Discussion - Conclusions - References.
The variability of the root canal system of multirooted teeth represents a challenge to both endodontic diagnosis and treatment. The preoperative awareness of potential anatomic variations is essential for the success of the endodontic treatment. The only way to detect root canal morphology and anatomy is the use of a preoperative radiograph and an additional radiographic view from a 20-degree mesial or distal projection. In this respect, it becomes clear that extreme variations in root fusion are difficult to ascertain with radiographs.
The present cases demonstrate a variation in the root canal anatomy of the maxillary first molar, which has only been reported twice in the endodontic literature (Newton & McDonald 1984, Dankner et al. 1990). From the anatomical structure of these teeth on the radiograph alone, it cannot be concluded whether the distal roots are the result of total fusion of the distobuccal and palatal roots and/or canals, as has been previously described (Dankner et al. 1990). The anatomy of the floor of the pulp chambers (Figs 10b, 14) of the extracted teeth, however, reflected the general topography of the canal orifices of a maxillary first molar, but, with a distortion of the anatomy of the pulp chamber. Examination (Figs 10, 13) and sectioning (Figs 10, 11, 4, 15) of the two extracted teeth clearly demonstrated that the distal root portion was indeed a fusion of a palatal and distobuccal root. Another finding was that the mesiobuccal root was well developed and that, in the extracted teeth, two mesiobuccal canals were present in both cases.
The impression that anatomical aberrations appear frequently contralaterally (Sabala et al. 1994) cannot be confirmed or refuted in the present cases, due to a lack of contralateral teeth.
In order to quantify the presence of this particular canal aberration, the anatomy of 2175 root-filled maxillary first molars treated during the last 10 years was evaluated radiographically; the incidence of C-shapes was 0.091%. However, this percentage is only an estimate and cannot be taken as the true prevalence in the general community. A review of the available literature has mentioned C-shapes in the distal portion of the pulp chamber in only two case reports and in no endodontic text books. A more recent article by Al Shalabi et al. (2000) mentions a fusion of the distobuccal and palatal root in one of 83 extracted maxillary first molars in an Irish population. In relation to the present report, it is unfortunate that there is not a more precise description of the particular configuration than the reference to the Vertucciâ€™s Classification (Vertucci 1984) as type II (two canals fusing into one canal in the apical area). On the other hand, the incidence of a connection between the distobuccal and the lingual root component has been described in a study of one-rooted maxillary second molars (Carlsen et al. 1992) as 7.69%. In an examination of 309 Chinese maxillary second molars, C-shaped root canals were encountered at a frequency of 4.9% (Yang et al. 1988). These canals, though, probably corresponded to both mesial and distal C-shapes. The Chinese frequencies were also derived from three-, two- and one-rooted maxillary second molars, whereas the Danish frequencies were from material that contained only one-rooted maxillary second molars. Ethnically related differences in the frequencies of number of root canals have also been reported (Trope et al. 1986, Walker 1988a,b) and therefore frequency differences are to be anticipated.
- The cases presented in this report demonstrated C-shaped root canal morphotypes in maxillary first molars, whereas this configuration is classically reported in mandibular molars.
- The radiographic outline of the combined palatal and distobuccal roots was not clear at any point during treatment.
- On the basis of the root structure and cross-sections of two extracted maxillary first molars, it can be concluded that the C-shape in the distal portion of the pulp chamber results from a fusion of the distobuccal and palatal roots.
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