the main objective of root canal treatment is thorough mechanical and chemical cleansing of the entire pulp space followed by complete obturation with an inert filling material . therefore , it is imperative that aberrant anatomy is identified prior to , and during the root canal treatment of such teeth . in 1974 , vertucci and william described the presence of an independent middle mesial canal in a mandibular first molar . since then unusual canal anatomy associated with mandibular first molar has been reported in several clinical studies / case reports . the present case report describes root canal treatment in a mandibular first molar with three separate root canal orifices and a single exiting foramen . a 20-year old female patient was referred to our department of conservative dentistry and endodontics with the chief complaint of pain in the lower right back tooth since the past 3 days . clinical examination revealed a deep disto - occlusal carious lesion in relation to right mandibular first molar ( tooth # 46 ) . the preoperative radiograph demonstrated a disto - occlusal radiolucency approaching the pulp space and widening of periodontal ligament space in relation to the mesial and distal root apices [ figure 1a ] . a diagnosis of necrotic pulp with symptomatic apical periodontitis was established and endodontic therapy was scheduled . ( a ) preoperative radiograph of 46 , ( b ) intraoral photograph showing three distal canal orifices in access cavity preparation , ( c ) working length radiograph , ( d ) postobturation radiograph , ( e ) postobturation radiograph with 30 degree mesial angulation following local anaesthesia , an endodontic access cavity was prepared under rubber dam isolation on tooth # 46 . examination of pulp chamber floor revealed five distinct root canal orifices : two were detected mesially ( mesiobuccal and mesiolingual ) ; and , three distally ( distobuccal , middle distal and distolingual ) [ figure 1b ] . cleaning and shaping of canals was done , and the canals were dried with absorbent points . the obturation was done by cold lateral compaction of gutta - percha [ figure 1d , e ] . the majority of mandibular first molars have two roots , one mesial and one distal , and their usual root canal distribution is two canals in the mesial root and one or two canals in the distal root . the major variant of root canal system of mandibular first molar is the presence of a middle mesial canal with 1 - 15 % incidence . incidence of three canals in distal root of mandibular first molar in an indian population is 1.7% ; 0.2% in senegalese population ; 1.7% in turkish population ; 0.7% in burmese population ; 1.6% in thai population ; and , in sudanese population 3% incidence has been reported . this case demonstrates a rare anatomical configuration and supports previous reports of the existence of such configuration in mandibular first molars . detailed review of case reports with three canals in the distal root / roots is summarized in table 1 . in this case report , distal root has three distinct root canal orifices with single apical termination , that could be described as type xviii canal configuration according to sert and bayirli supplemental canal configurations of root canal morphology . type xviii canal pattern in distal root of mandibular first molar is previously reported in only one case . diagnostic measures are important aids in location of root canal orifices including multiple pretreatment radiographs , examination of pulp chamber floor with a sharp explorer , troughing grooves with ultrasonic tips , staining of chamber floor with 1% methylene blue dye , performing sodium hypochlorite  champagne bubble test  , visualizing canal bleeding points , and use of dental operating microscope and magnification loupes . review of the case reports with the finding of three or more canals in distal root / roots of mandibular first molar usually , a prudent inspection of the pulp chamber floor by proper visualization allows the clinician to search for additional canals . proper and thorough instrumentation is one of the key factors in the success of endodontic therapy ; therefore , the clinician should be aware of the incidence of these extra canals in the mandibular first molar .
with the increasing number of reports of aberrant root canal morphology , the clinician needs to be aware of the variable anatomy . 
 various case reports have been published with the finding of middle mesial canal in mandibular first molar , however finding of middle distal canal in distal root of mandibular first molar is rare . 
 this case report describes root canal treatment of two rooted mandibular first molar with five root canals ( three in distal and two in mesial root ) , and sert and bayirli type xviii canal configuration in distal root .