Effect of vertical placement angle on the insertion torque of mini-implants in human alveolar bone.

OBJECTIVE: The aim of the present ex-vivo study was to evaluate the effect of the vertical placement angle of mini-implants on primary stability by analyzing maximum insertion torque (MIT). METHODS: Mini-implants were placed in 30 human cadavers, inserted at either a 90 degrees or 60 degrees angle to the buccal surface of the maxillary first molar. Out of 60 self-drilling mini-implants used, half were of the cylindrical type and half were of the conical type. Primary stability was assessed by means of measuring the MIT. Data were subjected to analysis of variance (ANOVA) and Newman-Keuls tests. A significance level of 5% was adopted. RESULTS: The MIT was higher for both mini-implant types when they were placed at a 90 degrees angle (17.27 and 14.40 Ncm) compared with those placed at a 60 degrees angle (14.13 and 11.40 Ncm). CONCLUSIONS: MIT values were differed according to the vertical mini-implant placement angle in the maxillary posterior area. Regardless of the type of mini-implant used, placement at a 90 degrees angle resulted in a higher MIT.