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    Bond strength of additively manufactured composite resins to dentin and titanium when bonded with dual-polymerizing resin cements
    (Mosby-Elsevier, 2024) Donmez, Mustafa Borga; Cakmak, Gulce; Yilmaz, Deniz; Schimmel, Martin; Abou-Ayash, Samir; Yilmaz, Burak; Peutzfeldt, Anne
    Statement of problem. Additively manufactured composite resins for definitive restorations have been recently introduced. The bond strength between these composite resins and different substrates has not been extensively studied. Purpose. The purpose of this in vitro study was to measure the shear bond strength (SBS) between additively manufactured composite resins and dentin and titanium substrates and compare those with the SBS between subtractively manufactured polymer-infiltrated ceramic and the same substrates (dentin and titanium), when different dual-polymerizing resin cements were used. Material and methods. One hundred and eighty cylinder-shaped specimens (& Oslash;5x5 mm) were prepared from 3 materials recommended for definitive restorations: an additively manufactured composite resin (Crowntec [CT]); an additively manufactured hybrid composite resin (VarseoSmile Crown Plus [VS]); and a subtractively manufactured polymer-infiltrated ceramic (Enamic [EN]) (n=60). Specimens were randomly divided into six subgroups to be cemented to the two substrates (dentin and titanium; n=30) with 1 of 3 resin cements (RelyX Universal, Panavia V5, and Variolink Esthetic DC) (n=10). The restoration surface to be bonded was treated according to the respective manufacturer's recommendations. Dentin surfaces were treated according to the resin cement (Scotchbond Universal Plus Adhesive for RelyX Universal, Panavia V5 Tooth Primer for Panavia V5, and Adhese Universal for Variolink Esthetic DC), while titanium surfaces were airborne-particle abraded, and only the specimens paired with Panavia V5 were treated with a ceramic primer (Clearfil Ceramic Primer Plus). SBS was measured in a universal testing machine at a crosshead speed of 1 mm/min. Failure modes were analyzed under a microscope at x12 magnification. Data were analyzed by using 2-way analysis of variance and Tukey honestly significant difference tests (a=.05). Results. When SBS to dentin was considered, only restorative material, as a main factor, had a significant effect (P<.001); EN had the highest SBS (P<.001), while the difference in SBS values of CT and VS was not significant (P=.145). As for SBS to titanium, the factors restorative material and resin cement and their interaction had a significant effect (P<.001). Within each resin cement, EN had the highest SBS to titanium (P<.001), and within each restorative material, Variolink resulted in the lowest SBS (P<.010). Overall, EN and RelyX were associated with the highest SBS to titanium (P<.013). Mixed failures were predominant in most groups. Conclusions. Regardless of the substrate or the resin cement used, the subtractively manufactured polymer-infiltrated ceramic had higher shear bond strength than the additively manufactured composite resins. The SBS of the additively manufactured composite resins, whether bonded to dentin or titanium, were not significantly different from each other. Regardless of the restorative material, Variolink DC resulted in the lowest SBS for titanium surfaces. (J Prosthet Dent 2024;132:1067.e1-e8)
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    Effect of polishing and denture cleansers on the surface roughness of new-generation denture base materials and their color change after cleansing
    (Wiley, 2024) Cakmak, Guelce; Hess, Julia Anouk; Donmez, Mustafa Borga; Yilmaz, Deniz; Alhotan, Abdulaziz; Schimmel, Martin; Peutzfeldt, Anne
    Purpose: To evaluate the effect of polishing and denture cleansers on the surface roughness (Ra) of new-generation denture basematerials that are additively, subtractively, and conventionally fabricated, while also assessing their color change after cleansing. Material and Methods: One hundred and fifty disk-shaped specimens (O10 x 2 mm) were prepared from five denture base materials (one subtractively manufactured nanographene-reinforced prepolymerized polymethylmethacrylate (PMMA) (SM-GC), one subtractively manufactured prepolymerized PMMA (SM-PM), two additively manufactured denture base resins (AM-DT and AM-ND), and one heat-polymerized PMMA (CV) (n = 30). The R-a of the specimens was measured before and after conventional laboratory polishing, while color coordinates were measured after polishing. Specimens were then divided into three subgroups based on the denture cleanser: distilled water, 1% sodium hypochlorite (NaOCl), and effervescent tablet (n = 10). The R-a and color coordinates were remeasured after nine cleansing cycles over a period of 20 days. The CIEDE2000 formula was used to calculate the color differences (Delta E-00). Two-way analysis of variance (ANOVA) was used to analyze the R-a values before (n = 30) and after (n = 10) cleansing, while repeated measures ANOVA was used to analyze the R-a of material-time point pairs within each denture cleanser (n = 10). Delta E-00 data after denture cleansing was also analyzed by using two-way ANOVA (n = 10) (a = 0.05). Results: Before polishing, Ra varied significantly among the materials. SM-GC and SM-PM had the lowest and AM-ND the highest Ra values (P < 0.001). Polishing significantly reduced R-a of all materials (P < 0.001), and after polishing, Ra differences among materials were nonsignificant (P >= 0.072). Regardless of the denture cleanser, the R-a of AM-DT, AM-ND, and CV was the highest before polishing when different time points were considered (P < 0.001). After cleansing, AM-ND had the highest R-a of all the materials, regardless of the cleanser (P <= 0.017). AM-DT had higher R-a than SM-PM when distilled water (P = 0.040) and higher R-a than SM-GC, SM-PM, and CV when NaOCl was used (P < 0.001). The type of cleanser significantly influenced the R-a of AM-DT, AM-ND, and CV. For AM-DT, NaOCl led to the highest R-a and the tablet led to the lowest R-a (P <= 0.042), while for AM-ND, distilled water led to the lowest R-a (P <= 0.024). For CV, the tablet led to lower R-a than distilled water (P = 0.009). Color change varied among the materials. When distilled water was used, SM-GC had higher Delta E-00 than SM-PM and AM-DT (P <= 0.034). When NaOCl was used, AM-ND had higher Delta E-00 than SM-GC, SM-PM, and AM-DT, while CV and SM-GC had higher Delta E-00 than SM-PM and AM-DT (P = 0.039). Finally, when the tablet was used, AM-ND and CV had the highest Delta E-00, while AM-DT had lower Delta E-00 than SM-GC (P = 0.015). Conclusions: The tested materials had unacceptable surface roughness (>0.2 mu m) before polishing. Roughness decreased significantly after polishing (<0.2 mu m). Denture cleansers did not significantly affect the surface roughness of the materials, and roughness remained clinically acceptable after cleansing (<0.2 mu m). Considering previously reported color thresholds, AM-ND and CV had unacceptable color change regardless of the denture cleanser, and the effervescent tablet led to perceptible, but acceptable color change for SM-GC, SM-PM, and AM-DT.