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    Analysis of Monomer Release from Different Composite Resins after Bleaching by HPLC
    (Mdpi, 2022) Demirel, Mehmet Gokberkkaan; Gonder, Hakan Yasin; Tuncdemir, Makbule Tugba
    (1) Background: This study aimed to examine the effect of bleaching agents on the release of triethylenae glycol dimethacrylate, 2-hydroxyethyl methacrylate, bisphenol A, urethane dimethacrylate, and bisphenol A-glycidyl methacrylate monomers, which are released from different composite resins, using the high-performance liquid chromatography (HPLC) method. (2) Methods: Ninety disc-shaped specimens were produced and immersed in artificial saliva. After different bleaching applications [office type bleaching (OB) and home type bleaching (HB)], the specimens were immersed in a 75 wt% ethanol/water solution, and the released monomers were analyzed by HPLC at predefined time intervals: 1, 7, and 28 days. The Kruskal-Wallis and Mann-Whitney U tests were conducted for statistical analysis (p = 0.05). (3) Results: The monomers were released at all times from all composite specimens. The monomer release was increased over time. The highest monomer release was detected on day 28. Bleaching applications affected monomer release. No statistical difference was found between OB and HB applications (p > 0.05). The most released monomer was Bisphenol-A in all composites. (4) Conclusion: Given that a residual monomer release from composite resins has a toxic effect and that bleaching treatments increase this release, a treatment protocol should be made in accordance with the manufacturer's instructions.
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    Crack Propagation and Fatigue Performance of Partial Posterior Indirect Restorations: An Extended Finite Element Method Study
    (Mdpi, 2023) Demirel, Mehmet Gokberkkaan; Mohammadi, Reza; Kececi, Murat
    Dental ceramics are susceptible to slow, progressive crack growth after cyclic loading. The purpose of this study was to investigate the progressive patterns of cracks in two different types of CAD/CAM ceramic materials used with three different partial posterior indirect restoration (PPIR) designs and to determine the materials' failure risk using a fatigue test. Standard initial cracks were formed in Standard Tessellation Language (STL) files prepared for three different PPIRs. The materials chosen were monolithic lithium disilicate (LS) and polymer-infiltrated ceramic networks (PICNs). The extended finite element method (XFEM) was applied, and the fatigue performance was examined by applying a 600 N axial load. The cracks propagated the most in onlay restorations, where the highest displacement was observed. In contrast, the most successful results were observed in overlay restorations. Overlay restorations also showed better fatigue performance. LS materials exhibited more successful results than PICN materials. LS materials, which can be used in PPIRs, yield better results compared to PICN materials. While inlay restorations demonstrated relatively successful results, overlay and onlay restorations can be specified as the most and the least successful PPIR types, respectively.
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    Urgent Solution for Single Tooth Loss: Fiber-Reinforced Composite Bridges
    (Aves, 2018) Demirel, Mehmet Gokberkkaan; Tuncdemir, Makbule Tugba
    Rehabilitation in maxillary anterior teeth loss is a serious challenge in the field of dentistry. Some patients may not wish to undergo implant treatment because of economic inconvenience or the tendency to avoid surgery. In such cases, rehabilitation with full crown teeth causes important amounts of loss material. Fiber-reinforced composite (FRC) bridges are a serious alternative to conventional treatments and present considerably more conservative solutions. This article describes the clinical technique and a 6-month follow-up. The patient had lost the maxillary anterior tooth after trauma. The adjacent teeth were periodontally healthy and had no mobility. The main advantage of this FRC bridge treatment was the improvement in oral hygiene with supragingival margins and the loss of minimum tooth structure. In particular, when the patient's teeth are used as a pontic, the esthetic results are very good and patient satisfaction can be achieved.