Effect of coronal cement base and its thickness on the fracture resistance of endodontically treated teeth

Objective: To compare the fracture resistance of endodontically treated teeth with mesiodistocclusal (MOD) cavities restored with only composite resin, 3 mm glass-ionomer cement (GIC) base + composite resin, and 5 mm GIC base + composite resin. Materials and Methods: Fifty extracted intact mandibular molars were randomly divided into five groups each including 10 teeth. Group 1: No cavity preparation or endodontic treatment was applied (intact teeth). Group 2-5: Root canals were prepared with step-back technique and filled lateral condensation of gutta-percha and sealer. Group 2: No coronal restoration was achieved. Group 3: Teeth were coronally restored with only composite resin. Group 4: Coronal restorations were performed with composite resin following 3 mm GIC base placement. Group 5: Composite resin placed over 5 mm GIC base. After finishing and polishing, all specimens were kept in an incubator at 37°C in 100% humidity for 24 h and fracture resistance was tested with a Universal Testing Machine. Mean force load for each sample was recorded in Newtons (N). Results were statistically analyzed with one-way analysis of variance (ANOVA) and post-hoc Tukey′s tests. Results: The mean force required to fracture each sample was as follows: Group 1: 2,745.3; Group 2: 325.9; Group 3: 1,958.1; Group 4: 1,756.3; and Group 5: 1,889.1. Fracture resistance of intact teeth (Group 1) was significantly higher than all other groups. Fracture resistance of teeth in Group 2 (not coronally restored) was significantly lower than all other groups. Fracture resistance values of other three experimental groups (Groups 3, 4, and 5) were not significantly different from each other. Conclusion: Placing a GIC base and its thickness did not significantly affect the fracture resistance compared with composite resin alone.