The Gradient of Microhardness in Cross-sectioned Sound Primary Molars

摘要

Understanding baseline information on the mechanical properties of primary teeth is important in pediatric dental care. The purpose of the present study was to investigate distributions of microhardness of entire cross-sectioned primary molars using a Vickers microhardness test and observe microstructure by a confocal laser scanning microscopy. Sound mandibular primary molars of Hellman's dental age HI B were sectioned and polished for indentation testing Sixty-five indentations in both enamel and dentin were made in each specimen, using eight indentation lines corresponding to eight directions and including an additional indentation in the center of each specimen. The features of microstructures were observed. The area of peritubular dentin and intertubular dentin were also evaluated. Microhardness was found to decrease progressively toward the center in all directions with the exception of the lingual and mesiolingual directions in enamel. In dentin, this trend was found in all directions with small deviations. Hard regions with large area of peritubular dentin were found at the microstructural level. The microhardness of cross-sectioned sound primary molars have a gradient. It is suggested that peritubular dentin is not negligible with respect to its microhardness from a structural point of view.