Color heterogeneity and individual color changes in dentin and enamel bleached in the presence of a metallic orthodontic bracket.

OBJECTIVE: This in-vitro study evaluated the color changes in enamel and dentin bleached in the presence of an orthodontic bracket, as well as the heterogeneity of the color and contribution of each tissue to the color change (CTCC). MATERIALS AND METHODS: Enamel-dentin specimens from extracted bovine teeth were bleached before or after bracket removal or maintained without any treatment (control). The colors of the dentin and enamel were measured individually and after recombining these substrates. The changes in the color (ΔE00 ) and whitening index (ΔWID) were estimated by the color difference between the bleached specimens and those of the control. The CTCC was also calculated by recombining the tissues from different treatments. Images of specimens obtained from a stereomicroscope were used to analyze the color homogeneity within each tissue. RESULTS: The highest values of ΔE00 and ΔWID were observed in the specimens bleached in the absence of a bracket. Bleaching in the presence of a bracket resulted in enamel with a center that was whiter than the periphery. Dentin and enamel presented similar CTCC values. CONCLUSIONS: Tooth bleaching performed in the presence of a metallic bracket resulted in a reduced bleaching effect and increased color heterogeneity within both tissues. CLINICAL SIGNIFICANCE: Tooth bleaching before the orthodontic bracket removal reduces the bleaching effect in both dentin and enamel. Moreover, a heterogeneous color of enamel surface can be observed after tooth bleaching in the presence of a nickel-free metallic orthodontic bracket.

Role of enamel and dentin on color changes after internal bleaching associated or not with external bleaching

Abstract Objective To evaluate the effect of the association between external and internal tooth bleaching on color changes in dentin and enamel, individually or recombined, previously stained with triple antibiotic paste (TAP). Methodology Forty enamel-dentin specimens from bovine incisors were separated into ten blocks according to similarity in their whiteness index (WID). Three specimens within each block were stained by dentin exposure to TAP, and the remaining specimen was used as control to estimate color changes. Specimens were sectioned to separate tissues, and dentin and enamel colors were measured individually and after being recombined. Alterations in color (CIEDE2000 - ΔE00) and translucency parameter (TP) resulting from staining were estimated by color difference between stained and control specimens. The contribution of each tissue to the color change (CTCC) was also calculated. Non-sectioned stained specimens were bleached by applying sodium perborate on dentin, associated or not with 35% hydrogen peroxide on enamel. Color changes caused by bleaching procedures were estimated and data were analyzed using the paired t-test or Two-way repeated measures ANOVA. Results TAP caused more pronounced changes in dentin, but enamel color was also affected. Both protocols presented a similar ΔE00, and dentin showed the greater color change. After exposure to TAP, we observed a reduction in WID; WID values were the same for bleached and control specimens regardless of protocol. We found no significant effect of substrate and bleaching technique on TP. Enamel played a more critical role in color changes caused by either staining or bleaching procedures. Conclusion Enamel color played a greater role on tooth color changes than dentin. External and internal bleaching association did not improve bleaching effect on specimens stained with TAP.

Role of enamel and dentin on color changes after internal bleaching associated or not with external bleaching.

OBJECTIVE: To evaluate the effect of the association between external and internal tooth bleaching on color changes in dentin and enamel, individually or recombined, previously stained with triple antibiotic paste (TAP). METHODOLOGY: Forty enamel-dentin specimens from bovine incisors were separated into ten blocks according to similarity in their whiteness index (WID). Three specimens within each block were stained by dentin exposure to TAP, and the remaining specimen was used as control to estimate color changes. Specimens were sectioned to separate tissues, and dentin and enamel colors were measured individually and after being recombined. Alterations in color (CIEDE2000 - ΔE00) and translucency parameter (TP) resulting from staining were estimated by color difference between stained and control specimens. The contribution of each tissue to the color change (CTCC) was also calculated. Non-sectioned stained specimens were bleached by applying sodium perborate on dentin, associated or not with 35% hydrogen peroxide on enamel. Color changes caused by bleaching procedures were estimated and data were analyzed using the paired t-test or Two-way repeated measures ANOVA. RESULTS: TAP caused more pronounced changes in dentin, but enamel color was also affected. Both protocols presented a similar ΔE00, and dentin showed the greater color change. After exposure to TAP, we observed a reduction in WID; WID values were the same for bleached and control specimens regardless of protocol. We found no significant effect of substrate and bleaching technique on TP. Enamel played a more critical role in color changes caused by either staining or bleaching procedures. CONCLUSION: Enamel color played a greater role on tooth color changes than dentin. External and internal bleaching association did not improve bleaching effect on specimens stained with TAP.

A simple method to increase the bleaching effectiveness of high-concentrated carbamide peroxide used for in-office bleaching.

This in vitro study aimed to evaluate the effect of two alternative clinical protocols on the tooth bleaching effectiveness of 37% carbamide peroxide. Thirty enamel-dentin blocks from bovine incisors were stained with a coffee solution for 1 week. After color measurement at baseline with a portable spectrophotometer, the blocks were bleached during two 45-min applications of 37% carbamide peroxide with a 2-day interval between bleaching procedures, according to one of the following protocols: 1) Control: placement of bleaching agent over dried enamel; 2) Moist enamel: placement of bleaching agent over enamel previously humidified with a damp gauze for 1 min; 3) Moist cotton pellet: covering the bleaching agent with a moist cotton pellet during the entire bleaching procedure. The tooth color was assessed 2 days after each bleaching procedure. The data of ΔL, Δa, Δb, and ΔE were individually analyzed using ANOVA and Tukey's test (α = 0.05). In general, applying the bleaching agent to the moist enamel resulted in lower Δa and Δb values, and higher ΔL and ΔE values than the control. No difference was observed between the control and the protocol of covering the bleaching agent with a moist cotton pellet. Regardless of the protocol, the second bleaching procedure resulted in a further increase in ΔL and ΔE, and a reduction in Δa. A further decrease in Δb was observed only for the moist enamel protocol. In conclusion, humidifying the enamel with a damp gauze prior to the placement of 37% carbamide peroxide improved the effectiveness of the bleaching.