Effects of dental monomeric resins on functions of odontoblasts <italic>in vitro</italic>.

Methacrylate-based dental resins polymerize incompletely, due in part to inhibitory effects of oxygen. Diffusion of residual monomeric resins through dentin to reach dental pulp, increased prevalence of dental pulp reactions of resin cavities with 0.5 mm or less dentin thickness and cytotoxicity of resins raised concerns of biocompatibility of resins with odontoblasts, the cells which secrete dentin. The toxic and subtoxic effects of four methacrylate-based resins on the functions of mouse odontoblast-like cells, MDPC.23, were studied. First, cytotoxicity of resins to MDPC.23 cells was assessed by measuring four metabolic functions of NMPC.23 cells. The results showed that the TC50 values measured by mitochondrial activity at 24-h exposure were as follows: HEMA, 8420 +/- 1974 muM; TENDENCY, 1252 +/- 145 muM; bisGMA, 52 +/- 14 muM; and UDMA 56 +/- 17 muM; Increased exposure time to the resins promoted toxicity of the resins. The rank of sensitivity of end-point measurements was as follows: mitochondrial activity (least) in vivo toxicity of resins. Third, mode of cell death of NMPC.23 (apoptosis or necrosis) caused by the resins was determined by flow cytometry and the TUNEL assay. The findings showed that MDPC.23 did not exhibit apoptosis, suggesting that necrosis may be the primary mode of cell death by resins. Fourth, effects of sublethal doses of resins on expression of three odontoblastic genes in NMPC.23 were investigated. Western analysis showed that the resins increased dentin sialoprotein expression. Nontoxic or slightly toxic concentrations of resins upregulated osteopontin and osteocalcin expression. Higher toxic concentrations interfered with osteopontin and osteocalcin expression, as seen in Northern analysis. Altered phenotypes of odontoblasts by resins suggests a role of resins in dentin mineralization.Ph.D.DentistryHealth and Environmental SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/132869/2/9990968.pd

Comparison between the efficacy of self-prepared chlorhexidine varnishes and of EC 40®

It was reported that clinical application of chlorhexidine (CHX) varnish could reduce dental caries occurrence effectively.However, this form of CHX is not commercially available in Thailand. Our previous study showed that the released CHX from 20% and 40% self-prepared CHX varnishes were sufficient to inhibit the growth of Streptococcus mutans. This study aimed to compare the efficacy of the 20% and 40% self-prepared CHX varnishes to commercial CHX varnish EC 40®. The study included CHX release, antibacterial activity against S. mutans ATCC 25175, and the cytotoxic effect of CHX on fibroblasts. The results showed that the greatest amount of CHX was released by EC 40® followed by 40% and 20% selfpreparedCHX, which were 4,111.29 g, 2,408.7 g, and 1,136.4 g, respectively. EC 40® gave the strongest antibacterial activity; however, there was no statistical significant difference. The 20% self-prepared CHX gave the highest viability of fibroblasts. This study indicates that the self-prepared CHX should be considered to be used as antimicrobial agents for the prevention of dental caries