الفهرس 
Influence of intra-radicular restorative technique in teeth with flared canals on their fracture resistance and failure mode : In vitro study
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Abstract
Endodontically treated teeth are known to have higher biomechanical failure risk than vital teeth due to loss of tooth structure, decreased fluid contents and subsequent brittleness. Although post and core system is a must when the remaining tooth structure is in sufficient to retain a crown, it cause further weakening to the tooth structure. The problem is magnified in teeth with flared root canal with excessive radicular dentine loss.This study was designed to study the fracture resistance and failure mode of flared endodontically treated teeth restored with different fiber post techniques.A total of 32 freshly extracted intact maxillary central incisors with nearly same dimentions were used in this study. Teeth were divided randomly to 4 groups, one control group, and 3 test groups received the same endodontic treatment, coronal and post space preparation as following: group 1: (n=8) control group, without endodontic treatment. group 2: (n=8) teeth restored with Radix fiber post. group 3: (n=8) teeth restored with Relined Radix post. group 4: (n=8) teeth restored with EverStick post. All posts were cemented using self-adhesive resin cement (RelyX U200). Teeth were mounted on epoxy resin and subjected to load at 135 degree until fracture. Fracture resistance (N) was measured. Shapiro-Wilk test (Ü=0.05) were applied, and failure mode was checked. Regarding the fracture strength, this study showed that the control group recorded a statistically insignificant fracture mean value with all groups except with Radix fiber post groups in which it recorded statistically significant lower fracture mean value. Also both Relined Radix Post group and EverStick Post groups recorded statistically significant higher fracture mean value when compared with the Radix group. However, there is no statistically significant between Relined Radix Post group and EverStick Post groups. Non-relined Radix fiber post showed lower fracture resistance and higher unfavorable failure among tested groups. All groups failed at higher load than normal masticatory forces in upper maxilla