Effect of coffee thermal cycling on the surface properties and stainability of additively manufactured denture base resins in different layer thicknesses

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Purpose: To compare the effect of coffee thermal cycling on surface roughness (Ra), Vickers microhardness (MH), and stainability of denture base resins additively manufactured in different layer thicknesses with those of subtractively manufactured denture base materials.Materials and methods: Eighty disk-shaped specimens (& Oslash;10x2 mm) were fabricated from two subtractively (Merz M-PM [SM-M] and G-CAM [SM-G]) and three additively (NextDent 3D+ [50 mu m, AM-N-50; 100 mu m, AM-N-100], FREEPRINT Denture [50 mu m, AM-F-50; 100 mu m, AM-F-100], and Denturetec [50 mu m, AM-S-50; 100 mu m, AM-S-100]) manufactured denture base materials (n = 10). Ra measurements were performed before and after polishing by using a non-contact optical profilometer, while MH values and color coordinates were measured after polishing. Specimens were then subjected to 5000 cycles of coffee thermal cycling, all measurements were repeated, and color differences (Delta E00) were calculated. A linear mixed effect model was used to analyze Ra and MH data, while one-way analysis of variance was used to analyze Delta E00 data (alpha = 0.05). Ra values were further evaluated according to a clinically acceptable threshold of 0.2 mu m, while Delta E00 values were evaluated according to perceptibility (1.72 units) and acceptability (4.08 units) thresholds. The interaction between the material type and the time interval affected both Ra and MH (p <= 0.001). Tested materials had their highest Ra before polishing (p <= 0.029). Before polishing, AM-F-100 had the highest, and SM-M and SM-G had the lowest Ra (p < 0.001). After polishing and after coffee thermal cycling, SM-G mostly had lower Ra than those of other materials (p <= 0.036). SM-G mostly had higher MH than that of other materials before and after coffee thermal cycling (p <= 0.025). Coffee thermal cycling reduced the MH of SM-M and increased that of AM-S-100 (p <= 0.024). AM-N-100 had higher Delta E00 than AM-F, AM-S-100, and SM-G (p <= 0.009), while AM-F and SM-G had lower Delta E00 than AM-S-50 and AM-N-50 (p <= 0.024).Conclusions: Polishing reduced the surface roughness of all materials, whereas the effect of coffee thermal cycling was nonsignificant. Most of the tested materials had acceptable surface roughness after polishing and after coffee thermal cycling according to the reported threshold. Layer thickness only affected the microhardness of tested additively manufactured resins, which was material-dependent. Subtractively manufactured specimens mostly had high microhardness and that of nonreinforced subtractively manufactured resin decreased after coffee thermal cycling. When reported color thresholds are considered, all materials had acceptable color stability.


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Denture Base, Layer Thickness, Microhardness, Stainability, Surface Roughness


Journal of Prosthodontics-Implant Esthetic and Reconstructive Dentistry

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