Evaluation of success rate and biomechanical stability of ultraviolet-photofunctionalized miniscrews with short lengths

Introduction: The aim of this research was to verify that ultraviolet light (UV)–photofunctionalization improves the success rate and biomechanical stability of miniscrews regardless of length, and to evaluate the comparability of biomechanical stability between UV-photofunctionalized miniscrews with short lengths and untreated miniscrews with conventional lengths. Methods: Eight male beagles (age, 12-15 months; weight, 10-13 kg) received a total of 64 miniscrews, including 7-mm and 4-mm untreated and UV-photofunctionalized, acid-etched miniscrews with the use of a random block design. The cumulative success rates were examined in all studied groups. The insertion and removal torques and screw mobility were measured. Microcomputed tomographic scans and histomorphometric analyses were performed at 8 weeks postoperatively. Results: The success rates of 7-mm UV-untreated and UV-photofunctionalized miniscrews were 87.5% and 100%, respectively, vs 43.8% for the 4-mm UV-untreated and 4-mm UV-photofunctionalized miniscrews. The rates were significantly different in accordance with the length (P <0.001). There were no differences in the insertion and removal torque and screw mobility between groups according to the length or UV treatment. However, the 4-mm UV-untreated miniscrews yielded a mean bone area ratio of 6.35 ± 7.43%, whereas the 7-mm UV-photofunctionalized miniscrew yielded a mean ratio of 32.17 ± 8.34% (P = 0.037). Conclusions: The UV-photofunctionalization significantly increased the biomechanical stability and led to increased bone and miniscrew contact area in dogs with miniscrews of the same length. However, the most important factor that affected the success rate of the miniscrew was the length.