SUMMARY The purpose of this in situ study was to evaluate the influence of staining solutions (coffee and cola) on the color change, microhardness, roughness, and micromorphology of the enamel surface during at-home and in-office dental bleaching. One hundred and thirty-five enamel bovine blocks were prepared to perform the evaluations. Fifteen volunteers used an intraoral appliance with nine enamel blocks for 15 days. The enamel blocks were randomly assigned among the different groups according to the three treatments: in-office bleaching with high hydrogen peroxide concentration (Opalescence Boost PF 40%, Ultradent) for 40 minutes in three sessions (first, eighth, and 15th days of treatment), at-home bleaching with low carbamide peroxide concentration (Opalescence PF 10%, Ultradent) for 60 minutes daily for 15 days, and a control group (no bleaching agent applied). The enamel blocks were immersed daily in different staining solutions (coffee or cola) for 30 minutes for 15 days or were not submitted to staining (control) to obtain a factorial scheme (3×3) of the dental bleaching treatment and staining solution (n=15). The microhardness analyses (Knoop), roughness evaluations (Ra), surface micromorphological observations, and color measurements (using the CIELAB system and the VITA Classical scale) were made before and after the bleaching treatments to assess immersion in staining solutions. Mixed model tests showed that there was a decrease in enamel microhardness after exposure to cola compared with coffee and the control group (p<0.0001) for both bleaching techniques. Roughness was higher for the cola groups (p<0.0001), and there was no significant difference between the coffee and the control groups. Generalized linear models showed that when no staining solution was applied, lighter color scores were found for the VITA Classical scale (p<0.0001). Without the staining solutions, there was an increase in luminosity (ΔL) (p=0.0444) for in-office bleaching. Lower values of Δa (p=0.0010) were observed when the staining solutions were not used. The Δb (p=0.3929) did not vary significantly between the bleaching agents, but when cola was applied, the values were significantly higher than for the control (p=0.0293). Higher values of ΔE (p=0.0089) were observed for in-office bleaching without staining solutions, while lower values of ΔE were observed for the in-office associated with coffee immersion. Regardless of whether being submitted to bleaching, the enamel stained with cola showed a decrease in microhardness, an increase in roughness, and changes in the micromorphology. The efficacy of the bleaching agents was greater when no staining solution (cola or coffee) was used, and in-office bleaching showed greater color change than the at-home bleaching technique.
The purpose of this study was to evaluate the calcium (Ca) and phosphorous (P) content in enamel bleached with high and low concentrations of hydrogen peroxide (HP) using Total Reflection X-Ray Fluorescence (TXRF) and colorimetric spectrophotometry (SPEC). Forty-eight sound human third molars were used. Their roots were embedded in polystyrene resin and immersed for seven days in an artificial saliva solution. Then they were distributed into six groups to receive the bleaching treatments. The agents of high HP concentration (for in-office use) evaluated were Whiteness HP Maxx/FGM (35% HP), Whiteness HP Blue/FGM (35% HP, 2% calcium gluconate), Pola Office+/SDI (37.5% HP, 5% potassium nitrate), and Opalescence Boost/Ultradent (38% HP, 1.1% ion fluoride, 3% potassium nitrate); these agents were applied to enamel in three sessions. The agents of low HP concentration (for home use) evaluated were Pola Day/SDI (9.5% HP) and White Class 10%/FGM (10% HP, potassium nitrate, calcium, fluoride), and these agents were applied for 14 days. Enamel microbiopsies were evaluated by TXRF and SPEC analysis before the bleaching treatment (baseline), during the treatment, and 14 days after the end of the treatment. For TXRF, the Kruskal-Wallis test showed that Ca and P were not influenced by agent (p>0.05). For SPEC, Pola Office+, Opalescence Boost, Pola Day, and White Class 10% caused a decrease of Ca over time; there was a significant decrease of P over time to Pola Office+ and White Class 10%. The Spearman test showed no correlation between the Ca (p=0.987; r=-0.020) and P (p=0.728, r=0.038) obtained by SPEC and TXRF. For TXRF and SPEC, changes in Ca and P during bleaching occurred independently of the HP concentration used.
This study aimed to evaluate the effect of endodontic sealer (ES) on bond strength (BS) of prefabricated or milled-CAD-CAM (computer-aided design and computer-aided manufacturing) glassfiber-posts (GFP). Canals of 90 single-rooted teeth were prepared for filling by the single-cone technique with gutta-percha and one of the following ES: AH Plus (epoxy resin), Endofill (zinc-oxide and eugenol), and Bio-C Sealer (calcium-silicate). After post-space preparation, toothspecimens were equally divided in half according to type of GFP to be used. In the half to receive milled-CAD-CAM posts, tooth specimens were molded with acrylic resin to obtain replicas. These were scanned to enable the laboratory to produce the milled-CAD-CAM GFPs (Fiber CAD Lab, Angelus) by the subtractive technique. The other half of samples received prefabricated GFPs (Exacto, Angelus) (n=15). The GFPs were cemented with dual-cure resin cement (Panavia F2.0, Kuraray). Each root was sectioned into two slices per root region (cervical, middle, apical) that were subjected to the push-out BS test, in a universal testing machine. Failure mode (FM) was classified by scores. The BS data were submitted to generalized linear model analyses, while FM was analyzed using the chi-square test (a=0.05). BS showed no significant difference among the three ES (p > 0.05). BS was significantly higher for prefabricated (mean 10.84 MPa) versus milled-CAD-CAM GFPs (mean 6.94 MPa) (p <0.0001), irrespective of ES. The majority showed mixed failures. It could be concluded that type of ES did not affect BS of GFPs to dentin, and prefabricated-GFPs had higher bond-strength than customized-milled-CAD-CAM GFPs.
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