%0 Journal Article %T Healing of an Extensive Periradicular Lesion Subsequent to a Proper Endodontic Treatment of a Mandibular First Premolar with Complex Anatomy %A Hengameh Ashraf %A Payam Paymanpour %A Maryam Mojtahed Bidabadi %A Reihaneh Hajrezai %J Case Reports in Dentistry %D 2013 %I Hindawi Publishing Corporation %R 10.1155/2013/972093 %X Long-term success of endodontic treatment is strictly dependent on proper shaping and cleaning of the root canal system followed by obturation of entire prepared space. Anatomical variations should be considered during radiographic and clinical evaluation as parts of endodontic treatment. A mandibular premolar with three canals is quite rare and such a tooth requires special canal preparation and obturation techniques. An astute clinician should identify different canal configurations and treat them endodontically well, because presence of an untreated canal could be a reason for failure of endodontic treatment. This paper describes the conventional orthograde endodontic therapy on an unusual mandibular first premolar with three root canals. 1. Introduction A thorough knowledge of anatomy and morphology of root canal system is essential for a successful root canal treatment. Bear in mind that parallel buccolingual radiographs may not always determine correct morphology of tooth. A two-dimensional radiographic view of a three-dimensional tooth, poses serious problems for anatomical assessment of a root canal system that need to be treated. Different horizontal angulations of X-ray cone are considered worthwhile adjuncts to clarify hidden aspects of root canal system. Because of anatomical variations, mandibular premolars are difficult for endodontic treatment and a higher failure rate is expected. As we know, main purpose of endodontic therapy is to prevent or resolve periradicular periodontitis. Periradicular radiolucencies develop depending on the balance between microbial virulence factors and host defenses [1]. A primary aim of all endodontic procedures, specially cleaning and shaping, is to remove infective microorganisms and necrotic tissues [2]. Considering that canals are often underprepared in apical one-third [3] and root canal systems cannot be completely disinfected [4¨C7], obturation of the prepared root canal space is necessary. Obturation reduces coronal leakage and bacterial recontamination, seals the apex from periapical tissue fluids, and entombs remaining irritants within canal [8]. Division of canals into two or more is a challenging situation for both cleaning shaping and obturation of root canal system that could result in periradicular periodontitis. Clinical exploration is essential to detect division of canal. During formation of the root, the apical foramen of each root has a wide opening limited by the epithelial diaphragm and the shape of the pulp canal is like a wide-open tube [9]. Differentiation of a root into separate %U http://www.hindawi.com/journals/crid/2013/972093/