Stability, Micromotion, and Microstrain in Short Implants with High C/I Ratios: Combined In Vitro and Finite Element Analysis Approach.

To evaluate the biomechanical behavior of short dental implants (4 mm) compared to longer implants (6-8-10 mm), especially in high crown-to-implant ratio scenarios. The study evaluates implant stability, micromotion under loading, and peri-implant bone microstrain, and investigates the effect of prosthetic splinting as a biomechanical strategy. Fifty implants with internal connections (Ø 4-6-8-10 mm) were placed in nine fresh bovine ribs and restored with standardized polymethylmethacrylate (PMMA) crowns to achieve C/I ratios of 1.22 (10 mm implants), 1.77 (8 mm), 2.7 (6 mm), and 4.55 (4 mm). Using resonance frequency analysis (RFA) and controlled loading (50N, 6° angulation), implant stability and micormotion were evaluated by image-based analysis. A subset of 4-mm implants was tested with a splinted PMMA bridge. Finite element analysis FEA) using models consistent with the in vitro setup was performed to evaluate bone microstrain, von Mises stress, and displacement. Implant stability (ISQ values) increased significantly with implant length, with the 10-mm group having the highest values (mean ISQ = 68.4, p < .05). Micromotion and FEA displacement were inversely correlated with implant length and positively correlated with the C/I ratio. The 4-mm implants had significantly higher micromotion and microstrain values, but splinting significantly reduced both parameters and achieved performance comparable to longer implants. Von Mises stress values in the peri-implant bone and abutments were highest in the 4mm.group. Short dental implants correlate with poorer values for dental implant stability than conventional implants. High C/I ratios in short implants are associated with increased micromovement and microloading of the bone, but splinting improves biomechanical performance and may be advisable when using short implants, especially in immediate loading protocols.