Influences of internal tapered abutment designs on bone stresses around a dental implant: three-dimensional finite element method with statistical evaluation.

Background: The aim of this study is to determine the effects of various designs of internal tapered abutment joints on the stress induced in peri-implant crestal bone by using the three-dimensional finite element method and statistical analyses.
Methods: Thirty-six models with various internal tapered abutment-implant interface designs including different abutment diameters (3.0, 3.5, and 4.0 mm), connection depths (4, 6, and 8 mm), and tapers (2°, 4°, 6°, and 8°) were constructed. A force of 170 N was applied to the top surface of the abutment either vertically or 45° obliquely. The maximum von Mises bone-stress values in the crestal bone surrounding the implant were statistically analyzed using analysis of variance. In addition, patterns of bone stress around the implant were examined.
Results: The results demonstrate that a smaller abutment diameter and a longer abutment connection significantly reduced the bone stresses (P <0.0001) in vertical and oblique loading conditions. Moreover, when the tapered abutment-implant interfaced connection was more parallel, bone stresses under vertical loading were less (P = 0.0002), whereas the abutment taper did not show significant effects on bone stresses under oblique loading (P = 0.83). Bone stresses were mainly influenced by the abutment diameter, followed by the abutment connection depth and the abutment taper.
Conclusion: For an internal tapered abutment design, it was suggested that a narrower and deeper abutment-implant interface produced the biomechanical advantage of reducing the stress concentration in the crestal region around an implant.