Impact of deep margin elevation on premolar endo-crown’s fracture resistance after thermocycling: an in vitro study

Deep Margin Elevation (DME) is a restorative technique that lifts deep proximal cavities, allowing for better restoration margins. The effect of DME materials on the fracture resistance of premolar endocrowns is not well understood. This study compared the fracture resistance of premolar endocrown employing two DME materials, SDR flowable composite and resin-modified glass ionomer (RMGI), after thermocycling. 54 endodontically treated premolars were assigned into three groups (n = 18) and prepared to receive polymer infiltrated ceramic (PIC) endocrowns. The cervical margins of the control group (E1) were set 2 mm below the cemento-enamel junction (CEJ) and restored directly with Endocrown. Group E2: Endocrown was used to reconstruct the teeth after a deep margin was raised to a height of 1 mm above the CEJ using flowable composite. Group E3: teeth were rebuilt as in the E2 group, and a deep margin was raised with RMGI. Following cementation, the samples underwent 10,000 cycles in two water baths with varying temperatures (5-55). Next, Standardized testing procedures were used to evaluate the fracture resistance. After thermocycling, Group E2 displayed the greatest mean fracture load value (621 to 833N). The group E3 values were found to be between (577 and 728 N), which was not significantly different from the values of group E1. SDR-based restorations would show improved durability compared to RMGI-based restoration. When isolation is possible, endocrowns made with the combination of SDR and PIC endocrowns may offer promising results without turning to more surgical treatment procedures.