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This study evaluated the effect of a non-rinse conditioner (NRC) associated with two adhesive systems, Prime & Bond NT and Prime & Bond 2.1. The study also evaluated a self-etching adhesive, comparing it with the 37% phosphoric acid effects related to the regularity and infiltration depth of adhesives in human tooth enamel via observation using Scanning Electronic Microscopy (SEM). Fifteen third molars were longitudinally sectioned into four parts by means of a mesio-distal cut and facio-lingual cut. All pieces were flattened with silicon carbide paper, randomly separated and divided into five groups where the enamel surfaces were treated with different materials according to the manufacturers' instructions as follows: Group 1-Prime & Bond NT (Dentsply); Group 2-37% phosphoric acid + Prime & Bond NT; Group 3-Non-Rinse Conditioner (Dentsply) + Prime & Bond NT; Group 4-NRC + Prime & Bond 2.1 (Dentsply); Group 5-Prompt L-Pop (3M ESPE). All teeth were covered with Dyract AP (Dentsply). Specimens were decalcified, metalized and the inner portions of Dyract were observed in SEM and evaluated by calibrated examiners to evaluate resin penetration on enamel. Resin penetration was ranked from 0 = no penetration, to 3 = maximum penetration. The Kruskal-Wallis and Mann-Whitney U tests (p<0.05) showed only three statistically homogeneous groups: {1}, {2,3} and {4,5}. The authors concluded that Prime & Bond NT showed the lowest penetration, NRC showed similar effects compared to phosphoric acid when associated with Prime & Bond NT, and concluded that Prompt L-Pop showed similar effects to NRC, which was associated with Prime & Bond 2.1.

Dentinal surfaces prepared with Er:YAG laser have significantly different characteristics from those prepared with conventional instruments. Different hybrid layer morphologies and thicknesses occur, which may result in differences in the quality of restorations placed on dentinal surfaces prepared with a diamond bur when compared with using an Er:YAG Laser. This study compared the hybrid layer thickness and morphology formed utilizing Scotchbond Multipurpose Plus (SBMP) on dentin prepared with a diamond bur in a high speed handpiece and dentin prepared with an Er:YAG laser. Flat dentin surfaces obtained from five human teeth were treated with the two methods and then with the dentin adhesive system according to the manufacturer's instructions. After a layer of composite was applied, the specimens were sectioned, flattened, polished and prepared for SEM observation. Ten different measurements of hybrid layer thickness were obtained along the bonded surface in each specimen. Results showed that SBMP produced a 3.43 +/- 0.75 microm hybrid layer in dentin prepared with a diamond bur. This hybrid layer was regular and constantly found. In the laser group, the dentin adhesive system produced a 1.54 +/- 0.35 microm hybrid layer that was very irregular and not found constantly. Statistical analysis of variance (p < 0.05) showed that there was a statistically significant difference between the groups. These data indicate that the Er:YAG laser, with parameters used in the experiment, is not a preparation method that allows for a thick hybrid layer formation, which is in opposition to using a diamond bur in a high speed turbine.

The purpose of this study was to compare the effect of a self-etching primer and a non-rinse conditioner with the effect of a conventional adhesive system on the penetration depth in dentin of human teeth, using scanning electronic microscopy (SEM). Fifteen human third molar teeth were sectioned into 2 pieces. All pieces were flattened with grade 600 to 1200 silicon carbide paper and divided into 6 groups: group 1 - Prime & Bond NT (NT), negative control; group 2 - 37% phosphoric acid + Prime & Bond NT (PANT), positive control; group 3 - Non-rinse Conditioner (NRC) + Prime & Bond NT (NRCNT); group 4 - NRC + Prime & Bond 2.1 (NRCPB); group 5 - NRC + Scotchbond MP (NRCSB); group 6 - Prompt L-Pop (PLP). All teeth were covered with Dyract AP. The tooth fragments were decalcified, and its resin replicas were evaluated by SEM by three previously standardized examiners. The penetration was scored from 0 (no penetration) to 3 (maximum penetration). The Kruskal-Wallis and Mann-Whitney U tests (p<0.05) showed three statistically homogeneous groups: (NT, NRCPB, NRCSB and PLP), (NRCNT) and [PANT]. The authors concluded that the self-etching primer and the non-rinse conditioner provide a lower penetration depth in human tooth dentin than the conventional adhesive system.

This study evaluated the "in vitro" shear bond strength of two materials to bovine enamel when used as porcelain laminate veneer bonding systems. The authors used the dual-cured resin cement Variolink II (Vivadent) and the light-cured flowable composite Natural-Flow (DFL). Porcelain cylinders were bonded to bovine enamel following manufacturers' directions. After 24 hours of storage in distilled water and thermocycling, the specimens were tested on a universal testing machine to determine the shear bond strengths. Mean strengths found in Groups 1 (resin cement) and 2 (flowable composite) were not statistically different (p < or = 0.05). The authors concluded that the shear bond strength of Natural-Flow is not different from Variolink II and that flowable composites can be a suitable alternative when used as porcelain laminate veneer bonding systems.

"Home bleaching" methods are commonly used in dentistry to correct tooth discoloration. This technique employs carbamide peroxide, in several concentrations, where the active component is hydrogen peroxide. In patients undertaking this treatment, this exposure can cause biological effects mainly due to the activity of hydrogen peroxide. Hydrogen peroxide is associated with effects induced by chemical (natural and synthetic substances) and physical agents (ionizing radiations). We have evaluated the cytotoxic effects of four commercial dental bleaching agents: Insta-Brite, Karisma, Opalescence and Whiteness. We have studied the effects of these agents on the survival of different E. coli strains with various capabilities to repair damages on the deoxyribonucleic acid (DNA): AB1157 (wild type), AB2463 (recA) and BW9091 (xthA). To determine the effect of the bleaching agents on the survival of E. coli AB1157, AB2463 and BW9091, cultures in exponential growth-phase were incubated with the bleaching agent or with 0.9% NaCl, as a control. After plating, the survival fractions were determined. The bleaching agents tested decreased the survival fractions of all strains studied and the E. coli BW9091 was the most sensitive and, moreover, these bleaching agents are capable of inducing damage to the DNA molecule. In conclusion, our results indicate that dental bleaching agents can generate biological effects like the ionizing radiations, and we suggest that dental professionals involved in bleaching to correct tooth discoloration, should control the clinical environment strictly, thus preventing contact between the oral mucosa/gingival tissues and the bleaching agents.

Endodontically-treated, pulpless teeth tend to become brittle and loose their natural resistance to intraoral functional stress. To retain the core to the root, posts are placed in such teeth. This article presents the rationale for placing the posts, reports past results, and discusses the current materials and implementation procedures. Understanding those principles is the learning objective of this article.