Two-session root canal treatment using a calcium hydroxide-based dressing was associated with significantly smaller periapical lesions at 90 days and characterized by progressive repair.

Considering the increase in esthetic restorative materials and need for improvement in unsatisfactory restoration substitution with minimal inadvertent removal of healthy tissues, this study assessed the efficacy of erbium:yttrium-aluminum-garnet (Er:YAG) laser for composite resin removal and the influence of pulse repetition rate on the morphological analyses of the cavity by scanning electron microscope. Composite resin fillings were placed in cavities (1.0 mm deep) prepared in bovine teeth, and the 75 specimens were randomly assigned to five groups according to the technique used for composite filling removal (high-speed diamond bur, group I, as a control, and Er:YAG laser, 250 mJ output energy and 80 J/cm(2) energy density, using different pulse repetition rates: group II, 2 Hz; group III, 4 Hz; group IV, 6 Hz; group V, 10 Hz). After the removal, the specimens were split in the middle, and we analyzed the surrounding and deep walls to check for the presence of restorative material. The estimation was qualitative. The surfaces were examined with a scanning electron microscope. The results revealed that the experimental groups presented bigger amounts of remaining restorative material. The scanning electron microscopy (SEM) analyses showed irregularities of the resultant cavities of the experimental groups that increased proportionally with increase in repetition rate.

The 10.6-μm CO(2) laser irradiation diminishes the carbonate and water contents in the enamel after irradiation.

This study aimed to assess the in vitro efficacy of the lasers Er:YAG, Nd:YAG, and CO(2) operating in the low energy mode for caries prevention in pits and fissures. Forty-five caries-free enamel occlusal sections were randomly divided into three groups: G1 - Er:YAG (80 mJ/2 Hz); G2 - Nd:YAG Laser (1 W and 10 Hz); and G3 - CO(2) Laser (0.4 W and 20 Hz). After surface treatment, the samples were submitted to challenge with acid consisting of a 10-day immersion in demineralizing (6 h) and remineralizing solution (18 h). Next, enamel demineralization was quantitatively evaluated by subsurface microhardness test and polarized-light microscopy (PLM, mm(2)) and qualitatively assessed by scanning electron microscopy. The Wilcoxon test was used for comparison of each group with its own control. ANOVA (α = 5%) was employed for comparison among groups, and Fisher's LSD multiple comparison test was applied, to check the difference in means. Concerning the microhardness analyses, statistical difference between control, and experimental areas was only detected for the CO(2) group. Experimental values were higher than the controls. As for PLM analyses, smaller demineralized areas were measured for G2 (Nd:YAG) and G3 (CO(2)) compared with the control areas. In conclusion, the present findings suggest that the CO(2) laser should be selected in order to increase the enamel resistance to acid in pits and fissures.

Cigarette smoke is a significant source of cadmium, lead, and toxic elements, which are absorbed into the human organism. In this context, the aim of this study was to investigate in vitro the presence of toxic elements, cadmium, and lead deriving from cigarette smoke in the resin composite, dentine, and dental enamel. Eight cylindrical specimens were fabricated from resin composite, bovine enamel, and root dentin fragments that were wet ground and polished with abrasive paper to obtain sections with 6-mm diameter and 2-mm thickness. All specimens were exposed to the smoke of 10 cigarettes/day during 8 days. After the simulation of the cigarette smoke, the specimens were examined with scanning electron microscopy (SEM) and the energy-dispersive X-ray analysis. In the photomicrographic analysis in SEM, no morphological alterations were found; however, the microanalysis identified the presence of cadmium, arsenic, and lead in the different specimens. These findings suggest that the deposition of these elements derived from cigarette smoke could be favored by dental structures and resin composite.

Under the tested conditions, Er:YAG laser irradiation was efficient for composite resin ablation and did not cause a temperature increase above the limit considered safe for the pulp. Among the tested pulse repetition rates, 6 Hz produced minimal temperature change compared to the control group (high-speed bur), and allowed composite filling removal within a time period that is acceptable for clinical conditions.

Based on the results from the present study, it may be concluded that the CO(2) and Nd:YAG lasers increased the enamel acid resistance in pits and fissures.

The laser promoted a greater increase in temperature only when compared with high-speed handpiece and water flow rate of 100 mL/min.