Obstructive sleep apnea (OSA) is a common condition, with a prevalence of approximately 17% in adult women and 34% in adult men. The underlying problem is the repeated collapse of the throat during sleep, leading to poor ventilation and even apnea.
OSA (Obstructive Sleep Apnea) poses numerous health risks. Patients often experience excessive daytime sleepiness, fatigue, and difficulty concentrating, leading to a decreased quality of life and an increased risk of accidents at work and while driving due to fatigue.
In the long term, it is also a significant risk factor for metabolic problems, hypertension, and cardiovascular disease, and is associated with a higher risk of death.
For patients with moderate to severe OSA, the standard treatment is continuous positive airway pressure (CPAP). This device delivers gentle, positive pressure air during sleep, acting like a “gas stent” to support the throat and prevent collapse.
Although CPAP is highly effective in eliminating sleep apnea, its actual effectiveness is often significantly reduced due to poor user experience and difficulty in long-term adherence by patients.
In this context, orthodontic appliances have become an increasingly popular non-surgical treatment option. Orthodontic appliances expand the throat space by moving the jaw forward or fixing the tongue, reducing the occurrence of sleep apnea.
They are suitable for patients with mild to moderate obstructive sleep apnea, especially those with a receding jaw. They are particularly suitable for patients with mild to moderate OSA who prefer orthodontic appliances, cannot tolerate or adapt to CPAP therapy, or have failed CPAP therapy.
The device helps patients keep their airway open during sleep by moving the jaw or tongue forward.
What are oral appliance for sleep apnea?
Oral appliances are primarily used to help improve breathing problems during sleep. Common types include tongue retractors, palatal actuators, and mandibular advancement appliances. Among these, mandibular advancement appliances are the most commonly used in practice.
Oral appliances guide the mandible to move slightly forward and downward, strengthening the muscles in the mouth and consequently moving the tongue forward.
This action reduces pressure on the posterior pharyngeal wall from the base of the tongue, while enhancing the stability of the pharyngeal muscles, thereby expanding the space in the upper airway, helping to maintain airway patency, and improving nighttime breathing.
The extent to which the orthodontic appliance moves the mandible forward and the vertical opening distance are crucial in determining the treatment outcome.
- Insufficient forward movement may have limited effectiveness;
- Appropriately increasing the forward movement within a reasonable range usually improves the effect.
- However, excessive forward movement may increase the burden on the teeth, periodontal tissues, temporomandibular joint, and facial muscles.
Studies show that it is currently unclear whether a larger forward movement (e.g., 75% of the maximum protrusion) is more advantageous than a smaller one (e.g., 50%). Furthermore, effectiveness does not increase proportionally with the amount of forward movement; that is, more forward movement does not necessarily lead to better results.
Other studies have found that when the appliance is in place, if the temporomandibular joint head is positioned close to a specific area of the articular tubercle, it often more effectively improves sleep apnea problems.
Because everyone’s oral structure, joint condition, and medical condition are different, the ideal forward movement of the mandible is not fixed and must be individualized. During the wearing process, the doctor will fine-tune the appliance to the most suitable position for the user, based on treatment principles, to achieve the best treatment results.
Types of oral appliances
Although various OAs differ in design, they can be categorized into three main types based on their site of action: soft palate actuators, tongue actuators, and mandibular advancement devices. Among these, mandibular advancement devices are the most widely used and have the most diverse types.
OA treatment for obstructive sleep apnea syndrome (OSAS) has become a highly valued research area in the field of oral medicine.
1. Soft palate effector (SPL)
A soft palate lifter (SPL) is an oral appliance worn on the upper teeth. Its rear end extends outwards to gently support the soft tissues at the back of the palate (including the uvula), preventing them from sagging excessively during sleep.
This reduces contact between these loose tissues and the base of the tongue and the back of the throat, helping to keep the airway clear and prevent obstruction. It also reduces soft tissue vibration, thus alleviating snoring.
However, because this device directly contacts and lifts the soft palate, it can easily cause discomfort such as nausea, and users usually need a period of adaptation and training to get used to it. Therefore, the use of this type of appliance is now relatively rare.
2. Tongue retaining device (TRD）
A tongue retractor (TRD) is an oral device that helps keep the tongue in a forward position during sleep. It has a small ball at the tip that gently pulls the tongue forward, preventing it from slipping backward and obstructing the airway.
This effectively expands the space between the base of the tongue and the back of the palate, facilitating smoother breathing.
This device can be effective in improving simple snoring and certain sleep apnea problems, and is especially suitable for people with fewer or missing teeth, and those with a larger tongue (including macroglossia).
However, tongue retractors often cause a noticeable foreign body sensation when worn, and their stability is relatively average. Users often find them uncomfortable and difficult to adapt to. Therefore, they are now rarely used clinically.
3. Mandibular advancement device (MAD)
Mandibular advancement appliances expand the pharyngeal space by keeping the mandible in a protruding position during sleep, indirectly moving the tongue forward.
This widens the airway behind the tongue and reduces the tongue’s posterior pressure on the soft palate, thus widening the airway behind the soft palate as well.
Currently, these appliances are widely used in clinical practice. Common types include bite advancement appliances, anti-snoring appliances, mandibular advancement appliances, and mandibular positioning appliances.
Depending on their design, mandibular advancement appliances can be divided into fixed and adjustable types. Fixed appliances cannot be adjusted once the mandibular advancement position is determined; adjustable appliances allow for adjustment of the advancement distance during use.
The advantage is that if the initial treatment effect is not good, the mandible can be further advanced to widen the airway; if joint discomfort or pain occurs, it can be adjusted back appropriately to alleviate symptoms. Adjustable appliances, by moving the mandible gradually and slowly, are easier for patients to adapt to, thus improving wearing tolerance.
According to statistics, the overall satisfaction rate of using mandibular advancement appliances is about 77%, and the adjustable design is more favored in clinical practice due to its flexibility and comfort.
The effects of OA
The effectiveness of mandibular advancement appliances (MADs) in improving sleep apnea is influenced by various factors, and the criteria for evaluating “effectiveness” are not entirely uniform.
Based on various studies, most users experience significant improvement in snoring symptoms after using these appliances, with improvement rates ranging from 73% to 100%.
A meta-analysis of 304 patients found that approximately 51% experienced a return to normal breathing levels, but about 39% still had moderate to severe sleep apnea after treatment.
Another study showed that the appliances are up to 94.7% effective in reducing snoring.
Subjective evaluation of therapeutic effect
Besides objective assessments such as sleep monitoring, patients’ own feelings and experiences are also important aspects of evaluating the effectiveness of orthodontic appliances.
This mainly includes acceptance of the appliance, whether snoring has been reduced, whether nighttime awakenings or feelings of suffocation have decreased, whether sleep has become more restful, whether daytime sleepiness and drowsiness have improved, and whether symptoms such as dry mouth upon waking have been alleviated.
A survey of 39 patients’ roommates showed that 38 of them reported a significant reduction in snoring, indicating that the appliance effectively reduces snoring.
Meanwhile, most wearers reported that nighttime awakenings due to breathing difficulties had largely disappeared, and daytime alertness had improved, subjectively confirming the appliance’s effectiveness in reducing drowsiness.
Compared to continuous positive airway pressure (CPAP, i.e., mechanical ventilation) therapy, patients generally have a higher acceptance rate and a greater willingness to use orthodontic appliances long-term; therefore, most patients with mild to moderate symptoms will choose this treatment first.
Overall, based on user feedback, the orthodontic appliance is well tolerated, and long-term use can effectively improve nighttime breathing and daytime mental state, thus helping to improve quality of life.
Objective evaluation of therapeutic effect
Overnight sleep monitoring is the core examination for assessing the effectiveness of sleep apnea treatment. The effectiveness of treatment is mainly determined by changes in several key indicators before and after treatment, including: the number of apneas and shallow breathing episodes per hour, the lowest blood oxygen level, the duration of apneas, and the frequency of snoring.
Generally, if patients feel better after treatment and their apnea/shallow breathing index (AHI) decreases by more than half compared to before treatment, or if the index drops to below 5 times per hour after treatment, the treatment is considered effective.
Studies have shown that whether worn for a short period (within 1 year), a medium period (1-6 years), or a long period (over 6 years), wearing an orthodontic appliance improves patients’ apnea, as evidenced by a decrease in related indices and an increase in blood oxygen levels, indicating that the therapeutic effect can be maintained long-term.
X-rays and CT scans can visually show changes in the structure of the upper airway. After wearing an orthodontic appliance, the jaw position adjusts forward and downward, causing related soft tissues to move, thereby increasing the space in the throat, especially the lateral width, and expanding the overall volume.
It is worth noting that although the airway space is significantly improved after treatment, its size and shape usually still differ from those of healthy, non-snoring individuals.
Side effects of OA
When you first start wearing braces, you may experience some temporary discomfort, such as a feeling of something in your mouth, increased saliva or dryness, cheek soreness, a slight awkwardness when biting, or discomfort in the joints.
These symptoms usually occur in the first few days to weeks of wearing braces, and most people adapt gradually or experience improvement after adjustments by their dentist.
With prolonged wear, some people may experience changes in their bite. For example, the overlap of the front teeth may slightly decrease, and the back teeth may tend to shift forward.
A few people may experience some discomfort in their joints. However, these changes are usually slow and minor, and most people find them tolerable, generally requiring no discontinuation of braces.
It’s important to note that changes in tooth position can affect the effectiveness of braces in pushing the chin forward, potentially impacting the overall treatment outcome.
Therefore, regular checkups are crucial so your dentist can monitor your teeth and joint health and make necessary adjustments.
While previous studies have suggested that braces may affect the joints, recent follow-up observations have shown that even if discomfort occurs, it is often temporary, and many people adapt gradually over time.
Overall, wearing braces under a dentist’s guidance and attending regular follow-up appointments can effectively manage these potential changes.
Conclusion
Orthodontic appliances have become a commonly used clinical treatment option due to their ease of use, relatively comfortable fit, moderate price, and definite effects.
They not only help improve nighttime breathing but also enhance overall quality of life. Some studies have also found that they may have a supplementary effect on patients with hypertension and daytime sleepiness, although more research is needed to support this claim.
Although some temporary or long-term discomfort may occur after wearing them, most users find them acceptable, and they do not affect their use as a routine treatment method.
Studies show that after three months of treatment with a mandibular advancement appliance, sleep apnea monitoring revealed a reduction in respiratory events, an increase in blood oxygen levels, and relief from symptoms such as nighttime awakenings and snoring, resulting in significantly improved sleep quality.
Therefore, it is an effective and long-term conservative treatment method besides continuous positive airway pressure (CPAP).
Similar to CPAP machines, orthodontic appliances are mainly used to control the condition and improve symptoms, generally requiring long-term wear to maintain their effects rather than providing a one-time cure. The key to encouraging patients to use them long-term lies in balancing effectiveness and comfort.
