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Bisphenol A (BPA) is a common ingredient in dental materials. However, its potential adverse effects on the oral cavity are unknown. The purpose of this study is to identify the genes responding to BPA in a human oral epithelial cell line using DNA microarray. Of the 10,368 genes examined, changes in mRNA levels were detected in seven genes: five were up-regulated and two were down-regulated. The expression levels of the calcium channel, voltage-dependent, L-type, alpha 1C subunit (CACNA1C), cell death activator CIDE-3 (CIDE-3), haptoglobin-related protein (HPR), importin 4 (IPO4), and POU domain, class 2 and transcription factor 3 (POU2F3) were significantly up-regulated in the cells exposed to 100 mM BPA. The spermatogenesis-associated, serine-rich 2 (SPATS2) and HSPC049 protein (HSPC049) were significantly down-regulated. The detailed knowledge of the changes in gene expression obtained using microarray technology will provide a basis for further elucidating the molecular mechanisms of the toxic effects of BPA in the oral cavity.

We studied the thermal properties of cavity liners that included calcium phosphate as inorganic filler, in contrast to the conventional pulp capping agents. Therefore, thermal diffusivity, specific heat capacity, and thermal conductivity were measured. In addition, thermal conductivity results were compared with those of restorative materials and human dentin to examine thermal insulation effects. The thermal conductivity of cavity liners ranged from 0.23 to 0.28 W m(-1) K(-1), and that of pulp capping agents ranged from 0.44 to 0.48 W m(-1) K(-1). Test results indicated that the thermal conductivity of cavity liner was lower than those of human dentin, pulp capping agent, cast alloy, and composite resin for restoration, hence suggesting that cavity liner has a good thermal insulation effect.

Light-activated dental composite resins undergo polymerization and curing by free-radical initiation like auto-cured resins. We studied the polymerization and curing properties of some commercially available light activated composites by using argon-ion laser.Results are summarized as: (1) The volume of a cured resion is dependent on the wavelength, and the maximum volume is obtained at 466 and 477 nm; (2) The volume of the cured resin increases with increasing irradiation power and time; (3) The rate of polymerization shrinkage gradually increases, before the saturation and (4) A correlation was observed between light transmittance and polymerization shrinkage for the composites of hybrid and traditional types which are relatively highly filled, but not for MFR type resins containing less micro-filler.