Following a baseline home sleep test (HST), 12 participants will enter the study wearing a MAS during sleep that protrudes the mandible to 60% of its maximal advancement. This approximates the minimum amount of jaw advancement that is expected to be efficacious. A HST will be repeated at the end of Week #4. If that HST shows that the MAS is not efficacious (i.e. has not reduced baseline apnea hypopnea index (AHI) by ≥50% or the AHI is ≥10**), and if TMD pain is not worse, the mandible will be advanced to 70% and the participant will repeat the HST at the end of Week #8. Once efficacy is achieved, there is no need for further HSTs. If efficacy is not achieved at the end of Week #8 and if TMD pain is not worse, the mandible will be advanced to 75% and the participant will repeat the HST at the end of Week #12. If efficacy is not yet achieved and if TMD pain is not worse, the mandibular will be further advanced to 80% and the participant will undergo a final HST at the end of Week #16. Once a HST indicates that the MAS is efficacious in reducing the AHI, the participant will maintain that level of advancement. The minimum number of HSTs for any one participant is 2 (baseline and 4-week follow-up) and the maximum number is 5.