Membrane-free bone regeneration using biphasic calcium phosphate, heterologous fibrin biopolymer, and photobiomodulation: an in vivo study.

BACKGROUND: Although bone tissue possesses inherent regenerative capacity, critical-sized defects require grafts for complete functional repair. This in vivo study evaluated the bone repair process using laser photobiomodulation therapy (PBM) in defects filled with a combination of hydroxyapatite, β-tricalcium phosphate and heterologous fibrin biopolymer (HFB). METHODS: Thirty male rats were divided into three groups: biomaterial alone (BG), biomaterial + HFB (BBG), and biomaterial + HFB + PBM (BBPG). A 5-mm circular calvarial osteotomy was performed and filled according to each protocol. In BBPG, an 830-nm laser was applied immediately post-surgery and three times weekly until euthanasia at 14 or 42 days. Analyses included micro-CT, histomorphology, histomorphometry, and polarized light microscopy of collagen fibers. RESULTS: Micro-CT showed centripetal bone regeneration restricted to defect margins, with biomaterial particles persisting centrally. Histologically, new bone progressed from immature trabecular architecture at day 14 to a mature lamellar conformation by day 42, notably in BBPG. All groups showed a significant temporal increase in new bone percentage. BBPG demonstrated superior bone growth at 42 days (26.64 ± 2.15%) compared to BG (14.85 ± 1.63%) and BBG (20.05 ± 1.70%). The birefringence of the collagen fibers showed a color transition from red to yellowish-green during the analyzed periods. CONCLUSION: The combination of the biomaterial, fibrin biopolymer and photobiomodulation significantly enhanced bone defect repair and matrix maturation without barrier membranes, presenting high translational potential for cost-effective clinical applications in regenerative medicine.