Comparative analysis of chromatic alterations of a Calcium Silicate-based Material: in vitro study

Abstract

Objective: The purpose of this study was to investigate and compare chromatic alterations of an inorganic silicate-based cement, also known as white mineral trioxide aggregate (WMTA), submitted to different environmental conditions using the CIE L*a*b* system evaluated by two different methods. Methods: Twenty-four samples of WMTA (ProRoot® MTA, Dentsply Tulsa Dental, Johnson City, TN) were randomly distributed in four groups (n=4). In group 1 the samples did not undergo any additional treatment (negative control group). In group 2 WMTA samples were light irradiated for 60 seconds using a LED poliwave curing unit. In group 3 and 4 WMTA samples were coated with a layer of glycerine and adhesive, respectively and light irradiated for 60 seconds. A commercial spectrophotometer (VITA Easyshade® Advance 4.0, VidentTM, California, USA) and calibrated photographic digital analysis were used to determine colour coordinates from the CIE L*a*b* system of each sample after three different time points: 30 minutes, 48 hours and 7 days. In order to understand the chemical alterations associated to colour variations of the material x-ray diffraction analysis was also conducted. Data was analysed using statistical software IBM® SPSS® Statistics, version 20. Results: Consistency between the two colour measuring methods was not observed. Significant colour variation was observed for group 3. X-ray diffraction analysis showed no differences between compounds. Conclusion: WMTA showed significant dark discolouration after irradiation with an LED poliwave curing unit in an oxygen-free environment promoted by glycerine although after 48 hours discolouration had faded. The same light irradiation protocol associated to an oxygen-free conditions achieved by an adhesive resin layer did not induce significant discolouration at the end of the experiment protocol.