Biomedical subjects

T Togaya

Publications and source records attributed to T Togaya.

11 recordsLinked to original sources

PubMed1997

Titanium for removable dentures. I. Laboratory procedures.

To test the hypothesis that titanium (Ti) removable partial dentures (RPDs) would function for a period of at least 2 years without failure, 10 patients were selected to receive dentures made from Ti and Co-Cr. The Ti RPDs were constructed identically to conventional cobalt-chromium (Co-Cr) dentures. Five complete Ti dentures were also included and the laboratory procedures involved for making both complete and partial dentures were evaluated. The detection of internal defects by radiography made the screening of Ti castings possible and led to a rejection of specimens showing porosities of more than 0.5 mm in flexible members. Co-Cr frames on the other hand cannot be screened in this way. The success rate in the casting of Ti was 60% for both partial and complete dentures, but as casting technology has since improved, the rate is expected to be higher, particularly where complete denture palates have optimum thickness. The success rate in the casting of Co-Cr RPDs was 100% without radiographic screening. The weight difference between Ti and Co-Cr RPDs was in the range of 1.3 to 3.9 g at issue and is generally higher as the volume of denture frames increases. A large difference would be of clinical significance in maxillary complete dentures. The low density of Ti allows for the adoption of a useful pre-clinical quality-control process using commonly available dental X-ray units.

Chromium Alloys↗

PubMed1995

Dentin surface treatment without acids.

Enhancement of the adhesiveness of dental restoratives, such as composite resins, has been clinically essential. A key point in enhancing adhesion is how to treat the dentin surface before bonding. We recently attempted to use an inorganic and non-acidic salt solution for pretreatment to dentin. We paid attention to the salting-in effect of rhodanides which promotes swelling of collagen and gelatin. For pretreatment, we used potassium thiocyanate (KSCN) solution. This study morphologically evaluated the effect of treatment of dentinal smear layer with rhodanides in combination with cross-linking agents such as ferric chloride. Scanning electron microscopy revealed effective removal of the smear layer on the treated dentin surface and obturation of dentinal plugs. Addition of the cross-linking agents to KSCN solution was more effective for pretreatment.

Alum Compounds↗

PubMed1994

The effect of investment type on the fit of cast titanium crowns.

In order to determine the best laboratory procedure for titanium crown casting, a set of thermal expansion measurements and casting experiments were carried out using a casting machine (argon arc, pressure difference type) and three different investments, two conventional SiO2 based investments and a new Al2O3/MgO based investment. The thermal expansion measurements involved a cycle of heating and cooling. The relatively low mould temperatures recommended (200 degrees C) or chosen (350 degrees C) for the conventional investments provided zero or negative mould expansion for the compensation of metal shrinkage. Crowns made from these investments exhibited heavy reaction with the mould, and the common cleaning method of sand blasting appeared to be essential. This cleaning process, however, was not adequate for the assessment of casting accuracy as the short sand blasting time (15 s) rapidly altered the fit of the crowns. The metal reacted little with the new investment and the best compensation (0.15 mm discrepancy) for the metal shrinkage, as assessed 'as cast', was achieved when the investment was heated to 950 degrees C and then cooled to the recommended mould temperature (600 degrees C).

Chemical Phenomena↗

PubMed1994

Effect of "Megafiller" insertion on the wear of composite resins.

We have previously reported that insertion of coarse particles of beta-Quartz Glass Ceramic Insert (Megafiller) into a composite resin markedly reduced the polymerization shrinkage of resin restorative materials. In this study, we examined the effects of Megafiller insertion on wear resistance evaluated by the glass beads abrasion test, and the conventional toothbrushing abrasion test. The depth of wear was determined by measuring the thickness of the specimen before and after the wear tests using a profile projector accurate to 1 micron. In general, the depth of wear of the composites was reduced by Megafiller insertion, but the differences in the depth of wear between composites with and without the Megafiller were not significant except for a few materials. There were slight differences in the wetness of Megafiller in some composite resins.

Acrylic Resins↗

PubMed1986