Mechanical Behaviour of Ceramic Layered Zirconia Restorations: A Three Dimensional Finite Element Analysis using Microcomputed Tomography Data

Abstract

Introduction: Combining the strength of zirconia cores with superior aesthetics of a weaker veneer ceramic can result in a reliable and more biocompatible restoration. Aim: To investigate the mechanical behaviour with respect to different designs of zirconia-ceramic veneer interface using three-dimensional finite element analysis. Materials and Methods: Tooth preparation of the indicated mandibular molar was done for three patients. Each patient was restored with a different design of zirconia-ceramic interface (Design I- full ceramic veneer, Design II- ceramic veneer on buccal surface extending upto occlusal surface, Design IIIceramic veneer on buccal surface only). Cone Beam Computed Tomography (CBCT) image was taken for each patient after the cementation of the restoration which was used to develop 3D finite element models by applying appropriate softwares (Mimics, Rapidform, Hypermesh, ANSYS). Four types of loads were applied to each of the 3D finite element model-600 N load was applied vertically, 225 N load was applied in three directions (vertically, oblique at 45° and horizontally) at different points on occlusal surface and their buccal inclines. Maximum principal stress and minimum principal stress were obtained by finite element analysis. Results: When vertical loads of 600 N and 225 N were applied, ceramic layer of design II experienced larger tensile stresses 21.83 MPa and 28.33 MPa. When horizontal load of 225 N was applied, tensile stress in ceramic layer was largest in design I i.e., 29.87 MPa. When an oblique load of 225 N was applied, largest tensile stress in ceramic layer of 12.82 MPa was observed in design I. Conclusion: The different design characteristics of the junction between ceramic and zirconia will affect the bond between zirconia core and ceramic veneer. Design III has the least chances of chipping of ceramic layer under masticatory loads. Design II is more prone to chipping of ceramic layer under masticatory loads. Design I may show chipping under high occlusal loads.

Keywords

• bite force
• compressive strength
• elastic modulus
• finite element models
• tensile strength