities orthognathic surgery has a positive treatment outcome in respect of TMD pain. After treatment the frequency of TMD was lower and comparable to that of a control group.(74)

45

Quality AnalysisThe research quality/methodological soundness for the included study was estimated as high. (74) Adequate sample size, in advance calculated by a power analysis, and selection description was provided. The study used a valid and well-known measurement method, method error analysis and adequate statistics. Confounders were discussed in the analysis. The only, but major, shortcoming was that the study design was not a RCT.

Evidence for differences in frequency of TMD before and after orthognathic treatmentOnly one study used RDC/TMD as a diagnostic tool when assessing frequencies of TMD. (74) Therefore, according to the definitions of evidence level by SBU (61) there is insufficient evidence for an effect on diagnosed TMD from orthognathic treatment.

The majority of the included studies in the systematic review, instead assessed signs and symptoms of TMD. The result from Paper I and the complementary search revealed that there is limited evidence for a decrease in pain on palpation in the masticatory muscles after orthognathic treatment. (44, 74)

There was insufficient scientific evidence, partly due to contradic-tory results, (44, 45, 74) to support an effect on TMJ sounds and TMJ pain on palpation from orthognathic treatment.

46

Tabl

e 3.

Res

ults

of

the

qual

ity

anal

ysis

and

the

tre

atm

ent

outc

ome

of t

he s

tudi

es in

clud

ed in

Pap

er I

and

the

new

lit

erat

ure

sear

ch.

Stud

yQua

lity

Score

Num

ber1o

f1pa

tients

Type

1of1

dentofacial1

deform

ity

Follo

w9up1

after1surgery

Subd

iagnoses1of1

TMD

Pain1on1pa

lpation1of1th

e1masticatory1muscles1and

1TM

Js

TMJ1sou

nds

Oniza

wa'et

'al,'19

95M

oder

ate

530

Vario

us6'm

onth

sno

Unc

hang

edUnc

hang

edPa

nula'et'a

l,'20

00Lo

w4

60Va

rious

29'm

onth

sno

Decrea

se'in

'bot

h'm

ucsle

'an

d'joint'p

ain'on

'pa

lpat

ion

Unc

hang

ed

Derv

is'et

'al,'20

02M

oder

ate

550

Vario

us24

'mon

ths

noDe

crea

se'in

'mus

clep

ain'

on'palpa

tion,'jo

int'p

ain'

on'palpa

tion'un

chan

ged

Unc

hang

ed

Abra

ham

sson

'et'a

l'201

3Hi

gh8

121

Vario

us18

'mon

ths

yes'(

RDC/

TMD)

'De

crea

se'in

'm

yofa

scial'p

ain,'

arth

ralgia'and

'disc

'disp

lace

men

t

Decrea

se'in

'bot

h'm

uscle'

and'joint'p

ain'on

'pa

lpat

ion

Joint'c

licking

'de

crea

sed,'

crep

itatio

ns'

increa

sed

47

paper iiAnamnestic findingsThe self-rated level of anxiousness was similar in the treatment and control groups, with median VAS scores of 19.5 (Q1 = 7, Q3 = 47) and 19.0 (Q1 = 6, Q3 = 43), respectively. Furthermore, there were no differences between the groups with regard to reported weekly headaches or awareness of para-functional habits such as tooth clenching and tooth grinding. No subject in either of the two groups reported heart or joint disease. No significant differences were found between the groups regarding frequencies of allergies, stomach and dermatologic diseases.

The severity of the overall symptoms of TMD was rated higher on a verbal scale in the treatment group compared with the control group (P = .001).

The reasons for seeking treatment reported by the patients were (more than one answer was possible):• impaired mastication (75 %)• symptoms from masticatory muscles, TMJs, and headaches (72 %)• aesthetic reasons (66 %)

TMD diagnosesThe treatment group had a significantly higher frequency of myofas- cial pain, disc displacement with reduction (DDR), and arthral-gia compared with the control group (Figure 8). The frequency of myofascial pain with limited opening, osteoarthritis, and osteoar-throsis was low, with no differences found between the two groups.

There were no significant differences in the frequency of dia gnosed TMD(19) between the different malocclusion traits, shown in Table 4.

48

Figure 8. Percentage distribution of TMD diagnoses according to RDC/TMD in the treatment group (n =121) and the control group (n = 56) before treatment.

Table 4. Distribution of different kinds of malocclusions and performed surgery in the treatment group.

paper iiiTMD diagnosesAfter treatment, the frequencies of myofascial pain, disc displa-cement and arthralgia were significantly reduced in the treatment group, but at the same time, there was a significant increase in osteo-arthrosis (Figure 9). At baseline, significantly more patients in the treatment group had myofascial pain and arthralgia compared with the control group, whereas there was no difference post-treatment

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49

(Figure 10). For the treatment group the number of patients with at least one TMD pain diagnosis had decreased with 42 %.

The only TMD diagnosis, in the treatment group, with a signifi-cant gender difference was myofascial pain. Before treatment (P = .015); it was more common in women (32%) than in men (12%), but at follow-up, no gender-related differences were found for this or any other of the TMD diagnoses.

TMD diagnoses in relation to different kinds of dentofacial deformitiesAfter treatment, there were significantly decreased frequencies of myofascial pain (P = .022) and arthralgia (P = .031) in Class III patients (with a normal vertical jaw relationship). None of the other subgroups showed significant differences in TMD diagnoses between baseline and follow-up.

Figure 9. Percentage distribution of TMD diagnoses in the treatment group (n=98) before and after treatment.

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50

Figure 10. Percentage distribution of TMD diagnoses in the treatment group (n=98) and control group (n=56) after treatment.

Symptoms of TMDIn the treatment group, both self-evaluated severity of overall symptoms of TMD and pain from the masticatory muscles and TMJs, decreased significantly from baseline to follow-up (P < .001). No such difference was found in the control group (Figures 11-13).

Figure 11. Self-evaluated overall symptoms of TMD, in the treatment group (n=97), at baseline and follow-up (P < .001). For one patient no answer was registered.

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51

Figure 12. Self-evaluated overall symptoms of TMD, in the control group, at baseline and follow-up (P = NS).

Figure 13. Reported pain from the masticatory muscles and TMJs during rest, wide opening and/or mastication, in the treatment (n=97) and control group (n=38), before and after treatment. For one patient in the treatment group no answer was registered.

Mandibular movement capacityAt both baseline and follow-up, the maximum mandibular opening capacity in the treatment group was lower than in the control group (P = .005, P < .001 respectively). The opening capacity in the treatment group had decreased at follow-up, from 50 ± 8 mm to 48 ± 7 mm (P = .009). For the control group, no significant changes in mandibular opening capacity were recorded from baseline to follow-up examinations (mean 54±5 mm and 53±6 mm, respec-tively).

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Treatment group Control group Baseline Follow-up Baseline Follow up

~3 years ~3 years

No pain

46 40 66 30 24 28 26 4 6 6 Pain 51 25 31 8 4 10 P < .001 P = .170

52

Occlusal interferencesAt baseline, the treatment group had significantly more interferen-ces (P < .05) than the control group, except for lateral deviation between RCP and ICP. At follow-up, the number of subjects in the treatment group with interferences had decreased significantly (P < .05) and no inter-group differences were disclosed.

Patients’ satisfaction with treatmentWhen asked about their satisfaction with the treatment, 82% of the patients in the treatment group reported improved aesthetics, 80% reported improved masticatory comfort and 61% reported fewer symptoms of TMD after treatment. Ninety-two percent were satisfied with the information received before treatment. Sixty-eight percent reported their experience of treatment to be as they had expected, or less burdensome than expected. There were no gender differences with regard to treatment satisfaction.

level of anxietyThe median self-evaluated level of anxiety registered on a VAS decreased from 19 to 11 after treatment (P = .001). The correspon-ding figures for the control group were 20 at baseline and 25 at follow-up examination (P = .871).

paper iVSelf estimated masticatory abilityAt baseline, the patients rated their masticatory ability significantly lower (mean = 52.2 ± 29.5) than the control group (mean = 85.7 ± 17.4, P < .001). They also found it more difficult to chew meat (P < .001), raw carrots (P = .019), toffee (P = .002), French loaf (P < .001) and cold cuts of ham, cheese and cucumber (P < .001). At follow-up, the masticatory ability had significantly improved in the treatment group (mean = 83.9 ± 19.2, P < .001) and reached a level similar to that of the control group with no significant difference between the groups.

Factors influencing the self estimated masticatory abilityThe only factors significantly associated with the masticatory ability in the treatment group were the number of occlusal contacts during

53

maximum biting pressure and self-estimated overall symptoms of TMD. When the treatment group and control group were merged a significant association between TMD pain and masticatory ability was found (Table 5).

In a linear regression analysis adjusted for age, factors like number of occlusal contacts during maximal biting pressure, severity of overall symptoms of TMD and study group belonging explained 45 % of the total variation of the masticatory ability. Fewer occlusal contacts during maximal biting pressure, a higher severity of the overall symptoms of TMD and belonging to the treatment group all had a negative association with the masticatory ability.When subgroups of dentofacial deformities were assessed it was found that patients with a Class II relation (n = 27) rated their masti-catory ability higher (mean = 68.7, +- 25.9) compared with patients with Class III and normal sagittal relations (n = 71, mean = 46.5, +-28.7, P = .002, 95 % CI 8.4-35.9). No significant differences were found between separate vertical jaw relations.

Masticatory performanceThere were large individual variations of the masticatory perfor-mance index (MPI), within the groups. At baseline, the treatment group had a lower MPI than the control group (mean 10.4+ -10.4 versus mean 37.3+-16.8). For the treatment group, the MPI increased at follow-up (mean 21.0+-19.2) but was still low compared with the baseline level in the control group (P < .001).

After stratifying the material into sagittal and vertical deformities it was found that the MPI improved after treatment in patients with: • Class III malocclusion (normal vertical relation) • Mean: 12.8 ± 11.0 to 23.7 ±18.5 (P < .001)• Open bite (normal sagittal relation)• Mean 6.3 ± 6.0 to 19.9 ± 19.9 (P = .038)• Class III combined with open bite

Mean 7.9 ± 8.4 to 24.7 ± 20.6 (P = .003)

No significant differences after treatment were found in patients with deep bite or Class II malocclusion.Factors influencing MPi

54

When the treatment group and control group were analysed alto-gether the variables gender; number of occlusal contacts during maximal biting pressure; self reported severity of overall symptoms of TMD and TMD pain diagnoses were all found to significantly have an influence on the MPI at baseline, (Table 6). When the treatment group and control group were analysed separately only gender and occlusal contacts had an influence on the MPI in the treatment group whereas gender and a TMD pain diagnosis influ-enced the MPI in the control group. No association was found between age and MPI for any of the groups (Table 6).

A linear regression analysis, adjusted for age and group belonging, explained 37 % of the total variation of MPI. The number of occlusal contacts during maximal biting pressure was the factor that had the highest influence on MPI, with increased MPI with a higher number of contacts. Open bite was the only kind of dentofacial deformity with a significant influence on MPI, showing a negative effect on MPI.

Patients with an open bite (n = 41) were also found to have an impaired masticatory performance (mean = 6.7, SD 6.8) compared with patients with deep bite or a normal vertical relation (n = 57, mean = 13.2, SD 11.8, P = 001, 95 % CI 2.7-10.2). No significant differences were found between separate sagittal relations.

CorrelationsBefore treatment, significant correlations were found between:• Self-estimated masticatory ability and masticatory performance

(0.483, P < .001).• Self-estimated masticatory ability and number of occlusal con-

tacts during maximum biting pressure (0.428, P < .001). • Masticatory performance and number of occlusal contacts

during maximum biting pressure (0.509, P < .001).

55

Occlusion Before treatment, there were no significant differences in number of teeth between the treatment (mean = 28 ± 1.9) and the control group (mean = 29 ± 2.0). During treatment teeth were extracted in some of the patients and at follow-up there were significant differences between the two groups (mean = 27 ± 2.1 and 29 ± 2.0 respectively, P = .002).

The treatment group had significantly fewer occlusal contacts during maximum biting pressure than the control group (mean = 13 ± 6.4 versus 18 ± 5.5, (P < .001). After treatment the number of contacts increased (Mean = 16 ± 6.1, P < .001) and did not signifi-cantly differ from the control group.

When subgroups of sagittal and vertical discrepancies were assessed before treatment, the 41 patients with open bite had signifi-cantly fewer occlusal contacts during maximum biting pressure compared with the 48 patients with normal vertical relation (mean = 14 ± 5.8, P = .014) and the the 9 patients with deep bite (mean =10 +- 5.0 versus 19 +-9.5, P < .001) and the 48 patients with normal vertical relation (mean = 14 +- 5.8, P = .014). No significant dif - ferences between sagittal discrepancies were found before treatment. After treatment there were no significant differences between any of the subgroups.

56

       

Pat

ient

gro

up

C

ontr

ol G

roup

B

oth

grou

ps

Influ

enci

ng b

inar

y pa

ram

eter

s

n

M

PI

SD

P

95

% C

I

n

M

PI

SD

P

95

% C

I

n

M

PI

SD

P

95

% C

I

Fem

ale

50

57

.1

31.5

33

86.6

15

.3

83

68

.8

30.7

M

ale

36

45.4

25

.4

NS

23

84.3

14

.9

NS

59

60.6

29

.1

NS

N

umbe

r of o

cclu

sal c

onta

cts

durin

g

max

imal

biti

ng p

ress

ure

<

10

28

38

.7

25.5

3

83.7

8.

1

31

43

.1

27.8

!

10

58

58

.7

29.3

.0

03 7

.1 –

32.

9

53

85.8

17

.8

NS

111

71.6

27

.9

.000

17

.4

- 39

.8

O

ne d

iagn

ose

of T

MD

pai

n

No

59

56.4

28

.4

50

87

.5

13.3

109

70.7

27

.5

Y

es

27

43

.1

30.4

N

S

6

70

.3

35.8

N

S

33

48

.0

32.6

.0

00

11.3

-

33.9

Sev

erity

of o

vera

ll sy

mpt

oms

of T

MD

Insi

gnifi

cant

-ligh

t

60

60.1

26

.8

51

88

.0

13.2

101

74.2

25

.2

M

oder

ate-

very

sev

ere

36

41.2

29

.9

.003

6.

7 –

31.2

5

61.8

34

.5

NS

41

43.7

30

.8

.000

20

.7

– 40

.4

Tabl

e 5.

Sta

tist

ical

ly s

igni

fica

nt d

iffe

renc

es o

f th

e M

ean

self

-eva

luat

ed m

asti

cato

ry a

bilit

y by

leve

ls o

f O

cclu

sal f

acto

rs

and

TM

D in

the

who

le s

tudy

gro

up (

Bot

h T

reat

men

t an

d C

ontr

ol g

roup

) n

= 15

3 an

d th

e tw

o gr

oups

sep

arat

ely.

Tw

elve

pat

ient

s w

ere

not

aske

d fo

r th

eir

mas

tica

tory

abi

lity

befo

re t

reat

men

t.

57

Tabl

e 6.

Sta

tist

ical

ly s

igni

fica

nt d

iffe

renc

es o

f th

e m

ean

Mas

tica

tory

Per

form

ance

Ind

ex (

MP

I) b

y le

vels

of

Occ

lusa

l fa

ctor

s an

d T

MD

in t

he w

hole

stu

dy g

roup

(B

oth

Tre

atm

ent

and

Con

trol

gro

up)

n =

153

and

the

two

grou

ps s

epar

atel

y.        

Pat

ient

gro

up

C

ontr

ol G

roup

B

oth

grou

ps

Influ

enci

ng b

inar

y pa

ram

eter

s

n

M

PI

SD

P

95

% C

I

n

M

PI

SD

P

95

% C

I

n

M

PI

SD

P

95

% C

I

Fem

ale

60

8.

2 8.

0

33

33.1

17

.0

93

17

.0

16.9

M

ale

37

14.1

12

.7

.013

1.

3 - 1

0.6

23

43.3

14

.9

.024

1.

4 –

18.8

60

25.3

19

.6

.008

2.

2 –

14.4

N

umbe

r of o

cclu

sal c

onta

cts

durin

g

max

imal

biti

ng p

ress

ure

<

10

34

5.

6 7.

0

3

25.4

16

.9

37

7.

2 9.

5

!

10

63

13

.0

11.1

.0

00 3

.8 –

11.

1

53

38.0

16

.7

NS

116

24.4

18

.7

.001

12

.6

- 21

.9

O

ne d

iagn

ose

of T

MD

pai

n

No

65

11.6

11

.4

50

39

.6

16.1

115

23.8

18

.8

Y

es

32

8.

2 7.

7 N

S

6

18

.5

8.9

.001

11

.5 -

30.6

38

9.6

12.2

.0

00

9.6

- 18

.7

Sev

erity

of o

vera

ll sy

mpt

oms

of T

MD

Insi

gnifi

cant

-ligh

t

55

11.5

11

.0

51

38

.6

16.2

106

24.5

19

.3

M

oder

ate-

very

sev

ere

42

9.0

9.5

NS

5

24.8

19

.8

NS

47

10.6

11

.8

.001

8.

9 –

18.9

58

discussion

This thesis is based on a series of studies evaluating TMD and masti-catory function in patients with dentofacial deformities referred for orthognathic surgery. The first part of the thesis (Paper I) reviewed previous literature to determine whether there was evidence for a positive or negative outcome with respect to TMD after orthog-nathic treatment. The clinical studies (Paper II-IV) were unique as they provided a longitudinal comparison of a patient group with a control group that had no or minor malocclusions. Studies with a controlled and longitudinal study design are scarce in this field of research.

The main finding of the initial systematic review (Paper I) was that there are very few controlled studies that longitudinally assess TMD in patients treated with orthognathic surgery. Thus, it was very difficult to draw any conclusions regarding treatment outcomes. This lack of studies may reflect the difficulties in performing these kind of clinical trials.

The main findings of the clinical studies (Paper II-IV) were that patients with dentofacial deformities and referred for orthognathic surgery had more TMD than a normal population. These patients also estimated their masticatory ability lower and was tested having lower masticatory performance than the control group. After treatment the frequency of TMD had been reduced in the treatment group and were similar to the levels found in the control group. Also the masticatory ability and the masticatory performance had improved, although the masticatory performance was still lower compared to the control group.

59

systematic reviewIn 1992 Davidoff et al(75) estimated that dedicated health care professionals would have to read and critically review about 17 original articles every day to keep up to date with the recent published science. Today the figures are probably even higher, and consequently this task is obviously impossible to implement for most clinicians, making systematic reviews valuable.

In a systematic review a well-formulated question is addressed by analysing all available evidence. It includes an objective search of the literature, critically appraising what is found to be relevant. Then data is extracted, synthesized and summarized. The process is aimed at minimizing bias in order to have a more reliable basis for clinical decision-making. (76, 77) There is also the view that system-atic reviews should always precede new research projects in order to improve study designs, and consequently to produce new trials with a higher impact. (78)

In the present systematic review the formulated question was “Does orthognathic surgery affect the prevalence of signs and symptoms of TMDs?” and the inclusion criteria were: • Studies comparing signs and symptoms of TMD before and

after orthognathic surgery in patients with malocclusion.• Randomized controlled trials (RCTs) or controlled, prospective

or retrospective studies.

The result of the literature search in the initial and the complemen-tary review revealed a limited number of studies that correspon-ded to the inclusion criteria. (43-45, 79) Furthermore, neither of these studies were RCTs. In research, a well-designed and properly executed RCT, is claimed to provide the highest level of evidence on the efficacy of health care interventions and is therefore consi-dered the gold standard(80-82). Unfortunately, often due to ethical reasons, it is not possible to perform randomised trials, instead leaving observational studies like cohort or case-control studies as the only choice. Considering patients with dentofacial deformities, scheduled for orthognathic surgery, it can be considered unethical to randomize one group of patients for treatment and postpone treatment for another group of patients for one or two years. With this in mind, it was even more surprising that there were so few

60

observational studies with a well-defined control group as it is well known that studies without a control group only provide low scien-tific evidence.

The methodology for data extraction and the quality assessment used in the present systematic review was partly adopted from Antczak et al (62) and partly from SBU. (64)

It can be discussed whether the scoring criteria were too ambitious since RCT can be difficult to implement in this type of research. Even so, one study (Paper III in this thesis) was judged as high value of evidence, confirming that well-designed observational studies can reach as high level of evidence equivalent to RCTs. (64, 81)

When grading studies as high, medium or low value of evidence, there is always the possibility of subjective impact on the assessment. All of the retrieved articles in Paper I was therefore independently analysed by all four authors. Consensus was then reached through discussion.

The systematic review, complemented with the new literature survey, found limited scientific evidence for a decrease in pain on palpation of the masticatory muscles and insufficient evidence for alterations of TMJ pain and sounds after treatment. Only one study (74) used TMD diagnoses according to RDC/TMD(19) when assessing treatment outcomes, consequently the evidence for alter-ations of TMD after orthognathic treatment was insufficient. One more study estimated as high, or two studies estimated as moderate value of evidence (66), confirming the results of Paper III in this thesis, are needed for implementation in clinical decision-making.

methodological aspectsPaper ii-iiiRCTs are, as discussed earlier, the golden standard in evidence-based research. In the present study, due to ethical reasons, an observa-tional design in the form of a case-control study was the preferred choice. It has been argued that observational studies can exaggerate treatment results but there are also reports showing no differences in the treatment outcome between RCTs and observational studies. (81) Because of the case-control design the present study cannot present epidemiologic figures with regard to the prevalence of TMD in individuals with dentofacial deformities in the population, since these types of trials should be population-based.

61

The number of patients included in our study, exceeded the power-calculations, with the intention to have the possibility to subgroup the material for different kinds of dentofacial deformities. Obviously, some of the subgroups, most notably deep bite, became too small and could not be statistically calculated with any significance. What could have been done differently in this regard? The size of the subgroups could conceivably have been set before the collection of patients started. However, the data collection was carried out during two time periods 1992-1995 and 2000-2002, a period of totally 7 years. It would have taken many more years to get sufficient subgroups, especially for the deep bite diagnoses.

Another methodological issue was the choice of definitions for the subgroups. In both Paper II and III it was decided to subgroup the different dentofacial deformities as a combination of vertical and sagittal discrepancies resulting in relatively well defined but small groups. Another possibility for classification, which was used in Paper IV, was to separate the dentofacial deformities in vertical and sagittal discrepancies. This meant that the treatment outcome was related to sagittal discrepancies and to vertical discrepancies independently. Every patient had both a sagittal and a vertical diagnosis. This alternative created larger subgroups but implies a higher risk of biases, in form of overlap between different kinds of malocclusion.

In the early 1990’s, when this study was initiated, the RDC/TMD (19) had recently been introduced and accepted in TMD research but not yet been established as a diagnostic tool worldwide. Therefore, the individuals in this study were assessed for signs and symptoms of TMD according to an examination form used at the time in the clinic, at the department of Stomatognathic Physiology in Malmö. The RDC/TMD diagnoses for myofascial pain disorders and arthritic disorders were thereafter implicated. Since the measurements of reciprocal clicking had not been assessed exactly as prescribed in the RDC/TMD it was, in Paper III, deliberately chosen, not to use RDC/TMD diagnoses for disc displacements with reduction. The RDC/TMD has been found to demonstrate sufficiently high reliability for the most common TMD diagnoses, supporting its use in clinical research and decision-making.(83)The validity of the RDC/TMD has in a review(84)been estimated to range from poor to extremely

62

good, depending on the diagnosis to be tested. Myofascial pain (limited opening included) was found to have acceptable sensitiv-ity and extremely good specificity. The authors concluded that indi-viduals where unlikely to be over-diagnosed when using the RDC/TMD. (84) Recently there has been a revision of the RDC/TMD and a new index, the diagnostic criteria for TMD (DC/TMD), (85) is claimed to be more suitable for routine clinical implementation, since psychological and biological data are better integrated. (84)

When assessing frequencies of TMD, it could be argued that the results of the present study are biased, since patients are prone to highlight physical disorders, like TMD to gain attention in the finan-cially subsidized health care system. In order to avoid this phenom-enon, the stomatognathic examination was performed at a separate occasion and in a department separate from the one in which the orthognathic treatment was performed in. Furthermore the special-ists that performed the examinations were not involved in the deci-sion-making regarding the orthognathic treatment of the patients.

Some of the participants in the initial sample withdrew at follow-up (Paper III and IV). In spite of this, both the treatment and control group included a sufficient number of participants according to the initial power calculation. An analysis of the drop-outs revealed no significant differences with respect to age, gender, self-reported anxiety, pain in the jaws and related muscles, diagnosed TMD or masticatory ability and performance compared to the remaining participants. Therefore, both the treatment and control group were considered having sufficient participants to ensure reliability between the baseline and follow-up examinations.

The strength of the studies was that the patients were consecu-tively included, with the size of the study groups calculated before-hand by a power analysis, and a low-rate of dropouts. A control group was included, with the aim to, as far as possible, reflect a normal population. The specialists conducting the stomatognathic examinations were calibrated and blinded to the extent that was possible; as to they were not informed whether the individual belonged to the treatment or the control group. Despite this, there were obviously for some of the patients before treatment, anatomi-cal features that could be detectable.

63

Before the analysis of the results in Paper III, the sub-diagnoses of different kinds of dentofacial deformities were rechecked with the surgery protocols. There were three patients diagnosed with “open bite and normal vertical relation” in Paper II and one patient diagnosed with “open bite and Class II relation” that were re- diagnosed as “open bite with a Class III relationship”. When frequencies of TMD were analysed with the correct diagnosis of dentofacial deformity no significant differences could be found compared with the results in Paper I.

Furthermore, the sub-diagnoses of TMD were rechecked between Paper II and Paper III, and one patient was found to have osteoar-throsis at baseline, which had not been registered for Paper II.

Paper ivThe self-estimated masticatory ability in Paper IV was assessed by a questionnaire. A shortcoming was that the questions involving masticatory ability were limited. Since the present study was initiated in 1992, a Jaw Function Limitation Scale (JFLS) has been developed. (86) This scale has been shown to exhibit good reliabil-ity and validity in assessing limitations in mastication, jaw mobility and verbal and emotional expression (86). Since, the questionnaire in Paper IV focused solely on mastication, it would have been inter-esting to extend it according to the JFLS to have the possibility to assess also if patients with dentofacial deformities are limited in their daily life when talking, swallowing, making facial expressions etc.

In the present study it was chosen to test the masticatory perfor-mance by methods developed by Edlund and Lamm.(73) The advan-tages of using Optosil® tablets were the standardization of size and texture of the tablets, together with the water and age resistance. (73) Unfortunately, the weight composition of the Optosil® material was changed by the manufacturer over the years, and therefore it was decided for the control group not to perform the masticatory performance test at the follow-up examination. The follow-up tests for the treatment group were performed using the former variant of the Optosil® tablets, and the collected data were checked for inconsistencies.

64

anamnestic findingsThe questionnaire in Paper II revealed no anamnestic differences between the treatment and control group. Neither were there any differences for self-estimated level of anxiety, reported on a VAS. The VAS is a rough instrument for assessing psychological variables but the result still gave an indication that the treatment group did not differ from the control group in respect of self-perception.

For the patients with dentofacial deformities, impaired mastica-tory function, symptoms from the masticatory muscles, TMJs and headaches followed by aesthetics were the most common reasons for seeking treatment, which is in line with other studies (15, 87-89). However, in our study (Paper II) the aesthetic reasons were rated relatively low compared with earlier studies reporting that facial appearance was the most important reason for seeking treatment. (90, 91) Cultural differences and financial aspects probably explain this divergence in results. (15, 87) Facial appearance has been suggested to be one of four dimensions in Oral-Health-related quality of life (92) and a new scale, the Oral Esthetical Scale (OES) has been developed, which has shown satisfying reliability and validity. (93) The use of such a scale would have been beneficial to assess the perception of aesthetics of the patients and individuals in this thesis.

frequency of tmdIn Paper II the most common diagnoses of TMD were myofascial pain, disc displacement and arthralgia. These results are in accor-dance with other studies. (19, 28, 83) These diagnoses were also significantly more common in the treatment group compared with the control group. Consequently, the hypothesis of Paper II, that there are no differences in the frequency of TMD between patients with dentofacial deformities and a normal control group, was rejected. This finding is diverging from previous controlled studies(43-45) that did not find any differences in frequency of TMD between the treatment groups and control groups at the baseline examina-tion. Probable causes for the diverging results between these studies and the present study are differences in measurement methods and the sizes of the control groups. It is well accepted that signs and symptoms of TMD are common in a population and therefore sub

65

diagnoses of TMD according to RDC/TMD are more suitable when assessing TMD. (19)

After treatment; myofascial pain, disc displacement and arthralgia was significantly reduced in the treatment group, while osteoarthro-sis increased. Taken together, despite the increase in frequency of osteoarthrosis, the present study clearly revealed a positive treatment outcome considering TMD pain and disc displacements and thereby the first hypothesis of Paper III was confirmed.

The second hypothesis yielded that there would be no differences between the treatment group and the control group after treatment and since no significant differences were found also this hypothesis was confirmed.

The increase of osteoarthrosis in the TMJs after orthognathic treatment has also been observed in studies by Rodrigues-Garcia et al (50) and Pahkala et al(94) and has been suggested to be a result of post-surgical changes of the condylar position in the glenoid fossa. (95) The results may also have been affected by the uncertainty in differentiating a specific joint sound (i.e. crepitus) from clicking or even from soft tissue sounds during digital palpation. Only marginal validity is reported for these signs due to low sensitivity and high specificity for crepitus. (84)

The present study also investigated the maximum mandibular opening capacity, which was significantly lower in the treatment group, compared with the control group, and also decreased after treatment. A reduction in opening capacity has also been noted in other studies. (47, 96) However, the posttreatment decrease of 2 mm in the present study was not considered clinically important. In a recent review (97) it was proposed that the opening capacity will increase gradually during the first years after orthognathic surgery. There was also a general understanding that the impaired lateral excursions that most patients experience after surgery improves over time and that most patients regain the full range of motion two years after surgery.(97)

The present study did not find any subgroup of dentofacial deformities that, separately, was significantly associated with TMD before treatment. Anyhow, it should be remembered, that most of the subgroups were too small to detect any statistical significance, as indicated by the power analysis. An interesting finding was that

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patients with Class III bite in combination with normal vertical relation showed less myofascial pain and arthralgia after treatment. All of the Class III patients had intraoral vertical ramus osteotomy (IVRO) for setback of the mandible. A positive treatment outcome for patients with TMD has been an argument for using IVRO, instead of bilateral sagittal split osteotomy (BSSO), for correction of a protrusive mandible.(6, 14)

masticatory ability and performanceThe results of Paper IV supported the hypothesis that patients with dentofacial deformities has an impaired self estimated masticatory ability and masticatory performance in comparison with a control group without dentofacial deformities before treatment, which is in consistency with other controlled studies. (57, 58)

The masticatory ability improved after orthognathic treatment and at follow-up no differences were found between the treatment and the control group. However, there seems to be an overestima-tion of the masticatory ability, which was rated high compared with the tested masticatory performance, which also improved but not as much as the masticatory ability. This was particularly evident in Class II patients who reported significant higher levels of mastica-tory ability, compared with patients with other dentofacial deformi-ties, properties that were not confirmed in the masticatory perfor-mance test. In a study by Henrikson et al, (58) involving 11-15 year old girls with Class II malocclusions, the same overestimation of the masticatory ability was found.(58)

The reason for the modest improvement in masticatory perfor-mance in the present study may be the relatively short follow-up period (18 months). It has been suggested that a follow-up period of 5 years is more appropriate and beneficial for the masticatory performance, since the musculature needs a relatively long time to readapt before regaining full strength. (98, 99)

The factors that were found to have an association with the masti-catory ability and the masticatory performance differed slightly between the treatment and control groups. The number of occlusal contacts during maximal biting pressure affected both the masti-catory ability and performance in the treatment group, but had no association with mastication in the control group. This result is

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strengthened by the finding that patients with an open bite, the only type of dentofacial deformity associated with masticatory perfor-mance, had fewer occlusal contacts compared with patients with deep bite and normal vertical relations.

The masticatory performance was found to be significantly higher in men than in women. This result can be explained by the fact that men have a higher EMG activity of the masticatory muscles together with a higher muscle thickness, especially for the masseter muscle. (60, 61)

patient satisfactionThe patients were in general satisfied with the treatment. The variables most frequently reported as improved were masticatory function and aesthetics, followed by symptoms of TMD. In a study by Öland et al(89) it was shown that the pre-treatment motives correlated with the satisfaction after treatment. They also found that patients that, at baseline, rated oral function highest also expressed the lowest degree of treatment satisfaction, which is contradictory to our results (Paper III). In a study by Trovik et al(88) it was noticed that peer comments about appearance after treatment affected both self-esteem and quality of life.

A positive finding was that a great majority of the patients (92 %) were satisfied with the information that they had received before the treatment. It should be remembered though, that 32 % of the patients experienced the treatment as more difficult than they had expected, which should be taken into consideration when presurgi-cal information is given.

future researchThe results of this thesis showed that frequencies of TMD decreased after orthognathic treatment. However, as indicated by the system-atic review (Paper I) and the supplementary literature survey further research is required. A stronger evidence base to be able to evaluate whether orthognathic treatment alters frequencies of TMD would require one more study of high, or two more studies of medium value of evidence, assessing alterations of sub-diagnoses of TMD according to RDC/TMD.

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It should also be noted that in the present study we found an increase in the number of patients with osteoarthrosis 18 months post treatment. As it is well known that TMD fluctuates over time it would be valuable to carry out a 5 years follow-up to assess how the treatment outcome of TMD persists in the long run.

Moreover, since oral-health-related quality of life has been asso-ciated with both TMD and masticatory function in previous studies (56, 92, 100) it would be of interest to investigate how the psychoso-cial well-being is affected after orthognathic treatment by using the Swedish version of the Oral Health Impact Profile (OHIP-S). (100) Such a study is planned and will be presented in the future.

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conclusions

The systematic review, including the supplementary literature search, led to the following conclusions:• There is insufficient evidence for a decrease in TMD sub

diagnoses after orthognathic treatment.• There is low scientific evidence for an improvement of

masti catory muscle pain on palpation after orthognathic treatment.

• There is insufficient evidence considering alterations of TMJ pain on palpation and TMJ sounds after orthognathic surgery.

• Further controlled, well-designed studies assessing TMD before and after orthognathic treatment are needed to secure strong evidence considering treatment outcomes.

In the cross-sectional, case-control study comparing frequencies of TMD in patients referred for orthognathic treatment with a control group it was concluded that:• Patients with dentofacial deformities have higher frequencies

of signs and symptoms of TMD and diagnosed TMD compared with a normal group.

In the controlled, longitudinal, follow-up study comparing frequen-cies of TMD before and after orthognathic treatment, it was concluded that in patients with dentofacial deformities:• Frequencies of TMD decrease after orthognathic treatment.• Frequencies of TMD were after orthognathic treatment

comparable in the patient group and control group.

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In the controlled, longitudinal, follow-up study before and after orthognathic treatment of patients with dentofacial deformities, it was concluded that:• Masticatory ability and masticatory performance increased

after orthognathic treatment.• The number of occlusal contacts and severity of overall

symptoms of TMD influenced both the masticatory ability • and performance.• Open bite had a negative effect on masticatory performance.

Key conclusions and clinical implications:Patients with dentofacial deformities diagnosed with TMD do in most cases benefit from orthognathic treatment. In addition, masticatory ability and performance, which is impaired in patients with dentofacial deformities, improve after treatment. Thus, patients with dentofacial deformities that are to be treated with orthodontics in combination with orthognathic surgery can be recommended the treatment in order to relieve symptoms of TMD and impaired mastication.

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acKnowledgements

The work with this project has taken many years to accomplish. It started already in the 1990s when one of my supervisors, Thor Henrikson was curious and enthusiastic enough to gather special-ists from different disciplines of odontology to formulate a research programme in a field that at the time was not studied by many. About a decade later I gratefully got the opportunity to be a part of that research group and to complete the project.

During the years many individuals have been involved in the project and first of all I wish to humbly thank:

All the patients and the individuals in the control group who parti-cipated in the studies.

Associate Professor EwaCarin Ekberg, my main supervisor, co-author and friend for your never failing support and for always having time for me, for helping me find my research self-esteem when I needed it and for guiding me through hard times. Thank you for your enthusiastic participation in the clinical examinations in the project and for your invaluable advice during my doctoral education!

Professor Lars Bondemark, my assistant supervisor, and main super-visor during the first part of the project, co-author and friend for sharing your enormous knowledge and wisdom in research, for tire-lessly being there with the pencil when needed and for your generous

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support during a turbulent time of my life. Thank you for always having time for me!

Associate Professor Thor Henrikson, my assistant supervisor and co-author for first of all generously letting me into the project. In the beginning patiently guiding me through how to sieve silicon tablets, how to do a power-point presentation, register variables in the statistic programme and so on. Later on, pushing the project forward by sharing your knowledge and wisdom through fruitful discussions. It has been a privilege to work with you!

Associate Professor Bo Sunzel, my co-author of Papers II and III, for stimulating discussions, for generously sharing your knowledge about orthognathic surgery, for enthusiastic help with collecting data and for performing the orthognathic treatment for part of the patient group.

Professor Maria Nilner, my co-author of Papers II and III, for sharing your wisdom in research, for constructive criticism of the manuscripts and for your enthusiastic participation in the clinical examinations.

My colleagues, co-workers and friends at the Department of Ortho-dontics and the Department of Paediatric Dentistry, Faculty of Odontology, Malmö for encouragement and support over the years. Especially I want to thank Ingrid Carlin for assistance with the tablets used in the masticatory performance test, Hans Herrlander for scanning of the radiographs and Stella Giuseppin for secretarial assistance.

Staff members at the Department of Stomatognathic Physiology, Faculty of Odontolgy, Malmö for assistance with the clinical exami-nations.

Staff members at the Department of Oral and Maxillofacial surgery, Lund University Hospital and especially Ingela Nilsson for patiently gathering data about the patients in the studies.

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Staff members at the dental clinic of Oxie, for assistance during the clinical examinations of the individuals in the control group.

Associate professor Eva Lilja-Karlander, for friendship and support during the research education and for creating the fantastic illustra-tions at the front page.

Drs Liselotte Björnsson and Sofia Petrén, my colleagues and friends, for your encouragement and support, for lovely moments with our families, for answering my never ending questions about research. We have a lot of congresses left to visit and a lot of shopping left to do!

Dr Diana Girdo, my roommate, colleague and friend for cheering me up with relieving laughters, for patiently listening to my frus-trated sighs, for being the perfect travel mate and for sharing my newly awakened passion for macarons.

Associate Professor Krister Bjerklin, for friendship, for generously sharing your wisdom in orthodontic science and for invaluable advices during the revision of Paper III.

Per Egevad, for invaluable and enthusiastic help in a desperate crisis situation with a new computer and a non-working reference tool.

Per-Erik Isberg, for invaluable help with the statistical analysis.

Dr Birgitta Häggman Henrikson, for excellent revision of the English text.

Annika Österlind Hansen, my dear, dear sister and best friend for your love and support and for endless talks and relaxing runs during hard times.

My parents Gerd and Bo Österlind, for your endless love and for always being there for me when I need you. And in particular I thank my mother for patiently listening to me day as night when

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I’m feeling low and for cheering us up with home baked cookies and other little things that makes life a little more easy.

And most of all my soul mate and beloved husband Jonas, for your love, faith and understanding. With you by my side I am invincible! And to our fabulous children for bringing joy and happiness to life.

Klara - my lovely riding mate, for giving me daily laughter with your crazy and disarming jokes.

Alva – my sweet shopping companion, for always insuring me of your love.

Henrik – my cool football player, for always wanting to do your best and for your brilliant 6 year-old wisdom.

-I Love You!

The following financial support is gratefully acknowledged:TePe Scholarship Ltd, Sweden; Swedish Dental Society; Faculty of Odontology, Malmö University, Sweden.

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96. Athanasiou AE, Melsen B. Craniomandibular dysfunction following surgical correction of mandibular prognathism. Angle Orthod. 1992; 62: 9-14.

97. Al-Riyami S, Cunningham SJ, Moles DR. Orthognathic treatment and temporomandibular disorders: a systematic review. Part 2. Signs and symptoms and meta-analyses. Am J Orthod Dentofacial Orthop. 2009; 136: 626.e1-16, discussion 626-7.

98. Magalhaes IB, Pereira LJ, Marques LS, Gameiro GH. The influence of malocclusion on masticatory performance. A systematic review. Angle Orthod. 2010; 80: 981-987.

99. van den Braber W, van der Bilt A, van der Glas H, Rosenberg T, Koole R. The influence of mandibular advancement surgery on oral function in retrognathic patients: a 5-year follow-up study. J Oral Maxillofac Surg. 2006; 64: 1237-1240.

100. Larsson P, List T, Lundstrom I, Marcusson A, Ohrbach R. Reliability and validity of a Swedish version of the Oral Health Impact Profile (OHIP-S). Acta Odontol Scand. 2004; 62: 147-152.

Angle Orthodontist, Vol 77, No 4, 2007729DOI: 10.2319/052906-215

Review Article

Alterations of Temporomandibular Disordersbefore and after Orthognathic Surgery

A Systematic Review

Cecilia Abrahamssona; EwaCarin Ekbergb; Thor Henriksonc; Lars Bondemarkd

ABSTRACTObjective: To answer the question whether orthognathic surgery does affect the prevalence ofsigns and symptoms of temporomandibular disorders (TMDs).Materials and Methods: A literature survey in the PubMed and Cochrane Library electronic da-tabases was performed and covered the period from January 1966 to April 2006. The inclusioncriteria were controlled, prospective or retrospective studies comparing TMDs before and afterorthognathic surgery in patients with malocclusion. There were no language restrictions, and threereviewers selected and extracted the data independently. The quality of the retrieved articles wasevaluated by four reviewers.Results: The search strategy resulted in 467 articles, of which 3 met the inclusion criteria. Be-cause of few studies with unambiguous results and heterogeneity in study design, the scientificevidence was insufficient to evaluate the effects that orthognathic surgery had on TMD. Moreover,the studies had problems with inadequate selection description, confounding factors, and lack ofmethod error analysis.Conclusion: To obtain reliable scientific evidence, additional well-controlled and well-designedstudies are needed to determine how and if orthognathic surgery alters signs and symptoms ofTMD.

KEY WORDS: Temporomandibular disorders; Malocclusion; Orthognathic surgery; Systematicreview

INTRODUCTION

Temporomandibular disorders (TMDs) embrace dif-ferent signs and symptoms of the temporomandibularjoint (TMJ), masticatory muscles, and related struc-tures.1 These include orofacial pain, joint sounds, re-duced or asymmetric mandibular movement, and pain

a Research Fellow, Department of Orthodontics, Faculty ofOdontology, Malmo University, Malmo, Sweden.

b Associate Professor, Department of Stomatognathic Physi-ology, Faculty of Odontology, Malmo University, Malmo, Swe-den.

c Associate Professor, Department of Orthodontics, Faculty ofOdontology, Malmo University, Malmo, Sweden.

d Professor, Department of Orthodontics, Faculty of Odontol-ogy, Malmo University, Malmo, Sweden.

Corresponding author: Dr Cecilia Abrahamsson, Departmentof Orthodontics, Faculty of Odontology, Malmo University, CarlGustafs vag 34, SE-20506 Malmo, Sweden(e-mail: cecilia.abrahamsson@od.mah.se)

Accepted: September 2006. Submitted: May 2006.� 2007 by The EH Angle Education and Research Foundation,Inc.

on palpation of the TMJ and related muscles.2 Differ-ent kinds of occlusal factors are sometimes claimed tobe associated with TMD; however, the opinion as towhether this association has been proven differs be-tween different studies.3–9 It has been indicated thatorthodontic treatment does not, except for mild signs,increase prevalence of TMD10 and that orthodontictreatment, of some kinds of malocclusion, in childrenand adolescents may even reduce prevalence of signsand symptoms of TMD.11,12

In severe malocclusions with major skeletal discrep-ancies, orthodontic treatment in combination with or-thognathic surgery is sometimes needed. Orthognath-ic surgery and its effect on TMD have been examinedin several studies during the past decades, and a sys-tematic review of the present knowledge is motivated.In view of this and because evidence-based medicinehas grown in importance,13 a systematic review of thepresent knowledge seems desirable. Systematic re-views try to locate, appraise, and synthesize evidencefrom scientific studies to provide informative answers

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Angle Orthodontist, Vol 77, No 4, 2007

Table 1. Distribution of Excluded Articles

Exclusion Criteria

No. ofExcludedArticles

Studies not concerning the objectives of this review(analysis of surgery techniques or of electromyo-graphic activity in temporomandibular joint–relatedmuscles, management of mandibular condyle frac-tures, treatment of arthritis and arthros, treatment ofsyndromes as cleft, lip, or palate treatment) 386

Animal studies 5Case reports, case series, preliminary reports 64Review articles, discussions, interviews 9

Total 464

to scientific questions by including a comprehensivesummary of the available evidence.

The aim of this systematic review was to answer thequestion of whether orthognathic surgery affects theprevalence of signs and symptoms of TMDs.

MATERIALS AND METHODS

Search Strategy

To identify all studies that examined orthognathicsurgery and its effect on TMD in patients with severemalocclusion, a literature survey was performed usingthe PubMed (www.ncbi.nlm.nih.gov) and the Coch-rane Library electronic databases (www.cochrane.org). The search covered the period from January1966 to April 2006. The terms used in the search weremalocclusion, retrognathia, prognathia, open bite, anddeep bite in various combinations with craniomandi-bular disorders, temporomandibular disorders, tem-poromandibular dysfunction, temporomandibular jointdysfunction, temporomandibular joint pain and orthog-nathic surgery, surgical-orthodontic treatment, andsurgery.

Selection Criteria

Inclusion Criteria• Studies comparing symptoms and signs of TMDs

before and after orthognathic surgery in patients withmalocclusion

• Randomized clinical trials (RCT) or prospective, ret-rospective, controlled human studies.

Exclusion Criteria• Animal studies• Case reports, case series, and preliminary reports• Reviews, discussions, interviews• Treatment of patients with syndromes; cleft lip or pal-

ate treatment (or both)

Three reviewers independently assessed all the ar-ticle abstracts that appeared to meet the inclusion cri-teria. The article abstracts were collected irrespective-ly of the language in which they were published, andthe retrieved articles were read in their entirety. Thereference lists of the retrieved articles were alsochecked for relevant studies not found in the databasesearch. Any interexaminer conflicts were resolved bydiscussion to reach a consensus.

Data Collection and Analysis

Data were extracted on the following items: author,year of publication, study design, sample size, genderand age, surgical treatment methods, follow-up time,methods to determine TMD, outcomes, and authors’conclusions. In addition, to document the methodolog-

ical soundness of each article, a quality evaluationmodified by the methods described by Antczak et al14

and Jadad et al15 was performed with respect to pre-established characteristics. The following seven vari-ables were evaluated: study design (RCT � 3 points,prospective study � 2 points, retrospective study � 1point), adequate sample size � 1 point, adequate se-lection description � 1 point, valid measurement meth-ods � 1 point, use of method error analysis � 1 point,adequate statistics provided � 1 point, and conse-quences of confounders discussed in analysis � 1point. By summing the seven variables, a study couldscore a maximum of 9 points in quality. A study’s qual-ity was categorized as low (0 to 4 points), medium (5to 7 points), or high (8 or 9 points). The data extractionand quality scoring from each article were assessedindependently by four evaluators. Interexaminer con-flicts were resolved by discussion of each article toreach a consensus.

RESULTS

The search strategy resulted in 467 articles. Afteranalysis according to the inclusion/exclusion criteria,three articles16–18 remained to be qualified for the anal-ysis. The reasons for exclusion and the number of ex-cluded articles are listed in Table 1. An agreement ofmore than 90% was found between the reviewers inassessing the data extraction and quality scores of theincluded articles.

Study Design and Treatment Methods

Summarized data of the three articles are shown inTable 2. All of the studies were longitudinal, prospec-tive, and controlled clinical trials. In two of the stud-ies,17,18 the test and control samples were age and gen-der matched, whereas in the study by Onizawa et al,16

the control sample was only age matched. The controlgroup in Onizawa et al16 consisted of dental studentsand was without any description of dental deformities

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Table 2. Summarized Data of the Three Studies Included in This Review

Article Study DesignMaterial: Size, Gender,

and Age (y)TreatmentMethods

Follow-up

Methods ofDetermining

TMDOutcome/Authors’

Conclusion

Onizawa et al,199516

Prospective con-trolled clinicaltrial

T: 30 (20 women, 10 men)Age: mean 24.0 (17–34)C: 30 (11 women, 19 men)Age: mean 26.3 (22–39)

Bilateral sagittalsplit and/or LeFort I osteotomy;rigid fixation withminiplates

6 mo Questionnaire,clinical exami-nation

After surgical correc-tion changes in theTMJ, symptoms didnot always show im-provement, andsome patientsshowed changes forthe worse

Panula et al,200017

Prospective con-trolled clinicaltrial

T: 60 (49 women, 11 men)Age: mean 33.2 (16–56)C. 20 (16 women, 4 men)Age: mean 31.5 (15–44)

Bilateral sagittalsplit and/or LeFort I osteotomy;rigid fixation withminiplates

4 y Questionnaire;clinical exami-nation (Helki-mos index)

Functional status andheadache can be im-proved with ortho-gnathic surgery; nodirect relationshipbetween TMJ dys-function and dentofa-cial deformities

Dervis et al,200218

Prospective con-trolled clinicaltrial

T: 50 (29 women, 21 men)Age: median 29.3 (19–42)C: 50 (28 women, 22 men)Age: mean 29.8 (20–36)

Surgery methodnot described;non-rigid fixation;6 wk ofintermaxillaryfixation

2 y Questionnaire;clinical exami-nation (Helki-mos index)

Surgical correction hasa beneficial effect onTMJ pain and dys-function; TMD signsand symptoms donot always show im-provement after sur-gical correction

T indicates patient group; C, control group; TMD, temporomandibular disorder; and TMJ, temporomandibular joint.

and examined at only one time. In the study by Panulaet al,17 the control sample was composed of patientsthat had refused orthognathic treatment after the firstinformation, and in the study by Dervis et al,18 the con-trol group was composed of individuals without dento-facial deformities. In all of the studies,16–18 there werefew or no dropouts. Panula et al17 reported five dropoutswho were deleted from the study. Dervis et al18 andOnizawa et al16 did not report dropouts. However, in thestudy by Onizawa et al,16 there was a decrease in thenumber of class III patients from the initial to the finalexamination, on which the authors only partly com-mented.

The orthognathic surgical method was described intwo of the studies.16,17 Both studies used bilateral splitosteotomy only or in combination with Le Fort I oste-otomy. In the study by Dervis et al,18 no description ofthe surgical method was given.

In the study by Onizawa et al,16 evaluation of TMDwas assessed before and 6 months after surgery,whereas Dervis et al18 and Panula et al17 evaluatedsigns and symptoms 2 and 4 years, respectively, fromthe initial preoperative examination.

All studies16–18 used a questionnaire and performeda clinical examination before and after surgery whenassessing the patients’ signs and symptoms of TMD.Controls were examined with the same methods at twodifferent occasions except in the study by Onizawa et

al,16 in which the control group was examined on onlyone occasion. In addition, Panula et al17 and Dervis etal18 also evaluated the frequency of headache.

Orthognathic Surgery and Its Effect on TMD

When comparing signs and symptoms of TMD beforetreatment, neither study found any significant differenc-es between patients and control group or type of mal-occlusion. After treatment, two of the studies17,18 con-cluded that both signs and symptoms related to TMDcould be significantly improved (Table 2). On the otherhand, Onizawa et al16 declared that TMD symptoms didnot always show improvement after surgical correction,and for some patients, the symptoms changed for theworse (Table 2). When considering specific signs ofTMD, Panula et al17 and Dervis et al18 found a statisti-cally significant decrease in muscle palpation tender-ness after surgery, whereas in the study by Onizawa etal,16 there was no such change found. Furthermore,Panula et al17 also reported a significant decrease injoint palpation tenderness. Onizawa et al16 reported asignificant decrease in maximal mouth opening capac-ity, which was not observed by the other studies.17,18

Quality Analysis

A quality analysis of the three involved studies ispresented in Table 3. The research quality and meth-

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Table 3. Quality Evaluation of the Three Retrieved Studiesa

AuthorsStudyDesign

SampleSize

SelectionDescription

ValidMeasure-

mentMethods

MethodError

Analysis

AdequateStatisticsProvided

Conse-quencesof Con-founders

Dis-cussed

Judged QualityStandard

Onizawa et al,199516

Prospective, longi-tudinal, con-trolled clinicaltrial

Adequate Inadequate Yes No Yes No Medium (5 points)

Panula et al,200017

Prospective, longi-tudinal, con-trolled clinicaltrial

Inadequate,small controlsample

Inadequate Yes No Yes No Low (4 points)

Dervis et al,200218

Prospective, longi-tudinal, con-trolled clinicaltrial

Adequate Inadequate Yes No Yes No Medium (5 points)

a Maximum nine points were possible to reach.

odological standard was low in one study17 and me-dium in two studies.16,18 The reasons for the low qualitystandard were mainly inadequate sample selection ordescription and no method error analysis. In addition,the authors had not discussed the influence of con-founding factors on the results. Moreover, Panula etal17 had an inadequate control sample size.

DISCUSSION

The aim of this systematic review was to answer thequestion of whether orthognathic surgery affects theprevalence of signs and symptoms of TMDs in pa-tients with malocclusion. However, no conclusioncould be drawn because of the few studies locatedand their unambiguous results. Moreover, the includedstudies had problems with insufficient or lack of sam-ple selection description, no discussion of confoundingfactors, and no method error analysis.

The outcome or authors’ conclusion differed be-tween the articles. One of the reasons could be thedisparity of follow-up time between the study of Oni-zawa et al16 and the other two studies.17,18 The shortfollow-up time (6 months) used by Onizawa et al16 maynot be enough for the patients to fully recover from thesurgery. Orthognathic surgery is usually combinedwith presurgery and postsurgery orthodontic treat-ment. However, the description of the orthodontictreatment and its length of application was sparse17 orlacking.16,18 In Onizawa et al,16 there may have been apotential risk that the occlusion had not yet settled insome of the patients since the postsurgery orthodontictreatment may have been ongoing or recently com-pleted. When comparing the treatment outcome be-tween these three studies, one should also be awareof the heterogeneity in surgical methods and fixation,

which could have influenced the outcome. Stomato-gnathic treatment before surgery could have been aconfounding factor in the study by Panula et al17 andmight also have affected the results of this study andthereby affected the treatment outcome.

It is well known that uncontrolled studies and casereports imply low scientific evidence, and this was thereason why such studies were excluded. As signs andsymptoms of TMD have been proven to fluctuate overtime19 and because symptom frequencies appear to beage dependent,20 it is important to include an age- andgender-matched21 nonpatient control group as com-parison to diminish the risk that the results after treat-ment show only the normal fluctuation in prevalenceof TMD. The study by Panula et al17 was the only studyin which efforts were made to use an appropriate con-trol group (ie, a control group consisting of patientswith severe malocclusions and who refuse orthognath-ic surgery treatment). However, the control samplesize was judged to be too small and thereby inade-quate. Furthermore, no sample size calculation waspresented to prove that the control sample size wassufficient. Nevertheless, in all of the studies, it seemsit was difficult for the researchers to enroll appropriatecontrol groups. However, in this kind of clinical con-trolled trial, it might be very difficult to find a controlgroup with severe skeletal jaw discrepancy. It wouldbe unethical not to offer treatment to those kinds ofcontrols either conservatively, orthodontically, or bysurgical-orthodontic treatment.

In all of the studies,16–18 the methods of assessingsigns and symptoms of TMD were valid and wellknown. However, in two studies,17,18 the Helkimos in-dex22 was used, and it remains to be determinedwhether the Helkimos index is an appropriate method

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to determine TMD patients. Broad-based symptomscales (eg, the Helkimos indices) have often beenused in the past. However, advances in classificationmandate that future epidemiological studies use work-ing definitions that include patterns of signs and symp-toms of TMD and focus on more narrowly defined dis-ease groups.23 Furthermore, Storey24 stated that al-though TMD was viewed as one syndrome, currentresearch supports the view that TMDs are a cluster ofrelated disorders in the masticatory system that havemany common symptoms. Today, it is more suitableto use the research diagnostic criteria for TMD, whichis a valid instrument with good reliability among adultsto subdiagnose TMD.25,26

From a methodological point of view, it was notablethat none of the articles declared the use of blindingin measurements. However, the explanation for thismay be that even if the extraoral stomatognathic ex-amination is performed before the intraoral one, theblinding concerning test and control fails because thetest individuals often are exteriorly affected by theirskeletal malocclusion.

Today, the systematic literature search, data extrac-tion, and subsequent quality assessment of includedarticles are well-established measures in evidence-based medicine/dentistry. However, the precise meth-ods for the process can differ between various system-atic reviews. The methodology used in this review wasadopted from and based on the criteria for assessingstudy quality from the Centre for Reviews and Dissem-inations in York, United Kingdom.27 Many articles wereexcluded: the main reason was the lack of a controlgroup. Other excluded articles were those based onevaluation after the intervention without any registra-tions or analyses before the intervention started.

Several methods and scales to incorporate qualityinto systematic reviews have been proposed.14,15,27,28

However, many items were clearly not applicable, forexample, placebo appearance/taste or patient or ob-server blinded to treatment. Instead, the quality of thearticles was judged as low, medium, or high accordingto the scoring system based on the characteristics giv-en in Table 3.

The restrictions on the number of databases usedwhen searching the literature might imply that some ar-ticles were not identified. However, studies that are dif-ficult to find are often of lower quality. The strength ofthe evidence in a systematic review is probably moredependent on assessing the quality of the includedstudies than on the degree of comprehensiveness.29

CONCLUSIONS

• No conclusions could be drawn because of the fewstudies identified, heterogeneity in study design, and

unambiguous results. To obtain reliable scientific ev-idence, additional well-controlled and well-designedstudies are needed to determine if and how ortho-gnathic surgery alters signs and symptoms of TMDand headache.

REFERENCES

1. Okeson JP. Current diagnostic classification schema andassessment of patients with temporomandibular disorders.Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1997;83:61–64.

2. McNeill C. Definition of TMD. In: McNeill C, ed. Temporo-mandibular Disorders: Guidelines for Classification, Assess-ment and Management. The American Academy of Orofa-cial Pain. 2nd ed. Chicago, Ill: Quintessence; 1993:11–18.

3. Celic R, Jerolimov V, Panduric J. A study of the influenceof occlusal factors and parafunctional habits on the preva-lence of signs and symptoms of TMD. Int J Prosthodont.2002;15:43–48.

4. Wanman A, Agerberg G. Etiology of craniomandibular dis-orders: evaluation of some occlusal and psychosocial fac-tors in 19-year-olds. J Craniomandib Disord Facial OralPain. 1990;5:35–44.

5. Egermark-Eriksson I, Carlsson GE, Magnusson T, ThilanderB. A longitudinal study on malocclusion in relation to signsand symptoms of cranio-mandibular disorders in childrenand adolescents. Eur J Orthod. 1990;12:399–407.

6. Gesch D, Bernhardt O, Kocher T, John U, Hensel E, AlteD. Association of malocclusion and functional occlusion withsigns of temporomandibular disorders in adults: results ofthe population-based study of health in Pomerania. AngleOrthod. 2004;74:512–520.

7. John MT, Hirsch C, Drangsholt MT, Mancl LA, Setz JM.Overbite and overjet are not related to self-report of tem-poromandibular disorder symptoms. J Dent Res. 2002;81:164–169.

8. Hirsch C, John MT, Drangsholt MT, Mancl LA. Relationshipbetween overbite/overjet and clicking or crepitus of the tem-poromandibular joint. J Orofac Pain. 2005;19:218–225.

9. Pullinger AG, Seligman DA, Gornbein JA. A multiple logisticregression analysis of the risk and relative odds of tempo-romandibular disorders as a function of common occlusalfeatures. J Dent Res. 1993;72:968–979.

10. Kim M, Graber TM, Viana MA. Orthodontics and temporo-mandibular disorder: a meta-analysis. Am J Orthod Dento-facial Orthop. 2002;121:438–446.

11. Egermark I, Thilander B. Craniomandibular disorders withspecial reference to orthodontic treatment: an evaluationfrom childhood to adulthood. Am J Orthod Dentofacial Or-thop. 1992;101:28–34.

12. Henrikson T, Nilner M. Temporomandibular disorders andthe need for stomatognathic treatment in orthodonticallytreated and untreated girls. Eur J Orthod. 2000;22:283–292.

13. Evidence-Based Medicine Group. Evidence-based medi-cine: a new approach to teaching the practice of medicine.J Am Med Assoc. 1992;268:2420–2425.

14. Antczak AA, Tang J, Chalmers TC. Quality assessment ofrandomized clinical trials in dental research. I. Methods. JPeriodont Res. 1986;21:305–314.

15. Jadad AR, Moore RA, Carroll D, Jenkinson C, ReynoldsDJM, Gavaghan DJ, McQuay HJ. Assessing the quality ofreports of randomized clinical trials: is blinding necessary?Control Clin Trials. 1996;17:1–12.

16. Onizawa K, Schmelzeisen R, Vogt S. Alteration of tempo-

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romandibular joint symptoms after orthognathic surgery:comparison with healthy volunteers. J Oral Maxillofac Surg.1995;53:117–121.

17. Panula K, Somppi M, Finne K, Oikarinen K. Effects of or-thognathic surgery on temporomandibular joint dysfunction:a controlled prospective 4-year follow-up study. Int J OralMaxillofac Surg. 2000;29:183–187.

18. Dervis E, Tuncer E. Long-term evaluations of temporoman-dibular disorders in patients undergoing orthognathic sur-gery compared with a control group. Oral Surg Oral MedOral Pathol Oral Radiol Endod. 2002;94:554–560.

19. Magnusson T, Egermark I, Carlsson GE. A longitudinal ep-idemiologic study of signs and symptoms of temporoman-dibular disorders from 15 to 35 years of age. J Orofac Pain.2000;14:310–319.

20. Dibbets JMH, van deer Weele L. Orthodontic treatment inrelation to symptoms attributed to dysfunction of the tem-poromandibular joint. A 10-year report of the University ofGroningen study. Am J Orthod Dentofacial Orthop. 1987;91:193–199.

21. Wanman A. Longitudinal course of symptoms of cranio-mandibular disorders in men and woman. A 10-year follow-up study of an epidemiologic sample. Acta Odontol Scand.1996;54:337–342.

22. Helkimo M. Studies on function and dysfunction of the mas-

ticatory system. II. Index for anamnestic and clinical dys-function and occlusal state. Swed Dent J. 1974;67:101–121.

23. Okeson JP, ed. Orofacial Pain: Guidelines for Assessment,Diagnoses and Management. Chicago, Ill: Quintessence;1996.

24. Storey A. Unresolved issues and controversies. In: ZarbGA, Carlsson GE, Sessle BJ, Mohl ND, eds. Temporoman-dibular Joint and Masticatory Muscle Disorders. 2nd ed. Co-penhagen, Denmark: Munksgaard; 1994;584–615.

25. Dworkin SF, LeResce L. Research diagnostic criteria fortemporomandibular disorders: review, criteria, examinationsand specifications, critique. J Craniomandib Disord. 1992;6:301–355.

26. Zaki HRT, Turk D, Capriano M. Reliability of axis I researchdiagnostic criteria for TMD. J Dent Res. 1994;73:186.

27. National Health Service Center for Reviews and Dissemi-nation. Undertaking Systematic Reviews of Research on Ef-fectiveness Report No. 4. 2nd ed. York, UK: York PublishingServices; 2001.

28. Chalmers TC, Smith H Jr, Blackburn B, Silverman B,Schroeder B, Reitman D, Ambroz A. A method for assess-ing the quality of a randomized controlled trial. Control ClinTrials. 1981;3:31–49.

29. Egger M, Juni P, Bartlett C, Holenstein F, Sterne J. Howimportant are comprehensive literature searches and theassessment of trial quality in systematic reviews? Empiricalstudy. Health Technol Assess. 2003;7:1–76.

Angle Orthodontist, Vol 79, No 4, 2009621DOI: 10.2319/060408-293.1

Original Article

TMD in Consecutive Patients Referred for Orthognathic Surgery

Cecilia Abrahamssona; EwaCarin Ekbergb; Thor Henriksonc; Maria Nilnerd; Bo Sunzele;Lars Bondemarkf

ABSTRACTObjective: To answer the question whether temporomandibular disorders (TMD) were more com-mon in a group of individuals referred for orthognathic surgery than in a control group. The nullhypothesis was that neither the frequency of signs and symptoms of TMD or diagnosed TMDwould differ between the patient group and a control group.Materials and Methods: A sample of 121 consecutive patients referred for orthognathic surgeryat the Department of Oral Maxillofacial Surgery, Malmo University Hospital, Sweden, was inter-viewed and examined regarding signs and symptoms of TMD and headaches. A control groupwas formed by 56 age- and gender-matched individuals attending the Department of Oral Diag-nosis, Faculty of Odontology, Malmo University, Sweden, and Public Dental Health Clinic in Oxie,County of Skane, Sweden. TMD diagnoses were used according to Research Diagnostic Criteriafor Temporomandibular Disorders (RDC/TMD).Results: The patient group showed more myofascial pain without limited opening, disc displace-ment with reduction, and arthralgia according to RDC/TMD than the control group. The patientgroup also had more symptoms and signs of TMD in general.Conclusions: The null hypothesis was rejected because patients who were to be treated withorthognathic surgery had more signs and symptoms of TMD and higher frequency of diagnosedTMD compared with the matched control group. (Angle Orthod. 2009;79:621–627.)

KEY WORDS: Temporomandibular disorders; Orthognathic surgery; Controlled study; Malocclusion

INTRODUCTION

An increased prevalence of temporomandibular dis-orders (TMD) from adolescence to adulthood hasbeen reported in longitudinal studies, which also have

a Research Fellow, Department of Orthodontics, Faculty ofOdontology, Malmo University, Malmo, Sweden.

b Associate Professor, Department of Stomatognathic Physi-ology, Faculty of Odontology, Malmo University, Malmo, Swe-den.

c Odont Dr, Department of Orthodontics, Faculty of Odontol-ogy, Malmo University, Sweden.

d Chair and Professor, Department of Stomatognathic Physi-ology, Faculty of Odontology, Malmo University, Malmo, Swe-den

e Odont Dr, Department of Oral and Maxillofacial Surgery,Malmo University Hospital, Malmo, Sweden.

f Chair and Professor, Department of Orthodontics, Faculty ofOdontology, Malmo University, Malmo, Sweden.

Corresponding author: Dr Cecilia Abrahamsson, Departmentof Orthodontics, Faculty of Odontology, Malmo University, CarlGustafs vag 34, SE-205 06 Malmo, Sweden(e-mail: cecilia.abrahamsson@od.mah.se)

Accepted: September 2008. Submitted: June 2008.� 2009 by The EH Angle Education and Research Foundation,Inc.

shown a fluctuation of signs and symptoms of TMDover time, with both improvement and impairment onan individual basis.1–3 The most common subtypes ofTMD are myofascial pain, disc displacements with re-duction, and arthralgia.4–6

Factors that have shown associations with TMD areindirect or direct trauma to the masticatory system, an-atomic, pathophysiologic, and psychosocial factors.7–9

The importance of the occlusion and its role in causingthe onset or perpetuation of TMD, compared with otherfactors, has been studied and is still debated.8,10–12

Subjects with malocclusions have been suggested tohave a significantly higher prevalence of signs andsymptoms of TMD than others. These malocclusionsinclude Angle Class II, anterior open bite, deep bite,posterior crossbite, and extreme maxillary over-jet.10,12–16 In addition, severe mandibular retrognathismand a hyperdivergent skeletal pattern have been sug-gested to be risk factors for TMD.14,17,18

In a recent systematic review19 considering alter-ations of TMD before and after orthognathic surgery,heterogeneous study design and unambiguous resultsof the selected studies were found.

Thus, no clear picture exists whether individuals re-

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Table 1. Clinical Examination and Registration of Temporomandib-ular Disorders and Related Muscles

Measurement of mandibular mobility in millimetersMaximum opening capacity without assistanceMaximum laterotrusion, left/rightMaximum protrusionMaximum retrusionPain on movement of the mandibleMandibular deviation �2 mm on openingTemporomandibular joint (TMJ) clicking and crepitations registered

by palpation and auscultation during opening and closing of themandible

Tenderness on palpation of the TMJs; laterally and posteriorly andmasticatory musculature; the origin and the insertion of the tem-poral muscles, the superficial and deep portion of the massetermuscles, and the insertion of the medial pterygoid muscle

ferred for orthognathic surgery or with dentofacial de-formities have higher prevalence of TMD than normalindividuals.

The aim of this study was to investigate whetherTMD was more common in a group of individuals re-ferred for orthognathic surgery than in a control group.The null hypothesis was that neither frequency ofsigns and symptoms of TMD or diagnosed TMD ac-cording to Research Diagnostic Criteria for Temporo-mandibular Disorders (RDC/TMD) would differ be-tween the patient and control group.

MATERIALS AND METHODS

Subjects

A sample of 121 consecutive patients, mean age22.5 � 7.4 years, 70 females and 51 males, with den-tofacial deformities was included. All patients were re-ferred to the Department of Oral Maxillofacial Surgery,Malmo University Hospital, Malmo, Sweden, between1992 and 2002 for orthodontic treatment in combina-tion with orthognathic surgery.

A control group of 56 individuals, mean age 23.4 �7.4 years, 33 females and 23 males, were recruited tomatch the patients in the treatment group, consideringage and gender. These individuals were regular pa-tients, with or without minor malocclusion traits thatwere not needed to be corrected with either orthodon-tic therapy or orthognathic surgery, attending the De-partment of Oral Diagnostics, Faculty of Odontology,Malmo University, Sweden, and Public Dental HealthClinic in Oxie, County Skane, Sweden.

The exclusion criteria for the 2 groups were cranio-facial syndromes, systemic arthritic and muscle dis-eases, and a dentition of fewer than 24 teeth.

The study was approved by the Ethics Committeeof Lund University, Sweden (Ref No LU-241-01).

Questionnaire and Clinical Examination

All individuals in the patient group and control groupwere assessed for signs and symptoms of TMD bymeans of a questionnaire and clinical examination.

In the questionnaire, the individuals reported reasonsfor seeking treatment (impaired chewing capacity/symp-toms from the masticatory muscles, temporomandibularjoints [TMJs], and headaches/esthetic reasons), thestate of general health, use of painkillers for headacheand TMD (yes/no), as well as awareness of oral para-functions as tooth grinding (yes/no), or tooth clenching(yes/no). Frequency of TMD pain, tiredness of the jaws,TMJ clicking, and headache (never/once or twice amonth/once a week/once or twice a week/daily) was reg-istered as well as pain at rest (yes/no) and during man-dibular movements (yes/no) and reported TMJ clicking

(yes/no). The questionnaire also included questionsabout the severity of TMD discomfort on a visual ana-logue scale (VAS)20 with the endpoints none and severeand a verbal scale as follows: 0 � no or minimal dis-comfort, 1 � slight discomfort, 2 � moderate discomfort,3 � severe discomfort, 4 � very severe discomfort. Fur-thermore, the individuals rated themselves on the VASregarding their level of anxiousness with the endpointscalm and nervous/anxious.

Before the orthognathic treatment was started, theclinical examination was performed at the Departmentof Stomatognathic Physiology at Malmo University, byeither one of two calibrated21 specialists. The exami-nation included measurement of mandibular move-ments, pain during nonguided mandibular movements,registration of TMJ sounds, and tenderness of theTMJs and related muscles (Table 1). The reliability ofthe methods used for clinical registrations was im-proved by calibrating the examination technique be-tween two examiners. Thus, before the study, eightsubjects not included in the study were examined.21

Furthermore, the specialists conducting the examina-tions were not informed of the group to which the in-dividual belonged, and the extraoral examination wasperformed before the intraoral one.

Subdiagnoses of TMD were used according to RDC/TMD.4 The diagnoses are divided into three groups:

1. Muscle disorders: (a) myofascial pain, (b) myofas-cial pain with limited opening

2. Disc displacements: (a) disc displacement with re-duction; (b) disc displacement without reduction,with limited opening; (c) disc displacement withoutreduction, without limited opening

3. Arthralgia, arthritis, arthrosis: (a) arthralgia, (b) osteo-arthritis of the TMJ, (c) osteoarthrosis of the TMJ

The functional occlusion was assessed by methodspreviously described and investigated for observer er-ror.22,23 Nonworking side interferences within a lateral

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excursion of 3 mm, working side interferences, protru-sion interferences, and the distance and the directionof the slide between retruded contact position (RCP)and the intercuspal contact position (ICP) were regis-tered.

In both groups morphologic occlusion according toBjork et al24 was registered by intraoral examination.The patient group was further analyzed by dentalstudy casts, lateral cephalograms, and a cephalomet-ric analysis.25 A hyperdivergent facial profile was clas-sified as an NSL/ML angle of �40� and a hypodiver-gent facial profile as an NSL/ML angle of �26�. AClass II skeletal relationship between the dental arch-es was classified as an ANB angle of �6� and a ClassIII skeletal relationship as an ANB angle of �0�.

Statistical Methods

Power for test of the null hypothesis. One goal ofthe proposed study was to test the null hypothesis thatthe proportion positive was identical in the two popu-lations. The criterion for significance (alpha) was setat .05. The test was 2-tailed, which means that an ef-fect in either direction was interpreted.

With the proposed sample size of 35 in each sub-group, the study had a power of 89.8% to yield a sta-tistically significant result. This computation assumedthat the difference in proportions was �0.30 (specifi-cally, 0.05 vs 0.35) in prevalence of TMD pain. Thiseffect was selected as the smallest effect that wouldbe important to detect, in the sense that any smallereffect would not be of clinical or substantive signifi-cance.

Differences between groups and precision to esti-mate the effect size. Pearson’s chi-square test withYate’s correction for continuity was used when 2 � 2cross-tabulations were applicable. When the expectedcell value in a 2 � 2 table was less than 5, Fisher’sexact test was used. To compute the difference be-tween ranks and groups with ordinal data, the Mann-Whitney rank sum test was used.

A second goal of this study was to estimate the dif-ference between the two groups. Based on thesesame parameters and assumptions, the study enabledus to report the difference in proportions with a preci-sion (95% confidence level) of approximately �0.17points. Specifically, an observed difference of �0.30would be reported with a 95% confidence interval of�0.47 to �0.13.

When comparing means in numerical variables, thetwo-sample t-statistic was used. Median value andpercentiles (Q) were calculated when estimating re-ported anxiety on the VAS. All statistic procedureswere performed with statistical software SPSS 13.0 forWindows (SPSS Inc, Chicago, IL).

RESULTS

Anamnestic Findings

Twenty-one percent in the patient group and 2% inthe control group used painkillers for headache and/orTMD pain (P � .001). The self-rated level of anxious-ness on the VAS was similar in the two groups, witha median of 19.5 (Q1 � 7, Q3 � 47) and 19.0 (Q1 �6, Q3 � 43). There were no differences between thegroups concerning reported weekly headaches (P �.373) or awareness of parafunctional habits such astooth clenching (P � .665) and tooth grinding (P �.080). When the patients registered their reasons forseeking treatment, 75% answered impaired chewingcapacity and 72% symptoms from masticatory mus-cles, TMJs, and headaches. Sixty-six percent reportedesthetic reasons.

Symptoms of TMD

The patient group reported more subjective TMDdiscomfort on a verbal scale (P � .001) than did thecontrol group (Figure 1). Also, pain in the TMJs and/or masticatory muscles during rest, wide opening, andchewing were significantly more commonly reported inthe patient group than in the control group, as well asweekly TMD pain, weekly jaw tiredness, and weeklyjoint clicking (Table 2).

Clinical Findings

Signs of TMD. There were statistically significant dif-ferences between the patient group and the controlgroup with regard to pain on palpation of the TMJs andrelated muscles, deviation during opening and/or clos-ing of the mandible, and TMJ clicking (Table 3). How-ever, no differences were found in registered recipro-cal clicking or crepitations. During maximum opening,laterotrusion, and protrusion, the individuals in thecontrol group had significantly larger mandibularmovement capacity than the patient group did (Table4).

Occlusal interferences. A sagittal and vertical dis-tance of �1 mm between RCP and ICP was signifi-cantly more common in the patient group than in thecontrol group. Significantly more individuals in the pa-tient group had interferences in laterotrusion, medi-otrusion, and protrusion compared with the controlgroup (Table 5).

TMD diagnoses according to RDC/TMD. The patientgroup had a significantly higher frequency of myofas-cial pain, disc displacement with reduction, and ar-thralgia compared with the control group (Table 6).The frequency of myofascial pain with limited opening,osteoarthritis, and osteoarthrosis was low, and no dif-ferences could be found between the two groups.

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Figure 1. Reported temporomandibular disorder discomfort on a verbal scale.

Table 2. Percentage Distribution of Self-reported TMD Symptomsin the Patient Group (n � 121) and the Control Group (n � 56)a

Symptoms of TMDPatientGroup

ControlGroup

PValue

TMJs/muscles, pain atRest 18 2 .003Wide opening 34 11 .006Chewing 50 11 .000Rest, wide opening, and/or chewing 57 16 .000

Weekly TMD pain 38 5 .000Weekly jaw tiredness 64 9 .000Weekly TMJ clicking 47 8 .002

a TMD indicates temporomandibular disorder; TMJ, temporoman-dibular joint.

Table 3. Percentage Distribution of Clinical Signs of TMD in thePatient Group (n � 121) and the Control Group (n � 56)

Signs of TMDPatientGroup

ControlGroup

PValue

Pain on palpationMuscle pain on palpation �three sites 31 5 .000TMJ pain on lateral and/or posterior

palpation 21 5 .009TMJ sounds

Clicking during opening and/or closing 31 14 .021Reciprocal clicking 19 11 .166Crepitations 4 2 .422

Deviation on opening/closing of themandible �2 mm 41 13 .000

a TMD indicates temporomandibular disorder; TMJ, temporoman-dibular joint.

Subgrouping into different malocclusion traits. Thedistribution of malocclusion traits is shown in Table 7.No certain malocclusion trait could be associated withsymptoms of TMD or headache. No differences in thefrequency of diagnosed RDC/TMD could be seen be-tween different malocclusion traits.

DISCUSSION

The null hypothesis was rejected because patientswho were to be treated with orthognathic surgery hadmore signs and symptoms of TMD and a higher fre-quency of diagnosed TMD compared with the matchedcontrol group.

Previous studies assessing the frequency of TMD inpatients with dentofacial deformities have been het-erogeneous in study design and have shown ambig-

uous results.13,14,17–19,26,27 However, neither of thesestudies used RDC/TMD as a diagnostic tool.

It is well known that signs and symptoms of TMDare common in a healthy population and do not haveto be an indication of disease. Therefore, the use ofthe RDC/TMD is important since it allows standardi-zation and replication of the most common forms ofmuscle- and joint-related TMD.4 The RDC/TMD dem-onstrates sufficiently high reliability for the most com-mon TMD diagnoses,6 supporting its use in clinical re-search as well as in decision making. In the presentstudy, all individuals were diagnosed according toRDC/TMD, and the patient group had a significantlyhigher frequency of myofascial pain, disc displacementwith reduction, and arthralgia than the control group.

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Table 4. Mandibular Movement Capacity (in mm) in the Patient Group (n � 121) Compared with the Control Group (n � 56)

Maximum MandibularMovements

Patient Group

Mean SD

Control Group

Mean SD 95% CI P Value

Maximum opening capacity 49.8 8.0 54.3 6.1 2.1–6.8 .000Maximum laterotrusion, left 8.0 2.6 9.7 2.0 1.0–2.5 .000Maximum laterotrusion, right 8.2 2.6 9.7 2.1 0.8–2.3 .000Maximum protrusion 8.1 3.1 9.9 1.9 0.9–2.7 .000

Table 5. Percentage Distribution of Occlusal Interferences in thePatient Group (n � 121) and the Control Group (n � 56)

Occlusal InterferencesPatientGroup

ControlGroup

PValue

Sagittal distance between RCPand ICP �1.0 mm 41 18 .002

Vertical distance between RCPand ICP �1.0 mm 39 16 .002

Lateral deviation between RCPand ICP �0.5 mm 23 20 .602

Laterotrusion interferences 27 9 .006Mediotrusion interferences 80 18 .000Protrusion interferences 80 23 .000

a RCP indicates retruded contact position; ICP, intercuspal contactposition.

Table 7. Percentage Distribution of Diagnosed Malocclusion Traitsin the Patient Group (n � 121)

Skeletal Diagnosis %

Mandibular prognathism 45Mandibular retrognathism 7Open bite in combination with:

Orthognathic jaws 17Mandibular prognathism 8Mandibular retrognathism 16

Deep bite in combination with:Mandibular prognathism 4Mandibular retrognathism 3

Table 6. Percentage Distribution of Research Diagnostic Criteriafor Temporomandibular Disorders (RDC/TMD) Diagnoses in the Pa-tient Group (n � 121) and Control Group (n � 56)

RDC/TMD DiagnosisPatientGroup

ControlGroup

PValue

Myofascial pain 30 4 .000Myofascial pain with limited opening 1 0 .493Disc displacement with reduction 19 5 .017Arthralgia 21 5 .007Osteoarthritis 3 0 .235Osteoarthrosis 0 2 .140At least one diagnosis (RDC/TMD) 51 18 .000Having two or more diagnoses

(RDC/TMD) 19 2 .002

These TMD diagnoses were also the most prevalentin this material, as in the study by John et al.6

Because it is well known that signs and symptomsof TMD fluctuate over time3 and because symptom fre-quencies appear to be age dependent,28 it is importantto include an age- and gender-matched nonpatientcontrol group as a comparison when evaluating thefrequency of TMD. In evidence-based research, usu-ally a randomized controlled trial methodology is rec-ommended. However, in this kind of clinical trial, it isoften not possible for ethical or practical reasons torandomize and enroll subjects or patients into a treat-ment or a nontreatment group. Thus, the control groupdeliberately consisted of individuals with or without mi-nor malocclusion traits. No limitations were done con-sidering previous orthodontic treatment.

In this study, it was found that the patient group hadmore occlusal interferences than the control group did.In a recent review by Luther,29 it was concluded thatneither static nor dynamic factors can be said to causeTMD, and this current study has not proven otherwise.However, it is interesting to assess whether occlusalinterferences are altered by orthognathic surgery.Such a study has been commenced and will be pre-sented later.

The clinical registration of signs of TMD, mandibularfunction, and functional occlusal interferences wasperformed by standardized methods, and the reliabilityof these methods has been evaluated and found to beacceptable.4,30,31 In addition, it was decided to performthe orthognathic surgery and the clinical TMD exami-

nations separately to ensure the objectiveness of theclinical TMD examination. Furthermore, the reliabilityof the methods used for clinical registrations was im-proved by calibrating the examination technique be-tween the two examiners. Thus, before the study, eightsubjects not included in the study were examined. Inaddition, the specialists were not informed whichgroup their patients belonged to, and, moreover, theextraoral examination was carried out before the intra-oral examination in an attempt of blinding.

Two studies32,33 have reported that patients declaredan esthetic motive to be the main reason for seekingorthognathic surgery treatment. This was not con-firmed in this study. Instead, functional motives werethe most frequent, albeit not significantly higher thanesthetic reasons. In fact, many of the patients reportedmore than one motive for seeking treatment. It can bepointed out that many other factors, such as social andpsychological concerns, cultural values, cost of treat-

626 ABRAHAMSSON, EKBERG, HENRIKSON, NILNER, SUNZEL, BONDEMARK

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ment, recovery time, and perceived benefits, are in-volved and can encourage or discourage a patient topursue surgery.32

An attempt was made to evaluate whether psycho-logical stress could be a selection bias when compar-ing the frequency of TMD between the groups. How-ever, no differences were found between the twogroups when the subjects rated their level of anxious-ness on the VAS. Even if the VAS is a raw tool tomeasure psychological distress, it can still give an in-dication of the level of anxiousness in a group of in-dividuals.

In this study, it was convincingly demonstrated thatconsecutive patients referred for treatment with or-thognathic surgery had a higher frequency of diagno-ses according to RDC/TMD4 before this treatmentcompared with an age- and gender-matched controlgroup. However, the question still remains whether or-thognathic treatment in these patients significantly re-lieves signs and symptoms of TMD. Such informationwill be presented in a further study.

CONCLUSION

• The null hypothesis was rejected because patientswho were to be treated with orthognathic surgeryhad more signs and symptoms of TMD and a higherfrequency of diagnosed TMD according to RDC/TMD4 compared with the matched control group.

ACKNOWLEDGMENTS

We extend our sincere thanks to Ingrid Carlin and BirgittaZahlee, Faculty of Odontology, Malmo University, and IngelaNilsson at Department of Oral and Maxillofacial Surgery, MalmoUniversity Hospital, for clinical assistance during this study. Fur-thermore, we would like to thank the Public Dental Health Clinicin Oxie for providing patients and treatment rooms. This studywas supported by grants from the Swedish Dental Society andfrom Faculty of Odontology, Malmo University, Sweden.

REFERENCES

1. Wanman A, Agerberg G. Two-year longitudinal study ofsigns of mandibular dysfunction in adolescents. Acta Odon-tol Scand. 1986;44:333–342.

2. Wanman A, Agerberg G. Two-year longitudinal study ofsymptoms of mandibular dysfunction in adolescents. ActaOdontol Scand. 1986;44:321–331.

3. Magnusson T, Egermark I, Carlsson GE. A longitudinal ep-idemiologic study of signs and symptoms of temporoman-dibular disorders from 15 to 35 years of age. J Orofac Pain.2000;14:310–319.

4. Dworkin SF, LeResche L. Research diagnostic criteria fortemporomandibular disorders: review, criteria, examinationsand specifications, critique. J Craniomandib Disord. 1992;6:301–355.

5. List T, Dworkin SF. Comparing TMD diagnoses and clinicalfindings at Swedish and US TMD centers using researchdiagnostic criteria for temporomandibular disorders. J Oro-fac Pain. 1996;10:240–253.

6. John MT, Dworkin SF, Mancl LA. Reliability of clinical tem-poromandibular disorder diagnoses. Pain. 2005;118:61–69.

7. Pullinger AG, Seligman DA. Trauma history in diagnosticgroups of temporomandibular disorders. Oral Surg OralMed Oral Pathol. 1991;71:529–534.

8. Wanman A, Agerberg G. Etiology of craniomandibular dis-orders: evaluation of some occlusal and psychosocial fac-tors in 19-year-olds. J Craniomandib Disord. 1991;5:35–44.

9. American Academy of Orofacial Pain. In: Okeson JP, ed.Orofacial Pain Guidelines for Assessment, Classification,and Management the American Academy of Orofacial Pain.Chicago, IL: Quintessence Pub; 1996:113–184.

10. Riolo ML, Brandt D, TenHave TR. Associations betweenocclusal characteristics and signs and symptoms of TMJdysfunction in children and young adults. Am J Orthod Den-tofacial Orthop. 1987;92:467–477.

11. Pullinger AG, Seligman DA, Gornbein JA. A multiple logisticregression analysis of the risk and relative odds of tempo-romandibular disorders as a function of common occlusalfeatures. J Dent Res. 1993;72:968–979.

12. Celic R, Jerolimov V, Panduric J. A study of the influenceof occlusal factors and parafunctional habits on the preva-lence of signs and symptoms of TMD. Int J Prosthodont.2002;15:43–48.

13. Miller JR, Burgess JA, Critchlow CW. Association betweenmandibular retrognathia and TMJ disorders in adult fe-males. J Public Health Dent. 2004;64:157–163.

14. Miller JR, Mancl L, Critchlow C. Severe retrognathia as arisk factor for recent onset painful TMJ disorders amongadult females. J Orthod. 2005;32:249–256.

15. Thilander B, Rubio G, Pena L, de Mayorga C. Prevalenceof temporomandibular dysfunction and its association withmalocclusion in children and adolescents: an epidemiologicstudy related to specified stages of dental development. An-gle Orthod. 2002;72:146–154.

16. Pahkala RH, Laine-Alava MT. Do early signs of orofacialdysfunctions and occlusal variables predict development ofTMD in adolescence? J Oral Rehabil. 2002;29:737–743.

17. Nebbe B, Major PW, Prasad NG. Adolescent female cra-niofacial morphology associated with advanced bilateralTMJ disc displacement. Eur J Orthod. 1998;20:701–712.

18. Hwang CJ, Sung SJ, Kim SJ. Lateral cephalometric char-acteristics of malocclusion patients with temporomandibularjoint disorder symptoms. Am J Orthod Dentofacial Orthop.2006;129:497–503.

19. Abrahamsson C, Ekberg E, Henrikson T, Bondemark L. Al-terations of temporomandibular disorders before and afterorthognathic surgery: a systematic review. Angle Orthod.2007;77:729–734.

20. Huskisson EC. Measurement of pain. Lancet. 1974;2:1127–1131.

21. Henrikson T, Ekberg EC, Nilner M. Symptoms and signs oftemporomandibular disorders in girls with normal occlusionand class II malocclusion. Acta Odontol Scand. 1997;55:229–235.

22. Vallon D, Ekberg EC, Nilner M, Kopp S. Short-term effectof occlusal adjustment on craniomandibular disorders in-cluding headaches. Acta Odontol Scand. 1991;49:89–96.

23. Vallon D, Nilner M, Kopp S. Assessment of occlusal inter-ferences. J Oral Rehabil. 1989;16:279–286.

24. Bjork A, Krebs AA, Solow B. A method for epidemiologicalregistration of malocclusion. Acta Odontol Scand J. 1964;22:27–41.

25. Bjork A. The Face in Profile: An Anthropological X-ray In-vestigation on Swedish Children and Conscripts [disserta-tion]. Uppsala, Sweden: University of Lund; 1947.

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26. De Boever AL, Keeling SD, Hilsenbeck S, Van Sickels JE,Bays RA, Rugh JD. Signs of temporomandibular disordersin patients with horizontal mandibular deficiency. J OrofacPain. 1996;10:21–27.

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28. Dibbets JM, van der Weele LT. Orthodontic treatment inrelation to symptoms attributed to dysfunction of the tem-poromandibular joint. A 10-year report of the University ofGroningen study. Am J Orthod Dentofacial Orthop. 1987;91:193–199.

29. Luther F. TMD and occlusion part II. Damned if we don’t?Functional occlusal problems: TMD epidemiology in a widercontext. Br Dent J. 2007;202:E3.

30. Carlsson GE, Egermark-Eriksson I, Magnusson T. Intra-and inter-observer variation in functional examination of themasticatory system. Swed Dent J. 1980;4:187–194.

31. Mohlin B, Pilley JR, Shaw WC. A survey of craniomandib-ular disorders in 1000 12-year-olds: study design and base-line data in a follow-up study. Eur J Orthod. 1991;13:111–123.

32. Rivera SM, Hatch JP, Dolce C, Bays RA, Van Sickels JE,Rugh JD. Patients’ own reasons and patient-perceived rec-ommendations for orthognathic surgery. Am J Orthod Den-tofacial Orthop. 2000;118:134–141.

33. Magnusson T, Ahlborg G, Svartz K. Function of the masti-catory system in 20 patients with mandibular hypo- or hy-perplasia after correction by a sagittal split osteotomy. Int JOral Maxillofac Surg. 1990;19:289–293.

YIJOM-2534; No of Pages 7

Please cite this article in press as: Abrahamsson C, et al. TMD before and after correction of dentofacial deformities by orthodontic and

orthognathic treatment, Int J Oral Maxillofac Surg (2012), http://dx.doi.org/10.1016/j.ijom.2012.10.016

Clinical Paper

TMJ Disorders

TMD before and after correctionof dentofacial deformities byorthodontic and orthognathictreatmentC. Abrahamsson, T. Henrikson, M. Nilner, B. Sunzel, L. Bondemark, EC. Ekberg:TMD before and after correction of dentofacial deformities by orthodontic andorthognathic treatment. Int. J. Oral Maxillofac. Surg. 2012; xxx: xxx–xxx. # 2012International Association of Oral and Maxillofacial Surgeons. Published by ElsevierLtd. All rights reserved.

C. Abrahamsson, T. Henrikson,M. Nilner, B. Sunzel, L. Bondemark,EC.EkbergDepartment of Orthodontics, Faculty ofOdontology, Malmo University, Sweden

Abstract. The aims of the study were to investigate the alteration oftemporomandibular disorders (TMD) after correction of dentofacial deformities byorthodontic treatment in conjunction with orthognathic surgery; and to compare thefrequency of TMD in patients with dentofacial deformities with an age and gendermatched control group. TMD were evaluated in 121 consecutive patients (treatmentgroup), referred for orthognathic surgery, by a questionnaire and a clinicalexamination. 18 months after treatment, 81% of the patients completed a follow-upexamination. The control group comprised 56 age and gender matched subjects, ofwhom 68% presented for follow-up examination. TMD were diagnosed accordingto research diagnostic criteria for TMD. At baseline examination, the treatmentgroup had a higher frequency of myofascial pain (P = .035) and arthralgia(P = .040) than the control group. At follow-up, the frequencies of myofascial pain,arthralgia and disc displacement had decreased in the treatment group (P = .050,P = .004, P = .041, respectively). The frequency of TMD was comparable in the twogroups at follow-up. Patients with dentofacial deformities, corrected by orthodontictreatment in conjunction with orthognathic surgery, seem to have a positivetreatment outcome in respect of TMD pain.

Key words: TMD; dentofacial deformities;orthognathic surgery; orthodontics.

Accepted for publication 11 October 2012

In patients with dentofacial deformities,the major indications for undergoingorthodontic treatment in conjunctionwith orthognathic surgery are functionimprovement and aesthetic considera-tions.1,2 Motivation for treatment maybe influenced by many different factors,such as psychosocial concerns, culturalvalues, treatment costs, age at treatment,

expected treatment outcomes and gender.1

Orthodontic treatment in conjunction withorthognathic surgery is expensive, ardu-ous and not without complications. It istherefore important that the treatment out-comes meet patient expectations.

The aetiology of temporomandibulardisorders (TMD) is complex3 and todaymost researchers and clinicians agree that

the aetiology is multifactorial. Some stu-dies have shown that compared to thosewith normal occlusion, subjects with mal-occlusions have a significantly higher pre-valence of signs and symptoms of TMD.4–

7 It has also been suggested that alterationsin facial morphology, such as a hyperdi-vergent facial profile may influence thedevelopment of TMD.8,9 On the other

Int. J. Oral Maxillofac. Surg. 2012; xxx: xxx–xxxhttp://dx.doi.org/10.1016/j.ijom.2012.10.016, available online at http://www.sciencedirect.com

0901-5027/000001+07 $36.00/0 # 2012 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

hand, there are studies that have shown theopposite10 and the relative importance ofthe occlusion in the onset or perpetuationof the condition has been discussed.3,11

A number of studies have shown thatorthodontic correction of different types ofmalocclusion does not increase the risk ofdeveloping TMD.7,10,12,13 On the con-trary, in subjects with pre-treatment signsand symptoms, orthodontic treatment mayhave a beneficial effect on TMD.13 Incases of major skeletal jaw discrepancies(i.e. dentofacial deformities) orthognathicsurgery is indicated in conjunction withorthodontic treatment to correct the dentalrelationship.

Two recent systematic reviews,14,15 ofchanges in TMD after orthodontic treat-ment in conjunction with orthognathicsurgery, disclosed lack of uniformity instudy design and ambiguous results in theselected studies. The review by Abra-hamsson et al.14 was limited to controlledstudies only.

A well-designed study by Rodrigues-Garcia et al., albeit without a controlgroup, reported positive treatment out-comes with respect to signs and symptomsof TMD.16 TMD symptoms fluctuate overtime17 and the frequencies of symptomsappear to be age dependent.3 The impor-tance of a control group should, therefore,not be underestimated.

The aims of the present study weretwofold: to investigate whether correctionof dentofacial deformities by orthodontictreatment in conjunction with orthog-nathic surgery alters the frequency of

TMD, and over the same period of time,to compare and monitor the frequency ofTMD in an untreated normal group (con-trol group).

The hypothesis was that the patientswith dentofacial deformities would benefitfrom treatment, in respect of TMD, andthat post-treatment, the frequency of TMDwould be similar to that in the controlgroup.

Materials and methods

The study sample comprised 121 conse-cutive patients (51 males and 70 females)with dentofacial deformities, referred tothe Department of Oral Maxillofacial Sur-gery, Malmo University Hospital, Malmo,Sweden for orthodontic treatment in con-junction with orthognathic surgery (thetreatment group). The mean age was22.5 � 7.4 years. All patients wererecruited during two periods, between1992–1995 and 2000–2002. Under theSwedish National Health Service, patientswith such severe deformities are entitledto subsidized treatment. The exclusioncriteria were craniofacial syndromes, sys-temic arthritic and muscular diseases, anda dentition of fewer than 24 teeth. 23patients were excluded. 98 patients(81%) met the inclusion criteria and thefinal sample comprised 38 males and 60females, mean age 22.4 � 7.5 years(Fig. 1).

The control group comprised 56 sub-jects, 23 males and 33 females, mean age23.4 � 7.4 years, age and gender matched

with the subjects undergoing treatment.They were recruited from general dentalpatients at the Faculty of Odontology,Malmo University, Sweden, and the Pub-lic Dental Health Clinic in Oxie, CountySkane, Sweden. The inclusion criteriawere normal occlusion, or minor maloc-clusions for which neither orthodontictherapy nor orthognathic surgery was indi-cated. The same exclusion criteria appliedto the control group as to the treatmentgroup. Of the 56 recruits who underwentthe initial clinical examination and com-pleted the questionnaire, 38 (68%) pre-sented for the follow-up clinicalexamination and 47 (84%) completedthe follow-up questionnaire (Fig. 1).

In the treatment group, TMD wasassessed by means of a questionnaireand a clinical examination before (base-line) and 18 months after surgery. Theinterval between the two examinationswas approximately 3 years depending onlength of orthodontic treatment. The ques-tionnaire and the clinical examinationwere performed after treatment planning.The control group was similarly assessed,on two occasions, at an interval of at least3 years.

The following issues were addressed inthe baseline and follow-up questionnaires:frequency of TMD pain, jaw fatigue andtemporomandibular joint (TMJ) clicking(never; once or twice a month; once aweek; once or twice a week; daily); painat rest (yes/no) and during mandibularmovements (yes/no). The severityof discomfort associated with TMD was

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Study popula tion

n = 98

Treatment groupConsecutive patients assessed for eligibility

n = 121

Refused treatment, n = 15Unreachable, n = 8

Control gro upSubjects ma tched for

gender and agen = 56

Comp leted the question naire

n=47

Lost to follow-upMoved abroad, n =1Refused to participate in the clinical follow-up examination,n = 9

Study popula tion

n =38

Basel ine

~3years

Lost to follow-upRefused to participate in the follow up examination, n = 8

Treated patients

n = 106

Fig. 1. Flow chart: subjects included in the study.

estimated on the following scale: 0, littleor none; 1, slight; 2, moderate; 3, severe;4, very severe. The subjects rated theiranxiety levels on a visual analogue scale(VAS) with the endpoints calm andanxious/uneasy. The follow-up question-naire also included questions about treat-ment satisfaction, such as whether the pre-treatment information had been adequate(yes/no), whether treatment met expecta-tions (yes/no) and whether, post-treat-ment, the subjects had perceived anyalterations in masticatory capacity, aes-thetics and TMD symptoms (better,unchanged, worse).

The clinical examinations were con-ducted at the Department of Stomatog-nathic Physiology at the Faculty ofOdontology, Malmo University, by oneof two calibrated specialists in stomatog-nathic physiology.18 The extra oralexamination preceded the intraoral exam-ination. The examination included mea-surement of maximum mandibularopening capacity, registration of TMJsounds (clicking and crepitation), and ten-derness in the TMJs and related muscles.The clinical registrations were improvedby calibrating the examination techniquesof the two examiners before the start of thestudy. The calibration was performed byexamining eight patients, not included inthe study, and was achieved after discus-sion. Eight subjects not included in thestudy were examined regarding occlusalinterferences with an observer error thatwas found to be acceptable.19 The specia-lists conducting the examinations were notinformed whether the subject belonged tothe test or control group at the follow-up.

Subdiagnoses for TMD pain followedthe research diagnostic criteria (RDC) forTMD (Table 1).20 Disc displacement wasdiagnosed if, upon opening and closingfrom maximum intercuspation, a click wasnoted audible or by palpation. Osteoar-throsis was diagnosed as registered crepi-tations by palpation of the TMJ.

Functional occlusion was assessed bypreviously described methods and inves-tigated for observer error.19 Mediotrusioninterferences within a lateral excursion of3 mm, laterotrusion interferences, protru-sion interferences, and the distance and thedirection of the slide between retrudedcontact position (RCP) and the intercuspalcontact position (ICP) were registered.

Morphological occlusion according toBjork et al.21 was registered by intraoralexamination. Further data were obtainedfrom dental study casts, lateral cephalo-grams, and a cephalometric analysis.22

The diagnoses in the treatment group werealso separated into sagittal and vertical

discrepancies, according to a combinationof morphological and cephalometricvalues (Table 2).

All subjects in the treatment groupunderwent pre- and postsurgical orthodon-tic treatment with fixed orthodontic appli-ances in both arches. Ten specialistscarried out the orthodontic treatment;the duration varied between 18 and 24months.

The orthognathic surgery was underta-ken by four oral maxillofacial surgeons atthe Department of Oral Maxillofacial Sur-gery, Malmo University Hospital, Malmo,Sweden. Vertical deformities was cor-rected in the maxilla with a one pieceLe Fort I osteotomy or a segmental max-illary osteotomy.23 Sagittal adjustmentswere made either by sagittal split osteot-omy, to advance the mandible,24 or byintraoral vertical ramus osteotomy, to cor-rect mandibular prognathism.23 Whenbimaxillary surgery was indicated, in 27patients, maxillary osteotomies were com-bined with either sagittal split or verticalramus osteotomies. Maxillo-mandibularfixation was used for 4 weeks after

intraoral vertical ramus osteotomies. Inall other cases, rigid intra jaw fixationwas used.

Statistical methods

One goal of the proposed study was to testthe null hypothesis that the proportion ofpositive outcomes was identical in the twogroups. Significance (alpha) was set at .05.The test was two-tailed (i.e. an effect ineither direction was analysed). With theproposed sample size of 35 in each sub-group, the study had a power of 89.8% toyield a statistically significant result. Thiscomputation assumed that the differencein proportions in frequency of TMD painwas �.30 (specifically .05 vs .35). Thiswas selected as the cut-off point for mini-mum detection; any effect below this levelwould not be of clinical relevance or ofsubstantive significance.

A second goal of this study was toestimate the difference between the testand control groups and the precision inestimating the magnitude of the effect.Pearson’s x2 test with Yate’s correctionfor continuity was used when 2 � 2 crosstabulations were applicable. When theexpected cell value in a 2 � 2 table wasless than 5, Fisher’s exact test was used.The two-sample t-statistic was used tocompare means in numerical variables.To estimate self-reported anxiety on theVAS, median values and percentiles (Q)were calculated.

To assess the differences within groups,McNemar exact test was used to analyseordinal data before and after treatment.The paired t-test was used to comparethe means of maximum mandibular open-ing capacity.

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Table 1. Clinical examination and diagnoses of temporomandibular pain according to RDC/TMD.

Diagnoses of TMD

Muscle disordersMyofascial pain

1. Report of pain or ache in the jaw, temples, face, preauricular area, or inside theear at rest or during function; plus

2. Pain reported by the subject in response to palpation of three or more of 20 musclesites. At least one of the sites must be on the same site as the complaint of pain

Temporomandibular joint disordersArthralgia

1. Pain in one or both joint sites (lateral pole and or posterior attachment) during palpation;plus

2. One or more of the following self-reports of pain: pain in the region of the joint,pain in the joint during maximum unassisted opening, pain in the joint duringassisted opening, pain in the joint during lateral excursion.

3. For a diagnosis of simple arthralgia, coarse crepitus must be absentOsteoarthritis

Arthralgia; plus coarse crepitus of the joint

Table 2. Distribution of diagnosed malocclu-sion traits in the treatment group, according totype of discrepancy: sagittal and/or vertical(n = 98).

Skeletal diagnoses n

Class II 6Class III 42Open bite in combination with:

Normal sagittal relationship 13Class II 14Class III 14

Deep bite in combination with:Class II 7Class III 2

Results

Analysis of those who withdrew from thetreatment and control groups, (n = 23,19%, and n = 18, 32%, respectively)showed no significant differences com-pared with the final study groups withrespect to age, gender, self-rated level ofanxiety on VAS, pain in the jaws andrelated muscles or diagnosed TMDreported at baseline.2 Thus, the partici-pants who completed the study were con-sidered to be representative of the initialstudy sample.

TMD diagnoses

At baseline, the most common diagnosesin both treatment and control groups weremyofascial pain, disc displacement andarthralgia. At follow-up, the frequenciesof these diagnoses were significantlyreduced in the treatment group, but atthe same time, the treatment group exhib-ited a significant increase in osteoarthrosispost-treatment (Table 3). Compared withthe control group, significantly more sub-jects in the treatment group had myofas-

cial pain and arthralgia at baseline, butpost-treatment these differences had beeneliminated (Table 3).

Myofascial pain was the only TMDdiagnosis with a significant gender differ-ence before treatment (P = .015); it wasmore common in women (32%) than inmen (12%), but at follow-up, no gender-related differences were found for any ofthe TMD diagnoses.

After stratifying the treatment groupaccording to the type of dentofacial defor-mity (Table 2), those with a Class IIIrelationship combined with a normal ver-tical relationship of the jaws having myo-fascial pain (n = 13) and/or arthralgia(n = 8) had significantly decreased aftertreatment (n = 4, P = .022 and n = 2,P = .031 respectively). None of the othersubgroups showed significant differencesin TMD diagnoses between baseline andfollow-up.

Symptoms of TMD

In the treatment group, self-evaluatedTMD discomfort, evaluated on a verbal

scale, decreased significantly from base-line to follow-up (Fig. 2).

At baseline, the treatment groupreported significantly more TMD symp-toms than the control group (Table 4).With the exception of weekly jaw fatigue,there were no significant inter-group dif-ferences in TMD symptoms at follow-up.The treatment group experienced signifi-cantly fewer TMD symptoms at follow-upthan at baseline, except for weekly TMJclicking. In the control group, there wereno differences in TMD symptoms betweenbaseline and follow-up (Table 4). Withrespect to gender, there were no significantdifferences in frequency of TMD symp-toms in either group, at baseline or atfollow-up.

Mandibular movement capacity

The maximum mandibular opening capa-city in the treatment group had decreasedat follow-up, from 50 � 8 mm to48 � 7 mm (P = .009). At both baselineand follow-up, the opening capacity waslower in the treatment group than in the

4 Abrahamsson et al.

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orthognathic treatment, Int J Oral Maxillofac Surg (2012), http://dx.doi.org/10.1016/j.ijom.2012.10.016

Table 3. Distribution of TMD diagnoses in the treatment and control groups. Each subject may have multiple TMD diagnoses.

Treatment group (n = 98) Control group (n = 38) Group differences*

Baseline(P1)

Follow up(P2) �3 years

Baseline(C1)

Follow up(C2) �3 years Between groups Within groups

TMD diagnoses n (%) n (%) n (%) n (%) P1/C1 P2/C2 P1/P2 C1/C2

Myofascial pain 29 (30) 17 (17) 4 (10) 4 (10) P = .035 NS P = .050 NSDisc displacement 19 (19) 9 (9) 5 (13) 8 (21) NS NS P = .041 NSArthralgia 16 (16) 4 (4) 1 (3) 2 (5) P = .040 NS P = .004 NSOsteoarthritis 1 (1) 0 0 0 NS NS NS NSOsteoarthrosis 1 (1) 9 (9) 1 (3) 0 NS NS P = .008 NSAt least one

TMD diagnosis42 (43) 32 (33) 10 (26) 11 (29) NS NS NS NS

At least one TMDpain diagnosis

31 (32) 18 (18) 4 (10) 4 (10) P = .021 NS P = .029 NS

* NS: not significant.

Treatment group Control groupBaseline Follow-up Baseline Follow up

~3 years ~3 years

No-slight

discomfort 56 52 87 33 28 31

35 3

4 5Moderate-very severediscomfort 41 6 10 5 2 7

P < .001 P = .727

Fig. 2. Subjective TMD discomfort in the treatment group (n = 97) and the control group (n = 38) on a verbal scale. The five grade scale wasdichotomized as follows; no/minimal or slight discomfort was registered as no–slight discomfort and moderate, severe and very severe discomfortwas registered as moderate–very severe discomfort. For one individual in the treatment group no answer was registered.

control group (P = .005, P < .001 respec-tively). No significant changes in mandib-ular opening capacity were recorded in thecontrol group from baseline to follow-upexaminations.

Occlusal interferences

At baseline, the treatment group had sig-nificantly more interferences (P < .05)than the control group, except for lateraldeviation between RCP and ICP. At fol-low-up, the number of subjects in thetreatment group with interferences haddecreased (P < .05) significantly. Nointer-group differences were disclosed.

Patients’ satisfaction with treatment

82% of the subjects in the treatment groupreported improved aesthetics, 80%reported improved masticatory comfortand 61% reported fewer symptoms ofTMD after treatment. 92% were satisfiedwith the information received before treat-ment. 68% reported their experience oftreatment to be as they had expected, orless burdensome than expected.

In the treatment group, the self-evalu-ated level of anxiety registered on theVAS decreased (P = .001) after treatment(median (M) of 19, (25th percentile(Q1) = 6, 75th percentile (Q3) = 36) to11 M (Q1 = 3, Q3 = 31)). The correspond-ing figures for the control group were 20 M(Q1 = 8, Q3 = 43) at baseline and 25 M(Q1 = 13, Q3 = 48) at follow-up examina-tion (P = .871).

Discussion

The frequency of diagnosed myofascialpain and arthralgia20 as well as signsand symptoms of TMD pain in the treat-ment group decreased after orthodontic

treatment in conjunction with orthog-nathic surgery. At follow-up, there wereno differences in TMD between the treat-ment and the control group. Thus thehypothesis could not be rejected.

Only one previous study has applied theRDC/TMD as a diagnostic tool for asses-sing TMD in consecutive patients treatedby a combination of orthognathic surgeryand orthodontic treatment.25 Thus, com-parative data are limited. In the study byFarella et al.,25 including Class III patients,none of the patients had myofascial pain orarthralgia at baseline, or throughout theentire study period. In contrast, the presentstudy reports a significantly lower fre-quency of patients diagnosed with myofas-cial pain and arthralgia after treatment.Farella et al.,25 also found disc displace-ment with reduction in 7 of 14 patientsbefore treatment, and no significant differ-ence at follow-up. These findings are inaccordance with the present study: frombaseline to follow-up, patients with a ClassIII jaw relationship showed no significantchanges in the frequency of diagnosed discdisplacement.

Several factors in the study design mayhave contributed to inconsistencies in theresults of the two studies. First, samplesize, with a relatively small study group of14 subjects in the study by Farella et al.25

Second, surgical approach, the patients inthe study by Farella were treated by bilat-eral sagittal split osteotomy combinedwith a Le Fort I osteotomy, whereas inthe present study, all Class III patientswere treated by bilateral vertical ramusosteotomy, with or without maxillaryosteotomy. Jung et al.26 analysed treat-ment outcomes for sagittal split osteotomyand vertical ramus osteotomy and reportedthat Class III patients treated by bilateralvertical ramus osteotomy experienced adecrease in TMJ sounds and pain.

In the present study, osteoarthrosis wasmore common in the treatment group atfollow-up than at baseline. This is inaccordance with Rodrigues-Garciaet al.,16 who found a significant increaseof fine crepitus, from 4% to 13% in ClassII patients treated by bilateral sagittal splitosteotomy. The post-treatment increase inosteoarthrosis in Class II patients could beattributable to post-surgical changes inthe condylar position in the glenoidfossa.27 The results may also have beenaffected by the uncertainty inherent indetecting and differentiating a specificjoint sound (i.e. crepitus) from clickingor even from soft tissue sounds duringdigital palpation. Only marginal reliabil-ity is reported for these signs28 by show-ing low sensitivity and high specificity forcrepitus.20 It has been proposed that ima-ging aids the diagnosis of osteoarthrosis/osteoarthritis of the TMJ.20 Imaging wasnot used as a diagnostic tool in this study.Tomography has been found to offer onlyminor advantages in the management ofTMD.29 Limchaichana et al.30 showedthat abnormal TMJ findings on magneticresonance imaging were registered inTMD patients with pain of both myogen-ous and arthrogenous origin. In a study byMuir and Goss31 it was found that only10% of the asymptomatic TMJs examinedby MRI were absolutely normal radiolo-gically.

The decreased mandibular openingcapacity in the treatment group at fol-low-up examination was in accordancewith previous studies.25,32 This could bea consequence of immobilization of thejaws during post-surgical maxillo-man-dibular fixation or to surgical trauma tothe tissues.25,32 The reduction in openingcapacity found in this study was relativelyminor (2 mm) and probably of negligibleclinical relevance.

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Table 4. Distribution of self-reported symptoms of TMD in the treatment (N = 98) and control groups (N = 38).

Treatment group Control group* Group differences*

Baseline(P1)

Follow up(P2) �3 years

Baseline(C1)

Follow up(C2) �3 years Between groups Within groups

Symptoms of TMD n (%) n (%) n (%) n (%) P1/C1 P2/C2 P1/P2 C1/C2

Pain atRest 15 (15) 6 (6) 1 (3) 5 (13) P = .040 NS P = .049 NSWide opening 32 (33) 17 (17) 6 (16) 7 (18) NS NS P = .006 NSChewing 44 (45) 21 (21) 5 (13) 5 (13) P = .001 NS P < .001 NSRest, wide opening

and/or chewing51 (53) 31 (32) 8 (21) 10 (26) P = .002 NS P = .001 NS

WeeklyPain 33 (34) 16 (17) 3 (8) 7 (18) P = .004 NS P = .004 NSJaw tiredness 37 (40) 7 (7) 5 (13) 8 (21) P = .007 P = .031 P < .001 NSTMJ clicking 36 (37) 26 (26) 6 (17) 9 (24) P = .044 NS NS NS* NS: not significant.

At baseline, occlusal interferences wereregistered in significantly more subjects inthe treatment than in the control group: atfollow-up, the two groups were compar-able. This result was expected and is inaccordance with earlier studies.16,33

One of the strengths of the present studywas the incorporation of a control group,which was examined not only at baselinebut also at follow-up. A recent systematicreview has disclosed that there are fewsuch controlled studies in this field ofresearch.14 In subjects with dentofacialdeformities the main treatment objectiveof combined orthodontic and orthognathicsurgery treatment is to normalize bothmorphological and functional parameters.Therefore it was of interest to compare thetreatment group with a normal group.Another advantage of such a controlgroup, matched for age and gender, wasthe possibility to record and compare thefrequencies of TMD with a control grouplongitudinally since TMD fluctuates overthe course of time and seems to be agedependent.3,17 It would have been animprovement to include an untreated mal-occlusion group. For ethical reasons and toavoid too great a selection bias, it wasdecided not to compare the treatmentgroup with untreated subjects. Therefore,the control group consisted of generaldental patients that were age and gendermatched to the treatment group.

Another strength of the study was thatthe clinical TMD examination wasundertaken by specialists in stomatog-nathic physiology who were notinvolved in the orthodontic or orthog-nathic treatment of the patients. For thesame reason TMD was assessed after thedecision to perform orthognathic surgeryhad been made. The reliability of themethods used for clinical registrationwas improved by calibrating the exam-ination techniques of the two examiners.In addition, at follow-up, the examinerswere blinded as to whether the subjectbelonged to the treatment or controlgroup. At baseline, blinding could notbe fully achieved because of the obviousdentofacial deformities in some of thesubjects. Nevertheless, in order to meetat least in part the requirement for blind-ing, the extra-oral examination precededthe intraoral examination.

Although some subjects withdrew fromthe study, especially in the control group,analysis showed that those who withdrewdid not differ from the remainder in termsof age, gender, pain experienced in thejaws or related muscles, diagnosed TMDor self reported level of anxiety reported atbaseline. According to the original sample

size calculation, both treatment and con-trol groups included sufficient participantsto ensure reliability of the results despitesome withdrawals.

In a review by Al-Riyami et al.,15 it wassuggested that the incorporation of variousdentofacial deformities in a study is aconfounding factor, complicating compar-ison of the results of different studies.Owing to the low prevalence of specificmalocclusions in the population referredfor orthognathic surgery, most of the sub-groups of dentofacial deformities were toosmall to detect any significant changesafter surgery. Thus an increase in thenumber of subjects in the treatment groupmight have enhanced the results of thepresent study. In a larger treatment groupit might have been possible to disclosemore significant differences associatedwith specific dentofacial deformities.Despite this shortcoming, the subgroupof subjects in the treatment group withClass III jaw relationships and normalvertical angle showed significant allevia-tion of TMD pain after surgery.

The aim of this study was to investigatewhether correction of dentofacial defor-mities by orthodontic treatment in con-junction with orthognathic surgery altersthe frequency of TMD. The outcome inthe treatment and control group may havebeen influenced by trauma, distress, painconditions or alterations of the verticalfacial pattern related to the muscles.These factors were not considered in thisstudy.

Apart from aesthetics, one factor moti-vating patients to undergo orthodontictreatment in conjunction with orthog-nathic surgery is the discomfort associatedwith TMD.1,2 The present study has shownthat the treatment seems to reduce TMDpain in particular. Another major motiva-tion for treatment is to alleviate chewingproblems. While pre- and post-treatmentevaluation of chewing capability wasbeyond the scope of the present study, itis currently under investigation in a sepa-rate study.

Patients with dentofacial deformities,corrected by orthodontic treatment in con-junction with orthognathic surgery, seemto have a positive treatment outcome inrespect of TMD pain. After treatmentfrequency of TMD is low and comparableto that in a control group.

Funding

This study was supported by grants fromthe Swedish Dental Society and from theFaculty of Odontology, Malmo Univer-sity, Sweden.

Competing interests

None declared.

Ethical approval

The study was approved by the EthicsCommittee of Lund University, Sweden(Ref. No. LU-241-01), which follows theguidelines of the declaration of Helsinki.

Acknowledgments. The authors extendtheir sincere thanks to Ingela Nilsson atDepartment of Oral and Maxillofacial Sur-gery, Malmo University Hospital, foradministrative assistance. Furthermorethey thank Per-Erik Isberg, Departmentof Statistics, Lund University for adviceon statistic methods and co-evaluation ofstatistical analysis.

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Address:Cecilia AbrahamssonMalmo HogskolaOdontologiska fakulteten205 06 MalmoSwedenTel: +46 406658474E-mail: cecilia.abrahamsson@mah.se

TMD before and after correction of dentofacial deformities 7

YIJOM-2534; No of Pages 7

Please cite this article in press as: Abrahamsson C, et al. TMD before and after correction of dentofacial deformities by orthodontic and

orthognathic treatment, Int J Oral Maxillofac Surg (2012), http://dx.doi.org/10.1016/j.ijom.2012.10.016

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Masticatory function in patients with dentofacial deformities before and after orthognathic treatment – a prospective, longitudinal and controlled study.

Cecilia Abrahamsson, Thor Henrikson, Lars Bondemark, EwaCarin Ekberg

Submitted to the European Journal of Orthodontics, june 2013.

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SUMMARY The aim of this study was to investigate the self estimated masticatory ability and masticatory performance in patients with dentofacial deformities before and after orthognathic treatment; in comparison to an age- and gender-matched control group. The masticatory ability and masticatory performance were evaluated in 121 consecutive patients (treatment group), referred for orthognathic treatment. Masticatory ability was assessed on a visual analogic scale (VAS) while the masticatory performance was evaluated by a masticatory test using round silicon tablets. Signs and symptoms of temporomandibular disorders (TMD) were registered by a questionnaire and a clinical examination. The control group comprised 56 age- and gender-matched subjects who were examined at baseline.

At the baseline examination, the treatment group had a significantly lower masticatory ability and performance index compared with the control group. After treatment the masticatory ability significantly improved in the treatment group and reached the same level as in the control group. The masticatory performance index increased significantly but was still lower than in the control group. Both the masticatory ability and masticatory performance were affected by the number of occlusal contacts during maximal biting pressure and by the self estimated overall symptoms of TMD. The findings suggest that patients with dentofacial deformities, corrected by orthognathic treatment, have a significant positive treatment outcome in respect of masticatory ability and masticatory performance. Furthermore, the occlusion and symptoms of TMD have an impact on both masticatory ability and masticatory performance.

IntRodUctIon Mastication is the first step, and one of the main functions in the digestion process, in which food is broken down into smaller particles to facilitate the enzymatic activity. Continuously the mastication is adapting to food, occlusion and oral health. Mastication can be assessed by subjective and objective measurements. Self estimated masticatory ability has been defined as an individual’s own assessment of mastication. Masticatory ability has been shown to be lower in individuals having signs and symptoms of TMD (Henrikson et al., 1998; Kurita et al., 2001). Masticatory performance, defined as a

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person´s capacity to break down a standardized test food, has been shown to be related to maximum bite force, body size, salivary flow rates and to the number of interocclusal contacts during maximum intercuspidation (Henrikson et al., 1998; Fontijn-Tekamp et al., 2000; Harada et al., 2000; Kobayashi et al., 2001; Okiyama et al., 2003; Engelen et al., 2005). A reduced masticatory performance has been reported for patients with malocclusions (Henrikson et al., 1998; English et al., 2002) and especially skeletal open bite has been correlated to impaired bite force (Proffit et al., 1983). Individuals with an impaired masticatory performance often compensate it by a higher number of chewing cycles resulting in longer duration of masseter muscle activity before swallowing and by swallowing coarser particles than individuals with good masticatory performance (Engelen et al., 2005).

Brennan et al. (2008) concluded that the masticatory ability was correlated to the number of teeth in contact and positively associated with oral-health related quality of life assessed by the Oral Health Impact Profile 14-item version (OHIP-14). Still there is a discussion to what extent nutrition and general health might be affected by an impaired masticatory ability and performance (Pera et al., 2002; Brennan et al., 2008).

Impaired masticatory ability is, apart from TMD and aesthetics, one of the main indications for orthognathic surgery in patients with dentofacial deformities (Rivera et al., 2000; Modig et al., 2006; Abrahamsson et al., 2009) Previous controlled studies in patients with dentofacial deformities (Zarrinkelk et al., 1995; Kobayashi et al., 2001; van den Braber et al., 2004) indicate impaired masticatory ability and performance both before and after treatment compared with controls. The studies above disclose somewhat different results considering if treatment will be beneficial for the patients regarding masticatory ability and performance. There are few studies on this topic, and in general with small sample sizes, and also, using different methodologies. Therefore, a great need exist to evaluate longitudinally and in a controlled manner the masticatory ability and masticatory performance in patients who have undergone treatment of dentofacial deformities.

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The aim of this study was to investigate the self estimated masticatory ability and masticatory performance in patients with dentofacial deformities before and after orthognathic treatment, in comparison with an age- and gender-matched control group. A further aim was to investigate factors with possible impact on masticatory ability and masticatory performance.

The hypothesis was firstly, that patients with dentofacial deformities have, compared to controls, impaired masticatory ability and masti-catory performance. Secondly, the masticatory ability and masti-catory performance will be improved by orthognathic treatment.

MAteRIAl And MethodSSubjectsThe treatment group comprised 121 consecutive patients (51 males and 70 females) with dentofacial deformities, referred to the Department of Oral Maxillofacial Surgery, Malmö University Hospital, Sweden for orthodontic treatment in conjunction with orthognathic surgery (forward described as orthognathic treatment). The mean age was 22.5 ± 7.4 years. All patients were recruited during two periods, between 1992-1995 and 2000-2002. Under the Swedish National Health Service, patients with such severe deformities are entitled to subsidized treatment. The exclusion criteria were craniofacial syndromes, systemic arthritic and muscular diseases, and a dentition of fewer than 24 teeth. Twenty-three patients withdrew from the study after the baseline examination (Figure 1). Thus, 98 patients (81%) met the inclusion criteria and the final sample comprised 38 males and 60 females, mean age 22.4 ± 7.5 years.

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Figure 1. Flow chart: the patients included in the study.

The control group, age- and gender-matched with the subjects undergoing treatment, comprised 56 subjects, 23 males and 33 females, mean age 23.4 ±7.4 years. The controls were recruited from general dental patients at the Faculty of Odontology, Malmö University, Sweden, and the Public Dental Health Clinic in Oxie, County Skane, Sweden. The inclusion criteria were normal occlusion, or minor malocclusions for which neither orthodontic treatment nor ortho gnathic surgery was indicated. The same exclusion criteria applied to the control group as to the treatment group.

MethodsAll patients in the treatment group underwent pre- and postsurgical orthodontic treatment with fixed orthodontic appliances in both arches. Ten specialists carried out the orthodontic treatment and the treatment duration varied between 18 and 24 months.

The orthognathic surgery was undertaken by four oral maxillofacial surgeons at the Department of Oral Maxillofacial Surgery, Malmö. The methods for surgery and postsurgical fixation have been described in detail in Abrahamsson et al. (2012).

 

Study population n = 98

Treatment group Consecutive patients assessed for eligibility

n = 121

Refused treatment, n = 15

Baseline

~3years

Lost to follow-up Refused to participate in the follow up examination, n = 8

Treated patients n = 106

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In the treatment group, the masticatory ability, masticatory performance and signs and symptoms of TMD were assessed by means of a questionnaire, a test of masticatory performance and a clinical examination before and 18 months post-treatment. The interval between the two examinations was approximately three years. The questionnaire, the test of masticatory performance and the clinical examination were performed after treatment planning. The control group was examined at one occasion and in equal manner as the treatment group.

QuestionnaireThe following variables were addressed in the baseline and follow-up questionnaires: ability to masticate different kind of food; meat (yes/no), carrots (yes/no), toffee (yes/no), French loaf (yes/no) or coldcuts of ham, cheese and cucumber (yes/no). The subjects estimated their ability to masticate food on a visual analog scale (VAS) 0-100 mm with the end points “good” = 0 mm and “bad” =100 mm. The individuals also estimated the severity of overall symptoms of TMD on the following scale: 0 – little or none, 1- slight, 2 –moderate, 3 -severe, 4 -very severe.

Masticatory performance testFor assessment of masticatory performance (Edlund and Lamm, 1980), the individuals were instructed to chew round tablets of silicon impression material (Optosil®, Bayer, Germany) with a standardized weight. The test implies chewing for 20 strokes of 5 separate tablets. The chewed sample was expectorated in a plastic cup. The mouth was rinsed with water until all particles were removed from the mouth. The water was also collected in the cup and then filtered. The chewed material from each of the tablets was fractionated in a system of sieves with coarse, medium and fine meshes. Essentially, the more efficient the mastication was, the greater the quantity of material that passed through the finest sieve. The quantity of material was estimated by weight.

A masticatory performance value, by proportion of weight, was calculated for each test portion, and the mean of the best four values out of five was used as the masticatory performance index (MPI)

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(Edlund and Lamm, 1980). The index ranges from 0 to 100 - the highest number corresponds to the highest performance value. Data of the MPI test was lost from 1 patient at baseline and another 6 patients at follow-up in the treatment group.

Clinical examinationThe clinical examinations were conducted at the Department of Stomatognathic Physiology at the Faculty of Odontology, Malmö University, by two calibrated specialists in stomatognathic physiology (Abrahamsson et al., 2012). The extra oral examination preceded the intraoral examination. The methods for the clinical examination and the registration of signs and symptoms of TMD have been described in detail previously (Abrahamsson et al., 2012). TMD pain was diagnosed according to Research Diagnostic Criteria for TMD (RDC/TMD) (Dworkin and LeResche, 1992).

The number of tooth contacts was recorded in habitual intercuspal position during maximal isometric biting force. The indication of contacts was registered in the maxilla by means of a thin double folded plastic-foil (GHM occlusion foil® 8 μm, Hanel –Ghm Dental, Germany). The markings by the foil were registered as follows: single dot = one contact; line = two contacts; region of several small markings = three contacts. The evaluation of the method error for measuring the number of occlusal contacts has been described earlier and was found to be low (Henrikson et al., 1998).

The skeletal and morphological occlusion was registered by methods described previously (Abrahamsson et al., 2012). The diagnoses in the treatment group were separated into sagittal and vertical discrepancies, according to a combination of morphological and cephalometric values (Table 1).

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Table 1. Distribution of sagittal and vertical discrepancies in the treatment group (n=98).

Skeletal discrepancies n

Sagittal discrepancies;

Class I 13

Class II 28

Class III 57

total 98

Vertical discrepancies;

Open bite 41

Deep bite 9

Normal vertical relation 48

total 98

Statistical Methods Significance (alpha) was set at 0.05. The test was 2-tailed, i.e. an effect in either direction was analysed. With the proposed sample size of 35 in each subgroup, the study had a power of 89.8% to yield a statistically significant result. This computation assumed that the difference in proportions was 0.30 (specifically, 0.05 vs 0.35) in prevalence of TMD pain. This effect was selected as the smallest effect that would be important to detect, in the sense that any smaller effect would not be of clinical or substantive significance.

Differences between groups. Pearson’s chi square test with Yate’s correction for continuity was used when 2 x 2 cross tabulations were applicable. When the expected cell value in a 2 x 2 table was less than 5, Fisher’s exact test was used. The two-sample t-statistic was used to compare means in numerical variables. To calculate ordinal data Mann Whitney test was used. The tested masticatory performance index was con-sidered a numerical variable while the masticatory ability on a VAS

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was considered ordinal data. When comparing means between sub groups of sagittal and vertical discrepancies, analysis of variances (ANOVA) was used.

Differences within groups before and after treatment. McNemar exact test was used to compare ordinal data and the paired t-test for the numerical data.

For multivariate analysis a linear regression analysis, with the enter method to adjust for age and group belonging, was used.

ReSUltSAnalysis of those who withdrew from the treatment group (n = 23, 19 %), shown in Figure 1, did not differ from the final study group with respect to age, gender, self-estimated masticatory ability or masticatory performance. Thus, the patients who completed the study were considered to be representative of the initial study sample.

Self estimated masticatory abilityA large individual variation of the masticatory ability was found within the groups (Figure 2). At baseline, the patients (Mean = 52.2 ± 29.5, Median = 50.0) rated their masticatory ability lower than the control group (Mean = 85.7 ±17.4, Median = 92.0 P < .001), Figure 2. They also found it more difficult to chew meat (P < .001), raw carrots (P = .019), toffee (P = .002), French loaf (P < .001) and coldcuts of ham, cheese, cucumber (P < .001). At follow-up the masticatory ability had significantly improved in the treatment group (Mean = 83.9 ± 19.2, Median = 92.0 P < .001) and reached similar level as in the control group implying no significant difference between the groups.

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Figure 2. Before treatment the treatment group estimated their mas-ticatory ability, on a VAS, to be poorer than what the control group did (P < .001). After treatment there was no significant difference in the reported masticatory ability between the two groups. Fifty percent of the individuals have values within the box. The bar across the box represents the median. The whiskers show the largest and smallest value that is not an outlier. o = outliers, values more than 1.5 box lengths from the box; star = extreme, values more than 3 box lengths from the box.

Factors influencing the self estimated masticatory abilityOcclusal contacts during maximal biting pressure, severity of overall symptoms of TMD and study group belonging explained 45 percent of the total variation of the masticatory ability in a linear regression analysis adjusted for age (Table 2). The masticatory ability was in the regression analysis negatively affected by fewer occlusal contacts during maximal biting pressure, a higher severity of the overall symptoms of TMD and belonging to the treatment group (Table 2).

   

 

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Table 2. Multiple linear regression analysis (enter method) of the relation between self estimated masticatory ability and explanatory variables, adjusted for age.

explanatory variables B Se B P lower MPI

Study groupGenderNumber of occlusal contacts during maximal biting pressureSeverity of overall symptoms of TMD (verbally)

21.3

7.4

1.1

- 8.0

4.5

3.90.3

1.9

< .001

NS< .001

< .001

Treatment group

With lower number of occlusal contacts

With more severesymptoms

B = Regression coefficient; SE B = Standard error of B. Total factor of explanation (R2) = 45%.

Masticatory performanceThere was a large individual variation of the masticatory performance index (MPI), within the groups (Figure 3). At baseline, the treatment group had a lower MPI than the control group (Mean = 10.4 ± 10.4, Median = 7.1 versus Mean = 37.3 ± 16.8, Median = 37.1 respectively, P < .001, 95 % CI 21.3 – 30.9). For the treatment group the MPI increased at follow-up (Mean = 21.0 ± 19.2, Median = 12.9, P < .001) but was still lower than the control group (P < .001, 95 % CI 10.2-22.4).

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Figure 3. Individuals in the treatment group had a lower MPI com-pared with the control group (P < .001). Fifty percent of the individ-uals have values within the box. The bar across the box represents the median. The whiskers show the largest and smallest value that is not an outlier. o = outliers, values more than 1.5 box lengths from the box.

After stratifying the material into sagittal and vertical deformities it was found that the MPI improved after treatment in patients with a Class III malocclusion, from 11.7 ± 10.5 to 25.3 ±19.6 (P < .001, 95 % CI 8.2-19.0), and in patients with an open bite, from 7.0 ± 6.8 to 18.1 ± 18.7 (P < .001, 95 % CI 5.5 – 16.8). No significant alteration was found in patients with deep bite or Class II malocclusion.

Factors influencing MPI Variables like; gender; number of occlusal contacts during maximal biting pressure; self reported severity of overall symptoms of TMD and TMD pain diagnoses were all found to significantly have an influence on the MPI at baseline (Table 3). No association was found between age and MPI.

     

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Table 3. Statistically significant differences of the mean Masticatory Performance Index (MPI) by levels of Occlusal factors and TMD in the whole study group (Both Treatment and Control group) n = 153.

Influencing binary parameters

n MPI Sd p 95% confidence interval of the difference

Female 93 17.0 16.9

Male 60 25.3 19.6 .008 2.2–14.4

Number of occlusal contacts during maximal biting pressure

< 10 37 7 9.5

≥ 10 116 24 18.7 <.001 12.6–21.9

One diagnosis of TMD pain

No 115 23.8 18.8

Yes 38 9.6 12.2 <.001 9.6–18.7

Severity of overall symptoms of TMD

Insignificant-light

106 24.5 19.3

Moderate-very severe

47 10.6 11.8 <.001 8.9–18.9

A linear regression analysis, adjusted for age and group belonging, explained 37 % of the total variation of MPI (Table 4). Number of occlusal contacts during maximal biting pressure was the factor that had the highest influence on MPI and indicated that MPI increased with a higher number of contacts during maximum biting pressure. Open bite was the only kind of dentofacial deformity having a significant influence on MPI, i.e. open bite had negative effect on MPI.

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Table 4. Multiple linear regression analysis (enter method) of the relation between tested masticatory performance (MPI) and explana tory variables, adjusted for age and group belonging (treatment group or control group).

explanatory variables B Se B P lower MPI

Gender -6.5 1.9 .001 Women

Number of occlusal contacts during maximal biting pressure

0.6 0.1 < .001 With lower number of occlusal contacts

Open bite -4.3 2.0 .031 With open bite

Severity of overall symptoms of TMD (verbally)

-2.5 1.1 .028 With more severe symptoms

Pain in the masticatory muscles/TMJs

4.7 2.6 NS

B = Regression coefficient; SE B = Standard error of B. Total factor of explanation (R2) = 37%.

Occlusal contactsBefore treatment, there were no significant differences in number of teeth between the treatment (Mean = 28 ± 1.9) and the control group (Mean = 29 ± 2.0). The treatment group had significantly fewer intercuspal contacts during maximum biting pressure than the control group (Mean = 13 ± 6.4 versus 18 ± 5.5, P < .001, 95 % confidence interval (95 % CI) 3.5 – 7.5). At follow-up the number of occlusal contacts increased in the treatment group (Mean= 16 ± 6.1, P < .001, 95 % CI 2.1-5.2) and did not significantly differ from the control group. When sub groups of sagittal and vertical discrepancies were assessed before treatment, the 41 patients with open bite had significantly fewer intercuspal contacts during maximum biting pressure compared with the 9 patients with deep bite (Mean = 10 ± 5.0 versus 19 ± 9.5, P < .001) and those 48 patients with normal vertical relation (Mean = 14 ± 5.8, P = .014). No significant differences between sagittal discrepancies were found before treatment. After treatment there were no differences between neither of the sub groups.

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dIScUSSIonThe main findings in the present study were that patients with dentofacial deformities had impaired masticatory ability and performance in comparison with the control group before treatment. Furthermore, the masticatory ability and masticatory performance improved after orthognathic treatment why the hypotheses could not be rejected. The number of occlusal contacts during maximal biting pressure and the severity of overall symptoms of TMD were found to have an influence on both masticatory ability and masticatory performance.

In the present study both the masticatory ability and masticatory performance significantly improved after treatment. The masticatory ability was at the follow-up estimated equal in the patient and control group. However, the masticatory performance index did not reach the same level as in the control group, which may be explained by the limited follow-up period. It has been discussed that a follow-up period of 5 years after treatment, to be compared with 18 months in the present study, would be more appropriate and beneficial for the masticatory performance. Explained by that the musculature may need time to readapt after surgery before regaining full strength (van den Braber et al., 2006; Magalhaes et al., 2010). Van den Braber et al (2006) showed an improvement in masticatory performance in retrognathic individuals 5 years after treatment, which was not found in previous studies, with shorter follow-up, performed by the same research group (van den Braber et al., 2004; van den Braber et al., 2005). Neither did Zarrinkelk et al (1995) find any difference in masticatory performance 2 to 3 years after orthognathic treatment of individuals with dentofacial deformities. Anyhow, an interesting finding in the present study was that the individuals with a Class II bite did not show an improvement, which was in line with van Braber et al (2006).

The difference in masticatory performance between the treatment group and the control group before treatment is in accordance with other studies using similar testing methods (Henrikson et al., 1998; English et al., 2002;). English et al (2002) found that individuals with malocclusions had impaired masticatory performance compared

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with individuals with normal occlusion. They also found that individuals with a Class III malocclusion had the lowest masticatory performance compared with other malocclusion groups, however, vertical discrepancies were not considered. Their result was in contrast to the present study, in which an open bite was the only discrepancy that was found to have an impact on the MPI.

The linear regression analysis only explained 45 % of the total variation of the masticatory ability and 37 % of the total variation of MPI. Salivary flow rates, body builds and muscle strength are variables not assessed in the present study but are probably influential factors when evaluating mastication. It has been discussed that maximum bite force is related to body size (Proffit et al., 1983) and it has been shown that females have less muscular bite force than males (Helkimo et al., 1977; Tate et al., 1994). This could be a possible explanation to the result in this study where women were shown to have a lower masticatory performance compared with men.

Moreover, the positive treatment outcome implying increased amount of occlusal contacts may be one explanation of improvement in masticatory performance. The number of occlusal contacts has been suggested to be of major importance for the masticatory performance (Zarrinkelk et al., 1995; Kobayashi et al., 2001). This is in line with the present study since it was found that before treatment the number of occlusal contacts during maximal biting pressure was the greatest explanatory factor of the variance of the MPI. It is further confirmed by the fact that the open bite, the malocclusion with the lowest number of occlusal contacts, was another explanatory factor in the regression model.

A shortcoming of this study was the limited part in the questionnaire assessing masticatory ability. After this study was initiated, in 1992, a Jaw Function Limitation Scale (JFLS) has been developed (Ohrbach et al., 2008). The JFLS has been shown to exhibit good reliability and validity assessing limitations in mastication, jaw mobility and verbal and emotional expression (Ohrbach et al., 2008). The questionnaire in this study focused solely on mastication and it would have

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been interesting to extend it according to the JFLS to come to an understanding if patients with dentofacial deformities are limited in their daily life when talking, swallowing, in facial expressions etc.

A silicon material (Optosil®, Bayer, Germany) was chosen for testing masticatory performance (Edlund and Lamm, 1980). Silicon material and the sieving method has been used in other studies (Henrikson et al., 1998; English et al., 2002; van den Braber et al., 2005, Henrikson et al., 2009) but in the study by van den Braber et al (2005) the Optosil tablets were modified by heat to gain a softer consistency. It is known that the newer type of Optosil has higher tear strength than the one used in the study by Edlund and Lamm (1980). The main requirement of an ideal test material for studying masticatory efficiency with fractional sieving is that the material is pulverized by chewing in such a manner that the degree of pulverization can be clearly established and that the material is unaffected by water and saliva. If this requirement is met, both the fractionating and the laboratory procedure can be simplified. Optosil ® (Bayer, Germany) fulfilled the above mentioned criteria (Edlund and Lamm, 1980) and another advantage of using artificial food is that it can be standardized and easily reproduced in both form and consistency. Moreover, it has been reported that the use of artificial food gives a lower test-retest consistency variation compared with for example peanuts (Olthoff et al., 1984).

An interesting finding in the present study was that the self-estimated masticatory ability was significantly affected by group belonging but not by gender. In contrast to masticatory performance that was significantly affected by gender but not by group belonging. Could it be that patients, with dentofacial deformities, men and women equally, are more prone to report impaired masticatory ability since they feel it is a more acceptable reason for having orthognathic treatment compared with for example esthethics? And therefore the gender gap, found in masticatory performance disappears. Moreover, with these results in mind it would be of interest to assess the impact of oral health related quality of life on masticatory ability in patients with dentofacial deformities. However, this was not in the scope of the present study.

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Conclusions• Masticatory ability and performance increased after orthogna-

thic treatment. • The number of occlusal contacts and severity of overall symp-

toms of TMD influenced both the masticatory ability and performance.

• Open bite had a negative effect on masticatory performance.

AcknowledgementWe would like to thank Per-Erik Isberg, Department of Statistics, Lund University, Sweden for advice about statistical methods and performance of the statistical analyses.

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cecilia abrahamSSonmaSticatory function and temporomandibular diSorderS in patientS with dentofacial deformitieSStudies before and after orthodontic and orthognathic treatment

isbn 978-91-7104-395-5

issn 0348-6672

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Swedish Dental Journal, Supplement 231, 2013