Effect of Labial Frenum Notch Size and Palatal Vault Depth on Stress Concentration in Maxillary Complete Dentures: A Finite Element Study

Abstract

Fracture is a common cause of acrylic resin denture failure due to crack development in a site of excessive concentration of stress in the denture. The purpose of this study was to evaluate the effect of labial frenum notch size and palatal depth on stress concentration in maxillary complete dentures. Three-dimensional finite element models of maxillary complete dentures with different palatal vault depths (shallow, medium, and deep) and different frenum notch sizes (small, medium, and large) were constructed. The stress concentration was analyzed using Nastran software and displayed in terms of von Mises stress generated under two conditions: dropping on a hard flat surface from a standard distance and applying vertical load to the occlusal surface. The greatest stress concentration was observed in the labial frenum notch. Stress increased with an increase in the size of the labial frenum notch and a decrease in the depth of the palatal vault. The stress concentration in maxillary denture bases was greater when a vertical load was applied compared with dropping the denture on a hard surface from a standard distance. Using finite element analysis, the presence of a large labial frenum notch and a shallow palatal vault increased the concentration of stress in maxillary complete dentures. Stress concentration in a maxillary denture base is much greater during the application of a vertical load than when dropping the denture on a hard flat surface. The concentration of stress at the tip of a large frenum notch and in a shallow palatal vault could have a weakening effect on the maxillary complete acrylic resin denture base making it more vulnerable to fracture. In this scenario alternative denture base strengthening strategies, such as using a metal framework, should be considered in the fabrication of maxillary complete dentures.