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The objective of this study was to analyze the antimicrobial effect of 2% sodium hypochlorite (NaOCl) and 2% chlorhexidine (CHX) by agar diffusion test and by direct exposure test. Five microorganisms: Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, Bacillus subtilis, Candida albicans, and one mixture of these were used. These strains were inoculated in brain heart infusion (BHI) and incubated at 37ºC for 24 h. For the agar diffusion test (ADT), 18 Petri plates with 20 ml of BHI agar were inoculated with 0.1 ml of the microbial suspensions, using sterile swabs that were spread on the medium, obtaining growth in junction. Fifty-four paper disks (9 mm in diameter) were immersed in the experimental solutions for 1 min. Subsequently, three papers disks containing one of the substances were placed on the BHI agar surface in each agar plate. The plates were maintained for 1 h at room temperature, and then incubated at 37ºC for 48 h. The diameter of microbial inhibition was measured around the papers disks containing the substances. For the direct exposure test, 162 #50 sterile absorbent paper points were immersed in the experimental suspensions for 5 min, and were then placed on Petri plates and covered with one of the irrigant solutions, or with sterile distilled water (control group). After intervals of 5, 10 and 30 min, the paper points were removed from contact with the solutions and individually immersed in 7 ml of Letheen Broth, followed by incubation at 37ºC for 48 h. Microbial growth was evaluated by turbidity of the culture medium. A 0.1 ml inoculum obtained from the Letheen Broth was transferred to 7 ml of BHI, and incubated at 37ºC for 48 h. Bacterial growth was again evaluated by turbidity of the culture medium. Gram stain of BHI cultures was used for verification of contamination and growth was determined by macroscopic and microscopic examination. The best performance of antimicrobial effectiveness of NaOCl was observed in the direct exposure test, and of CHX was observed in the agar diffusion test. The magnitude of antimicrobial effect was influenced by the experimental methods, biological indicators and exposure time.

The aim of this study was to determine the minimum inhibitory concentration (MIC) and antimicrobial effectiveness by the direct exposure test of 4 endodontic irrigants [1% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), 1% calcium hydroxide (Ca(OH)2; prepared with 1 g of Ca(OH)2 and 100 mL of sterile distilled water), a solution of Ca(OH)2 + detergent (HCT20)] for S. aureus, E. faecalis, P. aeruginosa, B. subtilis, C. albicans and a mixed culture. Microbial growth was analyzed by two methods: turbidity of the culture medium that was confirmed by Gram stain and subculture in a specific nutrient broth. In the dilution test, NaOCl solution showed MIC equal to 0.1% for S. aureus, E. faecalis, P. aeruginosa and C. albicans and equal to 1% for B. subtilis and the mixed culture. CHX (2%) presented MIC equal to 0.000002% for S. aureus, 0.02% for E. faecalis, B. subtilis, C. albicans and the mixed culture and 0.002% for P. aeruginosa. Ca(OH)2 solution (1%) showed MIC greater than 1% for all the microorganisms except P. aeruginosa for which it was equal to 1%. Calcium hydroxide solution + detergent showed MIC equal to 4.5 mL for S. aureus, P. aeruginosa, B. subtilis, C. albicans and the mixed culture and greater than 4.5 mL for E. faecalis. In the direct exposure test, NaOCl had better antimicrobial effectiveness for all microorganisms at all times. CHX (2%) was effective for S. aureus, E. faecalis and C. albicans at all times, and ineffective for P. aeruginosa, B. subtilis and the mixed culture. The other solutions showed the worst results.

The effect of 1%, 3% and 5% EGTA (ethylene glycol-bis-(b-amino-ethyl ether) N,N,N,N-tetra-acetic acid) on the microhardness of root dentin of the cervical third of human teeth was studied. Five newly extracted maxillary incisors were sectioned transversely at the cementoenamel junction, and the crowns were discarded. The roots were embedded in blocks of high-speed polymerized acrylic resin and cut transversely into 1-mm sections. The second section of the cervical third of the root of each tooth was sectioned and divided into four parts. Each part was placed on an acrylic disc that was used as a base for microhardness measurement. Fifty microliters of 1% EGTA, 3% EGTA, or 5% EGTA were applied to the dentin surface. Deionized and distilled water was used as control. Dentin microhardness was then measured with a load of 50 g for 15 s. Statistical analysis showed that the three concentrations of the chelating solution EGTA significantly reduced dentin microhardness when compared with water (ANOVA, p

Purpose: The purpose of this study was to assess in vitro Er:YAG laser efficacy for composite resin removal, as well as the thermal alterations occurring during laser irradiation. Materials and Methods: Cavity preparations (1.0 mm deep) in bovine teeth were restored with resin and divided into 2 groups: the control group, in which restorations were removed with a high-speed bur, and the experimental group, in which restorations were removed with Er:YAG laser at 250 mJ output energy, 80 J/cm² energy density, and 6 Hz pulse repetition rate. The removal time was measured and the temperature alteration was checked. After the removal, the specimens were split in the middle, and the surrounding and deep walls were analyzed to check for the presence of restorative material. Results: The results revealed that the temperature rise during composite resin removal in both groups occurred on the substrate underneath the restoration. Although the temperature rose during composite filling removal, none of the groups presented a temperature increase higher than 5.6°C, which is considered the critical temperature increase above which there may be irreversible thermal damage to the pulp. Regarding the time for composite filling removal, it was observed that the laser group required more time than the control group for complete elimination of the material from the cavity walls. Conclusion: Although there was a greater temperature increase during composite resin removal with Er:YAG, it did not reach the critical temperature value above which there may be irreversible thermal damage to the pulp. [ABSTRACT FROM AUTHOR]

Purpose: This in vitro study assessed the tensile bond strength of glass-ionomer cements to dentin after surface treatment with Er:YAG laser. Materials and Methods: Sixty human dentin surfaces were assigned to 3 groups: 1) Er:YAG laser (80 mJ/2 Hz); 2) Er:YAG laser + conditioner; 3) control. Samples were fabricated from ProTec CEM (P) and Vitremer R (V). After 24 h of storage in water, bond strength was tested. Results: Averages (SD) in MPa for Vitremer R were: group 1, 5.49 (±1.54); group 2, 8.97 (±2.09); group 3, 14.06 (±2.67); and for ProTec CEM: group 1, 0.13 (±0.20); group 2, 4.19 (±2.04); group 3, 2.09 (±1.36). ProTec CEM yielded the highest bond strength when laser and conditioner were associated. For Vitremer R, better results were obtained without previous laser treatment. Conclusion: Er:YAG laser irradiation may influence glass-ionomer cement adhesion to dentin. [ABSTRACT FROM AUTHOR]