Influence of different crown heights on shorter implants with different lengths, diameters, and designs at atrophic posterior mandible: A finite element analysis

Abstract

Aim: The aim of the study is to compare the stresses cause of different crown heights on short implants with different lengths, diameters and designs under axial and oblique loads on the cortical bone and implant system using finite element analysis.
 Methodology: In the atrophic posterior mandible, 4 different implants of different sizes and designs were placed in the first molar region. Metal supported porcelain crowns with three different heights (10 mm, 12.5 mm, 15 mm) were designed on computer. Total of 12 study models were created. Axial and oblique loads were applied and by finite element analysis method Von Mises values in implant and abutment; maximum and minimum principal stress values in cortical bone were evaluated.
 Results
 Compared to axial load, significantly higher stress values were found at implant and cortical bone in obliquelly loaded models. As the length and diameter of the implant increased, the stresses on the cortical bone decreased. Compared to the threaded implant, the plateau design implant caused less stress on the bone under vertical loads, while causing more stress on the oblique.
 Unlike to the literature, it was observed that the stresses on the implant was higher in the larger diameter implant compared to the narrower.
 Conclusions
 As a result of the stress values obtained within the limits of the analysis, when the lengths of the crowns restored on short implants were compared, it was determined that the axial forces were at an acceptable level under all conditions.