An investigation of the effectiveness of miniscrews in orthodontics

  • Fahad Alharbi

Student thesis: Doctoral ThesisDoctor of Philosophy


Aims: The aims of this study were to systematically review the evidence on miniscrews failure rate, their effectiveness in anchorage reinforcement, to assess the quality of reporting clinical trials in orthodontic literature in an observational study, to audit their use in the UK and to compare the anchorage effectiveness when measured against headgear and transpalatal arch in a randomised clinical trial.

Methods: In two systematic reviews, databases were searched, data was extracted, the risk of bias was assessed and meta-analyses were performed when appropriate. In the observational study, clinical trials reports that were published in four major journals from 2008-2012 were identified and assessed against CONSORT checklist to evaluate the quality of reporting. The audit was a prospective multi-centre audit investigating the use of miniscrews in the UK. In a randomised clinical trial, orthodontic patients were randomly allocated into three groups (headgear, miniscrews or transpalatal arch). Digital models were measured to assess the anchorage loss.

Results: The first systematic review and meta-analysis demonstrated that the failure rate of miniscrews was 14.1%(95% CI, 12-16.5). The data were obtained from 43 studies (16 clinical trials and 27 cohort studies). The second systematic review showed that overall mean difference in molar movement was 2.206mm in favour of miniscrews ( MD = - 2.20; 95% - 1.21 to -3.19) when compared with conventional anchorage methods. The data were obtained from seven clinical trials.

The observational study assessed the reporting quality of 151 clinical trials and showed that clinical trials reports represented less than 5% of the articles published in four major journal and their reporting was suboptimal.

The audit showed that none of the agreed standards were met except for infection/inflammation around the screw resulting in loss or removal in 5.6% of the cases while the standards were being below 20%. The miniscrew failure rate in this audit was 24.2%. The total number of placed miniscrews was 1072.

The randomised clinical trial revealed no difference between headgear, transpalatal arch or miniscrews in regards to anchorage effectiveness. 51% of study models required to measure the primary outcome were missing.

•Based on the two systematic reviews, miniscrews have a modest failure rate and they are useful clinically to reinforce anchorage.
•Reporting clinical trials is suboptimal in orthodontic literature.
•The only item that met audit standards was failure due to infection /inflammation. The rest of the audit standards were not met. Recommendations are made to address these issues.
•In the clinical trial, no difference in anchorage effectiveness between headgear, transpalatal arch or miniscrews was found. The findings of this clinical trial should be interpreted with caution due to the missing data.
Date of Award2016
Original languageEnglish
SupervisorDavid Bearn (Supervisor) & Peter Mossey (Supervisor)

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