Low quality evidence on the stability of orthodontic mini-implants

Medline, Embase, LILACS, Cochrane Library, Google Scholar, Web of Science, African Journals Online, Digital Dissertations.

Randomised controlled trials (RCTs), prospective controlled clinical trials(CCTs) and prospective cohort studies were included. Studies on implants with a diameter greater than 2 mm were excluded.

Data were extracted independently by two authors. Bias in RCTs was assessed using the Cochrane risk of bias tool, with non-randomised studies being assessed using the Newcastle-Ottawa Scale. Failures of mini-screw implants were expressed as event rates with 95% confidence intervals. Risk factors were assessed using random effects model and sub-group and meta-regression analyses were also conducted.

Fifty-two studies; five RCTs, eight CCTs, twenty-seven prospective cohort studies and twelve studies with unclear designs that were assessed to be prospective cohort studies were included. A funnel plot suggested there may be publication bias. Analysis of 4987 miniscrew implants used in 2281 patients indicated an overall failure rate of 13.5% (95% confidence interval, 11.5%-15.8%). Failures were not associated with patient sex or age and mini-screw implant insertion side, whereas they were significantly associated with jaw of insertion. Some trends were identified through exploratory analysis but no definite conclusions could be drawn.

Orthodontic miniscrew implants have a modest small mean failure rate, indicating their usefulness in clinical practice. Although many factors seem to affect their failure rates, the majority of them still need additional evidence to support any possible associations.