Hisayoshi Tanaka

Restorative methods for the Er: YAG laser application

The purpose of this study was to determine if a cavity prepared using the Er: YAG laser could be restored with restorative materials other than composite resin. A class V cavity for the composite resin and a class I cavity for the amalgam, gold foil, and inlay, were prepared in the human premolars an using the Er: YAG. laser. The cavities were restored with these restorative materials. The boundaries between the teeth and the restorative materials were observed using a DIGITAL MICRO SCOPE-6300. The following results were odtained;1.Because all the margins of the cavities were rough, it was suggested that those should be trimmed using a rotary cutting instrument.2.For composite resin restoration, the need of the further investigation of the method of finishing the cavity wall and treating that surface, was suggested.3.Undercut was observed on the cavity wall. This undercut will be useful as a retention form for amalgam restoration and a convenient form for gold foil restoration.4.For inlay restoration it was suggested that lining was needed to make the roughness of the cavity wall smooth.

Comparison of the bond strength of composite resin to Er:YAG laser-irradiated enamel/dentin pre-treated with various methods

Abstract The purpose of this study was to compare the effects of pre-treatment on bond strength between composite resin and Er:YAG laser-irradiated enamel/dentin. The Er:YAG laser was irradiated on 60 extracted human teeth at following conditions; for enamel: 200 mJ/4 Hz, total energy 30 J, for dentin: 100 mJ, total energy 15 J. The irradiated 60 teeth were divided into six groups (n=5); Gr.1: ground with silicon carbide paper; Gr.2: laser was irradiated at foregoing condition; Gr.3: 37% phosphoric acid was applied to irradiated surface; Gr.4: ultrasonic scaler was applied to irradiated surface; Gr.5: air scaler was applied to irradiated surface; Gr.6; air-powder polisher applied to irradiated surface. SE bond and AP-X (Kuraray) were applied and cured. Tensile bond strengths (TBS) were measured after 24 h. The data were analyzed using ANOVA and Sheffes-tests. TBS of dentin was significantly higher than that of enamel. Significant differences among Gr.1 and 2, 3, 4, 5, Gr.2 and 3,4,5,6, Gr.3 and 6, Gr.4 and 6, Gr.5 and 6 were observed. The application of air-powder polisher for Er:YAG laser-irradiated enamel/dentin was effective to obtain high TBS.

Indentation creep of composite resins

Creep behavior of restorative materials is an important mechanical property. Indentation creep of 6 different composites was evaluated at ageing times of 15 min and 1 week using a Dynamic Ultra-Microhardness Tester. The influence of water on indentation creep was slso assessed. The results were as follows:1.All the composites showed creep and the amount of creep was different among the composites at 15min. and 1 week.2.Water absorption increased creep.3.All the materials showed a decrease in creep with time when stored in air.4.Under scanning probe microscopy, the ridges of the diamond triangular pyramid indenter were sharp and the three sides of indentation were bow-shaped toward the center of indentation.