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.
Objectives: the aim of this study was to examine the stress distribution of enamel, dentin, and restorative materials in sound first molar teeth with restored cavities with conventional resin composites and bulk–fill composites, as well as to determine their fracture lifetimes by using the three-dimensional finite element stress analysis method. Materials and Methods: an extracted sound number 26 tooth was scanned with a dental tomography device and recorded. Images were obtained as dicom files, and these files were transferred to the Mimics 12.00 program. In this program, different masks were created for each tooth tissue, and the density thresholds were adjusted manually to create a three-dimensional image of the tooth, and these were converted to a STL file. The obtained STL files were transferred to the Geomagic Design X program, and some necessary adjustments, such as smoothing, were made, and STP files were created. Cavity preparation and adhesive material layers were created by transferring STP files to the Solidworks program. Finally, a FE model was created in the ABAQUS program, and stress distributions were analyzed. Results: when the bulk–fill composite and conventional resin composite materials were used in the restoration of the cavity, the structures that were exposed to the most stress as a result of occlusal forces on the tooth were enamel, dentin, restorative material, and adhesive material. When the bulk–fill composite material was used in restoration, while the restorative material had the longest fracture life as a result of stresses, the enamel tissue had the shortest fracture life. When the conventional resin composite material was used as the restorative material, it had the longest fracture life, followed by dentin and enamel. Conclusion: when the bulk–fill composite material was used instead of the conventional resin composite material in the cavity, the stress values on enamel, dentin, and adhesive material increased as a result of occlusal forces, while the amount of stress on the restorative material decreased. In the fracture analysis, when the bulk–fill composite material was used instead of the conventional resin composite material, a decrease in the number of cycles required for the fracture of enamel, dentin, and restorative materials was observed as a result of the forces generated in the oral cavity.
Using a three-dimensional finite element analysis, this study aimed to evaluate the effect of different cements’ thicknesses and Poisson’s ratios on the stress distribution in enamel, dentin, restoration, and resin cement in a computer-aided design of a class II disto-occlusal cavity. Dental tomography was used to scan the maxillary first molar, creating a three-dimensional tooth model. A cavity was created with a 95 degree cavity edge angle. Resin cement with varying Poisson’s ratios (V1: 0.35 and V2: 0.24) was used under the amalgam. The simulated groups’ thicknesses ranged from 50 µm to 150 µm. A load of 600 N was applied to the chewing area. The finite element method was used to assess the stress distribution in the enamel, dentin, restorations, and resin cement. The stress in the restoration increased with the use of a 100 µm resin cement thickness and decreased with the use of a 150 µm resin cement thickness. For the V1 and V2 groups, the cement thickness with the maximum stress value for the enamel and dentin was 150 µm, while the cement thickness with the lowest stress value was 50 µm. The greatest stress values for V1 and V2 were obtained at a 150 µm cement thickness, while the lowest stress values were observed at a 100 µm cement thickness. Using resin cement with a low Poisson’s ratio under amalgam may reduce stress on enamel and restorations.
Purpose: The aim of this study is to evaluate the effect of changes in margin design on the stress distribution on the restoration in zirconia-based full-crown restorations using 3D finite element analysis. Material and Methods: To be used in the design of full-crown restorations, tooth number 16 was prepared in chamfer step type on a maxillary tooth-jaw model (AG-3: Tipodont, frasaco, Germany). The prepared tooth was scanned using a desktop scanner, and a 3D finite element analysis model was obtained. Zirconia frameworks are divided into 3 groups according to margin design: uniform thickness hood type (Model A), ¾ partial crown form (Model B), and lingual banded (Model C). The crown form was completed by using felspathic porcelain as the superstructure material. In order to examine the stress distributions of the margin design on the restoration, the maximum principal stress (MPa) values under 600 N vertical load were investigated. Result: The maximum stress on the zirconia framework was observed in Model A (82.90 MPa), and the maximum stress on the tooth was observed in Model B (49.34 MPa). The maximum stress on the feldspathic porcelain has the highest value in Model A (21,860 MPa). The minimum stress on the tooth occurred in Model B and is 13.33 MPa. In the zirconia framework, the lowest stress is 11.54 MPa in Model B. Conclusions: Within the results of the study, it is clear that the framework design affects the force generated on the restoration and transmitted to the tooth. The results of the study will benefit dentists in determining the infrastructure design in zirconia-based restorations. Lingual band designs have been found successful.
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