Mitsuharu Takeuchi

A Semi-Quantitative Determination of Streptococcus mutans Using Its Adherent Ability in a Selective Medium

A method differentiating the critical level of Streptococcus mutans in whole saliva was developed. The procedure is as follows: 100 μl whole saliva is inoculated into 2 ml of MSB broth, the test tube is set tilted at a 60° angle and incubated aerobically at 37 °C for 24 h. The degree of adherence is then scored. When the adherence score is + + +, S. mutans may be assumed to be present at a level higher than 105/ml of whole saliva. On the other hand, if adherence is scored – or + S. mutans is present at a level lower than 104/ml of whole saliva. The method is useful for handling many samples in preventive practice and epidemiological studies, because of its simplicity.

The Effect of Sodium Fluoride in Acid Etching Solution on Sealant Bond and Fluoride Uptake

Effects of etching with 30% H3PO4 containing NaF on the enamel surface were re-examined. Results indicated that 2-5% NaF in the etchant prevent the sealant bond, but addition of 0.02% NaF resulted in an increase in fluoride content of the enamel surface without a decrease in bond strength.

A Simple Fissure Sealant and Its Tensile Bond Strength to Etched Bovine Enamel

A simple and rapidly setting fissure sealant was developed using thixotropic ethyl 2-cyanoacrylate: before application, the sealant containing 10–20 parts of colloid-sized silica, is placed on a small amount of dimethylformamide as a mild initiator, mixed and then applied by brush to the occlusal surface treated with 3 M phosphoric acid for 30 sec. The applied sealant is instantaneously hardened by dropping the setter consisting of ethyl alcohol containing 1% (v/v) of dimethyl p-toluidine. The sealant has the mean tensile bond strengths of 90–150 kg/ cm2 to etched bovine enamel, depending on the composition and acid-conditioning after immersion in water at 37 °C for 24 h.

Effect of Pretreatment with Ethanol Containing Fluoride on Etched Enamel Surface as Evaluated by Scanning Electron Microscopy, Optical Microscopy, and Tensile Bond Strength Measurement

The effects of pretreatment with a fluoride-containing ethanol solution on etched enamel surfaces before application of sealant were examined using scanning electron microscopy, optical microscopy, and tensile bond strength determinations. The results suggested that when etched enamel surfaces are treated with ethanol containing no more than 250 ppm fluorine in potassium fluoride, there is no interference with the bonding of the sealant to the treated, etched enamel surface.