Nashwa M. Khalil, Hayam Y. Hassan And Dalia M. Fayyad,

ABSTRACT
The Present Study Evaluated The Fracture Resistance Of Endodontically Treated Teeth Restored With Two Different Fiber Post Designs (tapered Post And Parallel Tapered End Post) Using Different Irrigating Regimen, 5.25% Sodium Hypochlorite (NaOCl) And 5.25% NaOCl Followed By Ethylene-diamine-tetra-acetic Acid (17% EDTA). Ninety Extracted Human Two Rooted Maxillary Premolar Teeth With Average Length 20�1mm Were Collected. Eighty Specimens Were Divided Into Two Main Groups (n=40) According To The Type Of Irrigant Used During Instrumentation And Ten Specimens Left As Control Groups (five Specimens Were Left Without Preparation As Negative Control Group And The Other Five Specimens Were Prepared Without Post Placement As Positive Control Group) Each Main Group Were Subdivided Into Two Subgroups (n=20) According To The Type Of Fiber Post Design. Specimens Were Mounted And Louds Were Applied With Across Head Speed Of 1mm/min By Universal Testing Machine Till Failure Occurred. Data Were Calculated And Statistically Analyzed. The Results Showed That Irrigant Solution And Post Design Had A Statistically Significant Effect On Mean Fracture Resistance. NaOCl + EDTA Used With Parallel Tapered End Fiber Post Group Showed The Highest Mean Of Fracture Resistance Followed By NaOCl With Parallel Tapered End Fiber Post, Then With Tapered End Fiber Post And NaOCl With Tapered End Fiber Post Showed The Statistically Significantly Lowest Mean Fracture Resistance.