incompetence in locating , cleaning and shaping or obturating the complete root canal system causes primary and post - treatment infections which often lead to endodontic treatment failures . however , the most significant reason for the root canal treatment failure is insufficient knowledge about the root canal morphology and its variations .
this is because such unexplored areas of root canal system remain unaffected by instruments and antimicrobial substances and form the seat for the persistent infection .
thus , it is critical to assess the numerous morphological variations of the root canal system before initiating the endodontic procedure .
however , certain internal and external morphological variations in the mandibular canine like single or bifid roots with two or three canals have been reported in the literature . till date , no case report on management of two rooted three canaled mandibular canine with a fractured instrument has been reported in the literature . in the documented case ,
dental operating microscope is used to bypass the fractured instrument in the middle canal of a three canaled mandibular canine with the patients consent .
a 38-year - old healthy asian woman was referred to the endodontic clinic by a general dentist .
the patient presented to her dentist with a severe pain in left mandibular region ten days ago .
the dentist initiated the root canal treatment in left mandibular canine ( tooth # 22 ) . during the cleaning and shaping procedure , an iso # 10 k - file
the dentist could not bypass the fractured instrument and hence the case was opted for the referral . on clinical examination , tooth # 22 did not appear to have any coronal morphological variations and was identical to its right counterpart except it was mesially rotated .
it was tender to percussion without any evidence of mobility , swelling or sinus tract .
careful pre - operative radiographic examination revealed a two rooted three canaled ( i.e. buccal , middle and lingual canals ) mandibular canine with a fractured instrument in the middle canal [ figure 1 ] .
buccal ( a ) , middle ( b ) and lingual ( c ) with a fractured instrument in the middle canal prior to the initiation of root canal treatment , patient was explained about the aberrant root canal morphology and presence of a separated instrument in the middle canal .
patient was administered local anesthetic solution with adrenalin ( 2% lidocaine with 1 : 100000 epinephrine , lox 2% neon lab , india ) . under rubber dam isolation ( hygienic , coltne whaledent inc .
, usa ) , access opening was re - defined with the help of ultrasonic tips ( pro ultra endo tips no . 2 and 3 , dentsply maillefer , new york , usa ) .
careful clinical explorations of access opening with a dg-16 endodontic explorer ( hu - friedy , chicago , il , usa ) revealed two root canal orifices in bucco - lingual direction and were present more towards the buccal side .
moreover , a bleeding point was noted lingually at the end of a developmental fusion line indicating the location of unexplored third root canal orifice .
troughing the developmental fusion line lingually with ultrasonic tips under a dental operating microscope ( carl zeiss surgical gmbh , oberkochen , germany ) revealed a third root canal orifice [ figure 2 ] .
all three root canal orifices  buccal ( a ) , middle ( b ) and lingual ( c ) present alongside the developmental fusion line ( d ) are located with the help of ultrasonic tips and dental operating microscope all the three root canal orifices were coronally pre - flared using a nickel - titanium ( niti ) protaper sx rotary file ( dentsply maillefer , ballaigues , switzerland ) with a brushing outstroke action to improve the straight - line access .
dental operating microscope was used to visualize the fractured instrument present in the apical third of the middle canal . the maneuver to bypass the instrument was initiated in the presence of glyde ( dentsply maillefer , tulsa , ok ) by wedging an iso # 8 k - file ( dentsply maillefer , tulsa , ok ) between the fractured instrument and the canal walls with frequent radiographic checks .
the file was then advanced and withdrawn repeatedly in an attempt to widen the canal space and loosen the retained fragment from the root canal .
so it was decided to prepare the entire root canal system , and incorporate the fragment into the obturation .
the space created between the fractured instrument and the canal walls was enlarged with the larger sized files sequentially till iso # 25 k - file .
working lengths for all three canals were determined with an apex locator ( root zx ; morita , tokyo , japan ) and were confirmed radiographically [ figure 3 ] .
all three canals were prepared using protaper niti rotary instruments ( dentsply maillefer , ballaigues , switzerland ) according to manufacturer 's recommendations .
protaper s1/s2 rotary files were used with brushing outstroke action . finishing files f1 and f2
irrigation was performed using triple distilled water , 2.5% sodium hypochlorite solution ( cmident , india ) and 15% edta ( largal ultra , septodont , saint maur des fosses , france ) .
2% chlorhexidine digluconate ( r4 , septodont , saint maur des fosses , france ) . were used as the final irrigant .
the canals were dried with sterile paper points ( dentsply maillefer , tulsa , ok ) .
the access cavity was sealed temporarily with intermediate restorative material ( irm , caulk dentsply , milford , de ) .
the root canals were again irrigated with triple distilled water to remove the intracanal dressing of calcium hydroxide .
obturation was done by a single cone technique with the use of gutta - percha cones and epoxy resin - based root canal sealer ( ah plus sealer , dentsply maillefer , tulsa , ok ) . in the middle canal ,
tooth was restored using light cured composite resin ( z100 ; 3 m dental products ) .
subsequent follow - up x - ray was taken at 12 months [ figure 4b ] .
working length radiograph with fractured instrument bypassed in the middle canal ( a ) post - obturation radiograph with inclusion of a fractured instrument in the obturation .
essential pre - requisites for a successful endodontic treatment are careful interpretation of pre - operative radiographs , a thorough knowledge and detailed exploration of internal root canal morphology and its divergence under the magnification and illumination .
straight radiograph provides information about the mesio - distal root canal orientation where as angled radiographs ( radiographs at two different horizontal angulations ) provide information about the facio - lingual canal position . any attempt to reduce
the required number of radiographs runs the risk of missing information of the complex canal morphology .
furthermore , a careful tracing of periodontal ligament space suggested the presence of two separate roots with three canals .
the access cavity was extended buco - lingually with the help of ultrasonic tips in order to conserve the tooth structure while searching for an extra and elusive canal orifice .
the internal and external morphological variations of the mandibular canine were clearly appreciable from the radiographic and clinical examination in the present case .
hence , cone beam computed tomography ( cbct ) scan was not done to reduce any extra radiation dosages . even though the mandibular canine shows a single root and a single root canal with single apical foramen in about 92.2% of cases , clinicians should always search for any possible extra root or canal .
root canal morphological variations reported in the mandibular canine include two canals and one apical foramen in 4.9% of cases , two canals and two apical foramens in 1.2% of cases and two different roots each one with one canal in 1.7% of the cases . also two distinct case reports of mandibular canine with three canals in one root or two roots were reported in the past .
hence , it is always prudent to consider all anatomical variations in the mandibular canine while performing a root canal treatment .
any pre - determined assumption about the root canal morphology leads to failure to locate any morphological variation , if present .
it hinders the effective cleaning and shaping and creates a nidus of infection that directly compromises the long term prognosis of the tooth . in the documented case , the fractured k - file in the middle canal prevented the negotiation and thorough biomechanical preparation of the canal .
however , the chances of uneventful retrieval of the fractured instrument were not predictable considering the impossibility of visibility of instrument under dental operating microscope , strategic importance of tooth , the location of the instrument and the limited thickness of the root .
success in management of fractured instrument is defined as the complete removal or complete bypass of the fragment without creating a perforation .
hence , decision was made to bypass the instrument under dental operating microscope to enhance the visualization of operating field and to conserve the maximum root structure . during the bypassing maneuver ,
higher magnification was used with frequent radiographic checks to avoid intra - operative complications like root perforation , ledge formation , pushing the instrument more apically etc .
so , a clear understanding of pulp anatomy and its variations is essential if effective cleaning , shaping and obturation of the pulp space are to be achieved to assure the successful and predictable outcome of endodontic treatment .
mandibular canine with variations in number of roots and root canals should be treated without any pre - operative assumptions regarding its typical single rooted and single canaled anatomy .
thus the present case report highlights the endodontic management of an unusual case of mandibular canine with two roots and three canals .
it also highlights the need for use of dental operating microscope and ultrasonics in locating the elusive canal orifices .
so it is important to note the internal and external root canal morphological variations so that similar anatomy may be predicted and managed successfully . sometimes retrieval of a fractured instrument is impossible or undesirable . in these cases , bypassing the instrument under magnification is a valid alternative , which can lead to a favorable outcome as presented in the given case .
 it is important to assess the root canal morphology and its variations before initiating the endodontic procedure . 
 this is because the inability to clean the complete root canal system forms the seat for the persistent infection which ultimately leads to endodontic treatment failure . 
 this case reports the use of dental operating microscope for the successful endodontic management of a two rooted and three canaled mandibular canine with the fractured instrument in the middle canal of a 38-year - old healthy asian woman . 
 this case report highlights the need to use the dental operating microscope and ultrasonics in locating the elusive canal orifices . 
 it is important to note the internal and external root canal morphological variations before starting the endodontic treatment without any pre - operative assumptions about the usual anatomy of the toot . 