Fracture Resistance of Permanent Teeth Restored with Different Layering Techniques after Conventional Access Preparation in vitro Study

A BSTRACT Background: Polymeriztion shrinkage stress of composites is the cause for majority of composite failures. Incremental layering of composites helps in reducing the stress associated with polymerization shrinkage. Composites restoration by themselves can be conservative post endodontic restorations in comparison with full coverage restorations. Thus restoring conventional access with composites with different layering techniques could reduce shrinkage stress and improve fracture resistance of endodontically treated teeth. Aims and Objectives: This study aimed to compare the effect of different layering techniques on the fracture resistance of permanent teeth with conventional access cavity preparation. Materials and Methods: In this institutional committee approved (REF:IEC/TDCH/089/2023) vitro experimental study, 105 Maxillary premolar teeth were randomly divided into five groups. Each group consists of 21 teeth. Group 1 consisted of unprepared teeth, the positive control. conventional access cavity preparation was done in the remaining 84 teeth.21 teeth after access cavity preparation did not receive any restoration and were designated as group 2 (negative control) and group 3 ( n =21)was restored with sonic bulk fill composite resin. Group 4 ( n =21 ) was restored with a nanohybrid composite using the horizontal layering technique. Group 5 ( n =21) was restored with nanohybrid composite resin using the oblique layering technique of 2-3increments. Curing was done in all the 3 groups according to the manufacturer’s instructions. Fracture resistance was measured using the universal testing machine at a crosshead speed of 1mm/ min. Data were tabulated on an Excel sheet and analyzed using one-way ANOVA followed by post hoc analysis using Tukey HSD. Results: One-way ANOVA showed that there is a statistically significant difference in the fracture resistance of teeth restored using different layering techniques ( P =0.05 ). Tukey HSD post hoc analysis revealed that teeth restored with the layering technique possessed better fracture resistance than the bulk fill and control groups. Conclusions: Horizontal and oblique types of layering showed better fracture resistance than the bulk-fill composite resin.