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Volume 07 No. 05
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Accepted Papers


Complexity and Efficacy of Mandibular Advancement Splints: Understanding their Mode of Action

Fernanda Ribeiro de Almeida, D.D.S., Ph.D.
Department of Oral Health Sciences, University of British Columbia, Vancouver, BC, Canada

Mandibular advancement splints (MAS) are used to treat obstructive sleep apnea (OSA) patients by maintaining the lower jaw in a forward position. MAS are now widely used as primary therapy for the treatment of snoring and mild-moderate OSA, and also for severe OSA patients who are unwilling or unable to tolerate CPAP.1 Although CPAP therapy is consistently more effective, patients tolerate MAS better.2,3 The superior patient satisfaction associated with the use of MAS reflects the relative convenience of this form of treatment. Despite the wide use and acceptance of this type of therapy, the MAS mode of action is not fully understood. In awake patients, imaging studies have shown that MAS enlarge the upper airway dimensions by specifically increasing the lateral dimensions of the velopharynx.4,5 But one should question if the design and complexity of a MAS may influence the efficacy of this therapy. In this issue of the JCSM, Lettieri and collaborators (pp. 439-445) compared the efficacy rates between fixed and titratable appliances. This article is important since previous studies have often underestimated the impact of titration of MAS and compared trials which evaluate fixed or single jaw position appliances to titratable appliances. In addition the cost-benefit analysis of therapies is often overlooked, and the evaluation of simple and cheaper therapies is necessary.

In a systematic review of types of MAS, Ahrens and colleagues6 concluded that there is no one MAS design feature that influences treatment efficacy, although efficacy does depend on the method used for fabrication (pre-fabricated or custom-made), the degree of mandibular protrusion and the type of MAS (fixed or titratable). In this review all the studies comparing custom-made, titratable appliances have shown similar results, implying that specific design does not influence appliance efficacy, and that the appliances' modes of action are likely very similar. Vanderveken and collaborators7 have shown that pre-fabricated, off-the-shelf appliances are less effective and less accepted by patients and therefore should not be used either as a therapeutic option or as a screening tool to predict MAS responders. Titratable or adjustable appliances allow progressive protrusion of the mandible, and the amount of anteroposterior mandibular movement varies considerably between patients. Previous studies have shown that MAS efficacy is related to the amount of mandibular advancement,810 and determining the optimal degree of mandibular advancement is the most important step when using MAS therapy successfully.11,12 As an analogy, titration of MAS is very similar to CPAP. The amount of pressure required for each patient cannot be pre-determined based on OSA severity or craniofacial characteristics; therefore, to determine the amount of CPAP pressure required for each patient, there is a need of a titration night or use of an auto-CPAP. The further complexities of CPAP, such as humidification, BiPAP, or C-Flex have not translated into more effective treatments. In other words, the complexity of CPAP required is mainly related to the adjustability of the pressure, a unique pressure of 8 is not adequate for everyone, and the complexity required for effective MAS is mainly related to it being custom-made and allowing for titration/protrusion of the mandible.

Currently there are several published randomized controlled trials (RCTs) comparing MAS to CPAP. Most of these RCTs have found that MAS and CPAP have a similar impact on daytime sleepiness and quality of life.2,1315 Despite MAS being inferior to CPAP in reducing the AHI, it is hypothesized that a higher compliance to MAS likely translates into a similar adjusted AHI16 and effectiveness. However two other studies, Engleman17 and Lam,18 have shown an inferiority of MAS compared to CPAP. It is important to understand that these two studies, which are the only ones that are controversial in terms of treatment outcomes, have used a fixed, non-titratable, single jaw position appliance for their patients. Previous reports on effective single jaw positioners have proposed that, if this type of appliance is used, there should be the opportunity to remake these devices with further mandibular advancement, which represents titration with multiple appliances.19 The article published in this issue of JCSM reiterates that in future meta-analysis of treatment outcomes, fixed single-jaw positioners should not be evaluated together with titratable MAS, since these therapies have very different outcomes.

A second and important point to discuss is the cost-benefit analysis of a treatment. It is known that titratable appliances require consultation and adjustments provided by a dentist skilled in sleep medicine and that their fabrication is more expensive. Despite fixed MAS being typically less expensive and requiring a shorter period of adjustment, they are significantly less effective. Patients' economic status may be a factor in treatment choice. A patient-tailored treatment is synonymous with good medicine, and lifelong therapies are very dependent on the patient's cooperation and adherence. We believe that it is important to include patients in the decision-making process regarding their treatment and also to offer more than one type of therapy.


Dr. Almeida has indicated no financial conflicts of interest.


Almeida FR. Complexity and efficacy of mandibular advancement splints: understanding their mode of action. J Clin Sleep Med 2011;7(5):447-8.



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