Fibroblast growth factors (FGFs) are known to be required for embryonic growth, formation, and shaping of many tissues and organs during embryogenesis. Biochemical studies have indicated that heparan sulfate proteoglycans, which are present on most cell surfaces and in extracellular matrices, play essential roles in FGF binding to its receptors and subsequent signal transduction. N-deacetylase/N-sulfotransferases (NDSTs), which catalyze the first modifying step in the biosynthesis of heparan sulfate, are essential enzymes for the biosynthesis of heparan sulfate. The critical roles of heparan sulfate proteoglycan in developmental processes and specific signaling pathways have been illustrated by the identification of mutations in enzymes involved in the biosynthesis of heparan sulfate in Drosophila and mice. However, null mutation analyses of NDST-1 and NDST-2 have not clarified the embryonic regulation of morphogenesis by NDSTs. In the present study, we examined the temporal and spatial expression of NDST-1, and the temporal expression of NDST-2, in early rat embryogenesis, to investigate the role of NDSTs during embryogenesis. The expression pattern of rat NDST-1 appears to colocalize with certain FGFs and FGF receptors, suggesting possible roles of NDST in embryogenesis.
In open-bite cases at developing dental stages, oral morphologies have been thought to have a close relationship to tongue movement. The aim of this study was to design a new type of removable habit-breaker, and to examine its effects on tongue movement compared with the conventional habit-breaker. The examinees in the mixed dentition period, who had anterior open bite with tongue thrust, consisted of two groups: 10 children who had been treated with conventional habit-breakers with tongue cribs (the upper group), and 10 children treated with the modified habit-breakers (the lower group) . And 10 children with normal occlusion of the same age were added, as a control group. The tongue movements during swallowing, with and without the appliances, were analyzed twice: at the start of, and 6 months after, application of the appliances, by sonography. The results were as follows. 1. The design of a habit-breaker was decided according to the results of a preliminary experiment. The appliance had not only a resin-fence but also a tongue-lifting guide. 2. The upper group showed significant changes in the movement only at the lateral margin of the tongue after 6 months, with and without the appliance. 3. The lower group, however, showed significant changes in the movement at the wider area of the tongue, including the central groove formation, just after applying the appliance, and after 6 months, with and without the appliance. 4. The present results indicated that the modified appliance was more effective in improving tongue function than the conventional habit-breaker.
A new machinability test machine especially for dental materials was contrived. The purpose of this study was to evaluate the effects of grinding conditions on machinability of core built-up resins using this machine, and to confirm the relationship between machinability and other properties of composite resins. The experimental machinability test machine consisted of a dental air-turbine handpiece, a control weight unit, a driving unit of the stage fixing the test specimen, and so on. The machinability was evaluated as the change in volume after grinding using a diamond point. Five kinds of core built-up resins and human teeth were used in this study. The machinabilities of these composite resins increased with an increasing load during grinding, and decreased with repeated grinding. There was no obvious correlation between the machinability and Vickers' hardness; however, a negative correlation was observed between machinability and scratch width.
The purpose of the present study was to investigate the properties of the hydroxyapatite (HA) layer formed by an aerosol jet printing system, aimed at application to the field of dentistry. The HA particle was adhered to the metal substrate. The particles of HA were 1 μm or less in size and were packed closely. When the composition of the formed HA layer was compared to that of the raw material powder, oxygen was increased, but Ca was decreased. Moreover, Ca and P were almost evenly distributed in the layer, but oxygen was not. Dynamic hardness of HA coatings was 31.5±1.1. The peel strength of HA coating was the highest, at 58.7-39.6 MPa, in 10 μm layer thickness. Interface fractures were observed at 10 μm layer thickness, and cohesive fractures were observed for all other layer thicknesses. The wear amount of HA coating by tooth brush abrasion was significantly large at 100°C heating (p<0.05), compared with at 250°C and 500°C. At any substrate temperatures, the wear amount of stainless steel substrate tended to be smaller than that of titanium substrate.