Surface roughness and stainability of new-generation denture base materials after brushing and coffee thermocycling

Abstract

Disk-shaped specimens were prepared from additively (NX and DT), subtractively (MZ), and conventionally manufactured denture base resins (CV). Surface roughness and color coordinates were measured after polishing, simulated brushing, and coffee thermocycling, while surface roughness was also measured before polishing. Polishing reduced the surface roughness of all materials. Brushing and coffee thermocycling increased the surface roughness of only DT. CV had the highest susceptibility to consecutive brushing and coffee thermocycling as it had the highest surface roughness, which was above the clinically acceptable threshold. All materials had similar stainability; only MZ had perceptible color change after brushing. Even though stainability of tested denture base resins was similar, additively or subtractively manufactured computer-aided design and computer-aided manufacturing (CAD-CAM) resins had smoother surfaces after brushing and coffee thermocycling, regardless of the material. Therefore, complete dentures made out of these CAD-CAM resins may have favorable surface properties in the long term. Graphical abstract

Effect of coffee thermocycling on the surface roughness and stainability of denture base materials with different chemical compositions manufactured with additive and subtractive technologies

“…Given that the present study was the first on the R a and stainability of pink GSM, a priori power analysis based on the results of previous studies could not be performed, which could be considered as a limitation. Nevertheless, significant differences were observed among tested materials and the number of specimens in each group was based on previous studies on the R a and discoloration of additively and subtractively manufactured PMMAs 5,6,9,20 ; one of those studies reported the results of a priori power analysis based on a pilot study. 20 In addition, post hoc power analyses were performed for each parameter investigated and the sample size was deemed adequate for a minimum of 83% power with a minimum effect size of 0.62 and α = 0.05.…”

“…A digital spectrophotometer (CM-26d; Konica Minolta), which has a Commission International de I'Eclairage (CIE) D65 illuminant and uses CIE Standard (2-degree) human observer characteristics, was used to measure the color coordinates of each specimen on a gray background. 5,9,20 All measurements were performed in the same temperature-and humidity-controlled room with daylight by a single operator and the spectrophotometer was calibrated before each scan.…”

“…3 However, conventional PMMA's polymerization shrinkage, susceptibility to bacterial plaque accumulation, and possible allergic potential due to release of unreacted monomers, 4 along with the advancements in computeraided design and computer-aided manufacturing (CAD-CAM) technologies have increased the popularity of additively and subtractively manufacturing denture bases. [5][6][7][8] Reinforcement of PMMA with fibers and nanoparticles to improve different physical and mechanical properties has been investigated broadly. 1 Even though subtractively manufactured prepolymerized disks has improved mechanical properties, 9 reinforcement of prepolymerized PMMA disks with nanographene has also been introduced.…”

“…20 In addition, the number of studies on the R a and stainability of additively manufactured denture base materials after CTC is limited to one and that study did not involve a comparison with nanographene-reinforced PMMA. 5 Therefore, the present study aimed to evaluate the effect of CTC on the R a and stainability of denture base materials with different chemical compositions, one of which was a nanographene-reinforced PMMA, fabricated by using either additive or subtractive manufacturing. The hypotheses were that (i) time interval (before polishing, after polishing, and after CTC) would affect the R a within each material, (ii) material type would affect the R a within each time interval, (iii) material type would affect the stainability of tested materials after CTC, and (iv) CTC would affect the color coordinates of tested materials.…”

“…The hypotheses were that (i) time interval (before polishing, after polishing, and after CTC) would affect the R a within each material, (ii) material type would affect the R a within each time interval, (iii) material type would affect the stainability of tested materials after CTC, and (iv) CTC would affect the color coordinates of tested materials. 5,6,9 or subtractively manufactured nanographene-reinforced PMMA. 20 In addition, a priori power analysis based on the results of a pilot study that investigated the effect of polishing and CTC on the R a and stainability of polymers had been conducted in one of those studies and yielded 10 specimens per material sufficient to detect an effect size of 0.1 with 1 À β = 80% and α = 0.05.…”