Abstract:

Objective To evaluate the effect of taper and inserting angle on stability of micro-implants in type Ⅱ bone and toprovidetheoretical evidencefor clinical selectionoftaper andinsertingangle. Methods Three-dimensionalfinite element models of type Ⅱ bone sections and micro-implants were fabricated. They were designed using different tapers (diameter between 1.1 to 1.6 mm, taper between 0 to 0.062 5) and different inserting angles ranging from 30° to 90° (30°, 45°, 60°, 75°, 90°). Effects on the maximum von Mises stresses in mandible and micro-implants, as well as on the maximum displacements inmicro-implants, were analyzedunder an applied 2N horizontalforce. Results Theinserting anglehadasignificant effect on stresses and displacements, with lower distribution of stresses and displacements occurring at 60°. The effect of the taper wasalsorelatedtotheinsertingangle.Theminimumstresseswere5.0134MPa(corticalbone)and25.1310MPa(micro-implant) in modelD at 60°. The displacements of micro-implantswere proportional to the taper. Conclusion The insertingangle has a significant effect on stability of micro-implants, and the recommended inserting angle is 60°. The influence of taper on the stability of micro-implants is related to the inserting angle. The micro-implant with 0.037 5 taper(maximum diameter is 1.6 mm, minimum diameter is 1.3 mm) ismoresuitablefor type Ⅱ bones.

Key words: micro-implant, inserting angle, taper, stability