Evaluation of marginal adaptation and fracture strength of endocrowns manufactured with different restorative materials

Endocrowns, that can be applied to endodontically treated teeth with excessive material loss, are a kind of restoration that have a central retention cavity inside pulp chamber and adhesively bond to tooth tissues. With the development of computer assisted design/computer aided manufacturing (CAD/CAM) and the use of new materials in dentistry the interest in adhesive restorations is increasing. In this study, marginal adaptation and fracture strength of endocrowns manufactured with different materials by CAD/CAM and heat-pressure technique are evaluated. For this purpose, mandibular first molar teeth (N = 50) were endodontically treated and the teeth were divided into five groups (n = 10). Endocrowns were obtained from lithium disilicate glass ceramic ingots (GEP) by hot-press technique and feldspathic blocks (GC), polymer infiltrated ceramic network blocks (GE), lithium disilicate glass ceramic blocks (GEC), zirconia reinforced glass ceramic blocks (GS) by CAD/CAM technique. Restorations were semented with dual polymerized resin cement and then subjected to thermocycling (5-55 °C, 6000 cycles). Marginal adaptation evaluated under scanning electron microscope at 200x magnification. Fracture stength test of specimens were done at a Universal Test Machine with a speed of 1 mm/min. Fracture types evaluated under stereomicroscope. Statistical analyzes of the data were performed. Kruskal-Wallis test was used to determine for differences between groups for marginal adaptation and fracture strength. Dunn's test was used for post-hoc test after Kruskal-Wallis test. A statistically significant difference was observed between groups in terms of marginal adaptation (p=0.001). The highest marginal discrepancy values were found in the GEP. There was no significant difference between the other four groups (p> 0.05). A statistically significant difference was observed between groups in terms of fracture strength (p=0.019). Among the five groups, the higher fracture strength values were obtained from GEC, the lowest fracture strength values were obtained from GC. It is concluded that endocrowns manufactured with CAD/CAM show better marginal adaptation and lithium disilicate endocrowns have higher fracture strength values.