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    Öğe
    Effect of Print Orientation and Thermal Aging on the Flexural Strength of Zirconia-Reinforced Three-Dimensional-Printed Restorative Resin Materials
    (Mdpi, 2025) Ozden, Yunus Emre; Kaya, Bengu Dogu; Atali, Pinar Yilmaz; Ozer, Fusun; Kayahan, Zeynep Ozkurt
    This study evaluated the effects of print orientation and thermal aging on the flexural strength (FS) and flexural modulus (FM) of novel permanent three-dimensional (3D)-printed polymethyl methacrylate (PMMA) resins reinforced with nano-zirconia and nano-silica. Bar-shaped specimens (25 x 2 x 2 mm) were fabricated using a digital light processing (DLP) 3D printer (Asiga Max UV, Asiga Inc., Australia) in two orientations (0 degrees and 90 degrees). Specimens underwent three-point bending tests at 24 h and after artificial thermal aging (10,000 and 30,000 cycles) to simulate one and three years of intraoral conditions. Scanning electron microscopy (SEM) was used to analyze fracture patterns. Print orientation did not significantly affect FS or FM (p > 0.05). However, artificial aging significantly reduced FS and FM after 10,000 cycles (p < 0.001), with further deterioration after 30,000 cycles. The micro hybrid resin composite exhibited higher FS than the 3D-printed materials throughout aging. SEM analysis revealed distinct fracture patterns, with 3D-printed resins displaying radial fractures and the micro hybrid composite exhibiting horizontal fractures. These findings indicate that aging plays a more critical role in the long-term mechanical performance of 3D-printed restorative resins than print orientation. This study provides original data on the effects of print orientation and prolonged thermal aging on the mechanical behavior of permanent three-dimensional (3D)-printed dental resins. Furthermore, the comparative evaluation of aging protocols simulating one and three years of intraoral service represents a novel contribution to the existing literature. Further studies are required to optimize the mechanical durability of 3D-printed dental restorations.
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    Öğe
    The effect of cavity depth on accuracy of intraoral scanners in intra-coronal restorations
    (Bmc, 2025) Ozden, Yunus Emre; Kaya, Bengu Dogu; Akbal, Cagla; Yilmaz Atali, Pinar; Ozkurt-Kayahan, Zeynep
    Purpose This study aimed to evaluate the effect of cavity depth on the accuracy of intraoral scanners (IOS) in intra-coronal restorations, focusing on trueness and precision as defined by International Organization for Standardization (ISO) 5725 standards. Materials and methods Three intra-coronal cavity designs with depths of 2.5 mm (n = 10), 5 mm (n = 10), and 7.5 mm (n = 10) were fabricated using 3-Dimentional (3D) printed tooth models. Scans (n = 30) were performed using the Trios 3 intraoral scanner, and accuracy was assessed by comparing scanned models to reference models. Trueness was measured as the root mean square (RMS) deviation, and precision was calculated from the interquartile range of average absolute distances. Statistical analyses were conducted using the Kruskal-Wallis test and Mann-Whitney U test with Bonferroni correction. Results The accuracy of the IOS was significantly lower at a cavity depth of 7.5 mm compared to 5 mm and 2.5 mm (p < 0.05). RMS values were highest for the 7.5 mm depth, while the lowest precision was observed at this depth. Conclusion Cavity depth significantly affects the accuracy of IOS in intra-coronal restorations, with deeper cavities resulting in reduced accuracy. This highlights the importance of considering cavity depth when planning IOS workflows. This study shows that scanning accuracy decreases when the distance between the cavity floor and the cusp tip exceeds 5 mm. Elevating the cavity floor with direct methods may help improve scanning accuracy and enhance restoration outcomes.