Five-year experience with orthodontic miniscrew implants: A retrospective investigation of factors influencing success rates

Introduction: Anchorage control is important for efficient orthodontic treatment with fixed appliances. Successful osseointegration encouraged many orthodontists to use dental implants as stationary anchorage units for force application. However, their use has some drawbacks, which led to the development of miniscrew implants (MIs). Our aim was to investigate factors significantly contributing to the success rates of MIs in various orthodontic treatment procedures in white patients. Methods: In total, 350 self-tapping (187 Abso Anchor [Dentos, Daegu, South Korea] and 163 Ortho Easy Pin [Forestadent, Pforzheim, Germany]) MIs used to reinforce orthodontic anchorage and placed in 130 consecutively chosen patients were assessed retrospectively. Clinical variables possibly influencing the success rates of MIs were categorized into patient-related, implant-related, location-related, and orthodontic-related. Statistical evaluation included descriptive statistics and survival analysis. The survival curves of the MIs with respect to the various factors were estimated and plotted by using the Kaplan-Meier product-limit estimate. The MI survival distributions for each factor were compared with the log rank test for simple comparisons or the Cox regression for multiple variables. Results: The overall success rates of MIs that remained stable during a mean treatment time of 19.2 +/- 2.3 months was 93.43%; this was considerably higher than in previous reports. Only a few factors were found to be associated with statistically significant higher success rates of MIs, including deep bites, placement in the attached gingiva of the maxilla, and en-masse distalization of teeth. Conclusions: The success rates of MIs in white patients were greater than the corresponding rates reported for Asian patients. Our results confirm the effectiveness of orthodontic MIs as temporary anchorage reinforcement devices and suggest various clinical factors as potential causes of failure. (Am J Orthod Dentofacial Orthop 2009;136:158.e1-158.e10)