Surface roughness of 3D printed and conventional interim restorative materials after dynamic loading.

Purpose: To investigate the surface roughness (Ra; µm) of three different interim resin materials, which were subjected to chewing simulation.

Methods: Three interim resin materials were evaluated: (1) LCD type (liquid crystal displays) 3D printed (LCD, n= 10); (2) conventional autopolymerizing bis-acrylic (CO, n= 10); (3) DLP type (digital light processing) 3D printed (DLP, n= 10) interim resin materials. The specimens were subjected to 30,000 cycles of chewing simulation. The surface roughness of the materials was compared and scanning electron microscope (SEM) images representing each group were obtained. The Kruskal-Wallis and Mann-Whitney U test were carried out for comparison of the groups. Paired samples t test was used to compare the Ra values of each group separately before and after chewing simulation (α= 0.05).

Results: The mean ± standard deviation values of baseline surface roughness values were 1.252 ± 0.426 for LCD printed resin, 0.715 ± 1.321 for conventional resin, 0.525 ± 0.963 for DLP printed resin. LCD group had the highest Ra 0 values. No statistically significant difference was observed between the CO and DLP group. After 30,000 cycles of simulated chewing, the mean surface roughness values for LCD, CO and DLP groups were 0.992 ± 0.160, 0.524 ± 0.288 and 0.542 ± 0.658, respectively. After chewing simulation, the difference among the Ra1 values of groups were statistically significant (P= 0.014). LCD group had the highest Ra1 values. No statistically significant difference was observed between the CO and DLP group. The difference of Ra values of all interim materials after chewing simulation compared to baseline were not statistically significant.

Clinical significance: Since the results showed that the Ra values in this study were above the plaque accumulation threshold Ra of 0.20 µm and SEM images were consistent with the Ra measurements, care should be taken to adequately polymerize and polish the restoration surface, especially when it is being used for an extended period of time.