Effects of Hyaluronic Acid on Rat Pulp Regeneration

Objective: Hyaluronic acid (HA) is widely utilized as biomaterials for wound healing and regeneration in a variety of tissues. In the present study, we examined whether HA is suitable for the inducer of pulp wound healing and the scaffold for pulp regeneration. Methods: Wistar rats were anesthetized, after which dental pulp was exposed on occlusal aspects of maxillary first molars, and HA and collagen sponge were implanted into exposed pulp. One and three weeks after implantation, molars were carefully isolated, fixed, and demineralized. Serial sections were stained with hematoxylin and eosin for histological analysis. We also examined effects of FGF-2 on reparative dentin formation in these implants. Results: One week after implantation, invasion of neutrophils, pulp cells, and endothelial cells into implants were observed in both groups. Inflammatory responses such as the invasion of neutrophils in collagen sponges were more severe than those in HA. In contrast, the invasion of pulp cells and endothelial cells were larger in HA than that in collagen sponges. Three weeks after implantation, the number of pulp cells and endothelial cells increased in both groups, especially implanted HA were almost replaced by pulp tissue. Intermediate inflammatory responses continued in the group implanted collagen sponges, whereas no inflammation was observed in the group implanted HA. Reparative dentin formation was almost same among these groups in one and three weeks. When FGF-2 were mixed in implants, intensive induction of reparative dentin formation was observed in HA, compared with collagen sponges. Conclusion: Our results suggest that HA shows better biocompatibility than collagen sponge as the inducer of pulp wound healing and the scaffold for pulp regeneration. FGF-2 may be essential for the induction of reparative dentin formation. Supported by Grants (18592094, 18209057) from The Ministry of Education, Science, and Culture of Japan, Tokyo, Japan.