Effect of Brushing on Surface Roughness, Microbial Adhesion, and Color stability of 3D-Printed Provisional Restorations Fabricated with Different Print Orientations: An In Vitro Study.

Background: This investigation evaluated the impact of brushing on surface roughness, microbial adhesion, and color stability of 3-unit, 3D-printed provisional restorations with different print orientations. Additionally, it aimed to compare these effects with those observed in commonly used provisional materials (PRMs).

Methods: 20 samples in each group were fabricated with four different provisional materials and techniques. A mandibular typodont was prepared for a 3-unit fixed partial denture with a missing first molar and scanned. The 3-unit provisional restoration was designed to fabricate polymethyl-methacrylate CAD/CAM milled and 3D-printed provisionals with print orientations of 0, 45, and 90 degrees. Putty index of the printed provisional was made to manually fabricate auto-polymerized and Bis-acrylic resin provisionals. All samples were polished and subjected to artificial brushing simulation using a brushing simulator. The surface roughness of the provisional restorations was evaluated before and after brushing simulation. Streptococcus Mutans were cultured and colony-forming units were measured before and after brushing. Color changes were measured after immersing the samples in coffee after 1, 7, and 15 days. Inter-group comparisons were performed, and the significance value was kept at P=.05.

Results: Brushing caused significant changes in surface roughness, microbial adhesion and color change in all the three print orientations (P<.05). The highest surface roughness, microbial adhesion and colour changes were observed in 0 degrees, and the least in 90 degrees. All print orientations showed significant differences from other PRM groups for microbial adhesion (p <0.05) and with Bis-acrylic resin for colour change on all the days.

Conclusion: Brushing caused significant changes in surface roughness, resulting in significant microbial adhesion and color change in 3D-printed provisionals. Further, 3D-printed samples with 90 degrees showed the most promising results and thus are suggested for use as a long-term provisional material. As compared to other PRMs, significant differences in surface roughness and microbial adhesionwere were observed with all 3 print orientations, and in color change with bis-acrylic resin.