Comparison of color stability and surface roughness of 3D printed and conventionally produced temporary materials

Introduction
Temporary restorations produced with a 3D printer have become very popular recently. There are limited studies in the literature comparing 3D printing and traditionally produced temporary materials.

Objectives
The aim of this study is to examine the color and roughness changes of different temporary mate­rials produced by a 3D printer and the traditional method after being kept in coffee, and also to evaluate the effect of the polishing process applied to the surfaces.

Material and methods
Two types of 3D printing resin and a conventional autopolymerized PMMA material were selected. Half of the samples in each group were polished with polishing paste (n = 15). The first color values and surface roughness were measured, then samples were kept in coffee. 48 hours later, the second color measurements of the samples were made with spectrophotometer and ∆E00 values were calculated. Surface roughness values were measured with a profilometer device. Data were analyzed with the two-way analysis of variance and Tukey test. The relationship between roughness and color change in the coloring process was evaluated by Spearman correlation analysis (p < 0.05).

Results
According to two-way ANOVA analysis the color change between the materials and the color change in the polishing state of the surface were found to be statistically significant. The ΔE values listed from the highest to the lowest were as follows: unpolished PMMA > polished PMMA > polished temporary 3D resin > unpolished temporary 3D resin > unpolished standard 3D resin group > polished standard 3D resin.

Conclusions
The conventionally produced PMMA group was the material that underwent the most color change. From the materials produced by 3D printing, the temporary resin is more colored than the standard resin. A significant relationship was found between color change and roughness change. Less color change was found on polished surfaces.