Conditioning effect on dentin, resin tags and hybrid layer of different acidity self-etch adhesives applied to thick and thin smear layer

Acid resistance of dentin after erbium:yttrium-aluminum-garnet laser irradiation

The purpose of this study was to evaluate the acid resistance of erbium:yttrium-aluminum-garnet (Er:YAG) lased sub-surface dentin using a scanning electron microscope (SEM). Dentin disks were exposed to a single pulse of Er:YAG laser irradiation at 80 mJ/pulse under water spray, with the contact sapphire tip vertical to the dentin surfaces (n = 15). Five specimens from the laser-ablated dentin surfaces were observed. Ten specimens were crosscut, exposing the center of the lased point. For five of the specimens, the sub-surface of the lased dentin, with or without 10% phosphoric acid treatment, was evaluated. We used the remaining five specimens to analyze the degree of acid treatment on crosscut surface by observing the re-crosscut surfaces at the lased point. The irradiated dentin surfaces were irregular, scaly or flaky. Three sub-layers were observed in the sub-surface: a superficial, less decalcified layer; an intermediate most decalcified layer; and a deep, normal shade layer. Er:YAG laser irradiation affected the acid resistance of sub-surface dentin.

Effects of filling techniques on the regional bond strength to lateral walls in Class I cavities

OBJECTIVES

Using the push-out technique, this study compared the influence of different composite insertion techniques in Class I cavities on the regional shear bond strength to lateral walls.

MATERIALS AND METHOD

Standardized Class I cavities were prepared on the occlusal surface of 60 freshly extracted third molars, which were randomly assigned to one of five groups (n = 10). The cavities were bonded with the self-etch adhesive AdheSE and restored with Tetric Ceram resin composite by one of five techniques: G1, incremental technique (four oblique layers); G2, flowable composite as liner and bulk technique; G3, bulk technique and G4, light cone technique. The total-etch adhesive (Single Bond) and incremental technique were used as the control procedure. Each specimen was sectioned perpendicular to the long axis of the tooth in 1 mm-thick dentin slices. A push-out test was performed to measure regional bond strengths and identify the type of failure. Two additional teeth per group were prepared for the morphological interface study using scanning electron microscopy.

RESULTS

Differences between the groups were tested by one-way ANOVA and Scheffé post hoc test (F = 29.635, p < 0.001). The highest shear bond strength values were obtained with the incremental technique, regardless of the adhesive used. Significant differences in bond strength to superficial and deep dentin were only found when a total-etch adhesive was used (Single Bond).

CONCLUSIONS

Use of the incremental technique with total-etch or self-etch adhesives is the most effective method of inserting resin-based composites in large Class I cavities.