Obstructive sleep apnea (OSA) is a highly prevalent breathing problem that occurs during sleep. OSA have been associated with the obesity epidemic in developing countries; additionally, high OSA prevalence rates are present in populations with cardiovascular and metabolic disorders. Two OSA treatments are currently available, oral appliance (OA) therapy and continuous positive airway pressure (CPAP). OAs are an underutilized non-surgical treatment and few studies have analyzed their long-term effectiveness for patients with OSA. The purpose of this study is to assess the long-term effectiveness of OA therapy in patients with OSA and to explore any changes on cardiovascular related morbidity and mortality related to this therapy.

Obstructive sleep apnea (OSA) is a chronic condition which may occur when an individual is sleeping. OSA incidence rates ranges from 4 to 16% of the adult population. The prevalence of OSA is even higher in populations with cardiovascular and metabolic disorders (e.g. stroke or diabetes mellitus).

OSA is characterized by five or more pauses in breathing per hour or partial obstruction of airway during sleep.

Obstructive sleep apnea (OSA) is currently being treated using two methods: oral appliance (OA) therapy and continuous positive airway pressure (CPAP). Although the American Academy of Sleep Medicine (AASM) has approved both methods as a first line treatment for mild and moderate OSA, oral appliances have been underutilized despite their non-invasive, quietness, the fact they are non-surgical and, cost effectiveness. OAs can also be an alternative for severe OSA patients who find CPAP treatment intolerable. There are two major groups of OAs available, one that acts on repositioning the mandible and tongue; this includes mandibular advancement splints (MAS) and Mandibular advancement devices (MAD). The other group of OAs, tongue retaining devices (TRD) focus on holding the tongue forward. It is because of the positioning of the tongue and mandible that OAs is effective in decreasing sleep apnea. OA therapy is a long-term treatment and therefore it is important that the appliance be comfortable to encourage patient use.

Despite the benefits to patients using OAs, previous studies have not looked at the relationship between OAs and OSA in long term studies or in a large number of patients. This lack of research and knowledge has led to an absence in training and education for dentists who are able to provide OA therapy to their patients. OAs have been shown to not be as effective as CPAP in helping with OSA, however, it has similar effects on blood pressure, quality of life, sleepiness and endothelial function. Previous studies have shown that the effects of OA therapy on patients' OSA are associated with more acceptance and adherence. Previous longitudinal studies that followed patients using CPAP showed great benefits in terms of cardiovascular health. It is therefore necessary for large sample size, long term prospective cohort studies to be done to determine how effective OA therapy is for patients with OSA, while also looking at potential effects on cardiovascular morbidity and mortality. It is for this reason that 15 centres from 9 counties around the world have formed a network called ORANGE (Oral Appliance Network on Global Effectiveness) dedicated on the long-term outcomes of OAs.

These centers included: University of Sidney (Australia), Stanford University (USA). Kaiser Permanente (USA), Cambridge University (UK), Paris Hospital (France), University of Antwerp (Belgium), Japan Somnology Center (Japan), Kyushu University (Japan), University of British Columbia (Canada), University of Montreal (Canada), Laval University (Canada), University of Gronigen (Netherlands), and Umea University (Sweden).

Inclusion Criteria:

• Patients are currently prescribed Oral Appliance for their Obstructive Sleep Apnea

Exclusion Criteria:

• Patients under the age of 18 years.
• Patients that do not understand the English language.
• Patients that refuse to sign the informed consent for any reason.

Patients who seek Oral Appliance therapy.