Influence of glass-fiber posts on the fracture resistance and failure pattern of endodontically treated premolars with varying substance loss: An in vitro study.

摘要

STATEMENT OF PROBLEM: It is unclear how the amount of substance loss affects whether the fracture strength of endodontically treated and crowned teeth is increased by post placement. PURPOSE: The purpose of this in vitro study was to evaluate the influence of glass-fiber post placement on the fracture resistance of endodontically treated premolars with varying degrees of substance loss. MATERIAL AND METHODS: Sixty-four extracted and endodontically treated mandibular premolars were divided into 4 test groups (n=16) depending on the number of residual coronal dentin walls that ranged from 3 to zero. Teeth in subgroups were either adhesively restored with composite resin without a post (-) or with an adhesively luted glass-fiber post (+). After receiving a 0.8-mm shoulder preparation, providing a ferrule of 0.5 mm, teeth were restored with complete metal crowns, which were cemented with glass ionomer cement. All specimens were subjected to dynamic loading in a masticatory simulator for 1.2 million loading cycles with a nominal load of 49 N at 1.2 Hz combined with thermal cycling (between 5 and 55 degrees C, 30-second dwell time). Then specimens were quasi-statically loaded at 30 degrees in a universal testing machine until fracture. Data were analyzed with 2-way ANOVA, followed by multiple comparisons using Tukey HSD test (alpha=.05). RESULTS: No specimen failed during masticatory simulation. Mean final fracture resistance ranged from 335.6 +/-39.7 N to 1064.9 +/-211.8 N. Two-way ANOVA revealed that both the number of residual coronal walls and post placement had a significant influence on the fracture resistance (P<.001). However, pair-wise comparisons of groups showed that in groups with 2 or 3 cavity walls, the post effect was not statistically significant (P=.378 and P=.175, respectively). CONCLUSIONS: The fracture resistance of endodontically treated premolars was dependent on the number of residual coronal dentin walls. Placement of a glass-fiber post had a significant influence on the fracture resistance when fewer than 2 cavity walls remained but no significant influence when 2 or 3 walls were present.