## 1 Introduction  
Obstructive sleep apnea syndrome (OSAS) is a common sleep disorder caused by the repetitive collapse of the upper airway during sleep interrupting (apnea) or reducing (hypopnea) the flow of air. The Apnea-Hypopnea Index (AHI) is calculated using the mean number of apnea and hypopnea events per hour and defines the severity of OSAS as follows: absence of sleep apnea \(<\) 5 events, mild sleep apnea from 5 to 15 events, moderate sleep apnea from 15 to 30 events and severe more than 30 events [1]. OSA syndrome is a really common disease, it is the second respiratory disorder in order of frequency, preceded by asthma. In terms of epidemiology, it has an incidence ranging at 2-5%. This appears to be more common in males and older people [2]. Although it is a very common condition there is inadequate public health knowledge on the subject and this is one reason why it is estimated that between 80% and 90% of people with OSA are undiagnosed [3]. There are several risk factors that contribute to the development of obstructive apneas. The anatomy of some structures can contribute to create a narrower oropharyngeal space, reducing the lumen of the upper airway (UAW): craniofacial alterations, increased tongue base, amygdala and uvula, maxillomandibularbular deficiencies. Obesity is another important risk factor as it leads to an increase in neck circumference and a predisposition in the reduction of air space. Supine sleep position predisposes to obstructive apnea because it results in gravitational retro-position of the tongue [1]. Diagnosis is usually made by polysomnography (PSG), a test that allows assessment of both neurological activity and cardio-respiratory parameters during sleep [4]. OSAS has a negative impact on the health and behavior and the scientific literature has described manyorbidities associated with OSAS such as cardiovascular and cerebrovascular pathologies: hypertension, increased risk of congestive heart failure, myocardial infarction, cardiac arrhythmias and stroke, also cognitive disorders such as deficiencies in memory and attention, behavioral disorders and also metabolic disorders [5; 6; 7; 8]. An Increase of masticatory muscles activity during sleep is showed in many researches [9]. This condition also called sleep bruzim is evaluated in patients with OSA and characterized by rhythmic (phasic) or nonrhythmic (tonic) movement [10]. Therefore, it is important to diagnose and treat this disease to avoid the development of worse health consequences. Continuous positive airway pressure (CPAP) introduced by Sullivan in 1981 [11] is still considered the gold standard treatment for OSAS, especially in severe cases [12]. The effectiveness of CPAP is undoubted but many patients do not tolerate its use, reported rates of nonadherence ranges from 46% to 83%, that is the reason why alternative treatments are needed [4]. Septoplasty, tongue reduction, uvupolapatopharyngoplasty, maxillomandibularular advancement and others surgery procedures can be other therapeutic strategies for OSA, although limited to particular cases. Oral appliances, such as mandibular advancement devices (MAD) and tongue-retaining devices, are definitely better tolerated by patients and can be an alternative for patients who do not tolerate CPAP. While tongue-retaining devices are not supported by a strong evidence [13], the use of MAD is considered a valid alternative in OSA patients, since it was demonstrated that it can markedly reduce the AHI and the oxygen desaturation index (ODI), improving patients' quality of life [14; 15]. The other important aspect evaluated was about the limited side effects on temporo-mandibular joint (TMJ) function by use of MAD in 12.5-33% of these patients [16]. Other treatment options can be used to reduce obstructive sleep apnea, they include dietary weight loss or bariatric surgery in case of obese patients, reducing alcohol and sedative medications, eliminate the habit of smoking [17].