
 in dentistry the role of endodontics has greatly broadened in scope in the past decade .
although many factors are responsible , the most important reason behind this growth is the extremely high predictability of endodontic success .
false assumptions about the root canal anatomy of teeth may lead to misdiagnosis , improper debridement , step formation and breakage of instruments during root canal treatment . 
 

problems during endodontic treatment of permanent maxillary molar teeth indicate the need for increased knowledge of the anatomy of root canal systems .
the mesiobuccal root of maxillary first molars has prompted more research and clinical investigation than any other tooth in the mouth .
green reported that two foramina were present in 14% of the mesiobuccal roots in his study of upper first molars , and two orifices were noted in 36% of the casies .
kulid and peters indicated that a second canal was present in the coronal half of 95.2% of the mesiobuccal roots examined .
the root canal configuration , according to the classification of vertucci , is usually type ii ( two separate root canals with a single apical exit ) ; however , the presence of two root canals of type iv configuration with two separate apical foramina has been reported to be as high as 42% .
other investigators have reported the prevalence of maxillary first molars with four canals to be 28 - 62% in caucasians.7 
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 9 weine et al reported that the mesiobuccal roots of maxillary first molar teeth of a japanese subpopulation had two root canals ( 54% ) of type ii or type iv configuration .
because of this complexity , the clinician should always assume there are two canals in the mesiobuccal root until it is proven there is only one .
the purpose of this in vitro study was to investigate variations in the root canal system of maxillary first molars in an iranian population in the north - west of iran . 


 one hundred thirty - seven maxillary first molar teeth were collected from a large supply of recently extracted teeth from dental faculty clinics and private offices in tabriz , a city in the north - west of iran .
teeth that demonstrated fully - formed roots and intact external morphology were selected for the study .
the teeth were collected in a period of one year and were stored in 10% formalin .
each tooth was cleaned of any adherent soft tissues , bone fragments and calculus by scaling and polishing .
an endodontic access cavity was then prepared in each tooth with diamond fissure burs ( d&z , wisbaden , germany ) .
the anatomic dark lines in the floor of the pulp chamber were examined with a dg16 endodontic explorer ( hu freiday , chicago , il , usa ) to identify the root canal orifices . 
 
 after locating the orifices ,
the teeth were placed in 5.25% sodium hypochlorite solution ( golrang , tehran , iran ) for 48h to dissolve debris and pulp remnants .
all the specimens were then thoroughly rinsed in running water for 4h to clean the root canals of any debris .
once washed , the teeth were demineralized for 3 days in 5% nitric acid ( merck , darmstadt , germany ) at room temperature .
india ink ( ab chemi , england ) was injected into the root canals before dehydration of the teeth .
the dehydration process consisted of a series of ethyl alcohol ( ararat , tehran , iran ) rinses starting with 80% solution over night , followed by 90% for 1h and then 100% ethyl alcohol rinse for 1h .
the dehydrated teeth were placed in methyl salicylate ( bp.63 , poland ) for 2h to render them transparent .
the cleared teeth were examined using a magnifying - glass ( lumagny , no.7540 , hong kong ) at 5 magnification .
the root canal systems were classified according to the classification of vertucci ( 1984 ) as follows : 
 
 type . one single root canal extending from the pulp chamber to the apex 
 
 type ii .
separate root canals leaving the pulp chamber and joining short of the apex to form one canal 
 
 type iii .
one root canal leaving the pulp chamber before dividing into two canals within the root and then merging to exit as one single canal 
 
 type iv .
one root canal leaving the pulp chamber and dividing short of the apex into two separate and distinct root canals with separate apical foramina 
 
 type vi .
two separate root canals leaving the pulp chamber , merging in the body of the root , and again dividing short of the root apex to exit as two separate and distinct canals 
 
 type vii .
one root canal leaving the pulp chamber , dividing and rejoining within the body of the root canal and finally re - dividing into two distinct canals short of the apex 
 
 type viii .

 out of 137 maxillary first permanent molar teeth studied , the mesiobuccal roots with a single canal were of type i ( 37.96% ) or type v ( 9.5% ) configuration .
those with two canals were of type ii ( 24.08% ) , type iv ( 24.18% ) or type vi ( 4.38% ) configuration .
the distal and palatal roots that presented with a single canal were of type i or v configuration .
no type iii , vii or viii canal configurations were found in the roots of these teeth .
the percentage distribution of accessory canals was 16.78% in the mesiobuccal roots , 2.91% in the distobuccal roots and 2.18% in the palatal roots . 


 false assumptions about the root canal anatomy of teeth may lead to misdiagnosis , improper debridement , step formation and breakage of instruments during root canal treatment . 
 

problems faced during endodontic treatment of permanent molar teeth indicate the need for increased knowledge of root canal systems .
the results of this study differ from those reported in investigations of samples obtained from caucasians ( table 2 ) .
these differences relate principally to the presence of type v and type vi configurations , with a relatively low incidence of , in particular , type i configuration in the mesiobuccal root .
there was a relatively high prevalence of type v configuration in the distal and palatal roots of maxillary first permanent molar teeth ( table 1 ) . 
 

wasti et al in a study ( 2001 ) on maxillary first molars in asian pakistanis found two canals in the mesiobuccal roots in 53% and one canal in 46.5% of cases .
the configuration of root canal system in the study carried out by wasti et al in the mesiobuccal root was type i ( 33.3% ) , type ii ( 23.3% ) , type iv ( 23.3% ) , type v ( 13.3% ) and type vi ( 6.8% ) .
they found type v root canal system in the distobuccal and palatal roots of maxillary first molars in 16.7% and 33.3% of cases , respectively .
the results of this study are consistent with the results of the study carried out by wasti .
regarding the diversity and the number of the teeth studied ( e.g. our study on 137 teeth and a study by wasti et al on 30 teeth ) , it seems that racial / ethnic differences are important factors in the differences observed in the root canal configuration , as sert and bayirli concluded that both gender and ethnic origin should be considered during preoperative evaluation of root canal therapy .
therefore , further studies are warranted in different parts of the world to prove that there is a relationship between the racial / ethnic differences and the anatomic differences in the first maxillary molars . 


 according to the results of the present study , there is a high prevalence of four root canals in the maxillary first permanent molars in the north - west of iran .
the distribution of different configurations of root canal system in the maxillary first permanent molars in north - western iranians differs from that in caucasian groups . 

 background and aims 
 it is critical to have a proper knowledge of the normal anatomy of the pulp and its variations for the success of endodontic treatment . 
 the purpose of this study was to investigate variations in the root canal system of maxillary first permanent molars in an iranian population . 
 
 materials and methods 
 in this study , 137 maxillary first molars were decalcified , dye - injected , cleared and studied . 
 
 results 
 the results demonstrated that 37.96% of the maxillary first molars under study had three canals , 58.4% had four canals and 3.64% had five canals . 
 
 conclusion according to the results of this study and considering variations in the root canal systems of maxillary first molars , it seems that great care should be taken in the root canal treatment of these teeth . 
Introduction
Materials and Methods
Results
Discussion
Conclusion