IPS-Empress II inlay-retained fixed partial denture reinforced with zirconia bar: Three-dimensional finite element and in-vitro studies

Abstract

Objective. This study evaluated von Mises stress distribution, flexural strength and interface micrographs of IPS-Empress II (IPS) inlay-retained fixed partial dentures (IRFPD) reinforced with Zirconia bars (Zb). Materials and methods: In the Finite element analysis, six three-dimensional models of IRFPD were designed using Solid Works 2006. Five models were reinforced with different Zb and a model without Zb was considered as a control. The bridges were loaded by 200 and 500 N forces at the middle of the pontic on the occlusal surface. Subsequently, von Mises stress and displacement of the models were evaluated along a defined path. In the experimental part, 21 bar shape specimens were fabricated from lithium disilicate and zirconia ceramic in three different designs. The zirconia-IPS interfaces and the fractured surfaces of flexural test were observed using SEM. Results. In the connector area, von Mises stress and displacement of the models with Zb under a load of 500 N were decreased compared to the model without the Zb; however, this difference was not considerable at a load of 200 N. In the mesial connector, Von Mises stress and displacement was decreased from 12.5 Mpa for the control model tested at 500 N to 7.0 Mpa for the model with Zb and from 0.0050–0.0041 mm, respectively. SEM analyses showed that, before fracture, interfacial gaps were not observed along the interfaces, but initiated cracks propagated along the interfaces after flexural loading. Conclusion: IPS IRFPD reinforced by Zb can tolerate higher stresses while still functioning effectively and the interfaces may have desirable adaption.

Key Words::

• dental stress analysis
• zirconia
• inlay-retained fixed partial denture
• mechanical loading

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.