Effect of different bonded base materials on the fracture resistance and failure mode of complex cavity of endodontically treated premolars. (An in Vitro Study)

Abstract

Objectives: Objective: The aim of this study was to evaluate the effect of different bonded base materials on fracture resistance of endodontically with complex cavities, and the assessment of the mode and type of fracture of each experimental group.
 Materials and Methods: Fifty freshly extracted, intact, non-carious human maxillary second premolar teeth with similar anatomic characteristics were selected, the teeth were classified according to their mesiodistal and buccolingual dimensions into five groups. Endodontic treatment performed for all the groups except Group 1
 Group 1 intact teeth (control group).
 Group 2 unrestored teeth with endodontic treatment.
 Group 3 endodontically treated as in group 2 and restored with (smart dentine replacement) SDR bulk-fill.
 Group 4 restored with Vertise flow self-adhering flowable composite with optibond technology.
 Group 5 endodontically treated as in group 2 and restored with GC EQUIA Fill.
 The cavities in group 3,4 and five were then filled with Filtek Z250XT composite. Fracture resistance testing: All specimens were subjected to axial compressive loading until fracture in Hydraulic Universal Testing Machine (WDW 2006, China). The force required fracturing each tooth was recorded in kilo-Newtons. Assessment of fracture type and mode: After using ink perfusion of each sample for 5 min. Macroscopic fracture patterns were observed.
 Results: the results showed that the mean fracture load values were (1.94, 1.61, 1.79, 1.91 and 1.89 Kn) for each group from group1 to group 5 respectively. The mean fracture load value recorded by each material (group3, 4 and 5) was near the mean value of the sound intact tooth (group 1) which means that all of the bonded base materials used in this study can improve the fracture resistance of the endodontically treated teeth to a great extent. Although the group 4 (self-bonded Vertise flow base material) showed the highest value of the other materials (group 3 and 5), there were no significant statistical differences.
 Conclusion: The results predict that the three types of bonded base materials can increase the fracture resistance of the endodontically treated teeth to different extents depending on their bonding mechanisms and physical characteristics.