In this study, it was aimed to use a finite element stress analysis method to determine the amount of stress on enamel, dentin, restoration, resin cement and glass ionomer cement in amalgam class II disto-occlusal (DO) cavities by using two different cements with different thicknesses and amalgams with different Young’ s modulus values, respectively. Methods: A three-dimensional tooth model was obtained by scanning an extracted human maxillary first molar with dental tomography. A class II DO cavity including 95-degree cavity margin angles was created. Resin cement (RC) and glass ionomer (GI) cement with different Young’ s modulus measures (RC: 7.7 GPa, GI: 10.8 GPa) were used in amalgam. Different thickness combination groups were simulated: 50 μm, 100 μm and 150 μm. Additionally, amalgams with different Young’ s modulus values were used with the same thickness of different cements (Amalgam Young’s modulus: 35 GPa and 50 GPa). A load of 600 N was delivered to the chewing area. The stress distributions on enamel, dentin, restoration, resin cement and class ionomer cement were then analyzed using finite element analysis. Results: The most stress accumulation was observed in the enamel tissue across all groups where resin cement or glass ionomer cement were used in different thicknesses and where amalgam restorations were used with different Young’s modulus values. The least stress accumulation was observed in the cement itself. Conclusion: According to the results obtained, there was no difference between the two cement types in terms of stress accumulations in the models. However, when the same cements with different thicknesses were evaluated, it was concluded that the presence of both glass ionomer and resin cement with a thickness of 150 μm causes less stress on the restoration surface. Furthermore, when the cements were combined with different thicknesses and with different amalgam Young’ s modulus values, it was concluded that 50 GPa causes less stress on restoration surface.
(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.
Aim: The aim of this study was to examine the effects of different preparation types and restorative materials on the endocrown restoration applied to endodontically treated maxillary first molar and the stress distribution on the related tissues. Methodology: A 3-dimensional (3D) image of a previously extracted intact tooth was obtained with CBCT. The resulting .dicom files were imported into the Mimics. Enamel, dentine and pulp were separated and extracted as an STL file. 4 different groups were determined and prepared in SolidWorks. The 3D images were imported into the relevant finite element analysis software (ABAQUS), and a load of 600 N was applied at the occlusal area of each model in the axial direction. Models are divided into 3 groups according to material type: Vita Suprinity (VS; VITA Zahnfabrik), Cerasmart (CS; GC Corp.), and Shofu Block HC (SB; Shofu). There is also a type of cement is used: RelyX ARC (3M ESPE). Results: Regardless of the results, any stresses on any tissue or restoration were not above the strength limits. In models with cusp preparation, the stress on the dental tissues was lower. In addition, higher stress was generally observed in groups where the lingual area was healthy. On the other hand, the stress occurring in zirconia-reinforced glass ceramics (VS) is higher compared to ceramic materials with a resin matrix (CS, SB). It has been determined that the stress transmitted to the supporting tissues is lower. Conclusion: As a result, endocrown restorations can be used in the restoration of endodontically treated first molars. In addition, when endocrown restoration is applied to molars with only one healthy area and excessive loss of coronal structure, reducing the cusp will be beneficial in terms of the distribution of stress on the healthy tissues.
Aim: The objective was to determine whether there were significant correlations in the three color coordinates of central incisors and canine teeth with age such as the Commission Internationale de l'Eclairage (CIE) L*, a*, b* system. Materials and Methods: The natural maxillary central incisor and maxillary canine teeth of a sample of 302 individuals (n=104 male, n=168 female) were measured by the Vita Easyshade V spectrophotometer. Pearson correlations between each pair of the color coordinates were determined (p<0.01). Results: Based on correlation analyses, for central incisors all the color coordinate parameters showed significant correlations but there was no correlation for canine teeth with all of three parameters. Conclusions: When age increases, the central incisors become darker, more red, and more yellow. The same correlation was found for the canine teth but the result is not significant.
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