Denture Tooth Thickness Influences the Fracture Mode of Denture Base

Objectives: To investigate the influence of denture tooth thickness on the fracture resistance of thin acrylic denture base.
Methods: Acrylic resin (AC), or composite-resin (CO) molar denture teeth were embedded in heat-polymerized denture base blocks of 2.0-mm in thickness. The distance from the central fossa to the tooth bottom was 0.5, 1.0, 2.0, or 2.5-mm for AC and CO (n = 7/gp), with a total thickness of 2.5-mm from the central fossa to the block bottom for all specimens. Each specimen was placed on a three-point flexural setup with a shorter (8-mm) or longer (12-mm) support span compared with the tooth-width and vertically loaded. Three-dimensional finite element models of the 1.0-mm or 2.0-mm-thick CO specimens with 2 support spans were constructed to simulate the loading test to assess the stress distributions. The effects of tooth thickness and support span were statistically tested using ANOVA, followed by post-hoc analysis (α= .05).
Results: Under the shorter support, the mean fracture load was higher in CO than AC, regardless of the tooth-thickness. Under the longer support, the mean fracture load with the CO significantly decreased as the tooth-thickness increased, with increased maximum stress. Some specimens with 2.0-mm or 2.5-mm-thick CO tooth failed at the tooth-denture base interface, at significantly lower loads compared to those exhibited tooth fractures.
Conclusions: Higher fracture resistance was indicated with CO. The acrylic resin layer underneath the tooth should be 1.0-mm thick at minimum. The in vitro experiment with the finite element analysis of this study suggests that a composite resin denture tooth is recommended in acrylic resin removable dentures for patients with reduced interarch distance, and that the acrylic resin denture base layer underneath the tooth bottom should have a thickness of at least 1.0-mm.