Evaluation of Complex Mesiobuccal Root Anatomy in Maxillary First Molar Teeth/ Evaluacion de la Anatomia de la Raiz Mesiobucal Compleja en los Primeros Dientes Molares Maxilares.
Mesiobuccal roots of maxillary first molars present complex root and canal anatomy. Due to the wide bucco lingual dimensions of mesiobuccal roots, multiple canals are more common in these roots as compared to the distobuccal and palatal roots (Ahmad & Al-Jadaa, 2014). When treating maxillary first molars, a major cause of endodontic failure is the inability to properly locate, debride, or obturate the additional canals in the mesiobuccal root (Weine et al, 1999).
Cleghorn et al. (2006) reviewed the studies on the morphology of maxillary first molars and showed that 57 % of mesibuccal roots had 2 or more root canals. Hartwell & Bellizi (1982) reported the incidence of additional canals in the mesiobuccal root as being between 40 % and 95 %. In an in vitro study, Baratto Filho et al. (2009) demonstrated that 67.14 % of maxillary first molars had an additional canal.
The occurrence of a third canal in the mesiobuccal root of maxillary first molar was first reported by Acosta Vigouroux & Trugeda Bosaans (1978). In the literature review, three canaled mesiobuccal roots have been reported to occur in 0.2-12.5 % (Ahmad & Al-Jadaa). Although many authors have studied the internal anatomy of the mesiobuccal roots, overall clinical studies (Neaverth et al, 1987; Fogel et al, 1994; Lee et al, 2011; Ahmad & Al-Jadaa; Silva et al., 2014) revealed a lower incidence of 3 canals than the laboratory studies did.
The design of the access cavity is very important in locating the orifice of the additional canals in the mesiobuccal root. Weller & Hartwell (1989) suggested modifying the traditional triangular access cavity design into a rhomboidal shape in order to find the additional canals in the mesiobuccal root. However, detection of the orifice of the additional canals in the mesiobuccal root is often difficult because it is generally covered by a ledge of dentin (Das et al, 2015). To eliminate the obstruction, most endodontists trough with round slow speed burs (Ferguson et al, 2005; Garg et al, 2010) or an ultrasonic tip (Alacam et al., 2008; Kottoor et al, 2011).
There is no evidence to suggest that in studies where the maxillary first molars were investigated by using the clearing technique, access cavity modification and pulpal floor deepening methods were included to find extra canals. The objective of this study therefore, was to further investigate the complex anatomy of mesiobuccal roots, supporting and complementing commonly applied clearing technique by use of access cavity modification and pulpal groove deepening methods
MATERIAL AND METHOD
Three hundred and ninety eight extracted intact human maxillary first molars were used in this study. The teeth had been extracted following appropriate consent procedures and were collected from hospital dental departments in Turkey. The age and sex of the patients was not recorded. Teeth with incompletely formed roots, fracture, caries cavities and root resorption were excluded. Morphological features were considered to confirm that all the studied teeth were maxillary first molars. The teeth were stored in a 10 % formalin solution. They were immersed in a 5 % sodium hypochlorite solution (Sultan, USA) for 30 min to clean out of organic debris or calculus from the surfaces. The traditional triangular shaped access cavities were modified into a more rhomboidal shape. Modified access cavities were prepared with a high-speed hand piece. After access cavities were prepared, a groove approximately 1 mm in depth was made along the floor of the pulp chamber lingual to the mesiobuccal canal orifice following the developmental groove between the mesiobuccal and palatal canals by using a round slow speed bur. Indian ink was injected in both the canal orifices of mesiobuccal roots and into the groove between mesiobuccal and palatal canals with the use of a 22 gauge syringe. The teeth were decalcified in a 10 % hydrocloric acid solut?on (Merck, Germany) which was followed by dehydration with a 70-99 % alcohol solution (Kimetsan, Turkey). To obtain transparent teeth, dehydrated stained teeth were stored in methyl salicylate solution (Sigma, Germany). The ink-dyed mesiobuccal root canal systems were inspected using a stereomicroscope (Olympus SZ-PT, Japan) at x10 magnification and photographed at x 3.5 magnification. The root canal systems were classified according to Vertucci's classification (1984).
In this study, in the mesiobuccal roots the incidence of one canal was 30.90 %, two canals was 62.07 %, three canals was 7.03 %. In twenty five (6.28 %) of the mesiobuccal roots, 8 root canal types, which are not included in Vertucci's classification, were seen (Table I). All these root canal types had three root canals (Figs. 1A-H).
Table II shows details of the roots with lateral canals and transverse anastomoses. Lateral canals were generally found in the apical third of the roots. Of the 398 roots, 7.54 % had lateral canals. The frequency of roots showing more than one lateral canal was only 1.25 % (Fig. 2). Transverse anastomoses were generally found in the middle third of the roots. 23.87 % of the roots had transverse anastomoses. Of the 398 roots, 6.03 % had apical deltas
The clearing technique used in this study has considerable value in the study of root canal anatomy by providing a three-dimensional view of the root canal system. This technique also renders it unnecessary to gain physical access into the specimens with instruments, thus retaining the original form and the shape of the canals (Vertucci, 1984). Even though different techniques have been used in root morphology studies, the canal staining and clearing technique is generally considered the gold standard method in these studies (Vertucci; Alavi et al, 2002). This technique is simple, nondestructive and accurate.
It is a challenge for clinicians to treat extra canals in the maxillary molars. The difficulty in identifying and treating these additional root canals may cause treatment failures. The clinician has a responsibility to identify additional canals particularly in maxillary molars, and the utmost care should be taken in recognizing and treating these extra canals. By using modern diagnostic technologies such as, dental operating microscopes, magnification loupes, ultrasonic tips and CBCT, detection of additional canals has become much easier (Ala?am et al.; Kottoor et al., 2011).
The establishment of adequate access to the entire pulp chamber is the most important step in successfully locating the additional canals in the mesiobuccal root. In our study (7 %), although a similar technique was used, the incidence of three canals was higher than in other studies (1-2.2 %) which used the clearing technique (Vertucci; Al Shalabi et al., 2000; Ng et al., 2001; Alavi et al.; Sert & Bayirli, 2004). This result is higher than those in previous studies. The more frequent observation of three canals can be explained by modified access cavity preparation and deepening of the pulpal floor in addition to the large sample size and the high clarity of the samples.
The morphology studies showed that the mesiobuccal root of the maxillary first molar has a rather complex morphology. The prevalence of two canals in the mesiobuccal root of maxillary first molars in this study closely coincides with the findings ofNeaverth et al., Alavi et al., Park et al. (2009) and Kim et al. (2013).
Ng et al. found two additional configurations in a more in depth morphology study of maxillary molar teeth having three canals (3-2, 2-3). These canal configurations were also observed in our study. Alavi et al. also reported one configuration (1-3-1) which was not classifiable in Thai maxillary first molars. Sert & Bayirli reported (3-21) and (2-3-2-1-2) canal types which were not classifiable. A (3-2-1) canal configuration was the most commonly seen three canal configuration in our study.
Kim et al. found three additional types in a microcomputed tomography study of the mesiobuccal root of the maxillary first molar (1-3) (2-3-2-3-2) (2-3-4-3-2). A (1-3) canal configuration was also reported in our study. In this study, 61.4 % mesiobuccal roots had two canals and 12 % had three or more canals. The incidence of three canals was higher than in our study. This is probably due to the different technique that was used to analyze the root canal configuration.
In the present study, in twenty five (6.28 %) of the mesiobuccal roots, 8 root canal types, which are not included in Vertucci's classification were seen. Three pCT studies (Gu et al., 2011; Verma & Love, 2011; Kim et al.) reported a high incidence of non-classifiable configurations which could not be categorized using Vertucci configurations, such as those in our study. Although mCT techniques allowed observations of the complexity of the root canal structures with greater accuracy, the technique is expensive, time consuming, and suitable only for laboratory use on a limited number of teeth.
In the present study, the prevalence of lateral canals was 7.54 % in the mesiobuccal root. This prevalence is somewhat less than the prevalence reported by Vertucci, Sert & Bayirli and al Shalabi et al. but closely agrees with the percentages reported by Alavi et al. and Ng et al. Ninety-six per cent of the lateral canals were found in the apical third area of the root, a result similar to that of Al Shalabi et al., Sert & Bayirli, Gu et al. and Verma & Love.
The prevalence of transverse anastomoses between canals in the mesiobuccal root was 23.87 %. This prevalence is less than the prevalence reported by Vertucci, Al Shalabi et al. and Sert & Bayirli. As the techniques were similar, this difference is probably due to the large sample size we used. The inter canal communications were generally located in the middle third of the root, consistent with the findings of the other morphology studies (Vertucci; Al Shalabi et al.; Sert & Bayirli; Gu et al.; Verma & Love).
The establishment of adequate access and deepening of the pulp chamber floor increased the probability of locating the third canal in the mesiobuccal root of maxillary first molars.
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Caption: Fig. 1 Non-classifiable configuration types that are not included in the Vertucci classification. Fig. 1A Type 3-2-1; Fig. 1B Type 3-1; Fig. 1C Type 3-2; Fig. 1D Type 3-1- 2; Fig. 1E Type 3-2-1-2; Fig. 1F Type 3-2-3-2; Fig. 1G Type 2-3-2 ; Fig. 1H Type 1-2-3.
Caption: Fig. 2. Lateral canals in the apical third.
Table I Number and percentage of canal system types of Vertucci classification and the additional types. Vertucci's Canal Morphology Roots n (%) Type I 123 (30.90%) Type II 109 (27.39%) Type III 3 (0.75%) Type IV 103 (25.88%) Type V 12 (3.02%) Type VI 17 (4.27%) Type VII 3 (0.75%) Type VIII 3 (0.75%) Total 373 (93.72%) Additional Types Roots n (%) 3-2-1 6 (1.51%) 3-1 3 (0.75%) 3-2 4 (1.01%) 3-1-2 2 (0.50%) 3-2-1-2 3 (0.75%) 3-2-3-2 1 (0.25%) 2-3-2 1 (0.25%) 1-2-3 5 (1.26%) Total 25 (6.28%) Table II Number and locnation of lateral canals, t ransverse anastomoses and the occurrence of apical deltas. No. of roots Cervical Middle Apical Lateral canals 30 -- 3 26 7.54% 0.75% 6.53% Transverse Anastomoses 95 17 26 9 23.87% 4.27% 6.53% 2.26% 24 Apical Deltas 6.03% Location Cervical+ Cervical Middle+ Middle +Apical Api cal Lateral canals -- -- 1 0,25 Transverse Anastomoses 15 6 17 3.77% 1.51% 4.27% Apical Deltas Number Cervical+Mid 1 2 3 and dle+Apical over Lateral canals -- 25 2 3 6.28% 0.50% 0.75% Transverse Anastomoses 5 51 38 6 1.26% 12.81% 9.55% 1.51% Apical Deltas