Obstructive Sleep Apnoea: Dental Implications & Treatment Strategies

Abstract

The management and treatment of patients who suffer from snoring and obstructive sleep apnoea (OSA) have long since been addressed by medical and specialist dental publications and were recently highlighted by a number of mainstream dental articles. These articles inform of the medical implications of the problem and the medical and dental treatment options available, but provide little technical information on constructing these appliances. The article reviews the concepts, rationale and technical aspects of appliance design and discusses clinical and financial issues. RATIONALE AND CONCEPTS OF APPLIANCE DESIGN Snoring is a sign of partial upper airway obstruction during sleep. Snoring and OSA are caused by abnormal airway (base of tongue and soft palate) anatomy and altered respiratory control mechanisms. Dental appliances may prevent snoring and OSA by modifying the position of the upper airway structures so as to enlarge and/or reduce collapsibility of the airway.[12345] Both the superior airway space (between the soft palate and posterior nasopharynx) and the posterior airway space (between the base of the tongue and posterior oropharynx) may be increased.[6] Three dimensional reconstructions of computed tomography and magnetic resonance imaging scans demonstrate significant increases in airway dimensions with the appliances.[78] The effectiveness of appliance therapy, however, depends on the severity of the sleeping disorder, the airway anatomy and whether the patient can tolerate the appliance. It is generally advocated for mild OSA and simple snoring (i.e. snoring in the absence of OSA) and moderate to severe OSA as an alternative to nasal continuous positive airway pressure (nCPAP) or craniofacial surgery.[9] The use of intra-oral appliances is simple, non-invasive, reversible and cost effective and may be the basis of definitive lifelong treatment. Originally there were three concepts for a dental appliance to modify the airway, which could be used alone or in combination depending on where the airway obstruction occurred: Soft palate lifting – the prosthesis lifts and/or stabilizes the soft palate, preventing vibration during sleep. Tongue retention – tongue-retaining devices (TRDs) incorporate an anterior hollow bulb, which generates a negative pressure vacuum when the tongue is inserted. The tongue is held forward, away from the posterior pharyngeal wall, opening up the airway. Owing to muscle anatomy, this appliance simultaneously modifies the position of the mandible. Mandibular repositioning – these appliances (MRAs) hold the mandible in an anteroinferior position, which, as a consequence of muscle attachment, indirectly brings the tongue forward, opening up the posterior airway (Figure 1). The repositioning may also stretch and reduce the collapsibility of the soft palate via its connection to the base of the tongue and increase the superior airway space. The soft palate lifting design is not often used because of patient tolerance and the fact that tongue posture rather than soft palate position is considered to have a significant influence on the patency of the upper airway.[10] An example of this type of appliance is clearly shown in the paper by Clark and Nako1no.5 Whilst TRDs directly move the tongue to open the airway, patient tolerance is not satisfactory. Obstructive Sleep Apnoea: Dental Implications & Treatment Strategies 2 of 6 When appliances are indicated the consensus appears to be a type of MRA, which Johal and Battagel consider most suitable for obstructions at the level of the tongue.[2] However, there is considerable variation with respect to the vertical and horizontal planes of mandibular repositioning and the material used for construction. MANDIBULAR REPOSITIONING CONSIDERATIONS Appliances for the treatment of snoring and OSA have been described with different degrees of horizontal and vertical repositioning. The most common mandibular repositioning dimension quoted is 50–75% of maximal protrusion (approximately 5–7 mm) with minimal vertical opening.[111215] The rationale for minimal opening is that, as the mandible opens, it rotates in an inferior and posterior direction. Concurrent posterior movement of the tongue and soft palate with wider opening may narrow the pharyngeal airway.7 An extensive review led by Ivanhoe found a variety of protrusive dimensions were associated with successful outcomes.[13] This, along with Lowe’s text [14] suggests that most protrusive positions are effective. MATERIAL CONSIDERATIONS To date either poly-vinyl vacuum-formed thermoplastic materials (soft or stiff blanks depending on the Shorehardness) or hard acrylic (predominantly heat cured) can be used. The choice of material often depends on appliance design and operator preference. To optimize retention for the vinyl appliances it is recommended that the flanges extend at least 3 mm past the gingival margin but, if softer vinyl is used, this depth should be increased.