Digital Image Correlation Validation of Finite Element Strain Analysis of Dental Implant Insertion for Two Implant Designs

Sufficient anchorage of dental implants, defined as mechanical engagement between implant and bone at the time of insertion, has been recommended for positive clinical outcomes, particularly in immediate loading protocols. Accurate measuring and analysis of stress and strain in the bone are imperative to understand anchorage from the biomechanics perspective. However, the stress and strain distributions at the bone-implant interface are impossible to measure in vivo. Therefore, the aim of this study was to develop and validate an explicit continuum finite element analysis (FEA) to investigate the stress and strain in a bone surrogate during the insertion of a dental implant: with cutting flute (CF) and without (NCF). Ten dental implants (five with CF and five with NCF) were inserted into ten rigid polyurethane (PU) foam blocks with a prepared pilot hole. During the insertion, a stereo digital image correlation (DIC) system was used to record in-plane deformation on the PU foam surface at a frequency of 1.0 Hz; and, surface von Mises strain, epsilon(v_DIC), was calculated (VIC-3D, Correlated Solutions Inc). In parallel, the insertion was simulated using FEA with explicit solver (Abaqus Explicit version 2017, Simulia). The PU foam was defined as an elastic-plastic material with a progressive crushable foam failure behaviour. The surface von Mises strain predicted from FEA, epsilon(v_FEA), was compared against epsilon(v_DIC). Uncertainty of DIC displacement measurement was 0.6 mu m; and the static noise floor for the strain measurement was 500 microstrain (mu epsilon). Coefficient of determination for epsilon(v_DIC) and epsilon(v_FEA) along a horizontal line for the CF and NCF implants were 0.80 and 0.78, respectively, which suggested the overall FEA performance was good. FEA results indicated that the cutting flute reduced the maximum shear stress in the PU foam and axial force which facilitated the insertion with less effort. This study demonstrated the successful combination of mechanical testing and FEA to better understand the mechanics of dental implant insertion.