Risk Factors for Secondary-Inserted Orthodontic Miniscrew Stability Following Original Insertion Failure.

Purpose: The objective of this study was to examine the variables that influence the stability of secondary orthodontic anchoring miniscrews after the occurrence of initial installation failure. The secondary insertion was defined as reinserted, which was inserted to the orthotopic (i.e., inserted between the roots of the original two adjacent teeth with the mesiodistal, height and insertion angle slightly altered) and ectopic (i.e., inserted between neighboring tooth roots).

Materials and methods: A total of 100 miniscrews were reinserted in 71 patients who experienced primary insertion failure. The analysis considered 15 independent variables related to systemic factors and site characteristics. The success rate and risk factors associated with reinsertion were assessed using univariate analysis (Chi-square Test for categorical variables and Mann-Whitney U test for continuous variables) and correlation analysis (Spearman correlation analysis to exclude variables that might cause interference in a multivariable model). Significant parameters from univariate analysis were then integrated into a generalized estimating equation (GEE) model.

Results: The success rate of reinsertion was 66.00% (66/100), and the cancellous bone density and the patient's age had a strong correlation with the stability of reinserted miniscrews.

Conclusion: The study indicates that younger patients with miniscrews reinserted in areas of high cancellous bone density are more likely to experience instability. This finding warrants careful consideration by orthodontists when performing miniscrew reinsertion procedures.