Distinct healing dynamics associated with xenograft selection in guided bone regeneration

Guided bone regeneration relies on biomaterials that support bone formation while modulating the healing environment; however, materials with similar indications may exhibit different biological behaviors over time. This study compared the performance of two bovine-derived bone substitutes containing collagen using a rat calvarial critical-size defect model. Fifty-four Wistar rats were allocated to three groups: blood clot (control), Bio-Oss Collagen^®, and Extra Graft XG13^®. Standardized 5-mm defects were created and treated under guided bone regeneration conditions using a resorbable collagen membrane. Animals were euthanized at 7, 14, and 28 days. Mineralized tissue formation and microarchitecture were assessed by micro-CT, while histological, histomorphometric, inflammatory, angiogenic, and collagen organization analyses were performed to characterize the healing process. Both biomaterials supported tissue formation within the defect compared to the control. Extra Graft XG13^® was associated with higher mineralized tissue volume and volume fraction at 14 and 28 days, with more favorable micro-CT-derived microarchitectural parameters and reduced porosity. Early inflammatory and angiogenic responses were comparable between biomaterials, yet defects treated with Extra Graft XG13^® exhibited greater new bone formation over time. A reduction in mineralized tissue volume from 14 to 28 days in this group, accompanied by increased collagen organization, may suggest a possible transition toward remodeling; however, this interpretation should be considered with caution due to the absence of direct remodeling markers. In contrast, Bio-Oss Collagen^® showed a more gradual pattern of tissue formation and delayed collagen maturation. Overall, Extra Graft XG13^® was associated with greater mineralized tissue formation and a higher proportion of organized collagen fibers at later time points, indicating differences in the progression of mineralized tissue formation and matrix organization over time compared to Bio-Oss Collagen^®. These findings should be interpreted within the limitations of the experimental model.