A three-dimensional finite element analysis of mechanical function for 4 removable partial denture designs with 3 framework materials: CoCr, Ti-6Al-4V alloy and PEEK

Xin Chen,Jiayi Yu,Yuqing Lu,Haiyang Yu,Qianqian Zhang,Li Yue,Bochun Mao,Zhuoli Zhu

doi:10.1038/s41598-019-50363-1

Abstract

Polyetheretherketone (PEEK) is a new material used for the frameworks of removable partial dentures (RPD). The questions whether the PEEK framework has similar stress distribution on oral tissue and displacement under masticatory forces as titanium alloy (Ti-6Al-4V) or cobalt-chromium alloy (CoCr) remain unclear and worth exploring. A patient’s intraoral data were obtained via CBCT and master model scan. Four RPDs were designed by 3Shape dental system, and the models were processed by three-dimensional finite element analysis. Among three materials tested, PEEK has the lowest maximum von Mises stress (VMS) on periodontal ligament (PDL), the greatest maximum VMS on mucosa, the maximum displacement on free-end of framework, and the lowest maximum VMS on framework. Results suggested that PEEK framework has a good protective effect on PDL, suggesting applications for patients with poor periodontal conditions. However, the maximum displacement of the free-end under masticatory force is not conducive for denture stability, along with large stress on the mucosa indicate that PEEK is unsuitable for patients with more loss of posterior teeth with free-end edentulism.

Highlights

Removable partial dentures (RPDs) have wide indications and flexible designs compared to fixed partial dentures or implant restorations[1,2], and they are frequently used to restore dentition defects during the clinical work of prosthesis
Compared with cobalt-chromium alloy (CoCr) and Ti-6Al-4V alloy, PEEK has the lowest maximum von Mises stress on the periodontal ligament (PDL), the greatest maximum von Mises stress on the mucosa, the largest displacement on the free-end and the lowest maximum von Mises stress on the framework with significant differences compared with those values of the other two materials (p < 0.05, SNK q test, Fig. 1)
The maximum stress of the PDL of PEEK group was only 77.8% of the Ti alloy and 69.2% of the CoCr alloy, indicating that PEEK was more conducive in the protection of PDL of the abutment

Summary

Introduction

Removable partial dentures (RPDs) have wide indications and flexible designs compared to fixed partial dentures or implant restorations[1,2], and they are frequently used to restore dentition defects during the clinical work of prosthesis. FEA has been widely used to predict the biomechanical behavior of various types of prosthetic bodies in oral environment[17], such as dental implants[18], removable and fixed prosthesis[19], implant-assisted RPD20 and bone metabolism[21] This method is quite useful for exploring mechanical behaviors of tissues that can hardly be investigated in vivo. The thickness of mucosa in patients’ mouth varies much among different areas of oral cavity[22], using one single parameter to represent the thickness could be at best a rough approximation Another common method of reconstructing mucosa exploits CBCT or CT data to reconstruct mucosa together with other hard tissues. This research revealed a new way of reconstructing mucosa more accurately with accurate thickness and morphology of mucosa reserved by involving both optical scan data and CBCT data

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