Comparison of the Biomechanical Behaviour of Short Dental Implants Placed Equicrestal and Subcrestally in D3 and D4 Bone - FEM Study

Abstract

Aim: To investigate the biomechanical performance of short equicrestal and subcrestal implants in D3 and D4 bone by 3D finite element analysis (FEA).
Methods and Materials: In this computational 3D FEA study, four implant configurations (lengths: 6, 7.5 mm; diameters: 4.6, 5.8 mm) in D3 and D4 bone were modelled. The axial and oblique (0°, 15°, 30°) loading of equicrestal and subcrestal (0.5, 1.0, 1.5, 2.0 mm) placements were investigated. No clinical sampling was done; all models were computational. Groups were defined by bone type (D3 vs. D4), implant diameter, implant length, implant placement depth and loading angle. Von Mises stresses at the bone-implant interface were determined, and statistical analysis used one-way ANOVA with Tukey’s HSD post-hoc test.
Results: Stress distribution was significantly related to bone quality, implant diameter, placement depth, and loading angle (p < 0.05), but not implant length (p = 0.1327). D4 bone showed approximately 30% higher stress than D3 bone (mean difference: −5.83 MPa, p < 0.0001). Wider implants (5.8 mm) reduced stress by 25-30% compared with narrower implants (4.6 mm), particularly in D4 bone (p < 0.0001). Greatest stress reduction occurred at 0.5 mm subcrestal placement (p = 0.0154). Loading angle had the strongest effect (F = 50.30) with stress almost doubled at 30°.
Conclusions: The implant diameter and depth of placement can be optimized to partially compensate for compromised bone quality, while the control of the loading direction is still essential. Clinically, in low density bone, wider implants and subcrestal placement of 0.5 mm are preferable with occlusal management to reduce non-axial loading.