The Influence of Surface Roughening of Orthodontic Miniscrews on Their Clinical Success Rate

Abstract

Introduction Today miniscrews have replaced traditional anchorage appliance systems. Although they have lots of advantages, their success rate is not as much as the conventional endoosseous implants. Implant surface roughening is one of the most relevant factors, which greatly increases the osseointegration of endosseous implants. Aim This study was designed to evaluate the efficacy of miniscrew surface roughening by sandblasting and acid etching on success and survival rate of miniscrews, and, the influence of using chlorhexidine 0.2% mouth-rinse on their immediate failure rate. Material and Method This was a randomized clinical trial with a split mouth design. In this study 62 miniscrews inserted in 31 patients, which their treatment plan consisted of placing one miniscrew on each side of their maxillary arch between the first molar and the second premolar (2 screws for each patient, regular and surface roughened). In the first fifteen patients, according to the admission to the office, a chlorhexidine 0.2 % rinsing before screw insertion and twice a day for one week, was prescribed. All the miniscrews were loaded six weeks after insertion. Chi-square test was done for comparing the insertion torque, effect of insertion side and chlorhexidine application on miniscrew success rate. Moreover, the Mann-Whitney U test was performed for comparing the insertion and removal torque in two screw types and success rate in different age groups. Paired sample t test was used due to comparing the insertion torques in both sides. And the survival rate analysis was done using log rank analysis. Results In the first six weeks after miniscrew insertion and before loading 13.3 % of the miniscrews in the group of patients whom were rinsed with chlorhexidine 0.2% mouth-rinse failed to meet the survival criteria, however, the failure rate for the other patients was 6.3 %. This difference was not statistically significant. Surface roughening did not significantly increase the long term success rate (90.3 % versus 83.9 %), whereas it caused a significant increase in the mean screw removal torque (15.71 versus 8.08 NCm). Moreover, there was no relationship between the miniscrews failure rate and the placement side (left or right). However, the failure rate of the miniscrews was statistically significantly higher in the younger patients. Conclusion The results of this study failed to show a relation between the miniscrews success rate and patients gender, rinsing with chlorhexidine 0.2%, surface roughening modification, insertion torque value and placement side (left or right side of the jaw) in the maxilla. However, there was a statistically significant difference regarding patients age and miniscrews success rate. Perhaps the higher success rate in elder patients could be due to lower bone mineral density. The results showed roughening the miniscrews surface increased the torque removal value, however, it did not increase the success rate