An in vitro study of the failure of short-fibre reinforced composite post and core restoration of endodontically treated teeth

Abstract

Statement of problem: There is insufficient data on the failure of ETT restored with SFRC as a post and core restoration. Objectives: To comprehensively analyse the failure of ETT restored with SFRC as a post and core by conducting the following investigations: (1) analysis of the internal structures of SFRC posts and cores using micro-CT; (2) evaluation of failure load and failure mode of ETT restored with SFRC as a post and core after subjecting the teeth to fracture resistance testing and (3) analysis of the fractured surfaces of SFRC using SEM (fractography). Methods: Extracted premolars were divided randomly into three groups (15 teeth/group); control group of untreated teeth (C), ETT restored with SFRC posts and cores(XFP), and ETT restored with prefabricated FRC posts (PFP). Teeth in XFP group and PFP group received RCT and were restored with posts and cores and ceramic crowns. Qualitative and quantitative analyses of SFRC posts and cores (XFP group) were performed using a micro-CT scanner and associated software. All groups were thermocycled and subjected to a gradual cyclic fracture resistance test followed by failure mode evaluation. Fractured XFP specimens were imaged using SEM for fractographic analysis. Results: The control group had the highest mean failure load (1209.20N±126.65). The mean failure load of the XFP group (731.25N±86.33) was significantly higher (P <0.0001) than the mean failure load of PFP group (373.85N±64.21). While all teeth in XFP group had restorable failures, four specimens (27%) in PFP group had non-restorable root fractures. Voids were detected inside SFRC post and core build-ups and at the interface between the posts and dentine. Voids were distributed evenly inside SFRC posts. 88.2%±2.6 of the voids were smaller than 100μm3. For every 1% increase in the post voids, the mean failure load of teeth restored with SFRC posts increased by 53.9N. Fractographic analysis indicated that fibre orientation and distribution influenced the failure of ETT restored with SFRC posts. Conclusions: Endodontically-treated premolars restored with SFRC posts and cores demonstrated high failure load and favourable failure modes. The presence of voids and alteration in fibre orientation and distribution can affect the failure of ETT restored with SFRC posts and cores.