Fixation screw minimizes bone graft loss following autogenous lateral block graft augmentation: An experimental in vivo study

Abstract

Purpose: Assess the role of tenting screws in the remodeling processes of autogenous bone blocks used for mandibular lateral augmentation in rabbits.

Methods: Eighteen rabbits, approximately 3.5-4.0 kg of weight and 4-5 months of age, were included in this study. One lateral side of the angle of the mandible was augmented with block autografts. Animals were euthanized after 7, 20 and 60 days of healing, respectively. Biopsies were taken for each period and specimens underwent microtomographic scanning. The total volume (TV, mm³), bone volume (BV: residual graft plus new bone, mm³), periimplant bone volume (PIBV), bone implant contact (BIC) along the screw and linear bone gain at five vertical points symmetrically dispersed from the fixation screw in the midline were measured. ANOVA and the t-test were performed.

Results: The total volume (TV) of autografts decreased between 7 and 60 days from 258.13±15.3 mm³ to 107.2 ± 17.5 mm³ (p < 0.05). Contraction rates of 58.5% were observed. BV was 52.8 ± 7.7 mm³, 27.2 ± 11.1 mm³, and 33.1 ± 2.8 mm³ after 7, 20, and 60 days of healing, respectively. PIBV and BIC remained unchanged along time demonstrating no contraction around the screw. Total linear bone gain demonstrated a total of 18% linear contraction after 60 days. Point 1, demonstrated no changes along time representing no resorption along time. Points 2 and 4 demonstrate a minimum linear contraction (10-15%) with borderline significance. Resembling the total results, contraction starts after 20 days. Points 3 and 5 demonstrate a statistically significant contraction (p<0.05) of 35-40% starting at 20 days.

Conclusion: Tenting screws may reduce bone resorption symmetrically in a model of lateral block augmentation.

Keywords: Autograft; Microtomography; Rabbits.