الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Endodontic treatment provides great clinical outcomes in cases of devitalized teeth, It increases the possibility of tooth survival in both esthetic and structural aspects over extended period of time after completion of the treatment. (2)
Endodontically treated teeth that are not restored with permanent restoration after root canal treatment are two to four times weaker, liable to failure of root canal treatment and have high possibility to extract when compared to teeth that are restored with permanent restoration. (2)
Many materials were used over the years to reinforce the endodontically treated teeth especially using post and core material. ideal restoration of the endodontically treated teeth includes two procedures, first procedure includes placement of post and core or core only and second procedure includes placement of final full coverage crown. (2)
Post and core material should withstand occlusal loads, prevent debonding of the post or fracture of the endodontically treated tooth so post it should provide mechanical properties similar to dentin. Therefore, all researches now are interested in post and core materials that have properties close to that of tooth structure like coefficient of thermal expansion, modulus of elasticity, compressive strength and optical properties. (37)
Prefabricated fiber post made from carbon or glass fiber became an alternative to cast metal post in restoration of endodontically treated teeth. Fiber post systems have mechanical properties close to that of dentin resulting in similar patterns of stress as those of intact teeth. Fiber post is more conservative solution as it requires less post space preparation. However, poor adaptation of fiber post in oval canals lead to decreased retention and increased thickness of the cement to fill the space between fiber post and walls of the root canal (4). Stress concentration and excessive deformation could result during function leading to marginal failure due to insufficient post rigidity. (5)
Polyetheretherketone (PEEK) is a thermoplastic polymer that has high mechanical properties and has been used recently in dentistry. It has high biocompatibility, lower reactivity than other materials, doesn’t corode and has low elastic modulus close to that of cortical bone and dentin tissue and this property is the most important property that makes it beneficial in dental prostheses. Due to numerous positive advantages, PEEK material is considered as an alternative to metal supported ceramics that have long been used in dentistry. PEEK can be used for crowns, implants, temporary abutments, implant supported hybrid prostheses and post. (7)
Objective: This in vitro study aimed to assess the fracture resistance of two different types of posts: customized fiber post, custom made PEEK post with core with or without ferrule preparation.
Methods: A total of twenty-eight single rooted human extracted mandibular premolars with approximate similarity in shape and size
and free of cracks or caries were selected for this study. Samples were divided to two groups with ferrule group and without ferrule group followed by coronal decapitation of all samples. Endodontic treatment was performed for all samples followed by mounting of samples in acrylic blocks and then preparation of post space. Each group of the two groups were subdivided into two subgroups, first subgroup received custom made PEEK post and core and second subgroup received customized fiber post and composite resin core. Aging of all samples was achieved using thermocycling and fracture resistance was tested using the universal testing machine.
Results: Both post type and ferrule condition had a significant effect on fracture strength (p<0.001), while the interaction effect was not statistically significant (p=0.790).
Custom PEEK post (740.41±92.41) had a significantly higher fracture resistance value than customized fiber post (440.13±67.61) (p<0.001).
Samples with ferrule (651.68±66.34) had a significantly higher fracture resistance value than samples without ferrule (528.86±60.85) (p<0.001).
Interaction: in with ferrule samples, Custom PEEK post (804.47±72.90) had a significantly higher value than customized fiber post (498.89±12.79) (p<0.001).
In without ferrule samples, Custom PEEK post (676.35±60.12) had a significantly higher value than customized fiber post (381.36±41.02) (p<0.001).