Comparison of material properties and biofilm formation in interim single crowns obtained by 3D printing and conventional methods

STATEMENT OF PROBLEM:Three-dimensionally printed interim restorations are among the recent technological advancements in dentistry. However, evidence of their performance is lacking. PURPOSE:The purpose of this in vitro study was to compare the properties of interim restorations made by 3D printing with different technologies, laser stereolithography (SLA), technology and selective laser sintering (SLS) with those obtained by conventional techniques from acrylic resin and bis-acryl resin. MATERIAL AND METHODS:Four different groups (acrylic resin, bis-acryl resin, SLS, SLA) were tested for flexural strength, Vickers microhardness, fatigue test, compressive strength, surface roughness before and after polishing, and biofilm formation. Specimens were made in the form of rectangular blocks, disks, and single crowns by following the manufacturing technique of each material. One-way ANOVA was used to test biofilm formation, Vickers microhardness, and the results of the 3-point bend flexural test, while the paired t test was used to assess differences in surface roughness between the materials (α=.05 for all tests). RESULTS:The highest Vickers microhardness value was for acrylic resin interim crowns, while the elastic moduli were lower for both the 3D printed materials. Only the SLA resin fractured during the fatigue test. For surface roughness, a statistically significant difference was found among the studied materials (P<.001), with SLA resin and bis-acryl resin having the lowest values. No statistically significant differences were found for biofilm formation (P>.05). CONCLUSIONS:SLS resin had favorable results for the Vickers microhardness, higher maximum flexural strength, and peak stress in load-to-fracture tests, the fatigue test, and biofilm formation compared with acrylic resin and bis-acryl resin, while SLA resin showed favorable results only for biofilm formation and surface roughness.