Investigation of the torsional deformation of the complete upper denture: A pilot study

Anthony E Prombonas,Nikolas A Poulis,Maria A Paralika

doi:10.4236/jbise.2013.64055

Anthony E Prombonas, Nikolas A Poulis + Show 1 more

Open Access

https://doi.org/10.4236/jbise.2013.64055

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Abstract

The aim of this research is to clarify whether the midline axis of the complete upper denture (CUD) is the axis of its torsion during loading, apart from the known bending deflection. Furthermore the present study is intended to estimate the influence of the anterior notches on the torsional deformation of the CUD. Using commercial edentulous molds and standardized procedures, six identical CUDs were fabricated with an initial fraenal notch of 5 mm. Two additional notch conditions were produced by deepening the notch to a total depth of 9 mm and by creating an incisal diastema of 7 mm. Five biaxial (also known as “fish bone”) strain gauges were cemented onto the palatal section of the dentures so that their middle axis coincided with the midline axis of the outer surface of the denture. For the denture specimen used in this study, the specific point of torsion was detected 2 cm from the point of contact of the two artificial central incisors. The presence of a deep fraenal notch and the combination of the deep fraenal notch with the presence of an incisal diastema increased the torsion of the CUD to a significant level (P = 0.006 and P = 0.05, respectively). It was shown that the midline can be the CUD’s axis of torsion. Biaxial strain gauges could be a reliable method of measuring the torsional deformation of the CUD.

Highlights

The fracture of the acrylic resin dentures is an unresolved problem in removable prosthodontics despite numerous attempts to determine its cause
The above consideration leads to the reasonable assumption that there may be a deficit in the study of the mechanical behavior of the complete upper denture (CUD) in functional loading conditions
Position 1 refers to the anterior palatal strain gauge, position 5 refers to the posterior palatal strain gauge, and positions 2, 3 and 4 refer to the intervening strain gauges (Figure 4)

Summary

Introduction

The fracture of the acrylic resin dentures is an unresolved problem in removable prosthodontics despite numerous attempts to determine its cause. Despite the high frequency of complete upper denture (CUD) fracture, there is surprising little discussion of the subject in the literature. It has been established, that the CUDs are subjected to bending deformation [1]. The above consideration leads to the reasonable assumption that there may be a deficit in the study of the mechanical behavior of the CUD in functional loading conditions. The above assumption in combination with the fact that the corresponding research has focused on the study of pure bending of the CUD, may be the reason why mechanical behavior of the CUD still remains a complicated problem. Recent studies have shown that the complexity of the loads applied during the normal function of the CUD, in both magnitude and direction, and the alterations in the directions and magnitudes of principal stresses induce a complex multiaxial stress state in the palatal stress field and in the field of the CUD’s labial flange [2,3,4]

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