Comparison of compression resistance of endocrone restorations prepared with two different material

Purpose: The aim of our study is the comparison of the compressive strength resistance of endocrown restorations with different cavity depths prepared from two different materials with CAD/CAM technique. Material and methods: In our study, a total of 40 extracted human lower first molar teeth were used. Standard root canal treatment was applied to the teeth and endocrown preparation was made. Endocrowns were randomly divided into two groups of 20 samples in each according to the CAD/CAM material used (Lithium disilicate ceramic IPS e.max-CAD, polyetheretherketone (PEEK). In addition, a total of 4 groups were formed by division of each group into 2 groups with a central retention cavity depth of 2 mm (n = 10) and 4 mm (n = 10). The restorations were cemented to the teeth using chemical polymerized Super-Bond C&B (Sun MedicalCompany, Kyoto, Japan) resin cement and samples were kept in distilled water at 37 ° C for 24 hours. All samples were subjected to thermo cycling for 5000 cycles in water baths between 5° C and 55°C. A compressive load was applied with universal testing machine at 45-degree angle to the long axis of the buccal cusp with a speed of 0,5 mm/min until the fracture occurred. The maximum fracture resistance (Newton) values of the restorations were recorded. The fracture modes of the samples were examined and photographed. The data obtained were analyzed with IBM SPSS Statistics Version 21 package program. Mann Whitney U and Kruskal Wallis H Test were used to examine the differences between groups. Result: There is a statistically significant difference between the materials in terms of fracture values (p <0.05). Lithium disilicate endocrowns (848.4±90.34 N) were ascertained to have higher fracture resistance compared to polyetheretherketone endocrowns (507±90.85 N) group. In addition, there is a statistically significant difference between the groups in terms of fracture values according to the cavity depth (p <0.05). The refraction value of lithium disilicate endocrowns with a cavity depth of 4 mm (912.8±68.22 N) is higher than that of lithium disilicate endocrowns with a cavity depth of 2 mm (784±57.95 N), PEEK endocrowns with a cavity depth of 2 mm (498.7±92.61 N) and PEEK endocrowns with 4 mm cavity depth (515.3±93.24 N). Conclusions: It has been found that lithium disilicate endocrowns show higher fracture resistance than polyetheretherketone endocrowns. When the relationship between the cavity depth and the groups was examined, it was concluded that the fracture strength increases as the depth of the cavity increases.