Obstructive sleep apnea (OSA) is a sleep related breathing disorder, affecting approximately 10% of adults. Mandibular advancement oral appliances (OAM) are an effective treatment for OSA, however, long term use has shown to lead to changes in teeth positioning and jaw alignment (bite changes), which has resulted in some patients stopping treatment.

It is becoming common clinical practice for doctors to prescribe the use of repositioning splints to help reduce the bite changes associated with using OAM. However, this has not been studied in a clinical trial.

This study will compare the bite changes between patients using OAM alone against patients using a morning repositioning splint in addition to OAM. Other variables, such as oral health, the size of mandibular advancement, and treatment adherence will also be measured to determine if they have an effect on the bite changes associated with OAM use.

By understanding the key the factors that influence the bite changes associated with OAM use and potentially validating a technique to reduce these changes, this study will improve the clinical practice of Dental Sleep Medicine, leading to improved health outcomes for OSA patients.

Mandibular advancement oral appliances (OAM) are an effective treatment for obstructive sleep apnea (OSA). However, prolonged OAM treatment leads to significant changes in occlusion for the majority of patients. As such it is not uncommon to find changes in occlusion and the resulting decrease in quality of life in long-term users of oral appliances to be cited as a reason for discontinuing OAM treatment. Understanding the determinants of occlusal changes and clinical strategies to minimize or prevent them are essential to the practice of Dental Sleep Medicine, where treatment success is predicated on high levels of adherence.

Morning Repositioners or alternative oral appliances/splints that counteract the muscle splinting of the mandible in a forward postured position have been advocated by some practitioners as a means of minimizing the occlusal changes associated with OAM treatment. However, this has not been studied in a prospective clinical trial.

The proposed study is a single-blinded prospective randomized controlled trial at three clinical centers, with the specific aim of assessing the effectiveness of mandibular repositioning splint use on minimizing the occlusal changes associated with OAM treatment. Secondary aims include also determining the effects of periodontal disease, treatment adherence, and magnitude of mandibular advancement on occlusal changes associated with OAM treatment.

90 OSA patients will receive OAM treatment following standard practices. A titration period of two months will be used to adjust the position of mandibular advancement for each patient, which will involve clinical follow-up visits at a minimum of 1 week, 1 month and 2 months after initiation of OAM treatment. Each participant will be randomly assigned to either the treatment or control group. The treatment group will receive a mandibular repositioning splint to wear for a minimum of 1 hour in the mornings following removal of OAM. A positive control group will receive no additional splint, and but will be managed using standard practices, including jaw stretching exercises as needed. A second negative control group consisting of 15 healthy adults not undergoing any oral appliance treatment will also be included.

Prior to receiving treatment, participants will undergo a baseline assessment where demographic, anthropometric, and specific periodontal health data will be collected. All measurements will be repeated at a minimum of 18 and 36 months after appliance insertion, with routine follow-up appointments and adherence data collected every six months.

To directly address the primary aim of this study, occlusal variables will be measured by a combination of methods including analysis of digitized dental models, cephalometric analysis and intra-oral radiography bone level measurements. Secondary outcome variables to assess the effectiveness of morning mandibular repositioning splint therapy will include average OAM adherence (hours/night), quality of life (Functional Outcomes of Sleep Questionnaire, FOSQ), and change in mandibular incisor root length and attachment loss. Adherence will be measured by compliance monitors embedded in the oral appliance and mandibular repositioning splints.

Inclusion Criteria:

• Treatment naive (have never used an oral appliance as treatment for OSA);
• Age 25 - 65 years old, who are able to freely provide informed consent;
• Body Mass Index (BMI) ≤ 35;
• 8 or more teeth per arch to support treatment with OAM;
• Apnea-Hypopnea Index (AHI) within the range 5≤AHI≤50 documented with polysomnography in the last 2 years ***OR***
• Respiratory Disturbance Index (RDI) within the range 20 ≤ RDI ≤ 50 documented with level III portable sleep test ***OR***
• Oxygen Desaturation Index (ODI) ≥ 10

Exclusion Criteria:

• Extensive periodontal disease with significant tooth mobility;
• Inability to protrude jaw;
• Insufficient vertical opening to accommodate treatment with OAM;
• Pregnancy (if a participant becomes pregnant during the trial, the participant will be withdrawn from the study).
• Uncontrolled congestive heart failure (defined as a prior clinical diagnosis, an ejection cut-off of 40% or clinical sign in the opinion of a primary care physician or cardiologist) that makes it unsafe in the opinion of the investigators for the subject to participate in the trial;
• Coronary artery disease unless stable for at least 6 months and considered by the investigators to have a stable disease;
• Any history of angina, myocardial infarction or stroke;
• Any history of major depressive disorder along with current moderate-severe disease;
• Active cancer management (unless in remission for more than 1 year);
• Known renal failure (with need for dialysis)

Analysis of primary outcomes will be performed by an examiner blinded to group allocation.