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    Effect of femtosecond laser induced surface patterns on the flexural strength of monolithic zirconia
    (Wiley, 2024) Okutan, Yener; Gündoğdu, Yasemin; Dönmez, Mustafa Borga; Şeker, Hüseyin; Kılıç, Hamdi Şükür
    To investigate how patterns generated by femtosecond (fs) laser and femtosecond laser power affect the surface roughness (Ra) and biaxial flexural strength (BFS) of monolithic zirconia. Eighty disk-shaped zirconia specimens were divided into eight subgroups (n = 10): Control (C), airborne-particle abrasion (APA), 400 mW fs laser (spiral [SP(400)], square [SQ((400))], circular [CI(400)]), and 700 mW fs laser ([SP(700)], [SQ((700))], [CI(700)]). Ra values were calculated by using a surface profilometer. One additional specimen per group was analyzed with scanning electron microscopy and x-ray diffractometry. BFS values were obtained by using the piston-on-3-ball test. One-way ANOVA and either Tukey's HSD (BFS) or Tamhane's T2 (Ra) tests were used to evaluate data (alpha = 0.05). Regardless of the pattern and power, fs laser groups had higher Ra than C and APA, while SP groups had lower Ra than CI and SQ groups (p <= 0.004). For each pattern, Ra increased with higher laser power (p < 0.001), while the laser power did not affect the BFS (p >= 0.793). CI and SQ groups had lower BFS than the other groups (p <= 0.040), whereas SP groups had similar BFS to C and APA (p >= 0.430). Fs laser microstructuring with spiral surface pattern increased the Ra without jeopardizing the BFS of zirconia. Thus, this treatment might be an option to roughen tested zirconia.
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    Effect of the thickness of CAD-CAM materials on the shear bond strength of light-polymerized resin cement
    (Wiley, 2022) Okutan, Yener; Kandemir, Banuçiçek; Dönmez, Mustafa Borga; Yücel, Münir Tolga
    This study aimed to investigate the effect of the thickness of computer aided design-computer aided manufacturing (CAD-CAM) restorative materials on the bond strength of light-polymerized resin cement. Ninety specimens were prepared from three different CAD-CAM materials (a leucite-based glass-ceramic [Empress CAD], a polymer-infiltrated ceramic network [Vita Enamic], and a zirconia-reinforced lithium silicate glass-ceramic [Vita Suprinity]) in different thicknesses (1, 2, and 3 mm). One surface of each specimen was treated by using a single-step self-etching ceramic primer (Monobond Etch & Prime). Light-polymerized resin cement was bonded to treated surfaces by exposure to a light-emitting diode curing unit from the untreated side of the samples. Shear bond strength (SBS) between the ceramic and the resin cement was measured by using a universal testing machine. The leucite-based glass-ceramic had higher SBS values than the other materials at each thickness. For each material, 1 mm-thick specimens had the highest SBS values. The difference between the SBS values of 2 mm- and 3 mm-thick polymer-infiltrated ceramic network was nonsignificant, whereas the SBS values of 2 mm-thick leucite-based glass-ceramic and the zirconia-reinforced lithium silicate glass-ceramic were significantly higher than those of the corresponding 3 mm-thick specimens. The choice of the material and its thickness may be highly important for clinical success when light-polymerized resin cements are used for cementation.
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    Marginal gap and fracture resistance of implant-supported 3D-printed definitive composite crowns: An in vitro study
    (Elsevier Science, 2022) Dönmez, Mustafa Borga; Okutan, Yener
    Objectives: To compare the marginal gap and fracture resistance of implant-supported 3-dimensional (3D) printed definitive composite crowns with those fabricated by using 3 different millable materials. Material and methods: A prefabricated abutment was digitized by using a laboratory scanner (E4 Lab Scanner) and a complete-coverage maxillary first premolar crown was designed (Dental Designer). Forty crowns were fabri- cated either by 3D printing (Saremco Print Crowntec, SP) or milling (Brilliant Crios, BC; Vita Enamic, VE; Cerasmart 270, CS) (n = 10). Baseline marginal gap values were evaluated by measuring 60 predetermined points on an abutment (15 points for each side) with a stereomicroscope at ×40 magnification. Marginal gap values were reevaluated after adhesive cementation. Load-to-fracture test was performed by using a universal testing machine. Two-way analysis of variance (ANOVA) was used to evaluate the effect of material type and cementation on marginal gap values. While Tukey HSD tests were used to compare the materials’ marginal gap values before and after cementation, the effect of cementation on marginal gap values within each material was analyzed by using paired samples t-tests. Fracture resistance data were analyzed by using 1-way ANOVA (?=0.05). Results: Material type and cementation significantly affected marginal gap values (P < .001). Regardless of cementation, SP had the lowest marginal gap values (P < .001), while the differences among milled crowns were nonsignificant (P ? .14). Cementation significantly increased the marginal gap values (P < .001). Material type did not affect fracture resistance values (F = 1.589, P = .209). Conclusion: Implant-supported 3D-printed composite crowns showed higher marginal adaptation compared with the milled crowns before and after cementation. In addition, all crowns endured similar forces before fracture.