Effects of graft materials on bone regeneration using the osseous shell technique: an experimental study in rats

BACKGROUND: Autogenous bone (AB) is considered the gold standard for alveolar bone grafting, but its limitations have prompted the development of synthetic alternatives. The Shell technique provides a stable framework for bone augmentation. However, few studies have directly compared different graft materials under intraoral-like conditions, especially in mandibular models. This study aimed to quantitatively compare the osteogenic capacity of four graft materials-autogenous bone (AB), β-tricalcium phosphate (β-TCP), octacalcium phosphate collagen composite (OCPC), and atelocollagen absorbable sponge (AAS)-using a rat mandibular shell model that simulates intraoral conditions. METHODS: Cortical bone blocks were harvested from the mandibular body of 36 male Wistar rats, and mandibular reconstruction was performed using the Shell technique with cortical bone plates. Four graft materials, particulate AB, β-tricalcium phosphate (β-TCP), octacalcium phosphate collagen composite (OCPC), and Atelocollagen Absorbable Sponge (AAS), were evaluated. Each postoperative cohort consisted of 12 rats in total (n = 3 per group × 4 groups), and histological and histomorphometric analyses were performed at 8, 12, and 16 weeks postoperatively. RESULTS: AB generated significantly more new bone than the other materials at all time points. OCPC induced moderate limited regeneration until later stages, while β-TCP and AAS resulted in limited bone growth. The mandibular model effectively simulated oral anatomy and provided reliable structural support throughout the procedure. CONCLUSIONS: AB showed better osteogenic capacity than synthetic and composite materials. Use of the mandibular Shell technique with a rat model of mandibular defects proved useful for evaluating bone grafts under clinically relevant conditions.