Type-dependent Mechanical Stability of Orthodontic Miniscrew Implants

Objectives:
Miniscrew has been widely used as an absolute anchorage in orthodontic treatment. Strong initial mechanical stability of miniscrew is critical to bear immediate loading, which is also responsible for maintaining its mechanical stability for a long-term clinical success during orthodontic treatment. Types of miniscrew with different diameter, length, shape, and thread dimensions may have a substantial effect on mechanical stability of the miniscrew system. Thus, the objective of this study was to evaluate miniscrew type-dependent mechanical stability to assess mechanical properties of miniscrew systems in various thickness of artificial bone block using different measurement tools.
Methods:
Two types of miniscrews (15 Tomas and 15 AbsoAnchor; 1.6 mm diameter and 6 mm length) were placed in artificial bone block with different thickness of 1.5, 2.0, 3.0 mm. Values of maximum insertion torque (MIT), removal torque (RT), Periotest, implant stability quotient (ISQ), static stiffness (K), dynamic stiffness (K^*), and energy dissipation ability (tan δ) were assessed for each miniscrew system. Multivariate analysis of variance was performed to compare those values between miniscrew types and the bone block thicknesses. Pearson’s correlations of each K, Periotest and ISQ values with those of other properties. Analysis of covariance (ANCOVA) was performed to test the correlation slope differences between the miniscrew types.
Results: The MIT, RT, ISQ, K, and K^* values significantly increased when the miniscrews were placed in thicker bone block while Periotest values decreased. The K, Periotest and ISQ values were significantly correlated each other and also with other mechanical properties (p<0.001) except tan δ (p>0.35). However, the slopes of some correlations and absolute values of measurement were significantly different dependent on the miniscrew types (p<0.025).
Conclusions: The current findings suggest that miniscrew type-dependent calibrations are required to estimate mechanical stability of the miniscrew systems despite the utilization of same measurement tool.