This study aimed to analyze the relationship between the hardness and the mineral contents of cementum. From previous research results, fifty extracted premolars were classified as soft, moderate, and hard according to the Vickers hardness test. In this study, six specimens selected randomly in each group were used for the experiments, and three representative premolars in each group of cementum hardness were analyzed.

The hard specimens had more calcium (Ca) content than did softer specimens, according to scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDS). In the element mapping image, magnesium (Mg) was densely distributed in the surface layer of the root apex in the softer specimens. X-ray μCT analysis revealed that the hard specimens had higher tissue mineral density (TMD) than did the other specimens (P<0.01).

The difference in density of Ca and Mg contained in cementum may be related to the variation of Vickers hardness, and may influence the susceptibility to orthodontic root resorption.

This study was designed to examine the effect of biodegradable gelatin hydrogel (Gel) containing bone morphogenetic protein-2 (BMP-2) on bone formation at palatal subperiosteal sites in 10-week-old (10w group) and 70-week-old (70w group) male Wistar rats. The experimental sites of both age groups were divided into two implants: Gel containing BMP-2 (BMP site) and Gel only (Gel site).

Four weeks after implantation, new bone formation was observed at every site and the thickness of new bone (TNB) of the BMP site was significantly greater than that of the Gel site of both age groups (p<0.05). The TNB of every site in the 10w group was significantly greater than that of the same experimental site in the 70w group (p<0.05).

These results suggest that gelatin hydrogel containing BMP-2 induces new bone formation, even in senescent rats that otherwise have decreasing new bone formation because of aging.

The terahertz wave, which is expected to be used in the future medical field, was examined for the possibility of being applied to conservative pulp treatment. For example, in order to avoid pulpectomy in the deep caries treatment, it is extremely useful to detect the remaining amount of carious dentin and the distance to the pulp in the cavity. As a pilot study of application to dental treatment, the propagation velocity of terahertz waves in enamel and dentin was measured. As controls, natural single crystal of apatite and HIP-treated powder apatite were also measured. As a result, enamel and dentin had different propagation velocities. It suggests that not only enamel and dentin in the oral cavity but also sound dentin and carious dentin with different calcification degrees can be identified by terahertz waves because the propagation rate increases depending on the density of apatite in the sample.