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

ABSTRACT 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° or 60° 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° angle (17.27 and 14.40 Ncm) compared with those placed at a 60° 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° angle resulted in a higher MIT.

摘要：
研究目的：本离体研究旨在通过分析最大植入扭矩（maximum insertion torque, MIT），评价微型种植体垂直放置角度对其初始稳定性的影响。
研究方法：将微型种植体植入30具人类尸体标本，分别以与上颌第一磨牙颊面呈90°或60°的角度植入。本次实验共使用60枚自钻式微型种植体，其中圆柱形与锥形种植体各占一半。通过测量最大植入扭矩（MIT）评估种植体初始稳定性。采用方差分析（Analysis of Variance, ANOVA）与Newman-Keuls检验对数据进行统计分析，设定显著性水平为5%。
研究结果：两种微型种植体在以90°角度植入时的最大植入扭矩（分别为17.27与14.40 N·cm）均高于以60°角度植入时的对应值（分别为14.13与11.40 N·cm）。
研究结论：上颌后牙区微型种植体的最大植入扭矩值随其垂直放置角度的不同而存在差异。无论使用何种类型的微型种植体，以90°角度植入均可获得更高的最大植入扭矩。