Spectrophotometric analysis of coronal discolouration induced by grey and white MTA

To evaluate the specific alterations in tooth colour with white and grey MTA when used to fill pulp chambers.

Forty-five fully developed, intact, mandibular third molars were sectioned 1 mm below their cemento-enamel junction (CEJ). Their pulp chambers were chemo-mechanically debrided, and the specimens were randomly assigned into three groups: Group 1-white MTA (Angelus(™)), Group 2-grey MTA (Angelus(™)) and Group 3-negative control (unfilled). During the experimental period, specimens were immersed in vials containing distilled water up to the CEJ (37±1 °C). Spectral reflectance lines were recorded by utilizing a UV-vis spectrophotometer equipped with an integration sphere in the visual spectrum, at baseline, 1 week and 1, 2 and 3 months after placement of the materials. Data were transformed into values of the CIE L*a*b* colour system, and the corresponding ΔΕ values were calculated. The results were analysed using two-way mixed anova models, whilst pairwise comparisons were conducted with Bonferroni's method at P < 0.05 level of significance.

Both types of MTA induced significant decreases in L*, a* and b* values. The colour change was greater with grey MTA. Grey MTA led to clinically perceptible crown discolouration after 1 month, whilst the total colour change caused by white MTA exceeded the perceptible threshold for the human eye after 3 months.

The application of both grey and white MTA formulations induced a decrease in lightness and reduction in redness and yellowness in teeth. The present findings suggest that application of grey MTA in the aesthetic zone should be avoided, whilst white MTA should be used with caution when filling pulp chambers with the materials.