الفهرس 
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Abstract
This study was carried out to evaluate and compare the fracture resistance of endodontically treated anterior teeth restored by two post systems in the presence of different ferrule lengths.
The crowns of forty human maxillary central incisors were removed at the cement-enamel junction and the roots were endodontically treated with a crown down technique. Each root was embedded in autopolymerizing resin with a 0.2-mm layer of silicone impression material to simulate the periodontal ligament.
An acrylic resin block was made by a specially designed split copper mould. To ensure an accurate and exact vertical and centralized position of the root in the acrylic block, a specially device: ”Axio-meter” was constructed to properly fix each root in an exact vertical direction.
Forty samples were equally divided into 2 groups according to the modalities of glass fiber post used. The first group was restored with a ready- made glass fiber post and core. The second group was restored using a ready- made glass fiber post. This was followed by the construction of a composite core. Each group was subdivided into four subgroups according to ferrule length. The first sub-group without ferrule, while the second and third and the fourth sub-groups was 1, 2.3 mm ferrule length, respectively.
Post space preparation for all teeth was carried out by using an axio drill, and then prefabricated fiber posts were cemented with dual- polymerizing resin cement. For the first group no need for core buildup .To fabricates the core for the second group, the composite resin cores were standardized using a core forming matrix.
Finally ceramic crown was constructed. All crowns were cemented with glass-ionomer cement. A Universal Testing Machine LRX-plus was used to apply load at a crosshead speed of 0.5 mm/ min at 135° to the middle third of the palatal surface of the centrals until failure occurred
The results have shown that no statistical significant differences were detected among the two groups concerning fracture resistance. At the same time, there was significant difference within groups. Fracture resistance results for both groups shown that the fracture resistance means value for the subgroup F3 was significantly greater than for the sub groups (F2, F1 & F0). The latter recorded the least values.