A three-dimensional finite element model of mesio-occluso-distal cavity zirconium dioxide inlay and its bonding interface:a stress analysis / 中国组织工程研究

ABSTRACT

BACKGROUND: Zirconia inlays have good mechanical, biocompatible and aesthetic properties in the field of dental prosthodontics, but there is no consensus on the standards of zirconia inlays for clinical cavity design, dental preparation and selection of bonding materials. OBJECTIVE: To investigate the stress distribution and characteristics of the bonding interface, tooth and periodontal tissues of the zirconia inlay model after 3 M RelyX Unicem or vario-link resin adhesive bonding. METHODS: Micro-CT was used to scan the right mandibular third molars. A three-dimensional finite element model of MOD zirconia inlay with different adhesives (3 M RelyX Unicem resin binder, vario-link resin binder) and cavity types (2, 3, 4 mm in the depth of the joint cavity) was constructed by software Mimics, Goemagic Studio and NX 10.0. Using ANSYS Workbench mesh generation, the stress distribution of each model was analyzed after loading 10 N·mm torque, 45° 175 N, 90° 600 N. RESULTS AND CONCLUSION: (1) After loading 10 N·mm torque, the bonding agent equivalent stress and root surface equivalent stress of the model with 3 mm cavity depth were largest, so the stress on the bonding interface, crown and root was largest. (2) After loading 175 N at 45° lingual direction, the bonding interface of the model with 4 mm cavity depth undertook a higher stress. The stress values of the root and periodontal tissue of 3 M RelyX Unicem resin bonding agent model with the same cavity depth were higher. (3) After loading 600 N at 90°, the root force of the model with 3 mm cavity depth was largest. The crown, root and periodontal tissue of the 3 M RelyX Unicem resin bonding agent model with the same cavity depth undertook a higher stress. The bonding interface of the vario-link resin bonding agent model was under greater stress. (4) The regions of stress concentration areas included the bifurcation zone of the root, the inlay edge line, the roof of pulp chamber, the gingival wall, 1/3 mesial part of the buccal surface near the neck, and 1/3 mesial part of the lingual surface near the neck. (5) All these findings indicate that vario-link resin adhesive and 3 M RelyX Unicem resin adhesive are suitable for the bonding of zirconia inlay, but the vario-link adhesive strength is larger and the bonding interface stress is larger. The factors such as cavity design, residual tooth tissue resistance, retention shape, and periodontal support should be considered comprehensively. The optimization of cavity design, tooth preparation, cushion bottom and high inlay should be adopted, in order to improve the long-term repair effect of zirconia inlay. However, further clinical trials are needed to verify the results of three-dimensional finite element model.