Monolitik Zirkonya Restorasyonlarda Sinterleme Süresindeki Değişimin Marjinal ve İnternal Aralığa Etkisi
Özden, Yunus Emre
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Özden Y.E, Effect of sintering time on the marginal and internal fit of monolithic zirconia restorations. Hacettepe University, Institute of Health Sciences, PhD Thesis in Prosthodontics, Ankara, 2017. Monolithic zirconia restorations are a good alternative to metal-supported restorations, particularly in the posterior region, where the chewing force is concentrated, given their high fracture toughness, counter-dental natural tooth-like abrasion behavior, and esthetic properties. Changes in temperature and the duration of the sintering process, which is one of the most important steps in the production of these restorations, can affect the physical properties of the material. The purpose of this in vitro study was to investigate the effect of changes in sintering time on marginal and internal fit of monolithic zirconia crowns. For this purpose, a total of 60 monolithic crowns were produced from LAVA® Plus, CEREC®, or KATANA® Y-TZP semi-sintered blocks, on the implant cement-retained abutment analogues at 4-mm height, in the form of the first molar tooth. The samples were divided into 3 groups according to the brand and 2 subgroups according to sintering time (2.25 or 7 h) (n = 10 per subgroup). The marginal and internal gaps were photographed using a light microscope (× 45 magnification) by a silicon replica method, and the measurements were made digitally, using Image J. The effect of the brand and sintering time on the marginal and internal gap values were examined concurrently using 2-way analysis of variance. According to long sintering time, no statistically significant difference was observed between the systems used in the study in terms of total cemented film thickness values (p>0.0001). Crowns fabricated from CEREC® and LAVA® blocks, marginal gap values were not affected as statistically significant due to the change of sintering time (p>0.0001). Crowns fabricated from the KATANA® blocks, the shortening of the sintering time caused a statistically significant increase in the marginal and occlusal gap values (p<0.0001). As a result of our work, the necessity of applying the sintering time in accordance with the manufacturer's recommendations is supported.