Comparison of colour properties and wear resistance of different permanent restoration resins produced by three dimensional printer

The aim of this in vitro study was to evaluate the colour properties of different permanent restoration resins produced with a 3-dimensional (3D) printer before and after thermal ageing under varying light sources at different production thicknesses. Our study also aimed to compare the wear resistance of different permanent restoration resins. Three different permanent restoration resins (P-Crown, Print Crowntec, VarseoSmile Crown Plus) were used in our study. Sample sizes were designed as 10x10 mm discs and 1, 1.5, 2 mm thicknesses. A total of 145 samples, n=15 for each thickness, were produced by 3D printing method. The samples were produced with a 3D printer (Varseo XS, BEGO, Bremen, Germany) operating with DLP technology. The samples were produced with 50 μm layer thickness and 90o printing angle. After production, the samples were polished with a bristle brush according to the manufacturer's instructions and then polished with pumice and polishing paste. A benchtop spectrophotometer (CM-3600A, Konika-Minolta Sensing, Inc., Osaka, Japan) was used to examine the colour properties of the samples. Colour measurements were performed at 5 different light sources (D65, D50, F2, F11, A) using a grey background before and after thermal aging. The samples whose colour measurements were completed before aging were subjected to 10,000 cycles of thermal aging (5-55oC). After thermal aging, the samples were kept in distilled water for 24 hours and then the second colour measurements were made in the same way. Using the data obtained from the colour measurement, the colour difference (ΔE00) of the samples under light sources was calculated. For this, CIEDE2000 formula was used and D65 (Daylight) was accepted as the control group. After the colour measurements were completed, 2 mm thick sample groups were separated for chewing test to determine the amount of wear. 240.000 chewing cycles were applied in the chewing simulator. Before and after the chewing test, the sample surfaces were scanned with a laser scanner (SD Mechatronik Laser Scanner LAS-20, Munich, Germany). The scanned data were imported into Geomagic DesignX reverse engineering software. The volume loss in mm3 was obtained by overlaying the pre and post wear data. IBM SPSS Statistics 22 programme was used for statistical analyses of the findings obtained in the study. The suitability of the parameters for normal distribution was evaluated by Kolmogorov-Smirnov test. Three-way repeated Anova test was applied to the ΔE00 values showing normal distribution. Between and within group (before and after ageing) values were analysed by post-hoc Bonferroni multiple comparison test. Since the wear data did not show normal distribution, Kruskal Wallis test was used for comparison between brands (p=0.05). As a result of the statistical analysis performed in our study, the effects of light source, restoration resin, restoration thickness and thermal aging on colour properties were found to be statistically significant (p<0.05). In all restoration groups and restoration thicknesses, ΔE00 values in type A light source were found above the clinically acceptable value. Increasing thickness caused a statistically significant decrease in ΔE00 values (p<0.05). P-Crown resin showed statistically less colour change than the other resin groups before and after thermal aging (p<0.05). A statistically significant decrease was observed in the ΔE00 values of all samples after thermal aging (p<0.05). As a result of the statistical analysis, no statistically significant difference was found between the wear values of the samples (p>0.05). Keywords: Additive manufacturing, 3D printing, Colour change, Wear resistance