Sixteen efficacy studies (including 14 crossover studies) were included in the review (n=511): 13 RCTs (n=473) and 3 non-randomised controlled trials (n=38). Thirteen studies (12 RCTs and one non-randomised controlled trial) were included in meta-analyses. Thirteen studies (n=677) evaluated co-morbidity: a controlled clinical trial (n=92) and 12 case series (n=585).
Efficacy.
Thirteen of the included efficacy studies were awarded 47 or more points during the quality assessment and were deemed methodologically sound. However, most studies did not fully describe the method of randomisation. Blinding of the patients and therapists was not often feasible, but most studies did not report reasons for not blinding the outcome assessor. Other flaws included the lack of intention-to-treat analysis.
MRA versus control therapy (4 studies): the meta-analysis (3 trials, n=134) showed that MRAs significantly improved the AHI compared with control (ES -0.96, 95% CI: -1.49, -0.42). There was no significant difference in the ESS between MRA and control therapy.
Variability in mandibular advancement and bite opening (1 study, n=24): the only identified study had an overall inadequate methodological quality and an ES was not calculated.
Variability in appliance design (3 studies, n=8, n=24 and n=26): the AHI was not calculated for one study due to the inadequate quality score; neither of the other 2 studies individually reported any significant difference between MRA and other appliances in the ESs of the AHI.
MRA versus UPPP (1 study, n=95): the study reported that the MRA significantly improved the AHI compared with UPPP (ES -0.47, 95% CI: -0.91, -0.02).
MRA versus CPAP (6 studies, n=169): the meta-analysis showed that CPAP significantly improved the AHI compared with MRA (ES 0.83, 95% CI: 0.59, 1.06). There was no significant difference in the ESS between CPAP and MRA.
Co-morbidity.
Craniomandibular complex: changes associated with MRAs included increased mouth opening in 28% (1 study). Other reported changes appeared to be non significant or minor. Craniofacial complex: changes associated with MRA were found./ These included a significant decrease in dental overbite and overjet associated with MRA treatment (5 studies), which was confirmed using cephalometry in 3 studies, although one shorter term study showed no significant change in dental occlusion; a mesial shift of the mandibular first molars relative to the maxillary first molars (4 studies); a significant decrease in maxillary intercanine width in one study but no significant inter-arch changes in another study. There was no consistency among studies regarding changes in the inclination of upper and lower incisors, changes in mandibular position and changes in upper face height. Two studies demonstrated increased lower face height.