Comparative Histological Evaluation of Collagen Matrix Architectures for Soft Tissue Augmentation in the Oral Cavity: A Preclinical Canine Model.

Intraoral soft-tissue defects are traditionally managed with autogenous connective tissue grafts, though donor site morbidity has driven interest in xenogeneic collagen matrices as alternatives. However, the impact of matrix architecture on soft-tissue integration remains poorly understood. This study compared soft-tissue responses to a sheet-form collagen matrix (ShCM) and a spongy collagen matrix (SpCM) placed beneath full-thickness flaps in a beagle mandibular defect model. Standardized bilateral defects were created in 23 skeletally mature female beagles. Defects were then assigned to serve as the negative control (sham) or were treated with porcine collagen matrix in (i) sheet form (ShCM) (Regenity Biosciences, Oakland, NJ, USA), or (ii) porous/spongy form (SpCM) (Fibro-Gide®, Geistlich Pharma North America, West Windsor Township, NJ, USA). The mandibular sites that received no surgical intervention served as positive controls. Experimental conditions were randomized and interpolated within each animal to minimize anatomical site bias and evaluated histologically at 4- (n = 7), 8- (n = 7), and 12-weeks (n = 9) postoperatively. Histologic sections were evaluated for matrix presence, inflammation, subepithelial healing, and matrix thickness. At 4 weeks, both matrices were present, though SpCM showed significantly higher inflammation scores (p = 0.013). By 8 weeks, ShCM demonstrated greater resorption (p = 0.003) alongside an organized collagen layer with fibroblasts and new microvessels, while SpCM remained thick and porous, with a persistent fibrous capsule and elevated inflammation versus both ShCM (p = 0.002) and sham (p = 0.009). At 12 weeks, inflammation declined and subepithelial healing improved similarly across matrix groups. These findings suggest matrix architecture influences soft-tissue healing outcomes in the oral cavity. Sheet-form matrices may be preferable where biocompatibility and predictable integration are priorities, while spongy matrices may better support long-term space maintenance and tissue ingrowth. However, clinical studies are needed to confirm these translational implications.