182 JDMT, Volume 8, Number 4, March 2019 Stress distribution in premolars Original Article Stress Distribution in Four Restorative Methods in Endodontically Treated Maxillary Premolar: A 3D Finite Element Analysis Alireza Daneshkazemi 1 , Mohammad Mehdi Jalili Bahabad 2 , Rahele Mirseifinejad 1 , Mohammad Hosein Amirzade Iranaq 3 , Elnaz Karimian 4 1 Associate Professor, Cosmetic and Restorative Department, Yazd Dental School, Yazd University of Medical Sciences, Yazd, Iran 2 Associate Professor, Mechanical Engineering, Yazd University, Yazd, Iran 3 Universal Network of Interdisciplinary Research in Oral and Maxillofacial Surgery (Uniroms), Universal Scientific Education and Research Network (Usern), Tehran, Iran 4 Post Graduated Student, Cosmetic and Restorative Dentistry, Mashhad Dental School, Mashhad University of Medical Sciences, Mashhad, Iran Received 23 May 2019 and Accepted 7 October 2019 Abstract Introduction: the Restoration of endodontically treated teeth is critical, and the Awareness of stresses developed by oblique and vertical forces in restorative methods take a great role in treatment plans. Due to the anatomical shape and inherent form of the stress distribution premolars, could be lost by fractures. Some fractures such as vertical fracture which is probable in endodontically treated teeth, makes the teeth a candidate for extraction and other surgical procedures. According to this fact that the dental restorations should be conservative, the aim of this study was to determine stress distribution using four composite restorative methods. Methods: Endodontically treated maxillary second premolars were restored with composite resin using four methods. For restoration, the models representing standard Mesio-occlusal-distal (MOD) restoration, cusps capping with thickness of 1 and 2mm, and the use of woven fiber in occlusal part, were prepared. The effects of the different restorative approaches on stress distribution were analyzed using three-dimensional finite element stress analysis. Results: the highest stress rate was observed in MOD tooth restoration and the amount of stress in natural parts of the tooth in woven fiber was found the lowest. Conclusion: The simulation results show that in all models, oblique forces caused more stress than vertical forces. Moreover, there was a slight difference between different types of restorations regarding the magnitude of stress; however, the results obtained from this study showed that woven fiber could partly reduce stresses. Keywords: Endodontically Treated, Finite Element Analysis, Restorative Dentistry, Resin Composites, Woven Fibers -------------------------------------------------------- Daneshkkazemi AR, Jalili Bahabad MM, Mirseifinejad R, Amirzade Iranaq MH, Karimian E. Stress Distribution in Four Restorative Methods in Endodontically Treated Maxillary Premolar: A 3D Finite Element Analysis. J Dent Mater Tech 2019; 8(4): 182-189. Introduction The Restoration the endodontically treated teeth is a critical step in successful treatments. Sometimes, endodontically treated teeth may fracture because of normal functional forces. The best predictor for this type of treatment’s success is the amount of remaining tooth structure (1).the preparation of endodontic access cavities and removal of the marginal ridges negatively affect the fracture resistance of endodontically treated teeth. Moreover, other changes, such as dehydration and collagen cross- linking alterations can affect the fracture resistance (1, 2). Posterior teeth, particularly maxillary premolars, are more susceptible to cusp fracture under occlusal loads due to their anatomic form (3). In recent years, the patient's demand for tooth colored restorations has increased; and the advances in resin based composite technology have indicated them as a good candidate for large restorations (4).