Oral devices such as the Mandibular Advancement Splints (MAS) have emerged in the last decade, as an effective treatment of Obstructive Sleep Apnoea (OSA).
The mechanism of action is theorised to reduce the ability of the upper airways to collapse.
This is achieved by wearing an individual designed mouthguard-type of device, intra-orally to protrude and hold the mandible in a forward position.
This enables a stretching of the soft tissue that connect the mandible and tongue to the soft palate and the surrounding lateral pharyngeal walls to increase the volume of the upper airway.
Collating prior research it is most effective in patients who have mild-moderate OSA, the success rate of abolishing OSA (reduction of AHI to less then 5/hour) is sitting at ~35-40% of patients, however a further 25% will show a significant improvement (reduction of the AHI by 50%), therefore two thirds of patients will experience a clinical benefit with 35-40% showing a non significant result, falling below a 50% reduction of AHI and some patients even experiencing a worsening of OSA.
Accurate methods to predict the treatment efficacy have not yet been developed, although associations with increased success rate has been uncovered, as summarised in Table 1, below.
Sutherland K, Cistulli PA. Mandibular advancement splints for the treatment of sleep apnoea syndrome. Swiss Med Wkly. 2011;141:w13276
The design of the MAS can cause some initial common side effects including; mouth dryness, salivation, gum irritation, dental discomfort and temporomandibular joint pain. The degree of side effects is individual and generally dependant on the type of device used and the degree of mandibular advancement as well as the dental expertise involved. Side effects can be rectified in time with regular use and/ or adjustment of the device. Some long-term dental and skeletal movements such as; changes in the occlusal contact area, increased facial height, mouth opening and changes in the inclination of the incisors, have been noticed, however are generally subclinical. There are extreme cases where the side-effects are severe and persistent, generally regarding pain, for which it is then recommended to cease using the device.
One of the biggest concerns is the individual response to MAS therapy. Some patients can have a high Epworth Sleepiness Scale scores with a low AHI. Furthermore there are physiological, structural, and individual characteristics to take into account which are yet to be predicted accurately. This means there is a risk that a patient may have to pay the expenses to trial a method that may or may not work for them, since there is no option to trial the therapy. Even though in direct comparison to CPAP, oral devices are consistently found to be less effective, prior studies recorded favourability of MAS therapy rather then CPAP, this should not be discounted as compliance is an important part of any treatment. Therefore taking into account these factors MAS has undoubtedly been shown to reduce OSA symptoms and snore which would suggest that it would be most effective in patients with mild-moderate OSA. However it is being used as a second option for patients that have severe OSA and are unable to tolerate CPAP therapy.
The advantages of MAS treatment compared to CPAP include simplicity and portability, no requirement for a power supply or battery pack and better patient acceptance. Apart from decreasing AHI, oral devices have been noted to improve other polysomngraphic measures of OSA, including; oxygen desaturation (although rarely to normal levels), sleep architecture and arousal indices. There have been studies re-evaluating patients from 1–5 years after treatment initiation that suggest that there is a reasonably high rate of sustained control even in severe OSA. Furthermore the need for dental and medical follow-up to sustain effectiveness is essential, as there is limited evidence to determine the efficacy of MAS therapy, with regards to the effects of; weight gain, age and device wear and tear, in the long term.