OBJECTIVETo evaluate the effect of taper and inserting angle on stability of micro-implants in type II bone and to provide theoretical evidence for clinical selection of taper and inserting angle.

METHODSThree-dimensional finite 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 0.0625) and different inserting angles ranging from 30 degrees to 90 degrees (30 degrees, 45 degrees, 60 degrees, 75 degrees, 90 degrees). Effects on the maximum von Mises stresses in mandible and micro-implants, as well as on the maximum displacements in micro-implants, were analyzed under an applied 2 N horizontal force.

RESULTSThe inserting angle had a significant effect on stresses and displacements, with lower distribution of stresses and displacements occurring at 60 degrees. The effect of the taper was also related to the inserting angle. The minimum stresses were 5.013 4 MPa (cortical bone) and 25.1310 MPa (micro-implant) in model D at 60 degrees. The displacements of micro-implants were proportional to the taper.

CONCLUSIONThe inserting angle has a significant effect on stability of micro-implants, and the recommended inserting angle is 60 degrees. The influence of taper on the stability of micro-implants is related to the inserting angle. The micro-implant with 0.0375 taper (maximum diameter is 1.6 mm, minimum diameter is 1.3 mm) is more suitable for type II bones.