Affiliation:
1. Department of Reconstructive Dentistry and Gerodontology School of Dental Medicine University of Bern Bern Switzerland
2. Division of Gerodontology and Removable Prosthodontics University Clinics of Dental Medicine University of Geneva Geneva Switzerland
3. Department of Prosthodontics Faculty of Dentistry Osmangazi University Eskisehir Turkey
4. Translational Medicine Research and Clinical Center Osmangazi University Eskisehir Turkey
5. Department of Prosthodontics Faculty of Dentistry Istinye University İstanbul Turkey
6. Department of Restorative Preventive and Pediatric Dentistry School of Dental Medicine University of Bern Bern Switzerland
7. Division of Restorative and Prosthetic Dentistry The Ohio State University Ohio USA
Abstract
AbstractPurposeTo 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 MethodsEighty disk‐shaped specimens (Ø10×2 mm) were fabricated from two subtractively (Merz M‐PM [SM‐M] and G‐CAM [SM‐G]) and three additively (NextDent 3D+ [50 µm, AM‐N‐50; 100 µm, AM‐N‐100], FREEPRINT Denture [50 µm, AM‐F‐50; 100 µm, AM‐F‐100], and Denturetec [50 µm, AM‐S‐50; 100 µm, 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 (ΔE00) 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 ΔE00 data (α = 0.05). Ra values were further evaluated according to a clinically acceptable threshold of 0.2 µm, while ΔE00 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 ΔE00 than AM‐F, AM‐S‐100, and SM‐G (p ≤ 0.009), while AM‐F and SM‐G had lower ΔE00 than AM‐S‐50 and AM‐N‐50 (p ≤ 0.024).ConclusionsPolishing 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.