Effect of remaining tooth structure on the fracture resistance of endodontically-treated maxillary premolars: An in vitro study

Abstract

Statement of problemAssessing the quantity and distribution of residual coronal dentin is important in deciding the restorability of endodontically treated teeth. PurposeThe purpose of this in vitro study was to investigate the relationship between the cross-sectional area and location of remaining coronal tooth structure and the fracture resistance of restored teeth after endodontic treatment. Material and methodsFifty-five extracted maxillary premolars received endodontic treatment and crown preparations. The teeth were assigned to 11 groups of 5 teeth according to the number and the location of missing axial walls. Impressions of the prepared teeth were made to fabricate dies. Each die was sectioned 1 mm above the finish line, and the dentin surface area was measured. All teeth were restored with composite resin cores and cast metal crowns. The specimens were thermocycled between 5°C and 55°C for 500 cycles before loading until failure with a universal testing machine. The results were analyzed with 1-way ANOVA and post hoc comparisons. ResultsSpecimens with all axial walls intact around the access cavity had the highest mean fracture strength (1380.5 ±393.9 N). Groups with the palatal and 1 or 2 proximal walls missing showed the lowest mean failure loads (398.4 N ±149.5 N and 344.7 N ±91.2 N). The correlation between the surface area and the fracture resistance was 0.72 ConclusionsFor restored endodontically treated maxillary premolars, a positive linear relationship was found between the remaining coronal dentin surface area and fracture strength. Residual dentin location influences fracture resistance.