Tatsuro Kojo

Disaggregated osteoclasts increase in resorption activity in response to roughness of bone surface.

The roughness of the bone matrix surface affects osteoblastic differentiation. However, the effect of the roughness of the matrix surface on osteoclastic bone resorption remains to be studied. We examined the latter effect using disaggregated osteoclasts from neonatal rats. The resorption pit number and the total pit area on the rough surface were not different from those on smooth surfaces after 1 day, but they were 2 or more times higher after 3 days. The number of osteoclasts was not different on bone slices with either smooth or rough surfaces at 3 days. The alkaline phosphatase (ALP)-positive osteoblasts were relatively rare in both types of slices at first, then the number and the diameter of the enzyme-positive cells and the clusters preferentially increased on the rough bone slices. When hydroxyurea was added to the culture in order to suppress the proliferation and the subsequent differentiation of osteoblastic cells on rough surfaces, the increase in resorption on the rough surfaces was effaced; however, this agent had little affect on resorption of the smooth surfaces. The addition of ALP-positive cells to disaggregated osteoclasts increased bone resorption on the smooth surface. The results suggest that osteoblast development and subsequently bone resorption by osteoclasts is enhanced by the roughness of matrix surfaces.

Preferential degradation of osteoclasts by titanium tetrachloride

Although titanium alloys are known to be biocompatible with bone tissue after implantation in human beings, the effect of titanium on osteoclasts remains to be studied. We examined the effect of titanium salt on the formation and survival of osteoclasts in cell culture. The addition of 10 microM titanium tetrachloride caused a decrease in the cell number of osteoclast-like cells induced in bone marrow cell cultures taken from mice. The addition of 10 microM titanium tetrachloride caused degradation of the disaggregated osteoclasts taken from neonatal rats and a decrease in bone resorption. Along with the increase in the degradation of osteoclasts, the number of apoptotic cells increased. Titanium tetrachloride dose-dependently decreased the cell number and alkaline phosphatase activity of osteoblastic cell cultures taken from rat calvaria. However, these concentrations were 30-40 times higher than those in the case of osteoclast-like cell formation. These results showed that titanium ions caused a preferential degradation of osteoclasts rather than osteoblasts, most likely by apoptosis.

DNA amplification using phi29 DNA polymerase validates gene polymorphism analysis from buccal mucosa samples

Venous blood is currently the most common source of DNA for gene polymorphism screening; however, blood sampling is invasive and difficult to perform in general dental treatment. Buccal mucosa samples provide an alternative source of DNA, but it is frequently difficult to effectively amplify the DNA owing to the small amounts of sample material obtained. This study was performed to establish a method for performing total genomic DNA amplification from buccal mucosa samples using phi29 DNA polymerase. Total genomic DNA was isolated from buccal mucosa samples obtained from healthy subjects and was amplified using phi29 DNA polymerase. To determine the suitability of the extracted DNA for genotyping, polymerase chain reaction and restriction fragment length polymorphism analyses were performed for the IL-1 gene polymorphism. Genotyping of the IL-1 polymorphism was successful using the amplified DNA from a buccal mucosa, but genotyping was unsuccessful using the unamplified control because of low DNA purity. The method of extracting DNA from a buccal mucosa is painless, simple, minimally invasive, and rapid. Genomic DNA from a buccal mucosa can be amplified by phi29 DNA polymerase in sufficient quantity and quality to conduct gene polymorphism analyses.

Abrasion Resistance of Veneer Materials for Crown and Bridge

Abrasion resistance of veneer materials for crown and bridge was examined by using the brushing machine of unidirectional rolling type. The veneer materials used are thermosetting resin with or without pre-treatment, light-activated microfilled composite resin, porcelain and heat -cured acrylic resin. The pre-treatment of the thermosetting resin consisted of storing the material under reduced pressure before curing to eliminate the pores. The changes in surface aspect was evaluated by abrasion loss, gloss change, photomicrograph and surface roughness. The measurements were taken before brushing and after 10.000, 20,OOO, 30,OOO, 40,OOO, and 50,OOO times brushing tests. The results obtained were as follows: 1 . Thermosetting resin and pre-treated thermosetting resin showed the same abrasion loss as acrylic resin. Light-activated composite resin showed abrasion loss about 1t3tv1,i4 times more than acrylic resin. Porcelain showed little abrasion loss, compared with the others. 2. Crown and bridge resins, including thermosetting resin, pre-treated thermosetting resin and light-activated composite resin showed lower specular gloss as bru

Wearing Behaviors of a Hybrid Composite Resin for Crown and Bridge

hing times increased. It was found that porcelain and acrylic rcsin had no change in gloss. Pre-treated thermosctting resin had a tendency of higher gloss than thermosctting resin without pre-treatment. 3. It was observed that the abrasion was dominant around the surface porosity. 4. Porosities in the thermosetting resins became smaller in their size and number by storing undcr reduced pressure, resulting in a tendency of lower abrasion loss and less