Stability of orthodontic miniscrews according to screw design

Abstract

Stability of orthodontic miniscrews according to screw designThis study was to evaluate the clinical efficiency of tapered and cylindrical miniscrews by estimating their success rate and long-term stability. There were 105 tapered and 122 cylindrical self-drilling miniscrews placed into the maxillary and mandibular buccal alveolar areas of 132 patients (43 males, 89 female) who were over 16 years old. The insertion torque (IT) and removal torque (RT) were measured using a torque sensor during implantation and removal of miniscrews and Periotest values (PTV) were recorded. And the miniscrews were checked after implantation to determine success or failure. The results of this study were as follows.1)The success rates of the tapered and cylindrical miniscrews examined were similar between two types of design. 2)In the buccal side of maxilla, the insertion torque of tapered miniscrews (8.3 Ncm) was significantly higher than that of cylindrical miniscrews (6.3 Ncm) (P <0.05). And the PTVs of the tapered miniscrews were significantly lower than that of cylindrical miniscrews in maxilla (P <0.05). 3) In the maxilla, the miniscrews falling within the low insertion torque range (below 3 Ncm) had a significantly lower success rate than the miniscrews in other groups. 4) The removal torque values showed no significant difference between the tapered and cylindrical miniscrews in the upper and lower buccal areas (P >0.05).5)The distal area of the first molar had significantly lower success rates than other sites of insertion (P <0.01). But there was no significant difference in success rates according to gender, jaw and side of insertion. Tapered type miniscrews had higher initial stability compared to cylindrical type miniscrews, whereas the clinical success rates and removal torques were similar between the two designs. The long term stability and success rate can be affected by various factors, such as insertion torque, individual anatomical variation and insertion site.