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.

Separate contribution of dentin and enamel to color changes caused by staining pigments and dental bleaching.

AIM: This study assessed the changes in color and translucency of dentin and enamel after staining and bleaching procedures as well as the contribution of the tissues to color change (CTCC). MATERIALS AND METHODS: Fifty enamel-dentin specimens were obtained from bovine incisors and grouped into 10 blocks based on the similarity of the baseline color. One specimen in each block was used as the control, and the others were intrinsically (blood) or extrinsically (coffee) stained. One stained specimen for each pigment was bleached with 35% hydrogen peroxide. The enamel was separated from the dentin, and the tooth color and translucency parameter (TP) were measured individually and after recombining these substrates. Changes in color (ΔE00), whitening index (WI), and TP caused by the staining and bleaching procedures were estimated through assessing the color differences compared with the controls. CTCC was also calculated by recombining the enamel and dentin tissues from different treatments. The data were analyzed using the paired t test or the two-way repeated measures ANOVA (α = 0.05). RESULTS: Extrinsic staining procedures produced higher color changes than intrinsic ones, except in dentin. The highest bleaching effect was observed in the dentin of specimens that were extrinsically stained. Similar CTCC values were observed for the dentin and enamel for both the staining and bleaching procedures. Except for the specimens that were treated with intrinsic staining and became more translucent after the bleaching procedure, the other treatments resulted in non-significant TP changes. CONCLUSIONS: Staining the specimens extrinsically resulted in higher color change than staining them intrinsically, and these specimens were more affected by the bleaching procedure. Enamel and dentin demonstrated similar CTCC values.