Effects of osteotomy preparation protocols and implant macrogeometry on primary stability in an ex vivo bovine-rib model

Purpose To evaluate the effects of four osteotomy preparation protocols and two implant designs on immediate mechanical stability outcomes in an ex vivo bovine-rib model. Trabecular density was not measured; therefore, the model is not classified as objectively low-density bone. Methods Eighty independent fresh bovine ribs (one implant per rib) were randomly allocated to eight groups ( n = 10). Two implant designs (V2 and Quattro) were placed after conventional drilling (lance-shaped initial drill, 2.0-mm helical drill, 3.0-mm helical drill, and 3.3-mm final helical drill), undersized drilling (lance-shaped initial drill, 2.0-mm helical drill, and 3.0-mm final helical drill), expansion (lance-shaped initial drill, 2.0-mm helical drill, and 2.6-, 3.0-, and 3.4-mm expanders), or osteodensification (lance-shaped initial drill, followed by a 2.0-mm helical drill clockwise and 2.3-, 2.5-, 3.0-, and 3.3-mm densifying burs counterclockwise). Peak insertion torque was recorded using a Ticare dynamometric torque wrench. Implant stability was assessed by Periotest and resonance frequency analysis (RFA; implant stability quotient [ISQ]) before reverse-torque testing. Neither trabecular density nor another objective bone-quality measure was available. Results Implant macrogeometry significantly affected insertion torque, reverse torque, and ISQ (all p < 0.001), whereas preparation technique affected insertion torque and reverse torque. Undersized drilling produced higher insertion torque than conventional drilling (Holm-adjusted p = 0.044); osteodensification did not differ significantly from conventional drilling. Macrogeometry-by-technique interactions were observed for reverse torque ( p < 0.001) and ISQ ( p = 0.032). The pooled insertion-torque–ISQ correlation ( r = 0.496; p < 0.001) remained significant after adjustment for macrogeometry, technique, and their interaction (B = 0.176 ISQ units/N·cm; 95% CI, 0.071–0.282; p = 0.001). Conclusions In this ex vivo bovine-rib model, outcomes varied by implant design, the complete preparation protocol, and the outcome measure. Because protocol components differed together, effects cannot be attributed to a single mechanism such as osteotomy diameter or densification. Findings are limited to the V2 and Quattro designs, the four preparation protocols tested, and immediate mechanical outcomes; they do not establish a general clinical hierarchy or characterize objectively low-density human alveolar bone. Clinical trial registration Not applicable.