Yazar "Guven, Mehmet Esad" seçeneğine göre listele

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    Effect of Hydrothermal Aging on the Flexural Strength and Microhardness of Materials Used for Additive or Subtractive Manufacturing of Definitive Restorations
    (Quintessence Publishing Co Inc, 2024) Yilmaz, Deniz; Cakmak, Gulce; Guven, Mehmet Esad; Pieralli, Stefano; Yoon, Hyung-In; Revilla-Leon, Marta; Yilmaz, Burak
    Purpose: To evaluate the flexural strength (FS) and microhardness of various CAD/CAM restorative materials intended for definitive use. The effect of hydrothermal aging on the mechanical properties of these materials was also investigated. Materials and Methods: A total of 210 bar-shaped specimens (17 x 4 x 1.5 mm +/- 0.02 mm) were fabricated via either subtractive manufacturing (SM) methods-reinforced composite resin (SM-CR), polymer-infiltrated ceramic network (SM-PICN), fine-structured feldspathic ceramic (SM-FC), nanographene-reinforced polymethyl methacrylate (PMMA; SM-GPMMA), PMMA-based resin (SM-PMMA)-or additive manufacturing (AM) methods with urethane acrylate-based resins (AM-UA1 and AM-UA2). Specimens were then divided into two subgroups (nonaged or hydrothermal aging; n = 15). A three-point flexural strength test was performed, and five specimens from the nonaged group were submitted to microhardness testing. Specimens were subjected to 10,000 thermal cycles, and the measurements were repeated. Results: Regardless of aging, SM-CR had the highest FS (P <.001), followed by SM-GPMMA (P =.042). In nonaged groups, AM-UA2 had a lower FS than all other materials except SM-FC (P = 1.000). In hydrothermal aging groups, AM specimens had lower FS values than other materials, except SM-PMMA. With regard to microhardness, there was no significant difference found between any of the tested materials (P =.945) in the nonaged and hydrothermal aging groups. Conclusions: The effect of hydrothermal aging on FS varied depending on the type of restorative material. Regardless of aging condition, SM-CR showed the highest FS values, whereas SM- FC had the highest microhardness. Hydrothermal aging had no significant influence on the microhardness of the tested materials.
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    Fabrication Trueness, Intaglio Surface Adaptation, and Marginal Integrity of Resin- Based Onlay Restorations Fabricated by Additive and Subtractive Manufacturing
    (Quintessence Publishing Co Inc, 2024) Cakmak, Gulce; Steigmeier, David; Guven, Mehmet Esad; Yilmaz, Deniz; Schimmel, Martin; Yoon, Hyung-In; Yilmaz, Burak
    Purpose: To evaluate the fabrication trueness, intaglio surface adaptation, and marginal integrity of resin- based onlay restorations made via additive manufacturing (AM) or subtractive manufacturing (SM). Materials and Methods: An onlay restoration was designed (DentalCAD Galway 3.0) and saved as an STL file to generate a design STL file (DO-STL). Using this design, 45 onlays were fabricated either with AM (3D-printed resin for definitive [AM-D; Tera Harz TC- 80DP] and interim [AM- I; Freeprint temp] restorations) or SM (composite resin, Tetric CAD) technologies. Onlays were scanned with an intraoral scanner (CEREC Primescan SW 5.2), and the scans were saved as test STL files (TO-STLs). For trueness evaluation, TO-STLs were superimposed over the DO-STL, and root mean square (RMS) values of overall and intaglio surfaces were measured (Geomagic Control X). For the intaglio surface adaptation and marginal integrity, a triple-scan protocol was performed. Kolmogorov-Smirnov, one- way ANOVA, and post-hoc Tukey honestly significant difference tests were used to analyze data (alpha =.05). Results: RMS values of intaglio and overall surfaces, intaglio adaptation, and marginal integrity varied among test groups (P <.001). AM- D had the greatest overall surface RMS (P <.001), while SM had the greatest intaglio surface RMS (P <.001). SM had the highest average distance deviations for intaglio surface adaptation and marginal integrity, whereas AM-D had the lowest (P <.001). Conclusions: AM-D onlays showed lower overall trueness than AM-I onlays and SM definitive onlays. However, AM-D onlays presented high intaglio surface trueness, intaglio surface adaptation, and marginal integrity.
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    Trueness and precision of combined healing abutment scan body system scans at different sites of maxilla after multiple repositioning of the scan body
    (Elsevier Sci Ltd, 2023) Donmez, Mustafa Borga; Guven, Mehmet Esad; Yilmaz, Deniz; Abou-Ayash, Samir; Cakmak, Gulce; Yilmaz, Burak
    Objectives: To evaluate the accuracy of the scans of the combined healing abutment-scan body (CHA-SB) system located at different sites of the maxilla when SBs are replaced in between each scan.Methods: Three SBs were seated into HAs located at the central incisor, first premolar, and first molar sites of a maxillary model inside a phantom head, and the model was scanned extraorally (CEREC Primescan SW 5.2). This procedure was repeated with new SBs until a total of 10 scans were performed. Standard tessellation language files of CHA-SBs at each implant location were isolated, transferred into analysis software (Geomagic Control X), and superimposed over the proprietary library files to analyze surface (root mean square), linear, and angular deviations. Trueness and precision were evaluated with one-way analysis of variance and Tukey tests. The correlation between surface and angular deviations was analyzed with Pearson's correlation (alpha=0.05).Results: Molar implant scans had the highest surface and angular deviations (P <=.006), while central incisor implant scans had higher precision (surface deviations) than premolar implant scans (P=.041). Premolar implant scans had higher accuracy than central incisor implant scans on the y-axis (P <=.029). Central incisor implant scans had the highest accuracy on the z-axis (P <=.018). A strong positive correlation was observed between surface and angular deviations (r = 0.864, P<.001).Conclusion: Central incisor implant scans mostly had high accuracy and molar implant scans mostly had lower trueness. SBs were mostly positioned apically; however, the effect of SB replacement can be considered small as measured deviations were similar to those in previous studies and the precision of scans was high.Clinical Significance: Repositioning of scan bodies into healing abutments would be expected to result in similar single crown positioning regardless of the location of the implant, considering high scan precision with the healing abutment-scan body system. The duration of the chairside adjustments of crowns in the posterior maxilla may be longer than those in the anterior region.