Validation and spectrophotometric analysis of crown discoloration induced by root canal sealers

A major cause of crown discoloration is root canal sealer remnants in the pulp chamber, after root canal obturation. The aim of this study was the evaluation of the chromogenic effect of common and new-generation root canal sealers. The tested null hypothesis was that none of the sealers induced clinically perceptible crown discoloration, ex vivo (H ₀: CIE color difference ∆Ε < 3.7).

The crowns of 80 intact, fully developed third mandibular molars were cross-sectioned 1 mm below the cementoenamel junction and stored in standard conditions (100 % humidity, 37 °C). The pulp chambers were chemomechanically debrided with hand files and sodium hypochlorite (NaOCl) and the specimens were randomly assigned into four experimental (1–4) and one control (5) groups. In the experimental groups, the internal axial walls of the pulp chambers were coated with sealers (Group 1; Roth 811, Group 2; AH26, Group 3; GuttaFlow, Group 4; Epiphany SE). The pulp chambers of the control group (Group 5) remained unfilled. The spectral reflectance lines of the crowns were recorded by a UV–Vis spectrophotometer. CIE total color differences \( (\varDelta \mathrm{E} = [{(\varDelta L*)^{2}} + {(\varDelta a*)^{2}} + {(\varDelta b*)^{2}} ]\frac{\text{$\scriptstyle 1$}}{\text{$\scriptstyle 2$}} ) \) were calculated after 1 week, 1 month, 3 months, and 6 months, respectively. A pilot study was also conducted for the validation of the experimental model. Two-way mixed ANOVA models were used for statistical data analysis.

The experimental model presented values of ∆Ε < 1 unit and high positive correlation values, after repeated measurements (p < 0.05). Roth 811 sealer (Group 1) induced clinically perceptible crown discoloration (∆Ε > 3.7, p < 0.05) and presented statistically significant differences from Groups 2–5 in all examination intervals (p < 0.05). In Groups 2–5, clinically perceptible crown discoloration was not observed (∆Ε < 3.7, p < 0.05).

Roth 811 sealer exhibited severe discoloration effects. Within the limitations of this study, it can be concluded that any sealer remnants should be removed from the pulp chamber after root canal obturation and before placement of a final restoration.

The chromogenic potential may play an important role in selecting proper root canal sealers.