The effect of the sleep apnea oral appliance is based on the forward displacement of the lower jaw and an increase in the tone of the muscles of the tongue (genioglossus) and the tissues of the palate. In this case, the air space in the pharynx increases and the soft tissues cannot swell to block the airways. The lower jaw brought forward by the sleep apnea rail increases the extent of the velopharyngeal space, especially in the lateral direction, due to the direct contact of the lateral tissues of the pharynx with the forward-moving jaw. The anterior transfer of the lower jaw also brings the tongue and lingual bone forward.
Because the pathophysiology of sleep apnea varies between patients, the effects of the sleep apnea oral appliance may be different. Patients with obstructive sleep apnea may have varying degrees of structural abnormalities of the upper airways, an increased tendency to constrict the velopharyngeal space, a hypersensitive system of respiratory regulation, and a decreased threshold for awakening. In general, patients with mild sleep apnea have a good response to sleep apnea rail therapy because their tissues in the pharyngeal area are more tendonous and do not collapse as easily. During sleep apnea oral appliance treatment, patients with mild disease have more throat opening compared to those with moderate to severe sleep apnea. These patient-specific factors can provide additional benefit in predicting and evaluating treatment success.
How much lower jaw can be brought forward with a sleep apnea oral appliance?
Forward import of the lower jaw is always determined on a case-by-case basis at the dentist’s office, on average it is set at 50-60% of the maximum protrusion position. In general, the more the lower jaw is brought forward, the better the treatment outcome achieved when looking at AHI (Apnea-Hypopnea Index). However, the relationship is not linear and the occurrence of possible side effects should be considered.
In the treatment of mild to moderate sleep apnea, treatment outcomes did not differ significantly depending on lower jaw forward importation. In the comparative study, 79% of the patients in the study, with a lower jaw position with the oral appliance in the mouth of 50% of the maximum protrusion, reached normal when measuring AHI. The same conclusion was reached by 73% of the subjects with 75% of the maximal protrusion in the lower jaw. The second study found that half of the subjects with the lower jaw set at 75% of the maximum protrusion and one-third, with a protrusion rate of 50% of maximal with an AHI <10, which means mild sleep apnea or a normal situation without sleep apnea.
In this study, some subjects had severe sleep apnea, which led to the conclusion that that maximizing the protrusion rate improves treatment outcome in severe sleep apnea cases. It is recommended that sleep apnea oral appliance therapy be initiated at ≤50% of the maximum protrusion of the mandible. In this case, the treatment provides an adequate response and the use of a sleep apnea oral appliance is more meaningful for patients. During follow-up visits, the degree of protrusion can be gradually increased if necessary, if a titratable oral appliance is used and there are no side effects.
Studies have also been conducted on the effect of sleep apnea oral appliance height on AHI and sleep apnea treatment outcomes. In the comparative study, sleep apnea oral appliances with the same amount of lower jaw forward import but different heights (4 mm and 14 mm) measured from the tips of the incisors were used. It was found that oral appliance height has no effect on treatment outcome or decrease in AHI, but patients preferred and used a lower device. In practice, too high a sleep apnea oral appliance has been found to move the lower jaw backwards, which increases airway obstruction in the pharyngeal area and may even worsen the symptoms of obstructive sleep apnea.
Sleep apnea oral appliance suitability
The sleep apnea oral appliance is designed based on a dentistry and bite examination performed by a dentist, after which the device is manufactured individually. Prior to oral appliance treatment, special attention is paid to the bite, the condition of the dental connective tissue and the function of the jaw joint. Contraindications to the use of the oral appliance are extensive tooth defects, a strong open bite, an opening face type, and severe connective tissue diseases of the teeth. Before preparing the device, basic treatment of the patient’s teeth should be done.
Patients with mild to moderate sleep apnea are best suited for sleep apnea oral appliance treatment. They have been found to have less congested pharyngeal airways, and during sleep apnea treatment, the pharynx expands more throughout compared to patients with severe disease. Sleep apnea oral appliance therapy is also recommended for snorers who have not been diagnosed with sleep apnea. Sleep apnea oral appliance treatment reduces the frequency and intensity of snoring, improves the sleep quality of the snorer and spouse, and improves the quality of life. Studies are incomplete when looking at the health effects of primary snoring treatment or the improvement in sleep quality of snorers using a sleep apnea oral appliance compared to other treatments. Therefore, sleep apnea oral appliance should be recommended for snorers only after failure of traditional treatments (weight loss, posture, and reduction of alcohol consumption) or after an inadequate response to treatment. Snoring is often associated with obstructive sleep apnea, so the patient must have the correct diagnosis when planning treatments.
The sleep apnea oral appliance can be helpful for patients suffering from CPAP device side effects. For example, if high pressure causes discomfort, a sleep apnea oral appliance can help lower the optimal pressure level while using CPAP. Sleep apnea rail therapy has been shown to be successful in patients using low air pressure in the CPAP and in whom sleep apnea has been shown to be posture-dependent. Treatment is also more likely to be successful in patients with large tongue, narrow retroglossal air space, retrogenous lower jaw, and low lower facial height. Sleep apnea oral appliance treatment is more likely to be successful in adolescents, women, and normal weight individuals, but these factors are not clinically relevant in assessing the success of treatment in an individual patient.
Weight gain during treatment has been found to be associated with oral appliance treatment failure. Patients who repeatedly wake up during sleep before starting oral appliance therapy are also likely to be less successful. Other significant factors in assessing treatment success are an increase in pharyngeal extent with a sleep apnea oral appliance as measured by a nasoendoscopy, and a sufficient reduction in AHI in an overnight study with a remote-controlled sleep apnea oral appliance. Initial AHI, neck circumference, smoking, and alcohol use have also been found to have an effect on treatment success. Cephalometric analysis from a lateral skull x-ray image and the structural variations observed from it cannot be used to predict the results of sleep apnea oral appliance therapy.
Sleep apnea oral appliance effectiveness
Sleep apnea oral appliance treatment has been shown to significantly reduce the patient’s daytime fatigue, the incidence of morning headaches and the need for daytime naps. Sleep apnea oral appliance therapy is considered effective if it results in a reduction in AHI by half the initial value or no further diagnosis of sleep apnea (AHI <5). The patient must also subjectively experience that, for example, daytime fatigue and snoring have decreased with treatment.
Subjective symptoms of sleep apnea
The subjective effect of treatment is usually greater than the clinically observed efficacy in the polysomnography study. Several studies have shown that the results of the Epworth Sleepiness Scale (ESS) improved with the active sleep apnea oral appliance compared to the inactive control device, but the placebo effect of inactive devices has also been observed with that ESS survey. The review article compares the effect of a sleep apnea oral appliance and an inactive mouthpiece on daytime sleepiness. Considering only studies involving patients with mild to moderate sleep apnea, there is no significant difference in ESS survey scores. The same article also states that no control study found lower ESS survey scores in those using a sleep apnea oral appliance compared to a placebo device. In a meta-analysis of patients with moderate sleep apnea, there was no difference based on the results of the somnolence survey when comparing placebo and sleep apnea oral appliance or sleep apnea oral appliance compared to CPAP. Therefore, in light of studies, it is unclear whether any of the treatments for obstructive sleep apnea significantly affect the perception of daytime fatigue and quality of life in mild to moderate forms of the disease.
In patients with severe sleep apnea, a reduction in somnolence was observed with the use of a sleep apnea oral appliance, but more effective results were obtained with the CPAP device. Thus, it is likely that mild to moderate sleep apnea causes less daytime fatigue than expected, and fatigue can be explained by other factors. This is also illustrated by the fact that one-third of patients still experience fatigue (ESS scores> 10), even though apnea and hypoapnea have been reduced as targeted with sleep apnea oral appliance or CPAP treatment.
Oral appliance and AHI
Sleep apnea oral appliance treatment has been shown to reduce AHI. In a randomized, double-blind study, sleep apnea oral appliance treatment was compared to an inactive placebo device. Nearly half of sleep apnea oral appliance users and only less than one-fifth of placebo users achieved a 50% reduction in AHI. Sleep apnea oral appliance users were more likely to be asymptomatic (AHI <5) compared to the placebo control group.
Oral appliance and snoring
In addition to the symptoms of fatigue, patients are interested in the treatment of snoring, as it disrupts the life of the partner and family in addition to the patient. Studies have generally reported patients’ subjective observations of reduced snoring, but objective measurements have also been made. Snoring has been found to be more reduced in those using a sleep apnea oral appliance compared to an inactive placebo device. However, CPAP is more effective than sleep apnea oral appliance in reducing snoring. If a patient snores despite the use of a oral appliance, the response and compliance of sleep apnea oral appliance treatment has been found to be poor.
How oral appliance affects cardiovascular disease and blood pressure?
Sleep apnea oral appliance therapy has been shown to be effective in lowering blood pressure, especially in patients with blood pressure greater than 135/85 mmHg and AHI ≤15. The reduction in blood pressure achieved with oral appliance therapy is significant for a correctly selected group of patients. The second study measured blood pressure and compared patients using a sleep apnea oral appliance with a control group using an inactive mouthpiece. There was a decrease in diastolic blood pressure in patients using the sleep apnea oral appliance, but no significant change in systolic blood pressure. Oral appliance treatment was not found to affect blood pressure during sleep. Sleep apnea oral appliance therapy and CPAP use have been found to have an almost equally effective lowering effect on blood pressure. The sleep apnea oral appliance has also been reported to have a positive effect on vascular endothelial function as well as cardiac function.
Very few studies have been done on the effect of sleep apnea oral appliance therapy on cardiovascular mortality. The cohort study compared patients with severe sleep apnea who were treated with either a sleep apnea oral appliance, CPAP, or no treatment for sleep apnea at all. The study found that mortality from cardiovascular disease was highest in the group of untreated sleep apnea patients and significantly lowest among patients treated for sleep apnea. No differences in the number of fatal cardiovascular events were observed between the CPAP and sleep apnea oral appliance groups, although the residual AHI for sleep apnea oral appliance treatment is higher in those using CPAP.
Sleep apnea oral appliance effects compared to CPAP and other treatment options
In studies involving all patients with severity of disease, the average success rate for oral appliance treatment was 64%. If only patients with mild to moderate sleep apnea were considered, treatment was considered successful in 79% of cases. When comparing the results with other studies, the results are similar. In patients with mild to moderate sleep apnea, the response to treatment is almost the same regardless of whether a sleep apnea oral appliance or CPAP is used. Patients with severe disease can also be successfully treated with sleep apnea oral appliance, but CPAP treatment is more likely to reduce the number of breathing breaks and hypopneas compared to sleep apnea. Sleep apnea oral appliance therapy can be considered as a second-line treatment for patients who do not achieve the desired response to treatment with CPAPs.
Studies show that CPAP and sleep apnea oral appliance improve impaired respiratory function in obstructive sleep apnea, but CPAP is more effective. The sleep apnea oral appliance significantly reduces AHI compared to placebo, but is not as effective as CPAP. If a complete response to treatment (AHI <5) is considered a criterion for treatment success, patients using a CPAP device are twice as likely to achieve the desired result as those using a sleep apnea oral appliance. The patient’s oxidation improves with sleep apnea oral appliance treatment at night, when blood desaturation values decrease and oxygen saturation increases. However, oral appliance therapy does not have as much effect on these values as the CPAP device. Sleep apnea oral appliance treatment does not appear to have a significant effect on sleep structure and efficiency, but an improvement in the physiological values of sleep may reduce the feeling of fatigue during the day and increase the quality of life.
The predictability of CPAP treatment outcomes is better compared to sleep apnea oral appliance treatment in short- and long-term studies. Sleep apnea oral appliance therapy may be used alone or in combination with other therapies, such as posture therapy or with a CPAP device, if these alone are not sufficient.
Other effects of sleep apnea oral appliance
Sleep apnea oral appliance treatment increases alertness and psychomotor speed, but the results are not directly proportional to the reduction in AHI and daytime fatigue. Oral appliance therapy has no effect on neurocognitive functions such as attention span, working memory, verbal memory, ability to perceive movement or space when comparing an active sleep apnea oral appliance to an inactive mouthpiece.
In summary, sleep apnea oral appliance treatment can significantly improve the physiological parameters of sleep quality, subjective quality of life, and reduce the symptoms of sleep apnea. The use of a sleep apnea oral appliance also causes relatively little inconvenience. The positive effects of sleep apnea oral appliance treatment are not as great as compared to CPAP treatment, but the use of an oral appliance provides a clear benefit compared to a situation where the device is not used. Patient selection also has a significant impact on the effectiveness of treatment. In addition, studies have found that the long-term efficacy of a sleep apnea oral appliance maintains quite well.