Dental Implants Macro Design Affects Stress in Low-Quality Bone Site

Objectives: The purpose of this study was to biomechanically evaluate the influence of macro design parameters (collar and thread designs) on stress and strain concentration in the implant anchored in maxillary low-quality bone.
Methods: Six models were obtained from the combination of two collar designs (smooth [SC] and microthread [MC]) and three thread shapes (square, trapezoidal, and triangular) in external hexagon implants (4×10-mm) supporting a single zirconia crown in the upper first molar region. A 200-N axial occlusal load was applied to the crown, and measurements were made of the von Mises stress (σ_vM) for the implant, and tensile stress (σ_max), shear stress (τ_max), and strain (ε_max) for the surrounding bone. Data were evaluated by one-way ANOVA at a 5% significance level in order to point the parameter that more influenced the results.
Results: Collar design significantly influenced biomechanical behavior in the implant and cortical bone. The MC increased σ_vM (54.91±1.06-MPa) in the implant, as well as τ_max (11.98±0.07-MPa) and ε_max (970±70-με) in the cortical bone, despite the more favorable stress/strain distribution pattern. Thread design affected the biomechanics in the trabecular bone. Triangular shape showed the lowest values of σ_max (3.83±0.34-MPa), τ_max (4.14±0.47-MPa), and ε_max (900±40-με).
Conclusions: Stress/strain distribution patterns were influenced by collar design in the implant and cortical bone, and by thread design in the trabecular bone. MC and triangular thread-shape designs presented improved biomechanical behavior in low-quality bone.