This systematic review clarifies the amount of effective protrusion in mandibular advancement devices of oral appliances required for obstructive sleep apnea (OSA). The systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Review Manager 5 and GRADEpro were used to combine trials and analyze data. The present review included three studies. In mild to moderate OSA cases, measured using the apnea-hypopnea index (AHI), 50% protrusion was more effective than 75% protrusion. However, 75% protrusion was more effective for severe cases. Sleep stage, Epworth Sleepiness Scale (ESS), snoring index, and side effects significantly differed between the groups. Additionally, 75% protrusion was more effective (AHI: 0.38, 95% CI: -0.89 to 1.65, p = 0.56; sleep stage 3: -1.20, 95% CI: 9.54-7.14, p = 0.78; ESS: 1.07, 95% CI: -0.09 to 2.24, p = 0.07; snoring index: 0.09, 95% CI: 0.05-0.13, p < 0.05; side effects: RR: 1.89, 95% CI: 0.36-9.92, p = 0.45). As per the AHI, 75% protrusion was effective in severe cases, whereas 50% protrusion was effective in moderate cases. Analysis of different surrogate outcomes indicated that 75% protrusion was more effective. Further, well-designed, larger trials should determine the benefits for patients. Additionally, investigations of adherence and side effects with long-term follow-up are needed.

Oral appliance (OAm) therapy has demonstrated efficacy in treating obstructive sleep apnea (OSA). The aim of this systematic review was to clarify the efficacy of device designs (Mono-block or Bi-block) in OAm therapy for OSA patients. We performed a meta-analysis using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system. Two studies (Mono-block OAm versus Bi-block OAm) remained eligible after applying the exclusion criteria. When comparing Mono-block OAm and Bi-block OAm, Mono-block OAm significantly reduced the apnea-hypopnea index (2.92; 95% confidence interval (95%CI), 1.26 to 4.58; p = 0.0006), and patient preference for Mono-block OAm was significantly higher (2.06; 95%CI, 1.44 to 2.06; p < 0.0001). Lowest SpO2, arousal index, non-REM stage 3, sleep efficiency, Epworth Sleepiness Scale (ESS), Snoring Scale, and side effects were not significantly different between the two groups (lowest SpO2: -11.18; 95%CI, -26.90 to 4.54; p = 0.16, arousal index: 4.40; 95%CI, -6.00 to 14.80; p = 0.41, non-REM stage 3: -2.00; 95%CI, -6.00 to 14.80; p = 0.41, sleep efficiency: -1.42, 95%CI, -4.71 to 1.86; p = 0.40, ESS: 0.12; 95%CI, -1.55 to 1.79; p = 0.89, Snoring Scale: 0.55; 95%CI, -0.73 to 1.83, p = 0.55, side effects: 1.00, 95%CI, 0.62 to 1.61, p = 1.00). In this systematic review, the use of Mono-block OAm was more effective than Bi-block OAm for OSA patients.