The Effect of Layer Thickness on Surface Roughness, Color Stability, and Microbial Adherence of Temporary Restoration Materials: An in vitro study

Objectives: This study aims to evaluate the effect of built layer thickness (BLT) on the surface roughness, color stability, and microbial adhesion of 3D-printed interim restorations, comparing them with conventional and milled resin materials. Materials and Methods: Disk-shaped samples (2 mm thickness, 10 mm diameter) were fabricated using three different manufacturing methods: conventional, 3D printing, and milling. The 3D-printed samples were produced using a Digital Light Processing (DLP) printer with BLTs of 30 μm, 50 μm, and 70 μm. Surface roughness was measured using confocal microscopy. Color stability was assessed after immersion in artificial saliva, coffee, and red wine for 14 days, with color differences determined using a dental spectrophotometer. Microbial adhesion was evaluated using bacterial and fungal strains, and adherence levels were classified. Results: Statistical analysis showed that BLT significantly influenced surface roughness, with 30 μm BLT exhibiting the smoothest surfaces. The highest discoloration was observed in the 70 μm BLT group, while the least discoloration was in the milling group. Microbial adhesion was higher on milled samples compared to 3D-printed materials and conventional acrylic resin. Conclusion: BLT significantly affects the surface properties of 3D-printed interim restorations. A 30 μm BLT provided the best surface characteristics with lower roughness and reduced discoloration. However, the monomer content of 3D printing resins remains unclear, necessitating further investigation. More comprehensive studies are required to optimize 3D-printed dental materials.