Methods: Orthodontic members of Northwest PRECEDENT were recruited for study participation. Patients in these practices planned for treatment using miniscrew TADs were enrolled in the study. The orthodontist and the patient completed a questionnaire at miniscrew placement, and each miniscrew was followed to observe any subsequent failures during treatment. Kaplan-Meier survival analysis, Cox regression model analysis, and the robust score test were performed to determine overall miniscrew survival rate and assess risk factors for failure. Failure was defined as miniscrew loss, fracture, or mobility too great for orthodontic forces. Summary statistics were reported on patient experiences with miniscrew placement.
Results: 68 subjects with 119 miniscrew TADs were enrolled in the study, with a mean age of 27.7 years. 18 miniscrews failed during the follow-up period. Mean follow-up was 191 days after placement. Cumulative survival rate was 84.9%. No failures occurred later than 100 days after placement. Miniscrews placed buccally and miniscrews ≤ 8 mm in length had a statistically significant increased risk of failure (p < 0.05). 64% of patients were nervous about having miniscrews placed, and pain and discomfort were the primary reasons given for nervousness. 66% of patients indicated that having miniscrews placed was no more uncomfortable than having orthodontic appliances placed.
Conclusions: Miniscrew TADs placed in orthodontic practice failed at a rate of 15.1%, and failures occurred during the first four months after placement. Buccal placement and length ≤ 8 mm are potential risk factors for miniscrew failure. Placement of miniscrew TADs appears to be well tolerated by patients. Supported by NIDCR grants DE016750 and DE016752.