F. Maggiore,Y. T. Jou & S. Kim
Department of Endodontics, School of Dental Medicine, University of Pennsylvania, Philadelphia, USA.

Introduction.
The goal of root canal treatment is to clean the root canal system as thoroughly as possible and to fill it in all its dimensions (Cohen & Burns 1998). In depth knowledge of the root canal anatomy of each tooth is crucial in order to reach this goal.
The maxillary first molar most commonly has three or four cana , with one canal in both the palatal and distobuccal roots and one or two in the mesiobuccal root. The incidence of a mesiolingual canal has been reported between 18% and 96.1% (Hartwell and Bellizzi 1982, Kulild & Peters 1990). Cecic et al. (1982), Jacobsen & Nii (1994), and Stone & Stroner (1981) found cases of maxillary first molars in which the palatal canal contained one orifice, a bifurcated canal and two separate foramina. Beatty (1984) presented a case of a maxillary first molar with five cana , three of which were located in the mesiobuccal root. Bond et al. (1988) reported a case of a maxillary first molar with six cana : two cana  with separate foramina in the mesiobuccal root, two cana  with separate foramina in the distobuccal root, and two cana  joining in the apical third of the palatal root. Hu mann (1997) presented a maxillary first molar with two distinct cana  in the distobuccal root. Slowey (1979) showed a case of a maxillary molar with two palatal cana  and separate foramina. Martinez-Berna & Ruiz-Badanelli (1983) reported three cases of maxillary first molars with six cana : three cana  in the mesiobuccal root, two in the distobuccal root and one in the palatal root and finally, Wong (1991) reported a case in which the palatal root had a single canal orifice, a trifurcation in the apical third and three separate foramina. This information is summarized in Table 1.

Table 1. Reported canal configuration of the maxillary first molar.


S: separate canalswith separate foramina.
J:Canals joining in the apical one-third.

The present case report describes a case of a maxillary first molar with a canal configuration not yet reported in the literature. This tooth had a trifurcation in the palatal canal in the apical third with three separate foramina, two distinct cana  in the mesiobuccal root and a single canal in the distobuccal root.