Katsuhiro Haraguchi

Socioeconomic factors and dental caries in developing countries: A cross-national study

The purpose of the present study was to analyze statistically correlations between socioeconomic factors and the prevalence of dental caries in developing countries. The DMFT index, which evaluates the incidence of dental caries, showed a positive correlation (P < 0.01) with several socioeconomic factors, such as life expectancy, adult literacy rate, school attendance rate, population employed in the service sector, population aged 15-64 years, and urban population. According to multiple regression analysis, population aged 15-64 years, population employed in the service sector, and urban population were the most influential independent socioeconomic variables, in descending order, with a regression coefficient of 0.635 and a coefficient of determination of 0.404 (P < 0.001). This finding suggests that the prevalence of dental caries in developing countries increases with the degree of urbanization.

Crystal growth by restorative filling materials

This study examined the activity and ability of materials to mineralize teeth in gaps, simulating microleakage between the materials and teeth. Three restorative materials (two glass ionomer cements and a compomer) were used in this study. Cured disks of restoratives were placed over flat human tooth surfaces (enamel and dentin), separated by a standardized 20-μm interfacial space, and stored in water for 24 h or 1 yr. After the water-storage period, the materials were detached from the teeth and the opposing surfaces were examined by scanning electron microscopy (SEM) and electron probe micro analysis (EPMA).Hemispherical-shaped precipitations, composed of minute semicircle plate-like crystals, were observed by SEM on the enamel surface after 1 yr of water storage for glass ionomer cement. The amount of crystal growth with the chemical-cured type of glass ionomer cement was greater than with the dual-cured type of glass ionomer cement. However, there was no crystal formation in the compomer. Moreover, no structural changes were observed on dentin surfaces for any material in water after 1 yr. The elements detected in the crystals by EPMA were calcium (Ca), phosphorus (P), and aluminum (Al). The two glass ionomer cements tested have the ability to induce crystals whose composition might be derived from cured glass ionomers.

The treatment of dental pit and fissure caries by an Er:YAG laser with an experimental tip

Abstract This is a report of newly developed experimental contact irradiation tip for an Er:YAG laser to remove dental pit and fissure caries. The purpose of this study was to examine the effectiveness of the experimental tip in the removal of dental pit and fissure caries and filling by the restoration with low viscous composite resin or compomer as a filling material. In experiment 1, we examined the removal effects of this tip and the characteristic properties using bovine extracted teeth. In experiment 2, we evaluated the sealing ability of the restorative filled cavity it prepared by laser using die penetration test. The cavity prepared with the laser was a narrow cone shape. There was no difference in the sealing ability of the filling material between cavities formed by the air turbine and the laser. It is suggested that the treatment of dental pit and fissure caries is possible with Er:YAG lasers using the experimental tip and low viscous filling materials.