Influence of polishing methods on the physical properties of temporary restorations

Although surface polishing of temporary restorations is a crucial clinical step, there is a lack of information about the effect of different polishing protocols on the surface properties of 3D printed resins for temporary restorations. This study had as goal to evaluate the effect of different polishing methods on the surface roughness, contact angle, and color stability of temporary restorations. One bis-acrylic resin (Integrity/IT) and 3 resins for 3D printing (Denture teeth, Formlabs/DT, Crown and Bridge MFH, Nextdent/CB, and Cosmos Temp, Yller/CT) were polished following 5 protocols (No polishing/Control, Jiffy Cup/JC, Jiffy Brush/JB, Sof-lex/SL, and Astropol/AS) and tested for surface roughness using a profilometer and for color stability using a spectrophotometer (after immersion in instant coffee for up to 7 days). Data were analyzed using 2-way ANOVA (surface roughness and contact angle) and 3-way repeated measurements ANOVA (color stability), all followed by Tukey test. Overall results of surface roughness showed CT > DT = CB = IT, and Control > JB > AS = SL = JC. The highest surface roughness was observed for IT control group, while the lowest values were observed for CB polished with SL. All groups showed lower surface roughness after being polished with multi-step polishing systems except for CB polished using AS, which showed similar values to CB polished with JB. Overall results of contact angle showed IT > CT > DT > CB, and JC > Control > AS > JB = SL. Highest contact angle was observed for CT control and all resins polished using JC, while the lowest values were observed for CB control group and CT polished using AS. Control groups for IT and CT were more hydrophobic than their respective polished groups, while CB and DT resins were more hydrophobic when polished compared to their respective control groups. Overall results of color variation showed CT > IT = CB > DT, and Control > JB > JC = SL = AS. All tested resins showed color variation higher than the 3.3 clinical threshold when immersed in coffee for 7 days, except DT and CT polished using JC. Different polishing methods can influence the physical properties of different resins used for temporary restorations. All materials showed better results when polished, especially when a multi-step polishing system was used.