Prevalence of Middle Mesial Canals in Mandibular Molars after Guided Troughing under High Magnification: An In Vivo Investigation

Published:October 30, 2014DOI:



      A limited number of in vivo studies have discussed the prevalence of middle mesial canals in root canal systems of mandibular molars. The reported results have varied between 1% and 25%, with no detailed description of the depth and direction of troughing needed to identify such small canal orifices. The objective of the present study was to determine (1) the prevalence of a middle mesial canal before and after troughing by using a standardized troughing technique, (2) the pathway of the middle mesial canal in relation to the mesiobuccal (MB) and mesiolingual (ML) canals, and (3) its correlation with the patient's age.


      Ninety-one mandibular molars from 87 patients were included in this study. The patient's age and tooth number were recorded. After access cavity preparation, a standardized troughing technique was performed between MB and ML canals to search for a middle mesial canal by using a dental operating microscope. If a middle mesial canal was located, it was recorded as separate or as joining the MB or the ML canals. Results were statistically analyzed by using Z test and logistic regression.


      A middle mesial canal was found in 42 of 91 mandibular molars (46.2%). Six middle mesial canals were located after conventional access preparation (6.6%). The other 36 were located after standardized troughing (39.6%). The results were statistically significant (P < .001). There was a higher tendency to locate the middle mesial canal in second molars (60%) versus first molars (37.5%). Younger patients had a significantly higher incidence of a middle mesial canal (P = .004).


      The middle mesial canal was present in 46.2% of mandibular molars. High magnification, troughing, and patient's age appeared to be determining factors in accessing the middle mesial canal.

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        • Vertucci F.J.
        Root canal anatomy of the human permanent teeth.
        Oral Surg Oral Med Oral Pathol. 1984; 58: 589-599
        • Walton R.E.
        Histologic evaluation of different methods of enlarging the pulp canal space.
        J Endod. 1976; 2: 304-311
        • Barker B.C.
        • Parsons K.C.
        • Mills P.R.
        • Williams G.L.
        Anatomy of root canals: III—permanent mandibular molars.
        Aust Dent J. 1974; 19: 408-413
        • Gulabivala K.
        • Aung T.H.
        • Alavi A.
        • Ng Y.L.
        Root and canal morphology of Burmese mandibular molars.
        Int Endod J. 2001; 34: 359-370
        • de Toubes K.M.
        • Cortes M.I.
        • Valadares M.A.
        • et al.
        Comparative analysis of accessory mesial canal identification in mandibular first molars by using four different diagnostic methods.
        J Endod. 2012; 38: 436-441
        • Karapinar-Kazandag M.
        • Basrani B.R.
        • Friedman S.
        The operating microscope enhances detection and negotiation of accessory mesial canals in mandibular molars.
        J Endod. 2010; 36: 1289-1294
        • Pomeranz H.H.
        • Eidelman D.L.
        • Goldberg M.G.
        Treatment considerations of the middle mesial canal of mandibular first and second molars.
        J Endod. 1981; 7: 565-568
        • de Carvalho M.C.
        • Zuolo M.L.
        Orifice locating with a microscope.
        J Endod. 2000; 26: 532-534
        • Teixeira F.B.
        • Sano C.L.
        • Gomes B.P.
        • et al.
        A preliminary in vitro study of the incidence and position of the root canal isthmus in maxillary and mandibular first molars.
        Int Endod J. 2003; 36: 276-280
        • von Arx T.
        Frequency and type of canal isthmuses in first molars detected by endoscopic inspection during periradicular surgery.
        Int Endod J. 2005; 38: 160-168
        • Baugh D.
        • Wallace J.
        Middle mesial canal of the mandibular first molar: a case report and literature review.
        J Endod. 2004; 30: 185-186
        • Nair P.N.
        On the causes of persistent apical periodontitis: a review.
        Int Endod J. 2006; 39: 249-281
        • Gorduysus M.O.
        • Gorduysus M.
        • Friedman S.
        Operating microscope improves negotiation of second mesiobuccal canals in maxillary molars.
        J Endod. 2001; 27: 683-686
        • Saunders W.P.
        • Saunders E.M.
        Conventional endodontics and the operating microscope.
        Dent Clin North Am. 1997; 41: 415-428
        • Schwarze T.
        • Baethge C.
        • Stecher T.
        • Geurtsen W.
        Identification of second canals in the mesiobuccal root of maxillary first and second molars using magnifying loupes or an operating microscope.
        Aust Endod J. 2002; 28: 57-60
        • Stropko J.J.
        Canal morphology of maxillary molars: clinical observations of canal configurations.
        J Endod. 1999; 25: 446-450
        • Kulild J.C.
        • Peters D.D.
        Incidence and configuration of canal systems in the mesiobuccal root of maxillary first and second molars.
        J Endod. 1990; 16: 311-317
        • Krupp C.
        • Bargholz C.
        • Brusehaber M.
        • Hulsmann M.
        Treatment outcome after repair of root perforations with mineral trioxide aggregate: a retrospective evaluation of 90 teeth.
        J Endod. 2013; 39: 1364-1368
        • Henry B.M.
        The fourth canal: its incidence in maxillary first molars.
        J Can Dent Assoc. 1993; 59: 995-996
        • Gu L.
        • Wei X.
        • Ling J.
        • Huang X.
        A microcomputed tomographic study of canal isthmuses in the mesial root of mandibular first molars in a Chinese population.
        J Endod. 2009; 35: 353-356
        • Peiris H.R.
        • Pitakotuwage T.N.
        • Takahashi M.
        • et al.
        Root canal morphology of mandibular permanent molars at different ages.
        Int Endod J. 2008; 41: 828-835
        • Philippas G.G.
        Influence of occlusal wear and age on formation of dentin and size of pulp chamber.
        J Dent Res. 1961; 40: 1186-1198
        • Tidmarsh B.G.
        Micromorphology of pulp chambers in human molar teeth.
        Int Endod J. 1980; 13: 69-75
        • Shaw L.
        • Jones A.D.
        Morphological considerations of the dental pulp chamber from radiographs of molar and premolar teeth.
        J Dent. 1984; 12: 139-145
        • Hess W.
        The Anatomy of the Root Canals of the Teeth of the Permanent Dentition.
        John Bale Sons and Danielsson, London1925: 36
        • Falk K.W.
        • Sedgley C.M.
        The influence of preparation size on the mechanical efficacy of root canal irrigation in vitro.
        J Endod. 2005; 31: 742-745
        • Reeh E.S.
        • Messer H.H.
        • Douglas W.H.
        Reduction in tooth stiffness as a result of endodontic and restorative procedures.
        J Endod. 1989; 15: 512-516