Root Canal Filling: Fracture Strength of Fiber-Reinforced Composite-Restored Roots and Finite Element Analysis

Marilia Pivetta Rippe,Manuela Favarin Santini,Carlos Alexandre Souza Bier,Alexandre Luiz Souto Borges,Luiz Felipe Valandro

doi:10.1590/0103-6440201301996

Marilia Pivetta Rippe, Manuela Favarin Santini + Show 3 more

Open Access

https://doi.org/10.1590/0103-6440201301996

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Abstract

The aims of this study were to evaluate the effect of root canal filling techniques on root fracture resistance and to analyze, by finite element analysis (FEA), the expansion of the endodontic sealer in two different root canal techniques. Thirty single-rooted human teeth were instrumented with rotary files to a standardized working length of 14 mm. The specimens were embedded in acrylic resin using plastic cylinders as molds, and allocated into 3 groups (n=10): G(lateral) - lateral condensation; G(single-cone) - single cone; G(tagger) - Tagger's hybrid technique. The root canals were prepared to a length of 11 mm with the #3 preparation bur of a tapered glass fiber-reinforced composite post system. All roots received glass fiber posts, which were adhesively cemented and a composite resin core was built. All groups were subjected to a fracture strength test (1 mm/min, 45°). Data were analyzed statistically by one-way ANOVA with a significance level of 5%. FEA was performed using two models: one simulated lateral condensation and Tagger's hybrid technique, and the other one simulated the single-cone technique. The second model was designed with an amount of gutta-percha two times smaller and a sealer layer two times thicker than the first model. The results were analyzed using von Mises stress criteria. One-way ANOVA indicated that the root canal filling technique affected the fracture strength (p=0.004). The G(lateral) and G(tagger) produced similar fracture strength values, while G(single-cone) showed the lowest values. The FEA showed that the single-cone model generated higher stress in the root canal walls. Sealer thickness seems to influence the fracture strength of restored endodontically treated teeth.

Highlights

Vertical root fracture (VRF) has been the cause of failure of many endodontically treated teeth
The possible causes of this condition have been examined and recent evidence indicates that VRFs are most likely caused by the propagation of small, critical and less pronounced defects rather than the force exerted during the canal preparation or filling [1]
One-way ANOVA indicated that the filling technique (p=0.0044) affected the fracture strength

Summary

Introduction

Vertical root fracture (VRF) has been the cause of failure of many endodontically treated teeth. The possible causes of this condition have been examined and recent evidence indicates that VRFs are most likely caused by the propagation of small, critical and less pronounced defects rather than the force exerted during the canal preparation or filling [1] These incomplete fractures may occur in areas of high stress concentration when force is applied during the restorative procedure or from occlusal stresses during mastication [2]. Saw and Messer [6] studied the influence of root canal techniques (lateral condensation, Obtura and Thermafil) on the tension of roots and concluded that the lateral condensation and Obtura withstood more than twice the load than with Thermafil obturation, which is a thermoplastic technique Another important factor to be considered as a cause of stress concentration in the root canal apart from the filling technique is sealer expansion. Research indicates that endodontic sealers undergo expansion that could weaken the root [7]

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