Ferrule Varlığının ve Yokluğunun; Farklı Endokron ve Estetik Post-Kor Restorasyonların Kırılma Dayanıklılığına Etkisinin, İn Vitro Olarak Karşılaştırılması
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AKSU, İ. The effect of ferrule presence on the fracture strength of different endocrown types and esthetic post-core restorations – An in vitro study. Hacettepe University Institute of Health Sciences, Ph.D. Thesis in Prosthodontics, Ankara, 2017. It is important to use a restoration with high durability and esthetic qualities by evaluating the height and design of the ferrule in the restorative treatment of the posterior endodontically treated teeth. The purpose of this study was; In the presence and absence of 2 mm circumferential ferrule, to evaluate and compare the fracture strength and failure modes of four groups; fiber post-core restorations, monoblock zirconia post-core restorations, standard endocrown restorations and endocrown restorations with intraradicular extension, applied to endodontically treated posterior teeth. Eighty mandibular first and second molar teeth randomly assigned 2 groups (n=40) to create test groups with ferrule (2 mm circumferential) and no ferrule. After the preparation of the teeth according to the ferrule condition, endodontic treatment was performed. Subsequently, 4 subgroups (n = 10) were randomly selected to form these 2 groups (n = 40), fiber post-core, monoblock zirconia post-core, standard endocrown and endocrown with intraradicular extension groups. After preparation of each group, crown restorations of fiber post-core group and all restorations of the other groups were manufactured from pre-sintered zirconia blocks. After completing the sintering phase, all the restorations were cemented with dual cure composite resin cement. The specimens were embedded in acrylic resin blocks 2 mm apical to the cemento-enamel junction. In order to measure the fracture strength of the specimens, a static load was applied with 45 degrees inclination to the long axis of each tooth using a Universal testing machine. Mean fracture strength of group with ferrule and no ferrule were recorded respectively; 619 N and 334 N. In addition to, mean fracture strength of fiber post-core, monoblock zirconia post-core, standard endocrown and endocrown with intraradicular extension groups were respectively; 461 N, 498 N, 412 N, and 532 N. The obtained data were analyzed statistically with One-Way ANNOVA and post hoc Tukey HSD tests. The results for p <0.05 were considered statistically significant. In the absence of ferrule; the fracture strength of the monoblock zirconia post-core group (403 N) was found to be statistically significantly higher than that of the standard endocrown group (229 N). In the presence of ferrule; the fracture strength of the endocrown with intraradicular extension group (730 N) was found to be statistically significantly higher than that of the standard endocrown group (576 N) and fiber post-core group (568 N). 2 mm circumferential ferrule presence; increased the fracture strength of all groups significantly, while the most effective was the fracture strength of the endocrown restorations. When all the study groups were compared, the highest fracture strength results were evaluated at the endocrown restorations with intraradicular extension.