IADR Abstract Archives
Stress Distribution in Occlusal Veneers With Varied Cement Thicknesses
Objectives: To investigate the influence of cement thicknesses (50 to 400 µm) on the stress distribution at the tooth-restoration interface of three types of 1-mm CAD/CAM occlusal veneers (lithium disilicate, zirconia-reinforced lithium silicate and resin nanoceramic) under 1000N load.
Methods: 3D scanned files of the typodont of a mandibular first with occlusal reduction and 1-mm CAD/CAM occlusal veneers were imported into Geomagic Design X (Artec Group Inc, Senningerberg, Luxembourg) and converted into editable CAD models. For Finite Element Analysis, they were further refined in SolidWorks and Abaqus CAE (Dassault Systèmes, Vélizy-Villacoublay, France). Orthotropic mechanical properties were applied to reflect the actual properties of enamel and dentine. All other components were assumed to have homogenous linear isotropic properties. The veneers were modelled as being made of lithium disilicate, zirconia-reinforced lithium silicate or resin nanoceramic, respectively (LS, ZLS, and RNC). Four cement thicknesses were modelled (50, 100, 200, 300, and 400 µm) under each veneer material. The von Mises and the maximum principal stresses produced by indentation with a 1000N load applied via a steel ball onto the occlusal veneers were calculated.
Results: For the lithium-silicate-based materials (LS and ZLS) with high elastic modulus, the von Mises and the maximum principal stresses concentrated within the tooth-restoration complex with no significant differences by varying cement thicknesses. However, RNC with similar elastic modulus to dentine showed lower stresses within the restoration; higher stresses dissipating into the cement layer and remaining hard dental tissue, especially in the models with thinner cement layers.
Conclusions: The models indicated RNC occlusal veneers could support a higher load than lithium-silicate-based materials. LS and ZLS occlusal veneers did not show significant differences in stress distribution patterns. An increase in cement thickness affects the stress distribution at the tooth-restoration interface in the lower modulus hybrid material, RNC, but not in the other materials.
Methods: 3D scanned files of the typodont of a mandibular first with occlusal reduction and 1-mm CAD/CAM occlusal veneers were imported into Geomagic Design X (Artec Group Inc, Senningerberg, Luxembourg) and converted into editable CAD models. For Finite Element Analysis, they were further refined in SolidWorks and Abaqus CAE (Dassault Systèmes, Vélizy-Villacoublay, France). Orthotropic mechanical properties were applied to reflect the actual properties of enamel and dentine. All other components were assumed to have homogenous linear isotropic properties. The veneers were modelled as being made of lithium disilicate, zirconia-reinforced lithium silicate or resin nanoceramic, respectively (LS, ZLS, and RNC). Four cement thicknesses were modelled (50, 100, 200, 300, and 400 µm) under each veneer material. The von Mises and the maximum principal stresses produced by indentation with a 1000N load applied via a steel ball onto the occlusal veneers were calculated.
Results: For the lithium-silicate-based materials (LS and ZLS) with high elastic modulus, the von Mises and the maximum principal stresses concentrated within the tooth-restoration complex with no significant differences by varying cement thicknesses. However, RNC with similar elastic modulus to dentine showed lower stresses within the restoration; higher stresses dissipating into the cement layer and remaining hard dental tissue, especially in the models with thinner cement layers.
Conclusions: The models indicated RNC occlusal veneers could support a higher load than lithium-silicate-based materials. LS and ZLS occlusal veneers did not show significant differences in stress distribution patterns. An increase in cement thickness affects the stress distribution at the tooth-restoration interface in the lower modulus hybrid material, RNC, but not in the other materials.