On the Significance and Predicted Functional Effects of the Crown-to-Implant Ratio: A Finite Element Study of Long-Term Implant Stability Using High-Resolution, Nonlinear Numerical Analysis

Abstract

With the rising popularity of short dental implants, the effects of the crown-to-implant (C/I) ratio on stress and strain distributions remain controversial. Previous research disagrees on results of interest and level of necessary technical detail. The present study aimed to evaluate the strain distribution and its functional implications in a single implant-supported crown with various C/I ratios placed in the maxillary molar region. A high-fidelity, nonlinear finite-element model was generated to simulate multiple clinical scenarios by laterally loading a set of single implants with various implant lengths (IL) and crown heights (CH). Strain distribution and maximum equivalent strain (MES) were analyzed to evaluate the effects and significance of the CH, IL and C/I. Predicted functional response to strain at the implant interface was analyzed by interface surface area. Results. Results were evaluated according to the mechanostat hypothesis to predict functional response. Overloading and effects of strain concentrations were more prevalent with increasing C/I. Overloading was predicted for all configurations to varying degrees, and increased with decreasing IL. Fracture in trabecular bone was predicted for at least one C/I and all IL of 10 mm or less. Higher C/I ratios and lower IL increase the risk of overloading and fracture. Increasing C/I augments the functional effects of other implant design factors. Greater C/I ratios may be achieved with implant designs that induce less significant strain concentrations.