Evaluating the color stability of temporary crowns fabricated by 3-dimensional printing and manual methods

This in vitro study aimed to compare the color stability of temporary crowns fabricated by 3-dimensional (3D) printing with that of crowns fabricated with 2 manual methods. An impression was made of a prepared central incisor, from which 90 dies were fabricated. The dies were randomly assigned to 3 groups (n = 30) based on crown fabrication method: 3D printing, automix bis-acryl resin, or powder-and-liquid polymethyl methacrylate. All specimens were immersed in a coffee, soft drink, or distilled water solution for 1 week (n = 10 per subgroup). Color change was measured using a spectrophotometer and the International Commission on Illumination's CIE L*a*b* method, and the values were converted to the National Bureau of Standards (NBS) index for assessment and comparison. When color change was assessed according to fabrication method, the highest (mean [SD]) ΔE* value was reported for the automix specimens (3.39 [2.86]), and the lowest was recorded for the powder-and-liquid specimens (2.05 [2.33]) (P < 0.05; Kruskal-Wallis test). The difference between ΔE* values of the 3D printing group (2.46 [1.75]) and the powder-and-liquid group was not statistically significant. When color change was assessed according to the immersion solution, the coffee solution showed a significantly higher (mean [SD]) ΔE* value (5.04 [2.67]) than the soft drink (1.43 [0.92]) and distilled water (3.41 [7.93]) solutions (P < 0.05; Kruskal-Wallis test). The color changes associated with the 3 methods were statistically equal in terms of the NBS index ranges, most frequently falling in the range of very minor to acceptable change. The powder-and-liquid method seems to be most suitable for fabricating temporary prostheses for long-term use.