Browsing by Author "Usumez, Aslihan"

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Citation Count: 15
The effect of artificial accelerated aging on the color stability, microhardness, and surface roughness of different dental laminate veneer materials
(Wiley, 2022) Tasin, Simge; Celik, Gozde; Ismatullaev, Artur; Usumez, Aslihan
Objective This study aimed to evaluate the effect of artificial accelerated aging (AAA) on color stability, surface roughness, and microhardness of three laminate veneer (LV) materials. Materials and Methods Specimens of ceramic LV (CLV-IPS E.max Press), hand-layered composite LV (hand-layered laminate veneer [HLV]-Tetric N-Ceram), and prefabricated composite LV (prefabricated laminate veneer [PLV]-Componeer Coltene) were prepared as discs (n = 10). CIE L*, a*, and b* color coordinates, the Vickers microhardness, and surface roughness were measured 24 hours after preparation and reevaluated after aging for 300 hours in an ultraviolet (UV)-AAA system (Ci35 Weather-Ometer). Color difference (CIEDE2000 [Delta E-00]) was calculated. Data were statistically analyzed with the Shapiro-Wilk test and the Kruskall-Wallis test followed by the Mann-Whitney U tests (alpha = .05). Results All of the LV groups showed significant differences in Delta E-00 after AAA (P < .001). Comparing the color changes of the HLVs with the PLVs, no significant difference could be found (P = .705). There was a statistically significant difference in the means of changes in microhardness among the LVs materials (P < .001). The changes in surface roughness results showed a significant difference after AAA in all the LVs (P < .001). Conclusions Within the limitations of this in vitro study, the color stability, the microhardness, and surface roughness of tested LVs were influenced by AAA. Clinical significance The prefabricated composite LV system does not replace the individualized ceramic LV technique, but rather offers an alternative to hand-layered LVs, which is delicate and time-consuming technique.
Citation Count: 4
Evaluation of bond strength of resin cement to Er:YAG laser-etched enamel and dentin after cementation of ceramic discs
(Springer London Ltd, 2021) Ismatullaev, Artur; Tasin, Simge; Usumez, Aslihan
The purpose of this study was to investigate the shear bond strength (SBS) of ceramic discs luted to differently etched enamel and dentin surfaces. Occlusal surfaces of 64 carious-free human molars and vestibule surfaces of 64 first maxillary incisors were ground to get flat superficial dentin and flattened enamel respectively. After generating 4 groups according to the surface etching method (37% orthophosphoric acid, Er:YAG laser-contact handpiece/scanning handpiece (1 or 2 times of scanning)), ceramic discs were luted to the surfaces with adhesive resin cement (Variolink N, Vivadent Ets., Schaan/Liechtenstein). After etching and cementation, thermocycling of 5000 cycles (Sd Mechatronik Gmbh, Feldkirchen-Westerham, Germany) and SBS test (Servopulser EHFFD1; Shimadzu, Kyoto, Japan) were performed respectively. The surface morphologies of 2 specimens, etched enamel and dentin, prepared for each group were examined with SEM analysis. Failure modes were determined under a USB digital microscope. Data were analyzed with one-way analysis of variance (ANOVA) and Tukey HSD test (alpha = 0.05). SBS values in dentin surfaces showed statistically significant differences (p < 0.05) among tested groups. The highest SBS among dentin groups was determined in the group which had 2 times etching by Er:YAG laser (11.42 MPa) by a scanning handpiece. No statistical differences were observed in the other dentin or enamel groups. Laser etching seems to be a viable alternative to acid etching on both enamel and dentin surfaces while double etching of dentin with a scanning handpiece can improve the adhesion.
Citation Count: 16
Evaluation of strain distribution on an edentulous mandible generated by cobalt-chromium metal alloy fixed complete dentures fabricated with different techniques: An in vitro study
(Mosby-elsevier, 2019) Tasin, Simge; Turp, Isil; Bozdag, Ergun; Sunbuloglu, Emin; Usumez, Aslihan
Statement of problem. Fixed complete dentures (FCDs) have been used in the treatment of completely edentulous patients for over 40 years. However, few reports have investigated misfit values and strain distribution in the context of FCDs fabricated with new technologies. Purpose. The purpose of this in vitro study was to evaluate misfit values and strain distribution in FCDs and their relation to the fabrication technique of the cobalt-chromium (Co-Cr) metal framework. Material and methods. Four implants were placed in the interforaminal region of a mandibular cast at the bone level. The Co-Cr metal alloy frameworks were fabricated using the following techniques: computer-aided design and computer-aided manufacturing (CAD-CAM), milling from hard blocks, CAD-CAM milling from soft blocks, and direct metal laser sintering (DMLS). The superstructures of equal sizes with acrylic resin bases and acrylic resin denture teeth were fabricated on the Co-Cr metal alloy framework, and a digital microscope was then used to measure the misfit between the abutments and the implants. The stress formed after the application of torque was measured with a strain-gauge stress analysis technique. Data were statistically analyzed using 1-way ANOVA and the Tukey Honestly Significant Difference test (alpha=.05). The correlation between the misfit and the strain values was evaluated with the Pearson Correlation test (alpha=.001). Results. The lowest mean misfit values (99 +/- 17 mu m) were observed in the hard block group (P<.05) and the highest in the DMLS group (139 +/- 29 mu m). A statistically significant positive relationship was found between the misfit and the stress distribution after torque application (P<.05). Moreover, the lowest misfit group, hard blocks, had the lowest mean strain values (81.1 +/- 54 MPa) after torque application. Conclusions. Within the limitations of this in vitro study, the fabrication technique used for Co-Cr metal alloy frameworks appears to influence the passive fit significantly (P<.05). The hard-block technique was found to be the most precise fabrication technique for Co-Cr metal alloy frameworks. A significant relationship was observed between the amount/distribution of misfit and the strain on the FCD (P<.05).