Sequential healing of onlay bone grafts using combining biomaterials with cross-linked collagen in dogs

Objectives: The aim of this study was to observe the sequential healing of onlay grafts in terms of the volumetric and histologic changes using different bone substances and absorbable membranes according to the presence of collagen cross-linking. Material and methods: Four groups involving onlay grafting with different materials were randomly assigned to both sides of the maxillae of 15 beagle dogs: (i) control group without any treatment; (ii) group NN, bovine hydroxyapatite incorporated into a non-cross-linked collagen matrix (BHC) + non-cross-linked collagen membrane (NCCM); (iii) group NC, BHC + cross-linked collagen membrane (CCM); and (iv) group CC, porcine hydroxyapatite incorporated into a cross-linked collagen matrix + CCM. Radiographic and histological analyses were performed after three different healing periods: 4, 8 and 12 weeks. Results: At week 4, the bone substances were well localized under the barrier membrane in groups NC and CC, while the bone substances became spread out and flattened in group NN. Similarly, the augmented height was significantly greater in groups NC and CC (2.55 and 2.51 mm, respectively; median) than in group NN (1.96 mm, P < 0.001, both). The percentages of newly formed bone were significantly higher at week 12 than at weeks 4 and 8 in all of the groups. The NCCM showed an earlier angiogenesis pattern than the CCM; however, earlier degradation was observed at week 12. Conclusion: Combining biomaterials with cross-linked collagen might contribute to maintaining its initial morphology with excellent biocompatibility in early healing period of lateral onlay grafts.