Retrospective evaluation of the success rate and factors associated with the stability of alveolar ridge orthodontic miniscrews: Pilot study.

BACKGROUND: An uncommon location for placing miniscrews, used to provide anchorage control in various tooth movements, is the alveolar ridge. This study aimed to provide an evaluation of the success rate of alveolar ridge miniscrews and examine variables that might impact their success. METHODS: Charts for 295 patients who had miniscrews were screened. Twenty patients (5 male and 15 female: average age = 38.15 +/- 15.10 years) with a total of 50 alveolar ridge miniscrews were analyzed. A customized data form was used to collect patients' and miniscrews' related variables. Kaplan-Meier estimator was used for the survival function, whereas Cox proportional hazards regression models were used to associate collected variables with alveolar ridge miniscrew survival. RESULTS: In total, 31 (62.0%) miniscrews were stable and 19 (38.0%) failed. The survival time for those that failed was 6.03 +/- 7.08 months. The follow-up period for those that survived was 35.84 +/- 19.47 months. Male gender versus female (hazard ratio [HR] 2.46; 95% confidence interval [CI] 1.35-4.48; P = 0.003), and if the miniscrew was a replacement versus non-replacement (HR 0.27; 95% CI 0.07-0.99; P = 0.048) influenced the survival. Additionally, miniscrews that were used for both indirect and direct or indirect anchorage alone plus those with evidence of splinting showed a 100% survival rate, which led to an HR 0 (P < 0.001). When the previously mentioned variables were modeled, none seemed to have a significant effect on failure except for splinting and type of anchorage (P < 0.001), because none of the splinted miniscrews failed. CONCLUSIONS: The failure rate of alveolar ridge miniscrews was (38.0%) over 6.03 +/- 7.08 months. The survival rate was (62.0%) over 35.84 +/- 19.47 months. The evidence of splinting and the type of anchorage had a significant effect on survival probability.