Effets de la longueur des mini-vis et de la densité osseuse sur la résistance d'ancrage: une étude in vitro

Introduction: With conventional anchorage, it is usually hard to accomplish a satisfactory result with an absolute anchorage, and this limitation could be resolved by the usage of mini-screw. The successful rate of miniscrew usage depends on its stability, which was determined by its length, bone density, cortical bone thickness, the insertion technique, the insertion angle, and the applied loads. Objective: To observe the effect of miniscrew length and bone density on anchorage resistance. Material and methods: Thirty pieces of miniscrew with 1.6 mm in diameter were divided into three groups based on its length (n = 10): 10 mm (L), 8 mm (M), and 6 mm (S). Each group was further divided into 2 sub-groups: to be planted in optimal density bovine ribs (L1, M1, S1) and to be planted in low-density bovine ribs (L2, M2, S2). The density of bovine ribs was measured by CBCT. After the insertion of miniscrews based on respective groups, tensile test was done by means of Autograf Univerval Testing Machine to measure its stability. The data recorded was analysed using the Least Significant Difference (LSD) Fisher's test. Results: The results of this study showed that L1 provided the greatest stability than other groups. On the other hand, the least stability was found in S2. Conclusion: The length of miniscrew and the density of bone affect the stability of miniscrew. In bone with optimum density, 10 mm and 8 mm miniscrew equipped good anchorage resistance while in bone with low-density only 10 mm miniscrew provided favourable anchorage resistance.