Influence of Residual Bone Thickness on Primary Stability of Hybrid Self-Tapping and Cylindric Non-Self-Tapping Implants in Vitro

Purpose: To assess the primary stability of a hybrid self-tapping implant and a cylindric non-self-tapping implant in an in vitro test model using polyurethane foam. Materials and Methods: Eighty standardized blocks of cellular rigid polyurethane foam, 2 cm long and 1 cm wide, with different thicknesses of 2, 4, 6, and 9 mm (n = 10 per group) were cut. Two implant systems-a hybrid self-tapping (Tapered Effect [TE], Straumann) and a cylindric non-self-tapping (Standard Plus [SP] Wide Neck, Straumann) were placed in the block specimens. Subsequently, resonance frequency analysis (RFA) was performed. The RFA measurements were made in triplicate on four aspects of each implant (mesial, distal, buccal, and oral), and the mean RFA value was calculated. Subsequently, the tensile load of the implants was determined by pull-out tests. The data were analyzed using one-way and two-way analysis of variance followed by a post hoc Scheffé test and a t test (α = .05). Additionally, the simple linear correlation between the RFA and tensile load values was evaluated. Results: No statistically significant differences were found between TE and SP in terms of RFA at different bone thicknesses. Starting from a bone thickness of 4 mm, TE implants showed significantly higher tensile load compared to SP implants (P = .016 to .040). A correlation was found between the RFA measurements and tensile load. Conclusions: Mechanically stable placement is possible with TE and SP implants in a trabecular bone model. RFA and tensile load increased with greater bone thickness. Keywords: bone density, dental implants, resonance frequency analysis, tensile load measurement