Effect of cavity design on tooth surface strain

Abstract

Statement of problem: The loss of tooth structure can increase cuspal flexure, thereby reducing the fracture resistance of the tooth, or open the tooth-restoration interface, leading to microleakage.

Purpose: The purpose of this study was to evaluate tooth strain in teeth with different cavity preparations after loading and unloading.

Material and methods: Ten intact human maxillary premolars were selected and embedded in epoxy resin molds. Constantan strain gauges were used and tested as an intact tooth (group I), occlusal cavity (group O), mesio-occlusal cavity (group MO), and finally mesio-occluso-distal cavity (group MOD). All teeth were subjected to gradual nondestructive occlusal loading and unloading (50 N, 70 N, 90 N, 110 N, 130 N, 50 N, 0 N) in a servohydraulic testing machine. All data were analyzed statistically by performing a repeated measures ANOVA with load and cavity as factors to compare the relevant mean strains, and a Bonferroni post hoc test was performed for multiple comparisons (α=.05).

Results: The repeated measures ANOVA did not provide any evidence of an interaction between load and cavity but indicated a significant difference in the mean strains both between the loads (P<.001) and between the cavity groups (P<.001).

Conclusions: MOD cavities presented statistically significantly higher values of strain than MO, O, or intact teeth, and a significant increase in the values of mean strain for all cavities was observed, even with intact teeth, when nondestructive occlusal loading was increased.