Comparison Between Different Isoelectric Points Of Biodegradable Gelatin Sponges Incorporating Beta-Tricalcium Phosphate And Recombinant Human Fibroblast Growth Factor-2 For Ridge Augmentation: A Preclinical Study Of Saddle-Type Defects In Dogs

Background and Objective It is well known that recombinant human fibroblast growth factor-2 (rhFGF-2) signaling plays an important role in tissue repair and regeneration. rhFGF-2 strongly binds to acidic gelatin via ionic linkages and is gradually released upon gelatin decomposition. On the other hand, the linkage between rhFGF-2 and basic gelatin is so weak that most rhFGF-2 is rapidly released from basic gelatin by simple desorption. Gelatin/beta-tricalcium phosphate (beta-TCP) sponges, which comprise 50 wt% gelatin and 50 wt% beta-TCP in a cross-linked structure, can release rhFGF-2 gradually owing to their electrical features. In a previous study, we reported that new bone height in the test group using rhFGF-2 with acidic gelatin/beta-TCP sponges was significantly greater than that in the control group using acidic gelatin/beta-TCP sponges alone in a ridge augmentation model in dogs. However, whether these results depend on controlled release by the gelatin/beta-TCP sponges remains controversial. In this study, we evaluated the effects of controlled release by comparing acidic and basic gelatin/beta-TCP sponges with different isoelectric points (IEP) on ridge augmentation in dogs. Materials and Methods Twelve weeks after extraction of the maxillary second and third incisors of six dogs, critically sized saddle-type defects (8 mm length x 4 mm depth) were surgically created bilaterally 2 mm from the mesial side of the canine. Acidic gelatin/beta-TCP sponges (IEP 5.0) soaked with 0.3% rhFGF-2 were applied to the defect in the acidic group, whereas basic gelatin/beta-TCP sponges (IEP 9.0) soaked with 0.3% rhFGF-2 were applied to the defect in the basic group. Twelve weeks after surgery, biopsy specimens were obtained and subjected to microcomputed tomography (micro-CT) and histological analyses. Results New bone area detected by micro-CT analysis was significantly smaller in the basic group than in the acidic group. New bone height calculated by histologic sections was significantly lower in the basic group than in the acidic group. The total tissue height was lower in the basic group than in the acidic group. However, the differences between both sites were not significant. Conclusions These findings suggest that in ridge augmentation of saddle-type defects, controlled release of rhFGF-2 induces notably more alveolar bone formation than does short-term application of rhFGF-2.