Effects of Cusp Inclination and Occlusal Table Dimensions on the Loading on Implant Systems and Simulated Bone

Abstract

Occlusal surface design is an important factor for controlling force magnitude and direction on implant components and supporting bone. It has been recommended that reducing cuspal inclination and occlusal table dimension is beneficial to the long-term success of the implants and bone. The appropriate superstructure design, including the occlusal surface design of cuspal inclination and the occlusal table dimensions in single-implant restorations, needs to be investigated in an attempt to understand this influence on occlusal load and bone. This study demonstrates a method to apply quantified axial forces to the four different occlusal design models – model one (30-degree cusp inclination with 6-mm occlusal table dimension), model two (30-degree cusp inclination with 3- mm occlusal table dimension), model three (10-degree cusp inclination with 6- mm occlusal table dimension), and model four (10-degree cusp inclination with 3-mm occlusal table dimension) by using an Instron universal testing system to simulate implant-supported single crowns and the supporting bone. Static loads from 50 N to 250 N were applied for 15 seconds and recorded. The applied forces were loaded on two loading sites; the central area and 2 mm buccally of the occlusal inclined plane. Data were analysed to compare the maximum principal strains (microstrains) registered by strain gauges in the buccal and lingual areas of the bone simulated model. This study has shown that there are differences between the four occlusal design models. Loading on the central area of the occlusal specimens caused a significant difference in mean maximum principal strains compared with the 2-mm buccal loading of the occlusal specimens. Under loading applied at 2 mm, the highest mean maximum principal strain was seen in the model one, followed by model three and two. The lowest was presented in model four. Univariate Analysis of Variance (ANOVA) with post hoc test comparing the maximum principal strains (microstrains) for four different occlusal design specimens indicated a significant difference of the maximum principal strains (microstrains) between model one, two, three, and four, when an applied axial loading at 2 mm buccal on the inclined plane with strain gauges attached on the bone simulated model (p = 0.000). The results from this study suggest that cusp inclination and occlusal table dimension significantly affect the magnitude of forces transmitted to implant supported prostheses, which would have an effect on surrounding bone strains of dental implants when occlusal loads are applied in the clinical situations. The occlusal table dimension seems to play a more important role than cusp inclination, although the cusp inclination is still a factor to be considered. Moreover, combination of the two factors, cusp inclination and occlusal table dimension, significantly affects the magnitude of forces transmitted to implant supported prostheses.