ROLE OF ORAL APPLIANCE IN CLINICAL MANAGEMENT OF

OBSTRUCTIVE SLEEP APNEA IN CHILDREN* Balaji K, **TarasinghP

* Assoeiate Professor** Asst. ProfessorDept of Pedodontics and Preventive Dentistry, SVS Institute of Dental Sciences, Mahabubnagar, Andhra Pradesh.

ABSTRACTObstructive sleep apnea (OSA) is repetitive episodes of upper airway obstruction that occur during sleep, usuallyassociated with a reduction in blood oxygen saturation. OSA syndrome is thought to affect 1 - 3% of children.OSA can be treated with continuous positive air pressure (CPAP), oral appliance (OAs) and surgical interventiondepending on the condition. In this article role of oral appliance, types and guideiines of using OAs in clinicalmanagement of OSA in children will be discussed

KEYWORDS: Obstruetive sleep apnea. Oral applianee, Polysomanogram, Management

INTRODUCTIONObstruetive sleep apnea (OSA) is

disturbanee in normal sleep patterns: wheneombined with day time symptoms this eondition istermed OSA syndrome.^ OSA is a sleep disorder inwhieh repeated reaetions or cessations in air flowoeeurs. This disorder may vary in its severity and isoften assoeiated with other physiologieal symptoms.The International Classifieation of Sleep Disorders ̂defines OSA as repetitive episodes of upper airwayobstruetion that oeeur during sleep, usuallyassoeiated with a reduction in blood oxygensaturation.OSA syndrome is thought to afteet 1 -3% of ehildren.^'^ Girls and boys show a prevaleneeof 2% for OSA: For snoring, it is between 3 and12%.* The soft tissue of the aryepiglottie folds andthe epiglottis in young ehildren are more suseeptibleto eollapsing into the airway and less resistant tosubmueosal edema in eomparison with adults.These eharaeteristics are believed to predispose thechild towards OSA. Common signs & symptomsassodated with OSA in children ean be divided intonoeturnal and daytime signs and symptoms.Noeturnal signs and symptoms are drooling ofsaliva, xerostomia, sleep restlessness, ehoking orgasping and diaphoresis where as daytimes signsand symptoms inelude exeessive sleepiness,xerostomia, morning headaehes, non-restorativesleep, gastro-oesophageal reflexes, impairedeoneentration, depression and irritability. Patientswith sleep apnea have a wide range of physieal

attributes. The population with OSA is aheterogeneous group, and patients with OSA maynot have all of these physieal features. The mosteommon oro-faeial eharacteristies eneounteredineludes retrognathie mandible, narrow palate, largeneek eireumferenee, long soft palate (which leads todentists' being unable to visualize the entire lengthof the uvula when the patient's mouth is open wide),tonsillar hypertrophy, nasal septal deviation andrelative maeroglossia. The gold standard fordiagnosing OSA involves having the patienteomplete polysomanography (an overnight sleepstudy) eondueted in a laboratory. Thepolysomanogram records parameters includingeleetroeephalogy (brain waves), eleetro-Oeelulography (Eye movement),

eleetroeardiography, eleetromyography (ehin & legmovement), sleep positioning, respiratory aetivityand oxygen saturation^ The sleep medieine teamdefines possible treatment options for ehildren withOSA based on the severity of the sleep disorder,patient's preferenee, the patient's overall health,and the experienee and preferenees of the teammembers. Treatment options for OSA divided in to 3eategories depending on the eondition and option ofthe clinician. They areas follows:-

1) CPAP (Continous Positive Airway pressure)2) ORAL APLIANCE (OAs)3) SURGICAL INTERVENTION

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The last two decades has seen theemergence of oral appliances in the clinicalmanagement of snoring and obstructive sleepapnea (OSA). This has driven the need for simpleand eftective treatment options for obstructive sleepapnea in children. Different oral appliance designto reduce upper airway obstruction is not new.Pierre Robin® described such a concept in childrenwith life-threatening upper airway obstructionrelated to micrognathia and glossoptosis, wellbefore OSA was even recognized as a disorder.The use of oral appliances for the treatment of sleeprelated upper airway obstruction was first reportedsome 25 years ago.'''^ A key milestone in the fieldwas the systematic review conducted by theAmerican Academy of Sleep Medicine (AASM)®,highlighting the inadequacy of existing evidence atthat time and the need for rigorous scientificevaluation.

Whilst it has taken a relatively long time for theevidence base to reach a level that supports theiruse in clinical practice, that time has now arrived,and it is important for clinicians involved in themanagement of snoring and OSA to have a soundworking knowledge about this treatment modality. Ingeneral terms, this treatment approach relies onrepositioning of the mandible and/or tongue andrelated soft tissues in such a way that the upperairway caliber is increased and the propensity tosleep-related airway narrowing and collapse ismitigated.^" The potential advantages of such anapproach, particularly relative to the current goldstandard continuous positive airway pressure(CPAP), include its simplicity, portability, lack ofnoise and need for a power source, and potentiallylower cost, all of which have a positive impact onpatient acceptance.

TYPES OF ORAL APPLIANCESOral appliances used for OSA generally fall into oneof two classes, viz. mandibular advancement splints(MAS) (figure 1) and tongue retaining devices(TRD) (figure 2). MAS induce protrusion of themandible by anchoring a removable device to partof or the entire upper and lower dental arches, whileTRD use a suction cavity to protrude the tongue outof the mouth. MAS are far more widely used inclinical practice and there is an extensive literatureon their use, compared to TRD. There are manydesigns available, but they generally fall into eitherone-piece (monobloc) or two-piece (duobloc)

configurations. Beyond this, they can diftersubstantially in size, type of material, degree ofcustomization to the patient's dentition, couplingmechanism, amount of occlusal coverage,titratability of mandibular advancement, degree ofmandibular mobility permitted (vertical and lateral),and allowance for oral respiration. The impact ofthese design differences on clinical outcomes islargely unknown at this stage, and this suggests theneed for caution in extrapolating the results ofstudies using one type of appliance to all types ofappliances.

Two-piece splints (figure 3) consist of anupper and a lower removable plate with some typeof inter-maxillary coupling. There are several modesof coupling between the upper and the lower plates,such as elastic or plastic connectors, metal pin andtube connectors, hook connectors, acrylicextensions or magnets. There has been a steadyshift toward the predominant use of two-pieceappliances in clinical practice because of theadvantages they often confer, including titratabilityover time and permission of movement (verticaland/or lateral). Although prefabricated appliancesare commercially available, it is considered that thebest retention, comfort and side-eftect profile isachieved with custom-made oral appliances.

MECHANISMS OF ACTIONThe prevailing view has been that the primarymechanism of action of MAS arises from theanterior movement of the tongue, and theconsequent increase in the anteroposteriordimensions of the oropharynx. It now appears thatthis is an overly simplistic view, based on a growingnumber of studies that indicate rather more complexanatomical changes. Such studies have used arange of imaging modalities, including computerizedtomography^\ magnetic resonance imaging(MRI)^^, and nasopharyngoscopy." Notsurprisingly, airway volume increases withmandibular advancement Of some surprise hasbeen the consistent observation of an increase incross-sectional area of the velopharynx, in both thelateral and anteroposterior dimensions andincreases in the lateral dimension of theoropharynx. These changes are thought to bemediated through the intricate linkages that existbetween the muscles of the tongue, soft palate,lateral pharyngeal walls, and the mandibularattachments. In particular, it has been proposed thatthe improvement in velopharyngeal dimensions is

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mediated through stretehing of the palatoglossaland palatopharyngeal arehes.̂ ** Notably, it appearsthat there is interindividual variability in the airwayeonfigurational ehanges that oeeur with mandibularadvaneement, and this is likely to have majorrelevanee to the variable elinieal responseassoeiated with this treatment modality. Thereremains uncertainty about the extent to which oralappliance eftects are mediated throughneuromuscular pathways. Whilst there are somestudies indicating that oral appliances stimulategenioglossus muscle activity,^^^^ the clinicalsignificance of this has not been borne out by"placebo" controlled studies using inactive oralappliances, which have shown little change insleep-disordered breathing parameters .̂ ''̂ ^ Thissuggests that the primary mechanism of action ismechanical rather than neuromuscular. Themechanical eftect results in greater airway stability,evidenced by reduced upper airway closingpressure during sleep.^^ In a study of anesthetizedOSA patients, Kato et al ^° found a dose dependentreduction in closing pressure of all pharyngealsegments.

The mechanism of action of TRD islikely to be a little difterent compared withmandibular advancement devices. The forwardmovement of the tongue out of the oral cavity tendsto be greater than the tongue advancementachieved with a mandibular advancement deviceand this may produce more favourable anatomicalchanges in the retroglossal region. In addition, it ispossible that they counteract the eftect of gravity onthe tongue in the supine position. A usefulconceptual model for understanding the mechanismof action of an oral appliance is to consider theupper airway as a lumen, surrounded by soft tissue,and contained within a bony box.̂ ^ Hence onewould predict that mandibular advancement wouldreduce tissue pressure by enlarging the box. Thishas been observed in an animal study, which foundthat mandibular advancement reduced tissue

pressure and upper airway resistance.22 Incontrast, one would hypothesize that TRD reducethe amount of tissue in the box by pulling the tongueout ofthe mouth, thereby reducing tissue pressure.

CLINICAL OUTCOMESSince the systematic review of 1995 ^ there hasbeen a substantial increase in the quantity andquality of research evaluating oral appliances.

Whilst the early focus was on polysomnographicoutcomes, there has been a necessary shift towardthe evaluation of the impact of oral appliances on arange of important health outcomes, includingdaytime symptoms, neurocognitive function. Themore recent studies have tended to employ rigorousrandomized controlled trial methodologies and haveadvocated stringent, clinically relevant, definitions oftreatment outcome. Comparisons with CPAP, otheractive and inactive oral devices, and oral tabletplacebo have been published, assessing a range ofimportant outcome measures. Despite thisprogress, there remain challenges in drawingdefinitive recommendations for clinical practicebecause of uncertainties about the generalizabilityof research findings to all types of oral appliancesand patient subgroups. A contemporary systematicreview, commissioned by the AASM, has formedthe basis of revisions to the AASM practiceparameters. '̂'̂ ^

PolysomnographyThe eftect of oral appliances on polysomnographicoutcomes has been extensively evaluated, andthere is strong evidence of clinical benefit incontrolling or significant reducing the number ofobstructive breathing events and arousals, andimproving arterial oxygen saturation, particularly inthe mild-to-moderate OSA range. The overallsuccess rate is dependent on the definition used,with almost 70% of patients achieving a greaterthan 50% reduction in the apnea-hypopnea index(AHI) ^^ and up to 50% achieving an AHI <5/hour17,18,26 Qjygf̂ ^^g^ ^^Q gjp_| Q^ treatment is to resolve

OSA, it is important that the more stringentdefinition of treatment outcome be used. Withregards to oxygen saturation parameters, studieshave identified improvements in the minimumoxygen saturation, but rarely to normal levels. Thisis not surprising as, unlike CPAP, oral appliancesdo not inflate the lungs. With regards to sleeparchitecture and arousals, the data are lessconsistent, with only some studies reporting anincrease in rapid eye movement sleep andreductions in the arousal index. '̂'̂ •̂̂ ^Less is known regarding the efficacy of TRD.Modest reductions in AHI ^^, and improvements inminimum oxygen saturation and oxygendesaturation index ^̂ have been reported.

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ORAL APPLIANCE PRACTICE PARAMETERS(An American Academy of Sleep Medicine Reportf ̂The presence or absence of OSA must bedetermined before initiating treatment with oralappliances to identify those patients at risk due tocomplications of sleep apnea and to provide abaseline to establish the effectiveness ofsubsequent treatment. The severity of sleep relatedrespiratory problems must be established in order tomake an appropriate treatment decision.

• * ^ H T B

Mandibular advancement splint

Fig.2 Tongue Retaining Device (TRD)

Fig. 3 SomnoMedMAS Duobloc

Dental management of patients with OAs should beoverseen by practitioners who have undertakenserious training in sleep medicine and/or sleeprelated breathing disorders with focused emphasison the proper protocol for diagnosis, treatment andfollow up. Although cephalometric evaluation is notalways required for patients who will use an oralappliance, appropriately trained professionalsshould perform these examinations when they aredeemed necessary

Treatment ObjectivesFor patients with primary snoring without features ofOSA or upper-airway resistance syndrome, thetreatment objective is to reduce the snoring to asubjectively acceptable level. For patients withOSA, the desired outcome of treatment ineludes theresolution of the elinieal signs and symptoms ofOSA and the normalization of the apnea-hypopneaindex and oxyhemoglobin saturation. Oralappliances are appropriate for use in patients withprimary snoring who do not respond to or are notappropriate candidates for treatment with behavioralmeasures such as weight loss or sleep-positionchange. Although not as efticacious as CPAP, oralappliances are indicated for use in patients with mildto moderate OSA who prefer OAs to CPAP, or whodo not respond to CPAP, are not appropriatecandidates for CPAP, or who fail treatment attemptswith CPAP or treatment with behavioral measuressuch as weight loss or sleep position change.Patients with severe OSA should have an initial trialof nasal CPAP because greater eftectiveness hasbeen shown with this intervention than with the useof oral appliances. Upper airway surgery (includingtonsillectomy and adenoidectomy, craniofacialoperations and tracheostomy) may also supersedeuse of oral appliances in patients for whom theseoperations are predicted to be highly eftective intreating sleep apnea.

Follow-upFollow-up sleep testing is not indicated for patientswith primary snoring. To ensure satisfactorytherapeutic benefit from OAs, patients with OSAshould undergo polysomnography or an attendedcardiorespiratory sleep study with the oral appliancein place after final adjustments of fit have beenperformed. Patients with OSA who are treated withoral appliances should return for follow-up oftieevisits with the dental specialist. Once optimal fit is

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obtained and efticacy shown, dental specialistfollow-up at every 6 months is recommended for thefirst year, and at least annually thereafter. Thepurpose of follow up is to monitor patientadherence, evaluate device deterioration ormaladjustment, evaluate the health of the oralstructures and integrity of the occlusion, and assessthe patient for s'gns and symptoms of worseningOSA. Intolerance and improper use of the deviceare potential problems for patients using oralappliances, which require patient eftort to useproperiy. Oral appliances may aggravatetemporomandibular joint disease and may causedental misalignment and discomfort that are uniqueto each device. In addition, oral appliances can berendered ineftective by patient alteration of thedevice. Patients with OSA who are treated with oralappliances should return for periodic follow-up officevisits with the referring clinician. The purpose offollow up is to assess the patient for signs andsymptoms of worsening OSA. Close communicationwith the dental specialist is most conducive to goodpatient care. An objective réévaluation of respirationduring sleep is indicated if signs or symptoms ofOSA worsen or reoccur

CONCLUSIONOral appliance has got vital role in treating OSA inchildren especially in mild to moderate cases.Dental clinicians should take help from sleepexperts to check the compatibility of the oralapplianee with polysomonography. Further researchto define more clearly patient characteristics forOAs acceptance, success, and adherence isneeded .

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Corresponding Author :

Balaji K,Associate Professor

Dept of Pedodontics and Preventive Dentistry,SVS Institute of Dentai Seienees, Mahabubnagar,

Andhra Pradesh.Ph : 9440724290 ,

e-mail : balaiipai(5)rediffmail.com

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