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Azerbaycan Saytlari

 »  Home  »  Endodontic Articles 1  »  Root and canal morphology of Thai mandibular molars
Root and canal morphology of Thai mandibular molars
Discussion.



The method of canal staining and root clearing was found to be excellent for three dimensional evaluation of root canal morphology. It was anticipated that examination of the fine details (intercanal communications, lateral canals) would require adequate ink penetration, however, it was found that the quality of clearing was sufficient to visualize such details without staining. In this context, the low prevalence of lateral canals found in this study is surprising, since it is not the result of non-penetration of ink.
In common with other studies using extracted teeth, the sample must be regarded as biased because it is not a random selection and therefore may not be representative of the overall population.

Mandibular first molars with three roots.
The prevalence of three roots in Thai mandibular first molars (13%) falls within the range seen for other Mongoloid populations (Somogyi-Csimazia & Simmons 1971, Curzon 1974, Walker & Quackenbush 1985). It is slightly lower than the figure (19%) reported by Reichart & Metah (1981) for a Thai population, which may reflect variations in the sample, but considerably higher than in white populations (Vertucci & Williams 1974). The additional root was found on the lingual aspect of the main distal root and has been regarded as a genetic trait rather than a developmental anomaly (Walker 1988a). The nature of this additional root is variable, ranging from a short conical extension to a full-length root, with pulp extending into the root even when it is short (Reichart & Metah 1981); it can occur unilaterally or bilaterally (Somogyi-Csimazia & Simmons 1971). Radiographically, a third root should normally be readily evident in about 90% of cases (Walker & Quackenbush 1985) but occasionally may be difficult to see because of its slender dimensions. Additionally, a file placed in such a root may give the artifactual appearance of a perforation. In such instances, an angled view (vertically and horizontally) may be helpful (Somogyi-Csimazia & Simmons 1971).
The presence of a third root indicates that there will be two distal canals in the tooth. The disto-lingual canal will invariably have type I configuration, may exit the pulp chamber with a marked lingual orientation and may have a subtle curve in the buccal direction at its apex. The difficulties in location and negotiation of the narrow additional disto-lingual canal may be a cause of treatment failure. Thirty per cent of mandibular first molars had four root canals, a figure comparable to other studies (Pineda & Kuttler 1972, Vertucci 1984). It is, therefore worth searching for additional orifices after initial preparation and debridement of the pulp chamber and canals is complete. In teeth with two roots, 58% of the mesial roots had a type IV (2–2) configuration, which indicates that in these teeth more mesial canals end in separate foramina than in Caucasian teeth (Vertucci 1984).

Mandibular second molars with C-shaped roots.
C-shaped canals were first documented in the endodontic literature by Cooke & Cox (1979) in three case reports. Later studies of the root canal anatomy of mandibular second molars from Japanese, Chinese, and Hong Kong Chinese populations found a high incidence of C-shaped roots and canals (14–52%). In the present study, the prevalence of 10% in Thai mandibular second molars falls within the lower end of the range for a Mongoloid group (Walker 1988b, Yang et al . 1988, Manning 1990a).
Radiographically, a C-shaped root may present as a single-fused root or as two distinct roots with a communication. Haddad et al . (1999) described four typical images: roots that appear to fuse apically, roots with close proximity, a large distal canal or the blurred image of a third canal in the middle of two roots. In some cases confirmation is necessary by exploring the access cavity, because the canal orifice may present with a C-shape. Additionally, fused and C-shaped roots may present with narrow root grooves that predispose to localized periodontal disease, which may be the first diagnostic indication of this anatomical variant.
Manning (1990b) reported that C-shaped roots most frequently had three canals. Other studies have reported a more diverse range of canal systems in C-shaped roots (Yang et al . 1988, Melton et al . 1991, Haddad et al . 1999). In the present study, the configuration of the canals in one-third of the C-shaped roots was type I (one canal), another one-third had type IV canals (two canals), and the remainder had 3–4 or 2–3 configurations (Table 4).
The pulp chamber in teeth with C-shaped canals may be large in the occluso-apical dimension with a low bifurcation. Alternatively, the canal can be calcified, disguising its C-shape. At the outset, several orifices may be probed that link up on further instrumentation. Radiographically, a file placed in the centre of a C-shaped canal may mimic a perforation through the furcation, especially when there is excessive haemorrhage during a vital pulpectomy (Cooke & Cox 1979). In this situation, the use of a third generation apex locator (i.e. one able to read canal lengths in the presence of electrolytes) should help to distinguish between the two. In a true C-shaped canal, it is possible to pass an instrument from the mesial to the distal aspect without obstruction. In other canal configurations, such passage is impeded by discontinuous dentine bridges (Melton et al . 1991).
Interestingly, the most common root canal configuration in the present study was type IV (two canals, two foramina) in the mesial roots and type I (one canal, one foramen) in the distal roots. This result differs from the studies of Vertucci (1984), Weine et al . (1988) and Manning (1990b), who found the most common configuration to be type II (two canals, one foramen) in the mesial roots. This may be another Mongoloid trait, previously unreported.

Mandibular third molars.
In this study, mandibular third molars were associated with various types of root and canal morphology (Tables 1–5). The findings are, on the whole, comparable with other studies (Pineda & Kuttler 1972). Most of these teeth had two roots which were either separate (68%) or fused (19%). Other root morphologies included three roots (1%), one conical root (1%), four roots (1%) and a surprisingly high prevalence of C-shaped roots (11%). Most of these teeth were also found to have only two root canals (61%).