Midline Final / orthodontic courses by Indian dental academy

TREATMENT OF MIDLINE TREATMENT OF MIDLINE DISCREPANCIES AND SKELETAL DISCREPANCIES AND SKELETAL ASYMMETRIESASYMMETRIES

INDIAN DENTAL ACADEMY

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INTRODUCTIONMidline coordination and relative symmetry are basic to an appreciation of facial harmony and balance. Although a subtle asymmetry of the midlines is within normal limits, significant midline discrepancies can be quite detrimental to dentofacial esthetics.


Stedman’s Medical Dictionary defines symmetry as “equality or correspondence in form of parts distributed around a center or an axis, at the two extremes or poles, or on the two opposite sides of the body.”

Clinically, symmetry means balance while significant asymmetry means imbalance.

Facial asymmetry, was probably first observed by the artists of early Greek staturary


Mammals have marked asymmetry as to the placement of the viscera in the body cavity.

Also functional as well as morphological asymmetries, e.g. right and left handedness, preference for one eye or one leg.

Some asymmetries are embryonically rooted and are associated with asymmetry in the central nervous system.


Each human being a unique individual. Variations in the size, shape and

relationship of the dental, skeletal and soft tissue facial structures are important in providing each individual with his or her own identity.

Perfect bilateral body symmetry is largely a theoretical concept that seldom exists in living organisms


Asymmetry in craniofacial areas can be recognized as differences in the size or relationship of the two sides of the face. This may be the result of discrepancies either in the form of individual bones, or a malposition of one or more bones in the craniofacial complex. The asymmetry may also be limited to the overlying soft tissues.


Peck and Peck evaluated bilateral facial symmetry in 52 “exceptionally well-balanced” white adults and observed that there is less asymmetry and more dimensional stability as the cranium is approached.

In a study, Vig and Hewitt evaluated 63 posteroanterior cephalograms of “normal” children 9–18 years of age.

Normal, in this case, meant that the child exhibited no clinically evident facial asymmetry


An overall asymmetry was found in most of the children with the left side being larger.

The cranial base, and mandibular regions exhibited a left side excess while the maxillary region showed a larger right side.

The dento-alveolar region exhibited the greatest degree of symmetry.

Vig and Hewitt concluded that compensatory changes seem to operate in the development of the dentoalveolar structures and enable bilateral symmetrical function and maximum intercuspation to occur, thus minimizing the effects of the underlying asymmetry


Results from a study by Miller et al indicate that the maxillary midline is situated in the exact middle of the mouth (using the philtrum as a guide) in approximately 70% of individuals, but that the maxillary and mandibular midlines coincide in only one fourth of the population.


Midline correction should be undertaken from the initiation of treatment and once all midlines are coordinated they should be maintained as a guide for any further force systems used in completing the case

Differential diagnosis and appropriate inter and intraarch mechanotherapy is necessary.


Careful attention to midline coordination and attendant facial symmetry can aid the practitioner in achieving the following:

1. Maximum intercuspation and function2. Stability in the finished result3. The promotion of anterior dental and

facial esthetics4. A decrease in the potential for TMJ

dysfunction5. Maximizing self-satisfaction by

achieving an increased number of ideal orthodontic results


Etiology of midline midline discrepanciesdiscrepancies andand Asymmetry Includes a) Genetic or congenital malformations

e.g. hemifacial microsomia and unilateral clefts of the lip and palate; multiple neurofibromatosis

b) Environmental factors, e.g. habits and trauma;

c) Functional deviations, e.g. mandibular shifts as a result of tooth interferences.


d. Epigenetic factors; and acquired factors, for example, infections or pathologyFacial asymmetries can be classified based on the time of onset, as outlined by Picuiniemi.

Anomalies may originate during the prenatal period and be embryonic in nature or may have developed during the fetal term.


Mandibulofacial asymmetries have a postnatal expression.

The causes are - Tumors in the TMJ region Condylar hyperplasia or hypoplasia, Hemifacial atrophy (Romberg

syndrome), Scleroderma


Inflammatory arthritic disease Ankylosis Intra-articular disorders with an

associated arthrosis Condylar fracture Damage to a nerve may indirectly lead

to asymmetry from the loss of muscle function and tone.


Other factors - Intra-uterine pressure during pregnancy

and significant pressure in the birth canal during parturition can have observable effects on the bones of the fetal skull. Molding of the parietal and facial bones from these pressures can result in facial asymmetry.

Osteochondroma of the mandibular condyle results in facial asymmetry, open bite on the involved side, and mandibular deviation


Localized factors Early loss of a deciduous tooth Rotation of the entire dental arch and

its supporting skeletal base. Asymmetric crowding in anterior section Prolonged retention of primary tooth Periodontal trauma and migration. Juvenile rheumatoidarthritis Dental caries Mandibular fractures Drifting and tipping of teeth. Congenitally missing teeth


Lundstrom stated that asymmetry can be genetic or nongenetic in origin and is usually a combination of both.

Some right-left asymmetries in the oral cavity could be the result of environmental factors, eg,

sucking habits or asymmetric chewing habits caused by dental caries, extractions, and trauma.


Hemifacial microsomia

Facial photographs of a patient with hemifacial microsomia. The discrepancies involve one side of the face only and include asymmetries in the mandibular body, ramus and condyle as well as the external and internal structures of the ear.


Asymmetry of Face due to fracture of TMJ


Intrauterine moulding resulting in midface deficiency


Deformation of second branchial arch with corresponding malformations


Facial asymmetry due to missing masseter muscle


Hemimandibular hypertrophy


According to Lundstrom, asymmetry can also be described as qualitative (all or none) or quantitative.

Examples of Quantitative asymmetries – differences in the number of teeth on each side

The presence of a cleft lip and palate. Qualitative asymmetries could be

differences in the size and shape of teeth, their location in the arches


Skeletal asymmetries-classification Obwegeser classification as described in the

Journal of Maxillofacial Surgery in 1986. Hemimandibular elongation Hemimandibular hyperplasia. It is important to differentiate between the two

types because: (1) The timing of growth cessation is different(2) The dentoalveolar compensations are different (3) The likelihood of successful interception is

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Hemimandibular elongation Can occur as elongation either of the

condyle or ramus in the vertical plane or the mandibular body in the horizontal plane.

Combinations are also possible.


Features Mandible deviates to the opposite side of the

deformity Exhibits flattening of the gonial angle on the

affected side The mandibular borders and occlusal planes

will superimpose on a centric relation cephalometric radiograph because there is no vertical component to the asymmetry


Mandibular elongation tends to stop when body or facial growth stops as it follows more of a somatic growth curve.

Presence of a unilateral posterior crossbite on the opposite side from the elongation.

Excessive growth occurs along normal growth axes.


Hemimandibular hyperplasia Recognized by entire half of the

mandible being enlarged. Features Mandibular lower border midline

“notching” on the panoramic film Increased distances from the tooth

apices to the lower border of the mandible when compared to the normal contralateral side.


Hyperplasia, tends to grow longer exhibiting “latent” growth.

The midline usually deviates to the same side as the deformity.

Hyperplasia shows a normal or more acute gonial angle due to excessive vertical development.

Vertical differences in both planes can be observed in mandibular hyperplasia.


Hemimandibular hyperplasia, however, is just about always overgrowth as in Angle Class III malocclusion that results from mandibular prognathism.

Most hemimandibular elongations are, in fact, Angle Class II or hypoplasias. This is why they are thought of as a variation of normal growth and not pathoses.


Structural classification of dentofacial asymmetriesa. Dental asymmetries: These can be

due to: local factors such as early loss of deciduous teeth , congenitally missing tooth, and habits such as thumb sucking. asymmetries in mesiodistal crown diameters.

Garn et al. found that tooth size asymmetry generally does not involve an entire side of the arch.


Teeth in the same morphological class tend to have the same direction of asymmetry.

Asymmetry tends to be greater for the more distal teeth in each morphological class i.e. the lateral incisors, second premolars and third molars.

Asymmetry may also be confined to the shape of the dental arches.


b.Skeletal asymmetries: The deviation may involve one bone such as the maxilla or mandible , or it may involve a number of skeletal and muscular structures on one side of the face, e.g.hemifacial microsomia

c. Muscular asymmetries- hemifacial atrophy or cerebral palsy.

Abnormal muscle function often results in skeletal and dental deviations


Patient with a skeletal mandibular asymmetry. The mandibular dental midline was shifted 7.0 mm to the left of the maxillary midline. The right side had a severe Class III relationship while the left side was closer to a Class I relationship


Post treatment photographs. Despite correction of the skeletal asymmetry some soft tissue facial asymmetry remained. Note that the mandibular midline was slightly over-corrected


d. Functional asymmetries: These can result from the mandible being deflected laterally or antero-posteriorly, if occlusal interferences prevent proper intercuspation

May be caused by a constricted maxillary arch or a malposed tooth, TMJ derangements and in-coordination


Intraoral view of a patient in centric relation. Note the shift in the lower midline. Posterior occlusion was cusp on cusp bucco-lingually.


CLASSIFICATION -According to Steenbergen and Nanda

Dental asymmetries can be divided into four groups:

1. Diverging occlusal planes2. Asymmetric left to right buccal

occlusion, with or without midline deviation

3. Unilateral crossbite4. Asymmetric arch form


DIAGNOSIS A: Clincial examination1. Evaluation of the dental midlines:

includes an evaluation of the dental midlines in the following positions: mouth open; in centric relation; at initial contact; and in centric occlusion


Location of midline Various points (landmarks) can be identified from the

frontal head film, the frontal photographs, or by clinical examination

Additional landmarks, such as crista galli, the intermaxillary suture, and hard tissue pogonion,can be seen on the headfilm.

These points happen to fall along the same line,. Unfortunately, this does not always happen. Because of a genuine asymmetry or by

(1) an inability to visualize the structures, (2) head rotation in the cephalostat, (3) soft tissue flexibility, (4) an inexact technique.


A symmetrical head can produce an asymmetrical posteroanterior film if the head is improperly oriented

Any rotation of the head distorts the constructed midpoints, with the greatest discrepancy noted at landmarks farthest from the film


Connecting the points-soft tissue nasion, subnasale and soft tissue pogonion- also locates midline

Can give variable results when repeated by the same orthodontist.

Some authors have proposed constructing additional landmarks by identifying bilateral structures and determining the midpoint between them.


Bisecting a line that connects corresponding bilateral landmarks may be invalid since absolute symmetry between right and left does not exist.

The closer bilateral structures are to the center of the face, the smaller the variation is in the midpoints as determined by a bisector


Another method for determining the facial midline is to establish a horizontal plane from skeletal structures and to construct a perpendicular line from a midpoint landmark

Two problems with this method. Difficulty of determining which landmark or

constructed point to use, Any small variation in the horizontal plane

can produce a large deviation in the facial midline.


A commonly used guide in the X-Z(occlusal) plane, in establishing a treatment midpoint, is the median palatal raphe.

Its limitations include Errors in the construction of a single line

since curvature may be present Correlation to other soft tissue facial

structures is lacking. www.indiandentalacademy.com

In some patients, the facial midline is not a straight line but rather a curve; hence, the facial midline could be referred to as the facial mid-arc.

Philtrum of upper lip can also be used to establish maxillary midline.


Mandibular midline It is more precise to mark the

anteriorpoint of the mandibular midline using the mental spine film or by using the lingualfrenum (Korkbaus1939).

The posterior point for construction of the mandibular midline is determined by a perpendicular, which runs from the posterior edge of the midpalatal raphe from the maxillary to the mandibular cast.


One more method is making lines connecting the corners of the mouth (chelion to chelion), the transverse occlusal plane, and the upper and lower lip horizontals

Soft tissue midpoints (cupid's bow, center of the philtrum, and subnasale) are projected onto the horizontal planes and are visually compared to the incisor midpoints. (TOP = treatment occlusal plane.)


Patient determination of midline


Found on apical bases of maxilla and mandible.

It is necessary to construct the apical base midpoints by placing a point at approximately the midpoint of each of the incisor roots occlusogingivally and then finding their average mediolaterally

These two midpoints, one in the maxilla and one in the mandible, are known as the upper and lower apical base midpoints

Incisor-Apical Base Midpoints


Incisor-Apical Base Midpoints Used to evaluate skeletal asymmetry In the sagittal view (Y-Z plane),

measuring the apical base points, A and B, relative to the occlusal plane, is helpful in determining the anteroposterior denture base discrepancy.

The farther apart they are, the more difficult it is to correct the Class II or Class III malocclusion.


In the frontal view (Y-Xplane), measuring the apical base midpoints relative to the transverse occlusal plane allows one to determine the transverse denture base discrepancy.


Rationale for selecting Biological : Forces exerted by muscles, transseptal

fibers and orthodontic appliances tend to tip teeth about a point, generally near the root center as measured from the cementoenamel junction to the root apex.

Apical base midpoints serve as useful functional landmarks in planning the position of the treatment midpoint and midline


MEASUREMENT A perpendicular line from the upper and

lower apical base midpoints is extended to the respective treatment occlusal plane.

Ideally, the upper and lower perpendicular lines coincide at their intersection with the occlusal plane, a sign of no transverse apical base discrepancy

A transverse apical base discrepancy exists when the upper and lower apical base midpoints do not coincide


In some patients, orthognathic surgery is required to achieve coincidence of the apical base midpoints.

For less severe apical base midpoint discrepancies or for patients who wish to avoid surgery,the choice of treatment midpoints is –

Asymmetric mechanics Minimal lateral translation Anchorage control


The posterior midpoint It is the geometric center of the arch

circumference. Starting from the desired position of the

first molars (red line), equal radii are marked off on the right and left sides (blue lines). Where the right and !eft radii cross anteriorly, the posterior midpoint is located.

Determines the mesiodistal location of the posterior teeth.


Intramaxillary asymmetry

-Transverse symmetry-Anteroposterior symmetry

These symmetry analyses estimate the right-left differences in transverse and anteroposterior tooth positions (Korbitz1909).

The midpalatal raphe defined by two anatomical points on the palatine raphe is the reference plane for the transverse symmetry analysis.


The tuberosity plane is the reference plane for comparing anteroposterior symmetry.

This plane is perpendicular to the midpalatal raphe and runs through the distal-most tuberosity.


Maxillary midline


The following findings are derived from this type of intramaxillary assessment of the study casts.

Symmetric/asymmetric width development between right and left sides of the arch

Congruence/incongruence between dental midline and skeletal midline of the arches (dental midline shift)


Reveals the following: Asymmetric mesiodistal tooth position of

corresponding teeth in the right and left sides of the dental arches

This analysis serves to diagnose any mesial tooth drift.

This involves drawing a line parallel to the tuberosity plane, which runs through the posterior surface of the distal-most first molar, and comparing the sagittal distances of the individual posterior teeth

Analysis of Anteroposterior Symmetry


2. Vertical occlusal evaluation: The presence of a canted occlusal plane The cant in the occlusal plane can be

readily observed by asking the patient to bite on a tongue blade to determine how it relates to the inter-pupillary plane.


3. Transverse and antero-posterior occlusal evaluations

Asymmetry in the bucco-lingual relationship e.g. a unilateral posterior crossbite


4. Transverse skeletal and soft tissue evaluation: In addition to the bilateral structural comparisons, deviations in the dorsum and tip of the nose as well as the philtrum and chin point need to be determined


The clinical examination should include an intraoral examination with an evaluation of the dental and facial midlines and detection of TMJ derangements.

Operator-assisted natural head position, mandibular centric relation, and soft tissue in repose are used to accurately assess the frontal and profile views.


•Facial and intraoral photographs are indispensable.A thorough facial examination must be conducted to evaluate asymmetries in facial morphology


Examination of each dental arch and quadrant should be evaluated by using-

Oriented dental casts Occlusograms Symmetroscopes


The diagnosis of a rotary displacement of the maxilla may require further evaluation by mounting the dental casts by face-bow transfer on to semiadjustable articulator

Finally, mounted dental casts and model surgery are essential in planning treatment for patients requiring surgical orthodontic


B: Radiographic examination

1.The lateral cephalogram:, provides useful information in ramal height, mandibular length and gonial angle.

It is limited by the fact that the right and left structures are superimposed on each other and are at different distances from the film and x-ray source resulting in significant differences in magnifications.


2.The panoramic radiograph: The presence of gross pathology, missing ,supernumerary teeth can be determined.

The shape of the mandibular ramus and condyles on both sides can be grossly compared

Geometric distortions are significant


3.Postero-anterior projection: It is a valuable tool in the study of the right and left structures since they are located at relatively equal distances from the film and x-ray source

Comparison between sides is therefore more accurate

PA cephalograms can be obtained in centric occlusion as well as with the mouth open.

The latter position might help determine the extent of the functional deviation


Refined diagnostic tools, such as computerized tomographic images and stereo photogrammetry, allow three-dimensional analyses of the craniofacial complex. These methods can generate, with the aid of a computer, a three-dimensional image of the patient's face. With a coordinate system, the asymmetries can be quantified.


TREATMENT Dental asymmetries and a variety of functional

deviations can be treated orthodontically. Significant structural facial asymmetries are

not easily amenable to orthodontic treatment. These problems may require orthopedic correction during the growth period and/or surgical management at a later point.

Patient complaints and desires need to be addressed since they may vary from unrealistic expectations to a lack of concern even in the presence of large deviations.


Treatment Strategies Breakspear advocates adapting the

occlusion by "stoning" (occlusal equilibration).

This method of treatment allows the occlusion to function more properly but may not correct the dental or facial asymmetry.


Lewis advocates a sliding yoke and intermaxillary elastics.

He states midline deviation exists mostly in Class II cases.

The more frequent causes are Mandibular shift resulting from a posterior crossbite Tipping or drifting of the teeth Lateral mandibular rotation resulting from occlusal

interferences, arch asymmetries, tooth size discrepancies

Overretraction of the canines on one side


Angle used a Class III elastic with a anterior diagonal elastic in conjunction with arch expansion for the correction of midline discrepancies


Proffit admits that minor discrepancies in midline coordination can be handled in the finishing stages with asymmetric Class II and Class III elastics

Or by using unilateral Class II or Class III intermaxillary elastics in tandem with an anterior diagonal elastic ,after extraction spaces have been closed.


If one side of the arch is corrected and other side is not, then heavy unilateral class II or class III elastics can be used on the affected side.

If there is abnormal transverse relationship (cross bite) posteriorly leading to mandibular shift ,POSTERIOR CROSS -ELASTICS can be given


Parallel cross-elastics can also be given when entire maxilla is displaced transversely in relation to mandible.

In finishing stages rectangular wire must be changed to round wire(.016 or .018) if asymmetric or unilateral elastics are used to facilitate midline correction.


Elastics along with coil springs can also be used.

Open coil springs on the side of deviation

Close coil springs on the side opposite of deviation

Activation should be controlled.


Alexander advocates use of a heavy anterior diagonal elastic supported by a Class II or Class III elastic, depending on whether the original malocclusion was a Class II or Class III during the finishing stages,

In an extraction case it may be performed during space closure ,anterior diagonal elastic is then attached to the closing loops


Begg and Kesling state that the proper balancing of space-closing classI elastics coupled with appropriate Class II traction during stage II keeps the midlines coordinated


Augmenting a unilateral Class II elastic, an anterior diagonal elastic, and a Class III elastic with uprighting springs to "walk the teeth" can effect midline changes


Begg also advocated use of asymmetric arch wire form for correcting asymmetric arches

He advocated use of round wire as it leads to efficient tipping facilitating midline correction.


Hazards of Asymmetric elastic wear May cause undesirable side effects if

skeletal balance already exists. The force vectors created by the

elastics impart a moment to the mandible, ie, a tendency for rotation that may lead to a transient alteration in mandibular position.


If mandibular shift or rotation is not the causative factor but rather the midline deviation was a result of a dental shifting or drifting of teeth, with the face being symmetric, then use of such mechanics would effect a change in mandibular position , potential for TMJ dysfunction.

Canting of occlusal plane can occur as a result of vertical force vector of elastics.


Gianelly and Paul advocated a biomechanical system for midline correction with second-order bends used to move teeth on one side distally and create a space for shifting the midline.


Lewis proposes the use of distal spring mechanics as opposed to second-order bends, bolstered by a sliding yoke off Class II traction to distalize upper posterior teeth in cases exhibiting arch asymmetry


Strang and Thompson introduced a double vertical spring loop assembly to move the four incisors "en masse"

A modification of this arch wire (rectangular) configuration using round wire has come


A 0.020-inch arch wire is divided into three parts: two posterior and one anterior. The arch wire thus is segmented.

The two vertical loops allow for stabilization of the posterior segments as long as molar stops are used; hence only anterior movement takes place. The incorporation of a helix in each loop provides greater flexibility and longer activation.

To activate, a ligature is passed through the circle on the closing loop side and tied to the contralateral lateral incisor bracket. Each tooth has been individually ligated to the anterior section of the arch, each posterior section having been ligated together as a unit.


The closing loop is constructed as close as possible to the canine, with the section to be activated lying anterior to the helix.

When the closing loop is activated, the opening loop is condensed and a push-pull reaction occurs whereby all four anterior teeth shift "en masse" toward the desired side


In cases in which the midline discrepancy is very slight (1 to 2 mm), it is tempting to tip the anterior teeth into a position that coordinates with the facial midline with the help of removable appliances such as finger spring.


Discrepancies due to bodily rotation as a result of crowding especially in mixed dentition are corrected -by using fixed appliance in the anterior section

-relieving the crowding -teeth are then pushed to attain a

proper midline, by using coil springs on side of deviation


Other appliances Unilateral molar distalization

appliances: -power arm face bow -spring attachment face bow -soldered arm face bow

Asymetric head gear Pendulum appliance


Power arm facebow: In this design the side to receive more

distalizing force is longer and wider than the other

Soldered offset facebow: Here the outer bow is attached to the side

favored to receive the distalizing force Spring attachment face bow bilateral face bow but with a open coil spring

placed distal to the stop on the side to be distalized


Asymmetric Extractions Used in the Treatment of Patients With Asymmetries

Creative approach for managing dental asymmetries is to extract a combination of teeth that will simplify intra-arch and interarch mechanics.

This reduces the dependency on patient compliance for elastic wear and may even shorten treatment time.


A case presenting a number of dental arch asymmetries including: retained mandibular left second deciduous molar; congenitally missing mandibular left second premolar; and unilateral anterior crossbite between the maxillary lateral incisor and mandibular canine.


Post treatment intraoral, facial and model photographs of the same patient. Treatment included extraction of the deciduous tooth and three premolars


Mandibular Dental Midline Deviation with Skeletal Symmetry In 50% of all Class II malocclusions, majority have

distally positioned mandibular molars on the Class II side with mandibular canine on that side also positioned distally.

If such a patient presented with the maxillary dental midline coincident with the facial midline,, a three- premolar extraction plan may be done

The extraction of a mandibular premolar on the Class I side relocates the canine in a more distal position to match the contralateral canine. The extraction of two upper premolars would maintain the maxillary midline symmetry to the facial midline.


If the molar on the Class II side is in an end-on relationship, Class I closure mechanics can be used in all three extraction buccal segments.

Differential extraction pattern on the Class II side, such as the removal of a maxillary first premolar and mandibular second premolar to help lose lower molar anchorage can also be used

The extraction of a mandibular premolar on the Class II side may minimize the flaring of incisors from Class II elastics by providing arch space for the mandibular molar to advance


Unilateral Class III malocclusion One premolar extraction on the Class III

side would allow for primarily Class I closure mechanics

If the molar is in a full-step Class III relationship, a lingual arch that is either passive or unilaterally activated can be used to maximize molar anchorage on that side.


Maxillary Dental Midline DeviationWith Skeletal Symmetry In the adult patient, non extraction correction

of the Class II buccal segment is less predictable.

Removal of a maxillary premolar on the Class II side would facilitate correction of the canine to a Class I relationship with no extraction in lower arch.

A passive or tightly activated transpalatal arch could be used to control molar anchorage, and space closure could be accomplished primarily through Class I mechanics


If extractions in the mandibular arch are necessary because of excessive crowding, and if a Bolton's tooth size discrepancy exists, the extraction of a lower incisor or lower incisor proximal reduction may simplify the biomechanical complexity of the case


Maxillary and Mandibular DentalMidline Deviation With SkeletalSymmetry

A) Both deviated to one side Extraction of ipsilateral upper and

lower premolars may be the plan to follow.

The decision to extract first or second premolars or a combination of these is dependent upon the amount of midline correction that is desired, and molar anchorage requirement


b) If the maxillary and mandibular midlines are both off from the facial midline, but in this instance on opposite sides from each other, it is likely the result of asymmetric arch crowding.

The appropriate plan in this situation may be the extraction of an upper premolar on the Class II side and a mandibular premolar on the Class III side.


Jasper Jumper for mid line correction Significant midline discrepancies,

often due to anchorage loss, must sometimes be corrected during the last phase of orthodontic treatment.

The Jasper Jumper, a flexible sagittal force module, was designed for the correction of Class II high angle malocclusions.


Flexible Jumper produces a range of force from 1-16oz, depending on its length when the teeth occlude.

Therefore used asymmetrically--one side with conventional Class II mechanics, the other with Class III mechanics--to correct a midline discrepancy and a possible mandibular shift resulting from maxillary deficiency.


Case example- Diagnosis A 10-year-old male showed a moderate facial

asymmetry,. A functional crossbite on the right side, resulting from a

narrow maxilla and the mandibular deviation to the right in habitual occlusion.

The patient had a full-cusp Class II molar and cuspid relationship on the right side, but a Class I relationship on the left.

collapsed maxillary arch, upper and lower anterior crowding, and a palatally positioned maxillary right lateral incisor.


Treatment Progress Treatment was initiated with a bonded Minne-Expander,

using a spring force of about 450g, to correct the transverse discrepancy

A unilateral medium-pull headgear was fitted later to the molar tubes embedded in the buccal acrylic of the expander to improve the skeletal relationship and to help correct the maxillary asymmetry.

Leveling of the maxillary incisors and cuspids was initiated with Straight-Edge brackets

After five months of unilateral headgear wear, similar mechanics were continued with a transpalatal bar ,also activated unilaterally


Despite the asymmetrical orthodontic mechanics and good dental alignment, the midline discrepancy remained

It was decided to use asymmetrical Jasper Jumpers to obtain a more continuous and intensive force system on the maxillary complex.

During the asymmetrical jumper application, the stiffest possible rectangular stainless steel archwires --.017" X .025" maxillary and .018" X .025" mandibular--were placed

The transpalatal bar was kept in place to counteract any side effects of the asymmetrical mechanics on the maxillary arch.


After about four months of this treatment, the intrusive effect of the Class III jumper could be observed in the maxillary left anterior region, so a 4.5oz diagonal elastic (Zebra) was added from the maxillary left lateral incisor to the mandibular right lateral incisor.

By the end of sixth month, the midline was overcorrected and the posterior occlusion was satisfactory.


Asymmetrical intermaxillary elastics can correct midline discrepancy of more than 3mm,but extrusive vertical force vectors of Class III (F_1) and diagonal (F_2) elastics will theoretically exceed force vector of Class II side (F_3). Maxillary occlusal plane (MOP) may therefore be lower on left side, causing difficulties with fixed appliance mechanics. B. With asymmetrical Jasper Jumpers, vertical force vectors of Class III jumper (F_1) and diagonal elastic (F_2) are opposite.Even if forces are unequal, adverse effects will be less likely.


Clinical results seem to indicate condyle -fossa remodeling as a normal adaptation to the maxillary skeletal and overall occlusal changes.

The dental effects of this force system are reciprocal--the incisors moved bodily in opposite directions, while the direction and amount of movement were controlled by the sizes of the jumpers.

The asymmetrical jumpers were well accepted by the patients, and no breakage occurred.


Facilitation of Midline Correctionwith a Premolar Extraction Sequence CASE EXAMPLE- Diagnosis A 16-year-old male presented with the chief

complaint of buccally erupting canines .The upper and lower midlines were shifted to the right by 4mm and 2mm, respectively.

The patient had a convex profile, an obtuse nasolabial angle, a retrognathic mandible, and excessive upper and lower facial heights. The molar relationship was Class II on the right and Class I on the left; the overjet was 7mm.


Camouflage comprehensive orthodontic treatment was planned as follows:

1. Sequential extraction of the four first premolars, with the maxillary left first premolar removed before the contralateral first premolar to allow correction of the upper midline and to conserve anchorage.

2. Maximum anchorage from a mandibular lingual holding arch and high-pull headgear.

3. Extraction of maxillary second molars as needed.


Treatment Progress The maxillary left first premolar and

mandibular first premolars were extracted. The maxillary right first premolar was left

in place to prevent distal drift of the right canine.

Preadjusted .018" brackets were bonded and an .016" nickel titanium archwire was placed.


Functional asymmetries-treatment Mild deviations are corrected with minor

occlusal adjustments. Severe deviations need orthodontic

treatment to align the teeth and to obtain proper function.

Occlusal splints may be necessary to properly evaluate the presence and extent of the functional shift by eliminating habitual posturing and deprogramming the musculature.


Functional shifts can also be the result of a skeletal asymmetry

Rapid maxillary expansion, orthognathic surgery and orthodontic treatment may be indicated in the management of these cases


Treatment of asymmetrries A) diverging occlusal planes Canted anterior occlusal plane (in

transverse direction). The conventional treatment for this problem is the use of vertical interarch elastics to extrude the side of the occlusal plane that is farthest from the treatment occlusal plane. The vertical elastic exerts an extrusive force on both the maxillary and mandibular arches.


B)Canted maxillary anterior occlusal plane and a deep bite One -piece intrusion arch of 0.017 ´

0.025-inch titanium molybolenum alloy (TMA) is tied to that side of the anterior segment requiring intrusion.

The intrusive force level should be approximately 60 gm for four maxillary incisors and approximately 50 gm or less for four mandibular incisors.


0.017 x 0.025-inch TMA intrusion arch comes from molar auxiliary tube and is tied to one side of anterior segment (0.018 x 0.025-inch stainless steel) delivering intrusive force on that side. B, Activated intrusion arch, before ligation on anterior segment. C, Intrusion arch tied in on one side only.


If the canine also requires intrusion, this is performed in a separate stage after the incisor intrusion.

A simple cantilever (0.017 ´ 0.025-inch TMA) exerting a force of 20 to 25 gm can be used


A. Anterior view of separate canine intrusion. 0.018 x 0.025-inch stainless steel arch wire bypasses canine. 0.017 x 0.025-inch TMA cantilever comes from molar auxiliary tube and is tied underneath canine bracket (point force contact) delivering intrusive force. B, Buccal view of separate canine intrusion. Ideally wire should not be tied into bracket slot to deliver force without moments. C, Buccal view of separate canine intrusion.


When only one side requires extrusion,

A unilateral cantilever can be used to correct the occlusal cant. The cantilever, 0.017 ´ 0.025-inch TMA, comes out of the auxiliary tube of the first molar on the side where the extrusion is to take place and is hooked around the anterior segment. A force of approximately 30 gm is sufficient


Diagrammatic representation of unilateral extrusion of canted anterior segment. 0.017 x 0.025-inch TMA cantilever coming from auxiliary tube of molar is tied to one side of anterior segment. B, Patient with canted maxillary occlusal plane. C, Correction of canted occlusal plane with cantilever hook tied on affected side.


C)Canted posterior occlusal plane (in anteroposterior direction) A variation of the intrusion arch can be

used to correct this along with a deep overbite.

The magnitude of force is increased to 150 gm that causes a large tip-back moment on the buccal segment, thereby, flattening the occlusal plane. This appliance delivers appropriate force to the area of the arch in need of correction.


To upright buccal segment, cantilever with hook can be used. Side effects are extrusion of buccal segment and unilateral intrusion of anterior segment.


D)Asymmetric arch form- treatment Orthodontists often use an asymmetrically shaped arch

wire or asymmetric interarch elastics to correct an asymmetric arch form.

A more efficient way is to use a cantilever (0.017 ´ 0.025-inch TMA) from the first molar, with a hook that is attached in the area where the arch needs to be expanded or narrowed. The cantilever can be inserted on top of a light arch wire, for example 0.016-inch TMA.

A transpalatal or lingual arch connecting the molars should be in place to prevent rotation of the molar to which the cantilever is attached.


E)Treatment of asymmetric left and/or right buccal occlusion Clinical example A: for example, Class I

on one side and Class II on the other. This can be due to differences in axial inclination of the molars

A lingual or palatal arch (0.032-inch TMA or 0.032 x 0.032-inch TMA) activation is made to deliver a tip forward moment on the Class I side and a tip-back moment on the Class II side


Clinical example B: differences in left and right molar rotation Rotated molars are frequently seen in the

maxillary arch. A mesial-in rotation of one molar often results in an asymmetric molar occlusion.

To correct this problem, a transpalatal arch is used with equal amounts of antirotation activation. An 0.018 x 0.025-inch stainless steel wire is tied into all teeth except the rotated molar


Clinical example C: no difference in molar rotation and/or axial inclination

The right and left molar relationship can be asymmetric without perverted axial inclinations or rotations.

A conventional approach to correct this problem is to use an asymmetric headgear.

This headgear has the potential to move one molar further distally than the other molar

Unilateral dental crossbite The treatment can be performed with a

lingual arch (0.032-inch TMA) in the mandible and transpalatal arch (TPA) in the maxilla


Treatment of skeletal asymmetries- Surgical The severity and nature of the skeletal

asymmetry will dictate whether the discrepancy can be completely or partially resolved solely through orthodontic treatment.

In growing individuals, orthopedic appliances in conjunction with orthodontic treatment are used to help improve or correct the developing skeletal imbalances.


Asymmetries of a skeletal nature treated with orthodontics alone might dictate certain compromises

Severe discrepancies may require a combination of surgery and orthodontic treatment.

Abnormalities of the coronoid and condylar processes as well as in the position and shape of the articular discs should be considered whenever limited opening, acute malocclusions, or mandibular deviations are found.


The mandible is the dominant contributor to dentofacial asymmetry in as much as it forms the skeletal support for the soft tissues of the lower face.

Conversely, the maxilla provides minimal soft-tissue support and has small part in asymmetry.

Most maxillary asymmetry is secondary to asymetric mandibular growth and measured simply by the location of the maxillary dental midline and the cant of the frontal occlusal plane.


The clinician should consider several guidelines

Thoroughly evaluate the initial history and diagnostic records.

Always check for a functional component to the malocclusion and take the appropriate records in centric relation.

Recognize the early signs of a progressive asymmetry.

Understand the dentoalveolar compensations associated.

Take progress records and reevaluate if there is progressive asymmetry.


Treatment objectives should be to coordinate arches

Minimize compensations such as axial inclinations of the maxillary and mandibular dentition and transverse occlusal plane canting

keeping the maxillary transverse occlusal plane as level as possible during growth by using splints and other types of passive appliances to prevent compensatory supraeruption.


Unilateral condylar hyperplasia (hemimandibular hyperplasia, hemimandibular elongation)

Because the surgical treatment strategy depends on condylar growth activity, skeletal scintigraphy growth analysis or

A technetium-99m methylene diphosphonate (Tc99m) bone scan can also be performed.


Unilateral condylectomy in a growing child with condylar hyperplasia can provide satisfactory resolution of facial asymmetry

Secondary deformities, such as canting of the maxillary frontal occlusal plane and chin deformities should also be corrected.


A Le Fort I osteotomy to superiorly reposition the affected side and bilateral mandibular ramus osteotomies will correct the cant of the frontal occlusal plane.

Osteotomies can be simultaneously used to correct any accompanying anteroposterior, vertical, or transverse discrepancies.

Condylar shave procedure can be done to correct minor deformities.


Genioplasty (augmentation or redeuction) to further correct the chin asymmetry

Inferior border mandibular osteotomy to correct the bowing on the affected side and/or augmentation of the inferior border on the contralateral side, may also be indicated


Orthodontic therapy is directed at ideally positioning the teeth over basal bone.

Segmented arch mechanics are often indicated, particularly when the surgical plan calls for segmental osteotomies, but also when precision in leveling by intrusion, maximum anchorage retraction, segmental torque and tip, and/or control of the transverse dimension is required.


Bony ankylosis of the TMJ- Gap arthroplasty Interpositional arthroplasty The

ankylosis should be surgically released, biocompatible interpositional material should be placed eg. sialistic implants or bone grafts

High condylar shave with disc stabilisation

Condylectomy Distraction osteogenesis etc are some

procedures to relieve ankylosiswww.indiandentalacademy.com

Unilateral internal derangenents are corrected by articular disc repositioning procedures, stabilisation or replacement followed by pharmacotherapy , occlusotherapy , physiotherapy, ultrasound etc

Rapid maxillary expansion can be used to correct transverse asymmetries


Hemifacial microsomia- Severity of this condition can be extremely

varied and treatment should be initiated early to help prevent greater expression of the asymmetry.

Distraction osteogenesis is an excellent treatment modality in the growing patient in an attempt to stimulate development of soft tissue as well as hard tissue.

In more severe cases, reconstruction of the TMJ with costochondral grafting will usually be required


Surgery for Hemifacial Microsomia There are three stages of surgical intervention

described by Converse. The initial surgery is at age 5 to 8 years. The goal is

to replace missing skeletal elements and augment severely deficient areas to create a more favourable environment for subsequent growth of unaffected areas.

At age 12 to 15, after the adolescent growth spurt, orthognathic concerns are addressed, with repositioning of both jaws as necessary.

The third stage, in the late teens, is designed to enhance the contour of the skeleton and the soft tissues.


Initial Surgical Phase: Augmentation of Deficiencies. Augmentation of mandible can be

accomplished by an inverted L osteotomy via an extra oral approach, with the placement of grafts as appropriate.

If the zygomatic arch is missing or severely deficient,one may be constructed at the initial stage.


Second Surgical Phase: Jaw Relationships. Depending on growth, additional

mandibular advancement, usually with vertical elongation of the affected ramus and the placement of a graft on that side, if necessary.

If sagittal correction is necessary, sagittal split osteotomies may be employed bilaterally.


Asymmetric inferior border osteotomy to bring the chin to the midline, which improves both lip function and esthetics.

Additional onlay bone grafting to the mandible or maxilla for contour purposes also is performed

If occlusal cant persists beyond age 15, a LeFort I osteotomy to correct it may be required.


When the bilateral osteotomies have been completed, the mandible is repositioned and bone grafts harvested from the cranium or the ilium are inserted into the vertical and horizontal defects and secured with wires, bone plates, or screws.

Maxillomandibular fixation including an occlusal wafer splint is applied and continued for 4 weeks while healing takes place.

Overcontouring the affected side with bone grafts helps camouflage some of the missing soft tissues.


Third Surgical Phase: Contour Modification. If severe problems persist, major

reconstructive surgery with placement of grafts in the zygomatic and/or mandibular ramus areas may be required

Orthognathic surgery to reposition the jaws may be needed

Occasionally, mandibular inferior border osteotomy or onlay bone grafts to augment deficient areas are planned to enhance the final result.


Many asymmetric surgical orthodontic cases are variations of other hypoplastic or hyperplastic mandibular deformiities and accordingly can be addressed by- asymmetric movement of the mandibular distal segment using bilateral ramal osteotomies.

Sagittal split ramus osteotomy and the intraoral vertical ramus osteotomy are also commonly indicated in these cases


Genioplasty Mandibuloplasty Soft -tissue augmentation/ reduction,

and inferior-border augmentation/reduction provide additional flexibility in correcting asymmetries.

Not infrequently, maxilllary form and position must be corrected, necessitating simultaneous maxillary and mandibular osteotomies.


Condylar Fractures: Asymmetry due to Trauma In most cases, the fractured condyle resorbs

and a new ramus articulation forms. When growth restriction occurs, the ramus

grows more on the normal side, the chin deviates toward the affected side.

Less tooth eruption takes place there Restricted movements of mandible occur,

termed as functional ankylosis because jaw movement and function occur but are impaired.


The recommended management for a child with a recent condylar fracture is immobilization of the jaw for a few days, until initial soft-tissue healing can occur

Followed by physiotherapy to maximize jaw movement

Functional appliance to guide mandible to the proper position is indicated.


When condylar segment is displaced laterally or wedged between the ramus and temporal bone, preventing motion on the injured side.

Closed manipulation to free the segment should be attempted first.

If mandibular motion is still restricted, an open approach is done , removing the condylar head or repositioning it.


Management of Posttraumatic Asymmetry occurs because there is more growth on the

normal than on the affected side. If possible bring the mandible to a normal

symmetric position in the midline without undue strain, so that the construction bite for a functional appliance can be taken, treatment of this type should be attempted before any surgery

Or ramus osteotomy to bring the mandible to its approximately normal position


Surgical intervention in the TM joint is decided when previous therapy hasn’t worked.

Release of the ankylosis to provide free movement involves removing soft tissue and bone and excessive scar tissue

The coronoid process must also be released or removed

Physical therapy follows surgery to maintain the degree of jaw motion attained


REFERENCES Shroff B, Siegel SM., Treatment of patients with asymmetries using

Semin Orthod. 1998 Sep;4(3):165-79. Review asymmetric mechanics

Nanda R, Margolis MJ., Treatment strategies for midline discrepancies.Semin Orthod. 1996 Jun;2(2):84-9. . : Jerrold L, Lowenstein LJ. The midline: diagnosis and treatment. Am J Orthod Dentofacial Orthop. 1990 Jun;97(6):453-62. : Rebellato J., Asymmetric extractions used in the treatment of patients with asymmetries.Semin Orthod. 1998 Sep;4(3):180-8. : van Steenbergen E, Nanda R, Biomechanics of orthodontic correction of dental asymmetries.Am J Orthod Dentofacial Orthop. 1995 Jun;107(6):618-24.

Burstone CJ., Diagnosis and treatment planning of patients with asymmetries.Semin Orthod. 1998 Sep;4(3):153-64. : Erdogan E, Erdogan E., Asymmetric application of the Jasper Jumper in the correction of midline discrepancies.J Clin Orthod. 1998 Mar;32(3):170-80..


Wong AM, Rabie AB ., Facilitation of midline correction with a premolar extraction sequence.J Clin Orthod. 2001 Jan;35(1):13-7

Joondeph DR. Mysteries of asymmetries.Am J Orthod Dentofacial Orthop. 2000 May;117(5):577-9.

Bishara SE, Burkey PS, Kharouf JG ., Dental and facial asymmetries: a review. Angle Orthod. 1994;64(2):89-98.

Contemporary orthodontics-proffit Surgical orthodontics-proffit and white Kusnoto J, Evans CA, BeGole EA, Obrez A . Orthodontic

correction of transverse arch asymmetries. Am J Orthod Dentofacial Orthop. 2002 Jan;121(1):38-45

Problem solving in orthodontics- Burstone


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Midline Final / orthodontic courses by Indian dental academy

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