Fracture Resistance and Micro-CT Evaluation of Endodontically Treated Teeth Restored with New Short Glass Fibre Reinforced Composite Used as Post and Core

Objectives:

(1)To evaluate the fracture resistance of ETT restored with (everX Posterior) post and core system.
(2)To evaluate the mode of failure of ETT restored with the (everX Posterior) post and core system.
(3)To perform qualitative and quantitative comprehensive analyses of the fractured ETT restored with everX Posterior using micro-CT.
Methods: 45 extracted upper premolars were divided randomly into three groups (15 teeth/group); one control (sound upper premolars) and two experimental groups restored with everX Posterior and prefabricated FRC post systems. Teeth in both experimental groups were subjected to decoronation, root canal treatment, post space preparation, post and core build up and ceramic crown fabrication and cementation. All teeth were subjected to thermo-cycling (500 cycles/ 5°C and 55°C). All teeth were then mounted in blocks to simulate PDL and bone structures. for fracture resistance test, specimens were mounted to Instron (8874) (Image 1)and exposed to gradual mechanical loading protocol (gradual increase of the compressive occlusal load by 50 N at a frequency of 0.5 HZ for 100 cycles/step of load) and failure load was recorded in Newton (N).The everX Posterior group specimens were then scanned using SkyScan 1076 micro-CT scanner and analysed in three-dimensions using SkyScan Data viewer, CTAn and CTVol software.
Results: There was a significant difference in failure load mean between all groups (95% confidence level, P value <.0001). Specimens restored with everX Posterior system recorded almost double (731.25±81.34) the fracture strength values of the specimens restored with prefabricated FRC posts (373.86±64.21).
While none of the everX Posterior specimens had a non-restorable failure mode four specimens (26.67%) of the prefabricated FRC post specimens had a non-restorable deep root fracture (Image 2 and 3).
There was a statistically significant association between failure load and the percentage (global P value=0.0004) and volume (P value=0.0125) of post and core voids.
Conclusions: ETT restored with everX Posterior as a post and core system demonstrated higher fracture resistance and more favourable fracture patterns than teeth restored with prefabricated FRC post. The presence of voids in the post build up can reduce the fracture strength of ETT restored with everX Posterior.