Purpose: The goal of this study was to assess the effect of two different types of resin-based composites used for cervical margin relocation (CMR) on fracture resistance and mode of failure of ceramic MOD-inlay restorations.
Materials and methods: Twenty-four MOD Class II cavities (3 mm in width and 2 mm in depth) were prepared in human first molars to receive indirect E-max CAD ceramic inlays; where mesially proximal boxes extend 2 mm below the cementoenamel junction (CEJ). Prepared cavities were allocated into three groups (n = 8) to perform the cervical margin relocation; Group I: inlay without CMR, Group II: restored with (SDR), Group III: restored with injectable composite. Thermocycling was performed at 5,000 cycles in water bath at (5-55 ˚C) in a standard thermocycling machine. Specimens were subjected to fracture resistance testing using the Universal Testing Machine. Data was statistically analyzed using one-way ANOVA followed by Tukey's post hoc test.
Results: There was a significant difference between different groups (p<0.001). The highest strength value was found in injectable composite samples (1760.88±240.05 N) while the lowest value was recorded by inlay without CMR (906.94±90.66 N).
Conclusion: High-strength injectable is the best base regarding enhancement to fracture resistance.