Impact of Smear Layer Removal Protocols on Color Dynamics and Dentin Hardness Following Intracoronal Bleaching
Abstract
Objective: This study evaluated the impact of smear layer removal protocols on intracoronal bleaching outcomes, focusing on color shifts and dentin hardness.
Material and Methods: Artificially stained human premolars underwent dentin surface treatments: distilled water, 17% EDTA, and 37% phosphoric acid (PA) before intracoronal bleaching with sodium perborate. Control teeth received no treatment. Tooth color and dentin hardness were measured at 7, 14, and 21 days post-bleaching with a VITA Easyshade spectrophotometer and Vickers hardness tests, respectively. Statistical analysis included Shapiro-Wilk and Levene’s tests, and two-way repeated ANOVA with Tukey’s HSD for shade and microhardness comparison (α=0.05).
Results: All the bleaching treatments effectively lightened teeth, with the most pronounced color change (ΔE00) observed after the first week. This was followed by a significant decrease in intensity during the second and third weeks. Color metrics showed reduced redness (a* values) and increased yellowness (b* values) across all the groups, with no significant differences in color change or dentin hardness between the treatments (p-value>0.05). However, a notable decrease in dentin hardness was observed in the cervical sections compared to the coronal sections in all the groups (p-value<0.05).
Conclusion: Smear layer removal with 37% PA or 17% EDTA did not significantly improve bleaching efficacy or affect dentin hardness. These findings support streamlined treatment protocols that omit smear layer removal without compromising clinical outcomes.
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