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    Effect of Thermomechanical Aging on the Surface Roughness and Color Stability of Novel CAD-CAM Materials: An In-Vitro Study
    (Marmara Univ, Inst Health Sciences, 2023) Turksayar, Almira Ada Diken; Donmez, Mustafa Borga; Hisarbeyli, Duygu; Kelten, Ozlem Seckin
    Objective: This in-vitro study aimed to evaluate the surface roughness (Ra) and color stability of novel monolithic CAD-CAM materials after thermomechanical aging. Methods: Forty specimens were obtained from 4 different materials (a resilient ceramic (RC), ceramic-reinforced PEEK (PE), lithium disilicate glass ceramic (EX), and a resin-based composites (CO) (n=10). Initial Ra and color coordinates were recorded. All specimens were than subjected to thermomechanical aging. Ra and color coordinate measurements were repeated. CIEDE2000 formula was used to calculate the color changes (& UDelta;E00). Kruskal-Wallis and Dunn tests were used to analyze data, while the effect of aging on Ra was analyzed with Wilcoxon test (& alpha;=.05). Results: Regardless of aging, PE showed higher Ra than EX (p< .001), whereas the differences between PE and the other materials were nonsignificant (p & GE; .202). Thermomechanical aging led to higher Ra for all materials tested (p= .005). The greatest & UDelta;E00was observed in PE (p & LE; .002), while the difference among the other materials was nonsignificant (p> .05). Ra of ceramic-reinforced PEEK was above clinical threshold, regardless of thermomechanical aging. Conclusion: Thermomechanical aging caused a color change that was perceptible for all the materials tested, while it was also unacceptable for ceramic-reinforced PEEK.
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    Fabrication trueness and internal fit of hybrid abutment crowns fabricated by using additively and subtractively manufactured resins
    (Elsevier Sci Ltd, 2023) Demirel, Muenir; Turksayar, Almira Ada Diken; Donmez, Mustafa Borga
    Objectives: To evaluate the fabrication trueness and internal fit of hybrid abutment crowns fabricated by using additively and subtractively manufactured restorative materials.Methods: A maxillary first premolar crown with a screw access channel was designed onto a digitized master titanium base abutment. This file was used to fabricate 40 crowns additively (Crowntec (CT) and VarseoSmile Crown Plus (VS)) or subtractively (Brilliant Crios (BC) and Vita Enamic (EN)) (n = 10). Crowns were digitized with an intraoral scanner and root mean square method was used to evaluate fabrication trueness. Master abutment and the crowns when seated on the abutment were also digitized with the same intraoral scanner and triple scan method was used to evaluate internal fit. Data were analyzed either with 1-way ANOVA (surface deviations) or Kruskal-Wallis (internal fit) tests (& alpha;= 0.05).Results: CT had the highest overall, external, and marginal surface deviations (P<.030), whereas BC had the lowest external (P<.001) and VS and EN had the lowest marginal surface deviations (P<.007). BC had the highest intaglio surface deviations (P<.001). BC and EN had higher average gap values CT and VS (P<.006); however, the differences within additively and subtractively manufactured materials were nonsignificant (P & GE;.858).Conclusions: One of the tested additively manufactured resins (CT) resulted in mostly lower trueness than that of other materials. However, deviations at the intaglio and marginal surfaces were generally small and the maximum mean difference among test groups when average gap was considered was 17.4 & mu;m. Therefore, clinical fit of hybrid abutment crowns fabricated with tested materials may be similar.
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    Optical properties, biaxial flexural strength, and reliability of new-generation lithium disilicate glass-ceramics after thermal cycling
    (Wiley, 2022) Turksayar, Almira Ada Diken; Demirel, Munir; Donmez, Mustafa Borga
    PurposeTo investigate the color stability, translucency, biaxial flexural strength (BFS), and reliability of nano-lithium disilicate and fully crystallized lithium disilicate after thermal cycling and to compare with those of a commonly used lithium disilicate. Materials and methodsThree lithium disilicate glass-ceramics were used to prepare disk-shaped specimens (o:12 mm, thickness: 1.2 mm) from A2 shaded HT blocks (Amber Mill, AM; Initial LiSi Block, IN; IPS e.max CAD, EX). AM and EX specimens were crystallized, and all specimens were polished with a polishing paste (Diamond Polish Mint). A spectrophotometer (CM-26d) was used to measure color coordinates before and after thermal cycling. BFS test was performed after thermal cycling. Color differences (Delta E-00) and relative translucency parameter (RTP) values were calculated. One-way analysis of variance (ANOVA) (Delta E-00 and BFS), two-way ANOVA followed by Tukey's HSD tests (RTP), and chi-square tests (Weibull modulus and characteristic strength) were used for the statistical analyses (alpha = 0.05). ResultsNo significant differences were observed among the Delta E-00 values of tested materials (df = 2, F = 2.933, p = 0.070). RTP values were only affected by material type (p < 0.001) as AM had the highest RTP (p < 0.001), whereas IN and EX had similar values (p >= 0.165). BFS values varied among tested materials (df = 2, F = 21.341, p < 0.001). AM and EX had similar BFS values (p = 0.067) that were higher than that of IN (p <= 0.001). Weibull moduli of the materials were similar (p = 0.305), whereas EX had the highest and IN had the lowest characteristic strength values (p < 0.001) ConclusionsAlthough nano-lithium disilicate had the highest translucency, all materials had imperceptible color and translucency changes after thermal cycling when reported threshold values were considered. Newly introduced lithium disilicate glass-ceramics had adequate flexural strength as compared to the precursor material.