Histological evaluation of bone graft healing in maxillary sinus floor augmentation at two healing time points: a randomized clinical trial

This study aims to compare the effects of two distinct healing periods (4 and 8 months) on bone formation after maxillary sinus floor elevation surgeries using sintered bovine bone grafts through histological and histomorphometric analyses. Using a split-mouth design, fourteen participants with bilateral edentulism in the posterior maxilla were included and randomized into two groups with 4 months (Test Group - TG) and 8 months (Control Group - CG) of healing periods. After the healing period, bone samples were collected and subjected to histomorphometric analysis to quantify the percentages of newly formed bone, residual bone substitute, and soft tissues. Comparison between the groups was performed using the paired Student's t-test (p<0.05). Twenty-eight maxillary sinus grafts were performed, and 54 dental implants were placed. Histological analysis revealed newly formed trabecular bone tissue in close contact with the bone substitute surface, with higher thickness observed in the CG. Collagen fibers in the CG exhibited greater birefringence, indicating increased thickness and organization compared to the TG. Histomorphometric analysis demonstrated a significant difference in the percentage of new bone formation between the CG (28.22 ± 6.29%) and TG (20.02 ± 5.97%; p<0,001), as well as in the percentage of residual bone substitute (TG: 39.12 ± 8.15%; CG: 31.65 ± 8.70%; p = 0.005). The proportion of soft tissues remained stable between groups. The 8-month healing period significantly increased bone tissue formation and maturation, suggesting that this interval optimizes the quality of grafted bone when using sintered bovine bone substitute.