Functional or Nonfunctional Cusps Preservation for Molars Restored with Indirect Composite or Glass-Ceramic Onlays: 3D FEA Study

Abstract

Evidence regarding the effect of the onlay preparation design for different CAD/CAM restorative materials considering the preservation of cusps is lacking. Molars were 3D-modeled in four preparation designs for onlay restoration: traditional design with functional cusp coverage (TFC), non-retentive design with functional cusp coverage (NFC), traditional design with non-functional cusp coverage (TNFC) and non-retentive design with non-functional cusp coverage (NNFC). The restorations were simulated with two CAD/CAM restorative materials: LD—lithium disilicate (IPS e.max CAD) and RC—resin composite (GrandioBloc). A 100 N axial load was applied to the occlusal surface, simulating the centric contact point. Von Mises (VM) and maximum principal (Pmax) stress were evaluated for restorations, cement layer and dental substrate. The non-retentive preparation design reduced the stress concentration in the tooth structure in comparison to the conventional retentive design. For LD onlays, the stress distribution on the restoration intaglio surface showed that the preparation design, as well as the prepared cusp, influenced the stress magnitude. The non-retentive preparation design provided better load distribution in both restorative materials and more advantageous for molar structure. The resin composite restoration on thenon-functional cusp is recommended when the functional cusp is preserved in order to associate conservative dentistry and low-stress magnitude.

Thickness and Substrate Effect on the Mechanical Behaviour of Direct Occlusal Veneers

“…The material properties have been considered as isotropic, with a Poisson ratio of 0.3. The elastic modulus values were 90 GPa for enamel, 18 GPa for dentin, 16.8 25 for CCR, and 8.8 26 for FCR. The contacts were defined based in the coincident nodes, previously merged at the meshing process with bonded behaviour.…”

“…For that, an occlusal veneer model was created based in the in vitro specimens and different thickness. A previously reported model 26 was exported and modified into the computer-aided design software (Rhinoceros version 5.0 SR8, McNeel North America). To allow a homogeneous interface between the restoration and the substrate, the cutplane was used to split the geometries, allowing a perfect adhesive region.…”

Elasto-Static Analysis of Composite Restorations in a Molar Tooth: A Meshless Approach

“…Nonetheless, determining accurate biomechanical properties for living tissues, especially bone tissue in numerical models, remains a challenging endeavour, c.f. [ 3 , 4 , 5 , 6 ].…”