The present study was undertaken to evaluate the applicability of chitosan monomer (D-glucosamine hydrochloride) as a Pulp capping medicament. Both hi vitro and in vivo experiments were carried out to study the cell metabolism and Wound healing mechanisms following the application of chitomonosaccharide. After 3 days of osteoblast culture, alkaline phosphatase (ALP) activity Significantly increased in the chitosan group. Reverse transcription polymerase chain reaction analysis revealed that chitosan induced an increase in the expression of ALP mRNA after 3 days and bone morphogenetic protein-2 mRNA after 7 days of osteoblast incubation. Inflammatory cytokine, interleukin (IL)-8, synthesis in fibroblasts was strongly suppressed in the medium Supplemented with chitosan monomer. Histopathological effects were evaluated in rat experiments. After day, inflammatory cell infiltrations were observed to be weak when compared with the application of chitosan polymer. After 3 days, a remarkable proliferation of fibroblasts was seen near the applied chitosan monomer. The inflammatory cell infiltration had almost completely disappeared. After 5 days, the fibroblastic proliferation progressed, and some odontoblastic cells appeared at the periphery of the proliferated fibroblasts. These findings indicate that the present study is the first report that chitosan monomer acts as a biocompatibly stable medicament even at the initial Stage Of wound healing in comparison with the application of chitosan polymer. (c) 2005 Wiley Periodicals, Inc.