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    Answers to comments on Comparison of severe acute respiratory syndrome coronavirus 2 (COVID-19) vaccine side effects by age groups
    (Assoc Medica Brasileira, 2023) Tosun, Fadime; Bulbul, Mehmet; Tosun, Ismail
    [No abstract available]
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    Effect of mastication simulation on the phase transformation of posterior 3-unit monolithic zirconia fixed dental prostheses
    (Mosby-Elsevier, 2021) Erdinc, Gulbahar; Bulbul, Mehmet
    Statement of problem. Monolithic zirconia restorations are directly exposed to cyclic loads and temperature changes in the oral cavity after cementation. These stresses may reduce the long-term success of the material by causing uncontrolled phase transformations within the zirconia. Purpose. The purpose of this in vitro study was to evaluate the effect of mastication simulation and different measurement points on the phase transformation of posterior 3-unit monolithic zirconia partial fixed dental prostheses (FDPs) in the posterior region. Material and methods. Posterior 3-unit FDPs of monolithic yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP), including BruxZir Shaded (group B), FireZr (group F), and Upcera (group U) (n=10), were machined from presintered blocks. All specimens were exposed to mastication simulation (240000 cycles/1.7 Hz/50 N). The monoclinic phase content was evaluated by X-ray diffraction (XRD). Phase transformation was measured at the mesial connector (group M), distal connector (group D), and pontic regions (group P) before and after mastication simulation. The relative monoclinic phase amount (Xm) was calculated for all specimens. The data were analyzed by ANOVA and post hoc tests (alpha=.05). Results. According to XRD analysis, Xm for all groups and regions showed higher results after aging than before aging (P<.05). Group B has the lowest Xm among the groups. Group B showed a statistically significant difference compared with both group F and group U (P<.05). There was no significant difference between group F and group U (P>.05). When the regions were evaluated regardless of brand and the groups were evaluated in terms of regions, no statistically significant difference was observed between connectors and the pontic region (P>.05). Conclusions. Mastication simulation causes an increase in the Xm. However, this increase was unlikely to be clinically significant. There may be differences in phase transformation depending on the contents of the brands and sintering procedures. Variations in the phase quantity were independent of the connector regions and pontic for FDPs.
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    Fracture strength and energy-dispersive spectroscopy analysis of 3-unit fixed partial dentures fabricated from different monolithic zirconia materials
    (Mosby-Elsevier, 2023) Erdinc, Gulbahar; Bulbul, Mehmet; Ozcan, Mutlu
    Statement of problem. Mastication forces in different regions affect the survival of multiunit posterior restorations. The fracture strength of 3-unit posterior monolithic zirconia fixed partial dentures (FPDs) and their fracture patterns require investigation. Purpose. The purpose of this in vitro study was to evaluate and compare the fracture strength and fracture pattern of 3-unit posterior FPDs fabricated from different monolithic zirconia materials. Material and methods. Thirty 3-unit FPDs were fabricated from BruxZir, FireZr, and Upcera (n=10 per group). Energy-dispersive spectroscopy analysis was performed on 2 selected specimens from each group. All specimens were exposed to a mastication simulator for 1.2x106 cycles and then monotonically loaded to fracture at a crosshead speed of 1 mm/min. The surfaces of a selected fractured specimen were examined at magnifications of x25 and x500 with scanning electron microscopy. Conformity to normal distribution was evaluated with the Shapiro-Wilk test. Oneway analysis of variance was used to compare the normally distributed initial crack formation load F initial (Fi) and catastrophic failure strength F maximum (Fm) means by group. Weibull statistics were calculated by using the maximum likelihood estimation method. The chi-square test was used to compare shape and scale parameters (a=.05). Results. The mean Fm values were fail1878.9 N for Upcera, 2177.8 N for BruxZir, and 2229.4 N for FireZr. Upcera and BruxZir showed statistically significant differences for the Fm mean values (P=.039). The differences between the fracture type distributions according to the groups were statistically similar (P>.05). For Fi, Upcera presented the highest Weibull modulus value (2.199), FireZr had the lowest (1.594), while for Fm, BruxZir had the highest Weibull modulus value (9.267) and FireZr the lowest (6.572). Conclusions. Using the zirconia materials BruxZir, FireZr, and Upcera resulted in high Fm values after aging procedures. With all materials, the fractures were most commonly found in the connector areas in the tested FPDs. (J Prosthet Dent 2023;129:938.e1-e7)
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    Identification of royal jelly as a potential new drug to protect the ovarian reserve and uterus against cyclophosphamide in rats
    (Korean Soc Reproductive Medicine, 2023) Bulbul, Mehmet; Tekce, Ali; Annac, Ebru; Korkmaz, Omer; Onderci, Muhittin; Korkmaz, Deniz; Demirci, Akin Mustafa
    Objective: The aim of this study was to investigate the effect of royal jelly (RJ), a powerful natural antioxidant, on cyclophosphamide-induced ovarian damage.Methods: Thirty-two Wistar albino rats were divided into four groups. Oral treatment was administered to all rats for 16 days after a single intraperitoneal injection. The control group received intraperitoneal and oral saline; the RJ group received intraperitoneal saline and 100 mg/ kg/day oral RJ; the cyclophosphamide group received intraperitoneal 100 mg/kg cyclophosphamide and oral saline; and the treatment group received intraperitoneal 100 mg/kg cyclophosphamide and 100 mg/kg/day oral RJ. The groups were compared in terms of ovarian reserve tests and histopathological changes in the ovary and uterus.Results: All follicle counts were higher in the treatment group than in the cyclophosphamide group. The increase in the number of preantral follicles (p=0.001) and the decrease in the number of atretic follicles (p=0.004) were statistically significant. RJ treatment significantly improved follicular degeneration and cortical fibrosis in the ovary and epithelial and gland degeneration in the uterus due to cyclophosphamide toxicity.Conclusion: According to these results, RJ reduces cyclophosphamide-related ovarian and endometrial damage in rats. For this reason, it should be further investigated to determine its effects on reproductive function.