Estimation of Fatigue Strength of Reinforced Complete Upper Denture Using a Newly Designed Testing Machine: A Laboratory Research Project

Anthony E Prombonas,Nikolas A Poulis,Evangelos A Prombonas

doi:10.4236/jbise.2021.142006

Abstract

In the present study, an aero pneumatic fatigue testing machine for complete dentures was designed, fabricated, and tested for the evaluation of the fatigue life of reinforced complete upper denture (CUD). On completion and testing, it was observed that the machine has the potential of generating reliable number of cyclic data. The machine’s performance was evaluated using test specimens of identical CUDs that were machined in conformity with standard procedures. The fatigue machine compressed the lower dental arch over the upper denture-specimen in centric occlusion, in the same way that the two masticatory muscles pull the lower jaw over the upper jaw during chewing. The incorporation of glass fibres into the CUD using a sandwich technique quadruples the lifespan of the denture (P = 0.004). The low standard deviation, along with the low coefficient of variation (CV) of the group of unreinforced dentures shows the repeatability of the results and the reliability of the machine. The high standard deviation and coefficient of variation of reinforced dentures was expected, since a high variation of results is usually recorded in fibre reinforcement cases. This research confirmed the view that the crack during denture fracture initiates in the anterior palatal area and propagates to the posterior.

Highlights

IntroductionReal (functional) loads can induce bending combined with torsional, axial, and shear stresses, generating bi- or tri-axial variable stress/strain histories at the critical point
To test and evaluate the machine, a pilot study was conducted on the effect of reinforcing the strength of the complete upper denture (CUD) in fatigue
1) The fatigue machine presented in this study provides a reliable way of straining the CUD in complete simulation of the oral conditions of mastication, by submitting the complete denture-specimens to a combination of flexural and torsional loading

Summary

Introduction

Real (functional) loads can induce bending combined with torsional, axial, and shear stresses, generating bi- or tri-axial variable stress/strain histories at the critical point Under these conditions, the midline of the palate of the CUD could be the torsion axis of the denture during loading in coexistence with the bending deflection. The midline of the palate of the CUD could be the torsion axis of the denture during loading in coexistence with the bending deflection For these reasons, fatigue strength is the most important mechanical property of the CUD, especially when it is measured under the simulated conditions of its operation during mastication. In some machines, repeated (cyclic) loading is achieved by the use of a motor (whose rotary motion is converted to pulsed motion), while in others by the use of a hydraulic or air piston that performs pulsed motion (thrust or traction) [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]

Methods

Results

Discussion

Conclusion