| Abstrakt: |
Background: There are differences in the research results regarding which edge design of occlusal veneers can achieve the best long-term success rate as a relatively new fixed prosthesis restoration method. Further research is needed. The three-dimensional finite element method was used to conduct stress analysis on occlusal veneers of maxillary first permanent molars with different thicknesses and margin preparation designs. The aim of this study was to provide mechanical research evidence and a reference for exploring standardized clinical protocols for the design of occlusal veneer restorations of maxillary first molars. Method: A 3Shape (Intraoral Scanner) was used to scan the maxillary first molar teeth in vitro, after which 3D printing was carried out. Three different edge designs were applied to identical teeth: straight-beveled finishing line(SFL), chamfer finishing line(CFL), and standard cuspal inclination(SCI). Preparation was carried out with a thickness of 0.5 mm. Using the surface deformation feature, the occlusal veneer was thickened to 0.5 mm and 1.0 mm, and periodontal ligaments were added. They were then placed into the upper and lower jaws and dental arches. Finite element analysis was performed after applying bite force dispersion to the loading area on the mandible following dynamic contact. Results: (1) As the thickness increased, the maximum Von Mises stress in the occlusal veneers SFL and CFL also increased, while the SCI exhibited the opposite trend. (2). The trend of the maximum Von Mises stress in the adhesive layer decrease gradually with increasing thickness of the occlusal veneer. The stresses of the SFL and CFL is concentrated primarily at the edge position below the functional cusp, resulting in relatively low adhesive stress. However, in the SCI group, the maximum stress at the edge of the adhesive layer exceeds the maximum shear strength of commonly used adhesives. Conclusions: Under the experimental conditions, the mechanical properties of the maximum Von Mises stress in the SFL, CFL, and SCI occlusal veneers meet clinical needs. Incorporating the minimally invasive concept of tooth preservation, a thickness of 1.0 mm are optimal for glass ceramic occlusal veneers on maxillary first molars. Highlights: This experiment combined finite element analysis with traditional mechanical experiments and prepared models with identical shapes using 3D printing. This approach avoided experimental errors caused by variations in the shape of natural teeth among individuals, uneven bonding agent thickness, and different design morphologies of the occlusal surface. Additionally, the roughness of the prepared surface more closely resembled the true roughness encountered in clinical settings. By incorporating periodontal ligament (PDL) hyperelastic materials into jaw dentition, a more realistic nonlinear analysis of periodontal ligament deformation was conducted. Dynamic contact results, which differed from the static loading stresses typically used in finite element analyses, were obtained by applying biting forces and simulating the movement of biting. Daily chewing is not merely a collision between highly elastic model materials and restorations or teeth, as in extraoral experiments. Instead, it simulates the mechanical properties of the daily foods of primates, using materials that closely match these properties. [ABSTRACT FROM AUTHOR] |
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