Introduction

One of the major causes of failure in endodontic treatment is the impossibility of locating and treating the entire root canal system, a result of the lack of knowledge regarding the dental, internal or external anatomy. ¹
Maxillary molars are the teeth that contain the greatest number of roots, with diverse shapes and formations, which is why their internal canal system is so variable. ²
Any existing root canals that remain undetected by the operator during the entire course of endodontic treatment are a major threat to the failure of treatment. ³
The aim of the current research was to describe the variations in the root canal anatomy of maxillary first molar in a tunisian population using sectioning.

Materials and Methods

In this study, we used 98 maxillary second molars that have been extracted mainly for periodontal reasons. The teeth were stored in a sodium hypochlorite solution diluted to 5% during 3 days and then washed in running water and dried.
Each tooth is macroscopically examined to determine the number of roots and grinded progressively at the root surface to highlight the path of the root canals.
Canal number and configurations are observed and analyzed using sections:

-Mesio buccal and disto buccal root: bucco-lingual sections
-Palatal root: mesio-distal sections.

Results

1- Number of roots by tooth (Table 1)

2- Number of canals by root (Table 2)

3- Canal configurations (Table 3)

4- Different canal configurations observed at the mesio buccal root (Figures 1, 2)

5- Different canal configurations observed at the disto buccal root (Figure 3)

6- Different canal configurations observed at the lingual root (Figure 4)

Discussion:

Number of roots

In the present study, 93 % of maxillary first molars were 3 rooted. Our results are similar to the findings of Libfeld ⁴ (90.6%), Neelakantan ⁵ (93.1%) and Sert ⁶ (91.27%).
We found 5.8% 2 rooted second maxillary molars. For consulted studies, the percentage was from 0% ⁵ to 21.86%. ⁷
We found 1.1% one rooted molars which is close to the majority of studies. ^7,4,8,6 Gu Y ⁷ found larger percentage (14.11%).
We didn’t find 4 rooted second maxillary molars which is similar to the study of Neelakantan.⁵ Other studies found percentages that do not exceed 1.4% ⁸ (table 4).

Internal morphology 

• Mesio buccal root

– Number of canals:

We found in our study that 97.5 % of cases have a single canal and 2.4 % have 2 canals.
The frequencies of 2 canals varied from 19.7% according to Al-Fouzan ⁹ to 93.7% according to Kulild ¹⁰; these results are not consistent with ours. These differences may be due to the variety of the used techniques.
This root can have more than two canals according to Ozcan et al. ¹¹ who reported a case of a maxillary second molar with 3 canals in the mesio buccal root and Caliskan et al. ¹² who showed that 16% of second maxillary molars had 3 canals in this root (Table 5).

– Canals configurations:

Our study showed that 97.5 % have type I configuration and 2.5 % have type II configuration. We have not found the types III, IV and V.
There is great variability in the results of literature; the percentage of type I varied from 34%¹⁴ to 86,9% ¹⁸; type II from 1, 8% ¹⁸ to 34% ¹⁴ and type III from 0% ¹⁴ to 15.6%. ¹⁹
For type IV, the results are divergent and span from 0% ¹⁹ to 40%. ²⁰ Type V presents 0% for most studies ^{18, 19, 22, 14, 21} (table 6).
The differences in results may be explained by differences in the number of samples or by heterogeneous populations.

• Disto buccal root

– Number of canals:

In the present study, this root had in 100% of cases one canal whitch agree with the study of Médioni et al. ²⁴

– Canals configurations:

All studies confirmed that the type I is predominant with a percentage that varies from 84.9%⁵ to 100%. ²⁴ Other configurations have a percentage not exceeding for the type II 2% ²³, for the type III 2.4% ⁵, for the type
IV 4.4% ⁵, and for the type V 6% ²³ (table 7).

• Palatal root

– Number of canals:

In the present study,the palatal root had  in  100% of cases only one canal whitch agrees with the findings of Médioni et al. ²⁴ and Sert et al. ⁶ Neelakantan et al ⁵ found only 87.7% of this root  with one canal. According to all studies, types III and V did not exceed 6% ^{23, 20, 25} and type IV did not exceed 3.4% ^{5, 25} and type II was not found.

– Canals configurations:

All studies confirmed that the type I is predominant with a percentage that varies from 87.8%⁵ to 100%. ^{24, 6} Other configurations have a percentage not exceeding for the type III 6% ^{20, 23}, for the type IV 3.4% ⁵, and for the type V 6%.²³ the type II is absent for all studies ^{24, 23, 5, 6, 20, 25} (table 8).

Conclusion

The present study showed that most of maxillary first molars were 3 rooted (93%), 5.8% were 2 rooted and 1.1% presented one root. In the mesio buccal root, the most prevalent configuration was type I (97.5%), type II represented 2.5%. In the disto buccal root and in the palatal root, we found  vertucci type I on 100% of cases.