Effect of enamel preparation method on in vitro marginal microleakage of a flowable composite used as pit and fissure sealant.

OBJECTIVES: The aim of this in vitro study was to evaluate the microleakage in occlusal surfaces, after preparation with Er:YAG laser and compared to the diamond-bur conventional technique. METHODS: Thirty premolars were divided into three groups: I - high-speed handpiece + 37% phosphoric acid; II - Er:YAG laser (350 mJ, 4 Hz and 112 J/cm(2)) + 37% phosphoric acid; and III - Er:YAG laser (350 mJ, 4 Hz and 112 J/cm(2)) + Er:YAG laser (80 mJ, 4 Hz, and 25 mJ/cm(2)). All cavities received the same adhesive system and were restored with flowable composite according to manufacturer's instructions. Teeth were submitted to thermal cycling and immersed in 50% silver nitrate solutions for 8 h in total darkness. Specimens were sectioned longitudinally in the bucco-lingual direction, in slices of 1 mm thick. Each slice was immersed into photo developing solution and was photographed, and microleakage was scored from 0 to 7, by three calibrated examiners. RESULTS: A statistically significant difference (P < 0.0001) was observed between Er:YAG laser prepared and etched specimens and those in the other groups. CONCLUSIONS: It can be concluded that no significant difference was noted between the two types of enamel preparation when etching was performed. Preparing and treating the enamel surface exclusively by Er:YAG laser resulted in the highest degree of leakage.

[Bond strength to dentin of resin composites associated with filled and unfilled adhesive systems]. / Resistência de união à dentina de resinas compostas associadas a sistemas adesivos com e sem carga.

This study analyzed in vitro two brands of one-step adhesive systems of fourth generation (Optisolo--Kerr, filled; and Single Bond--3M, unfilled) and two composite resins (Prodigy--Kerr and Z100--3M), aiming at evaluating their bond strength to dentin. Eighty human extracted molars were embedded in acrylic resin and grounded until dentin was exposed in longitudinal direction. The specimens were divided in 4 groups. Composite resin cones were bonded to the specimens using the mentioned adhesive systems, following the instructions of the manufacturers. The test-specimens were submitted to tensile tests using a 4442 Universal Mini-Instron Machine with the speed of 0.5 mm/min. The results were converted into MPa, according to the area of adhesion, and submitted to statistical analysis with ANOVA. There was significant statistical difference (p < 0.01) between the adhesive systems (F = 7.24). Optisolo (m = 11.03 +/- 4.23) showed better bond strength than Single Bond (m = 8.37 +/- 4.54). There was no significant statistical difference (p > 0.05) between the composites (F = 0.43).

Microhardness of Nd:YAG laser irradiated enamel surfaces.

Several studies have been conducted in order to verify effects of laser irradiation on dental structures. However, different settings and methods employed have led to inconclusive results. The aim of this study was to evaluate the effects of several settings of Nd:YAG laser irradiation on enamel microhardness. Fifteen groups of 10 human third molars each were submitted to Vickers microhardness indentations prior to and after laser irradiation. The data were submitted to the t-test for dependent samples (P < 0.05) for statistical evaluation. Lower total delivered energy (under 30 J) resulted in no statistically significant difference of microhardness between irradiated and non-irradiated samples, whereas higher energy settings decreased enamel surface microhardness significantly. This can be due to the significant temperature rise during irradiation. Thus, we conclude that laser irradiation, under the conditions of this study, is not suitable for improving enamel properties, because of decreased microhardness of irradiated samples.

Tensile bond strength of two dentin adhesive systems.

The tensile bond strength of one third-generation (XR Bond) and one fourth-generation (Optibond) adhesive system to dentin was compared. The influence of acid etching of dentin on the bond strength in the XR Bond system was also evaluated. In addition, two kinds of curing (photo and dual) of the Optibond system were evaluated. The Optibond system showed a statistically significant higher tensile bond strength to dentin than the XR Bond system. Etching of the dentin before application to XR Bond did not significantly improve the bond strength to dentin. Both photo and dual curing showed similar bond strengths two hours and seven days after sample preparation.

Bond strength to dentin with artificial carious lesions: influence of caries detecting dye.

PURPOSE: To evaluate the influence of dyes for caries detection on tensile bond strength of adhesive materials to artificial carious dentin. MATERIALS AND METHODS: Buccal and lingual enamel of human molars were removed leaving intact dentin surfaces. The entire surface of each specimen was covered with nail varnish, keeping a window area of 4 x 4 mm. Artificial carious lesions were induced with acidified gel. Three dyes (0.5% basic fuchsin; Caries Finder and Cari-D-Tect) were used according to manufacturers' recommendations. Specimens were etched with 35% phosphoric acid for 20 s, washed and dried, leaving a wet dentin surface. The adhesive system (Prime & Bond 2.0) was applied in two layers and light-cured. Restorative materials (TPH Spectrum, Dyract, Advance) were bonded using a 3-mm diameter inverted-cone mold. Control groups were made without dye. Eight samples were tested for each group. After 24 hrs of storage in distilled water, the samples were debonded using a testing machine at 0.5 mm/min crosshead speed. RESULTS: ANOVA and Tukey-Kramer test showed that TPH Spectrum (0.73 MPa) and Dyract (0.74 MPa) had similar bond strengths, and both were higher than Advance (0.0 MPa), which was statistically different (P < 0.01). The use of the dyes did not cause any changes in tensile bond strength for any tested materials.

Rugosimetric analysis of amalgam restorations polished using different techniques.

The objective of the present study was to submit specimens with amalgam restorations to 4 different polishing techniques and one control group without polishing. The specimens were then submitted to rugosimetric analysis and the differences compared.

Photopolymerized resins: surface hardness variation in relation to time of polymerization and setting.

The authors studied the superficial hardness of composite resins cured for two different times: 20 and 40 seconds of light exposure. The hardness values were read immediately and 24 hours after polymerization. A significant increase in hardness was observed with 40 s exposure as compared to 20 s. Hardness values were significantly higher at 24 h than immediately after polymerization.

Effect of the polishing technique at low or high speed on the micro-hardness of dental amalgam.

Dental cavities were prepared and restored with amalgam, using three different silver alloys. The surface of the restorations was finished 24 hours after condensation, with a rotatory instrument using a low- or high-speed handpiece. The specimens were then submitted to metallographic polishing and one of the margins of the amalgam restoration were then submitted to Vickers' micro-hardness test. Another micro-hardness test was accomplished 168 hours after condensation and the two sets of micro-hardness values were compared. No significant statistical differences were detected between the micro-hardness values obtained with low or high speed in the polishing technique.