Evaluation of Fracture strength in endodontically-treated teeth restored with composite resin and three different fiber insertion techniques and analysis of forces with finite element

Abstract

The aim of this study was to evaluate the effect of three methods of glass fiber insertion on fracture resistance of root-filled maxillary premolars in vitro and analysis of stress distribution with finite element method. Methods: Sixty extracted human maxillary premolars received endodontic treatment followed by preparation of mesioocclusodistal (MOD) cavities with 2.50.2 mm thicknesses of buccal and lingual cusps at height of contour. The gingival cavosurface margin was 1.5 mm coronal to the cementoenamel junction (CEJ). Subsequently, the teeth were randomly divided into four groups: no-fiber group (the cavities were restored with composite resin only); occlusal fiber group (a ribbon of glass fiber was placed in the occlusal third); circumferential fiber group (a ribbon of glass fiber was placed circumferentially in the cervical third); and dual-fiber group (occlusal and circumferential fibers). Subsequent to thermocycling, a compressive force was applied. Data was analyzed using one-way ANOVA and a post hoc Tukey test. Then different models were designed according to experimental groups. Load, simulating the load application of 300 N in mechanical test was applied. Finally a linear static analysis was performed on the prepared 3D solid models. Results: Fiber placement significantly increased fracture resistance. Fracture resistance in the dual-fiber group was significantly higher than that of the circumferential fiber group (p<0.007); however, there was no significant difference between the dual-fiber and occlusal fiber groups (p=0.706). The highest favorable fracture rate was observed in the circumferential fiber group (60%). Maximum Von Mises equivalent stress in dentin was recorded for occlusal and both fiber group. The normal displacement to the tooth axis for these groups was a little higher in occlusal. Conclusions: Composite restoration along with glass fiber in the occlusal third with circumferential fiber in the gingival third can be an acceptable treatment option for restoring root-filled upper premolars to increase fracture resistance. With regard to fracture mode, circumferential fiber in the gingival third demonstrated favorable fracture pattern, which was approved by the finite element method.