Evaluation of stress distribution patterns on short implants with differing crown heights: a three dimensional finite element analysis

Abstract

Statement of problem: The use of short dental implants is usually confined to areas of the mouth with limited vertical bone height. As a result, longer implant crowns are required to restore the occlusion with the opposing arch, leading to a disproportionate crown-to-implant ratio (C/I ratio). Purpose: The purpose of this study was to evaluate the stress distribution patterns on crestal bone of short implants plateau-designed connected with different crown heights, and to compare these findings with those of regular implants. Material and Methods: Two implant designs (∅5 mm×6 mm and ∅5 mm×11 mm) and abutments (∅5 mm×9 mm and ∅5 mm×5 mm) were scanned using a micro-CT scanner. STL surface models were subsequently extracted to generate surfaces. All models were imported to Abaqus CAE for three-dimensional non-linear finite element analysis. For each implant model, loadings of 100, 200, and 700 N were simulated in 2 directions: pure vertical and at an oblique angle of 15 degrees. Results: At 100 and 200 N oblique loads, peak compressive and tensile stresses ranged from 18.30 to 53.57 MPa and 7.39 to 43.95 MPa, respectively. At 700 N oblique loads, the ∅5 mm×6 mm implant with long abutment model exceeded the compressive and tensile strength of cortical bone, at 193.4 and 158.6 MPa correspondingly. For 700 N oblique loads, increasing crown height increased peak compressive stress by 28.6 % and peak tensile stress by 28.4 %. Stress distribution patterns showed the highest amounts of stress located at the implant crest module in cortical bone. Conclusion: Stress distribution patterns for the oblique loads of 100 and 200 N were similar in all models, regardless of the C/I ratios. All peak stresses were within physiological tolerance. At 700 N loads, increasing crown height resulted in bone failure.