Effect of Different Designs of Endodontic Access Cavities and Instrument Taper on the Fracture Resistance - An In vitro Study.

Objective: The aim of the study was to evaluate the effect of different designs of endodontic access cavities and instrument taper on fracture resistance.

Methods: Fifty-six extracted maxillary premolars were divided into three groups. In Group I (Negative control), the samples were left intact. In Group II, traditional cavities were prepared and in Group III truss cavities were prepared. Groups II and III were further subdivided into Subgroup A (no instrumentation), Subgroup B (instrumentation with variable taper files), and Subgroup C (instrumentation with constant taper files) followed by obturation. All samples were restored with composite restoration and subjected to compressive forces using an Instron Universal Testing Machine. Statistical analysis was performed using one-way ANOVA and Tukey's post hoc test.

Results: This showed a significant difference in fracture resistance between Group I and all the experimental groups. A significant difference between Group II A and III A was found. Statistically significant results were obtained II A and II B and II A and II C; III A and IIIB and III A and IIIC. No significant difference was observed in fracture resistance between groups II B and II C and III B and III C.

Conclusion: Ultraconservative cavities showed preservation of biomechanical integrity of the tooth and conservation of fracture strength in comparison with traditional cavities before instrumentation. Instrumentation of ultraconservative and traditional cavities further decreases the fracture resistance of the tooth. However, the type of taper seemed to have minimal effect on the structural and biomechanical integrity of the tooth.