RO0111

I 11 research _ mandibular first molars I roots1_2011 _Number of roots A literature review revealed a strong correlation between the presence of a third root in 13% of teeth and the ethnicity of the patients, particularly Asians, Mongolians and Eskimos.18 In order to determine the presence of additional roots visually, several radiographic exposures are required. Initial off-angle radiographs are essential during MFM treatment (Fig. 1a).19, 20 Initially, a file located in the extra root, may give the appearance of aperforation.21 Ifradiographicfindingsarenotdefin- itive, information provided by electronic foramen locators provides reliable readings to make a differ- ential diagnosis and confirm the presence of the additional canal. Walker and Quackenbush conclude that simple analysis of bitewings allows for the detectionofdisto-lingual(DL)rootsin90%ofcases.18 In1990,CarlsenandAlexanderreportedonastudy of398permanentmandibularmolarswithalingually located supernumerary root.22 This macrostructure, the radix entomolaris, presents high variation in regardstoshapeandcurvature.Whenthepositionof this third root is buccal, it is called the radix paramo- Table I_Results of mandibular first lower molar systematic review (Valencia de Pablo et al., 2010). Figs. 2a–f_Root-canal treatment on an MFM: pre-op radiograph (Fig. 2a); working length radiograph (Fig. 2b); post-op radiograph demonstrating a fine projection of sealer between MB and ML (Fig. 2c); working length radiograph of middle mesial canal (Fig. 2d); post-op, ortho-radial radiograph (Fig. 2e); post-op, off-angle radiograph demonstrating three canals treated on mesial root (Fig. 2f). Number of roots Numberofmolarsstudied 18,781 3-rooted molars in % 13 % (2,450) Total number of canals Numberofmolarsstudied 4,745 61.3 % 3 canals 35.7 % 4 canals 0.8 % 5 canals Number of canals in mesial root Numberofmesialrootsstudied 4,535 3.3 % 1 canal 94.2 % 2 canals 2.6 % 3 canals Mesial and distal roots. Canal system configuration Type I (1-1) Type II (2-1) Type IV (2-2) Type VIII (3-3) Numberofmesialrootsstudied 4,331 35 % 52.3 % 0.9 % Numberofdistalrootsstudied 2,992 62.7 % 14.5 % 12.4 % Number of foramina in mesial and distal roots 1 foramen 2 foramina 3 foramina Numberofmesialrootsstudied 4,817 38.2 % 59.2 % 1.6 % Numberofdistalrootsstudied 3,378 77.2 % 22.2 % Intercanal communications. Type V isthmuses Mesial root Distal root Numberofmolarsstudied 1,615 54.8 % middle & apical 1/3 20.2 % middle 1/3 Table I Fig. 2a Fig. 2b Fig. 2c Fig. 2d Fig. 2e Fig. 2f