
 the main purpose of endodontic therapy is a thorough mechanical and chemical cleansing of the entire pulp cavity and complete obturation with an inert filling material .
a clear knowledge of the anatomy of root canal systems is an essential prerequisite to carrying out root canal preparation .
many of the problems encountered during root canal treatment occur because of inadequate understanding of the pulp space anatomy . 
 

ingle et al have suggested that apical percolation is the main cause of endodontic failures .
the main reasons for this failure are incomplete obturation or the presence of an untreated canal .
thus , dentists must have a proper knowledge of root canal morphology and the variations of the root canal system before successfully treating a tooth.1 
 , 
 4 it is important to be familiar with variations in tooth anatomy and characteristic features among racial groups , as such knowledge can aid in locating , negotiation and management of canals . 
 

a number of studies have shown different trends in the shape and number of roots and root canals among different races.4 
 - 
 8 these variations appear to be genetically determined,5 
 , 
 7 and are important in tracing the racial origins of populations .
these have included various methods such as the use of polyester resin impressions , creating transparent samples and the use of radiographs in both in vivo and in vitro studies.,4 
 - 
 8 since there are differences in selection of materials and methods used as well as classification of canal configurations , different opinions have arisen about canal morphology . 
 

the purpose of this study was to evaluate root canal morphology and the prevalence of second root canal in mandibular permanent canines within an iranian subpopulation . 


 in this descriptive in vitro study , 100 extracted mandibular permanent canines were evaluated .
the age and gender of the patients and the reasons for the extraction were not recorded . 
 

teeth were immediately placed in 5.25% sodium hypochlorite for 30 minutes after extraction to be disinfected and to remove any organic tissue on the external root surfaces .
a box was made for each tooth using rose wax so that it covered from the cej to the apex and there was at least 1 mm space between the root surface and the walls of the box .
holding the tooth crown , the box was placed on a vibrator and fast - setting clear acrylic resin with relatively low viscosity was poured to fill it . once resin was set ,
the boxes were immersed in boiling water for 5 minutes and then rinsed under running cold water for 10 minutes .
thus , wax was removed and the teeth were surrounded in acrylic boxes from the cej to the apex .
the crowns of the teeth were cut and 2 mm cross sections were made from cej to the apex using diamond disks ( d&z , diamant , germany ) .
the sections were examined using a digital stereomicroscope ( olympus , tokyo , japan ) at 40 magnification .
the existence of a second canal , canal type and the position of apical foramen according to vertucci were recorded . in a blind manner
the samples were re - evaluated if there were any discrepancies and finally the results were recorded in common accord . 

the data relating to the existence of a second canal and canal type according to vertucci s classification are presented in table 1 . 
 
 from 100 teeth
evaluated , 12 ( 12% ) had 2 canals from which 5 canals were of  type ii ( having 2 orifices , 2 separate canals and one apex ) and 7 were of type iii ( having one orifice , 2 separate canals and one apex ) . 
 
 among the teeth with type iii canal , 4 samples had a bean - shaped orifice dividing into two canals which were separated with a thin wall and joined near the apex .
2 samples ( type iii ) had one orifice in the pulp chamber which was separated into two canals 1 mm further and joined in 4 mm from the apex ( table 2 ) .
the last tooth with type iii canal had an oval orifice which changed to a sand watch appearance in sections # 2 and # 3 where two canals were separated by a thin dentinal isthmus . in section # 4
, it had a bean - shaped appearance and 2 canals united in 4 mm from the apex . among the five teeth with type ii canals , three samples had 2 canals with 2 orifices in buccal and lingual which united in 2 mm from the apex .
the other two teeth had an orifice with sand watch appearance and 2 canals separated with a thin wall and united near the apex . 
 

no lateral canal was found in the specimens and all had one apical foramen . in six teeth ,
the apical foramina were not located at anatomical apex . in 4 of the latter ,

 in the present study , performed on 100 extracted mandibular canines in an iranian subpopulation , the existence of the second canal was 12% .
this is in agreement with the results of hessions ( 11% ) , green(13%)and kaffe et al ( 13.75% ) .
it is , however , higher than the results of bellizzi & hartwell ( 4.11% ) and ingle et al ( 6%)while it is lower than the results of vertucci ( 22% ) , calikan et al ( 19.5% ) and sert et al ( 24%).in vertucci s study , 22% of the evaluated mandibular canines had 2 canals , of which 14% were type ii , 2% type iii and 6% type iv.in the present study , 5% were type ii , 7% type iii , and none were of type iv ( 0% ) . the percentage of a second canal was reported to be 24% in the study of sert et al .
the existence of types ii , iii and iv in the latter study was estimated 16% , 6.5% and 1.5% , respectively . except for type iii ,
one - canal mandibular canines ( type i ) was estimated 88% in the present study which is higher than 78% , 80.5% and 76% reported in the similar studies.1 
 , 
 4 
 , 
 5 in calikan et al s study , 4% of mandibular canines were type iiwhich is similar to the present study .
they , however , reported 1.96% type iv canal configuration which was not seen in our study .
comparison of the present study with similar previous studies according to the samples size , methods and results is presented in table 2 . 
 

lambrianidis et al stated that differences between the results of morphological studies may be due to the differences in method of classification system , sample size and ethnic background of evaluated teeth . in the present study ,
sample size was chosen similar to previous studies for more precise evaluation.1 
 , 
 4 
 , 
 5 considering the low prevalence of the studied subject , higher sample size would result in more accurate findings and can be generalized . 
 
 in a number of studies , clearing technique with demineralization and staining
has been used.1 
 , 
 4 
 , 
 5 others have used only radiography.12 
 , 
 14 hession used radiography following infusion of an opaque material to the studied root canals . in the present study transversal sections were made and then evaluated using a stereomicroscope at high magnification .
different methods may be a reason for difference in the results of the studies . in almost all of the mentioned studies,4 
 - 
 6 ,
the classification of vertucci was used ; however in certain cases it was accompanied with other classifications .
none of the mandibular canines had lateral canal ( 0% ) while the prevalence was reported to be 30% , 33.33% , and 29% in other studies .
, one of the most important causes of this controversy seems to be the different techniques used in the studies .
the staining technique used in the mentioned studies increases the possibility of finding lateral canals compared to evaluating sections made without staining as we did in our study . 
 
 in 6% of cases of the present study ,
apical foramina were not located in anatomical apices ( 4 buccally and 2 lingually ) . in the remaining cases ,
apical foramina were located in anatomical apices ; however , their lateral or central position could not be evaluated due to the used technique . in vertucci
s study apical foramina were located centrally in 15% of the cases and laterally in 85% .
sert et al reported 47.5% of apical foramina in anatomical apices and 52.5% out of it .
another important cause of differences in results of these studies is the race of populations under study .
genetic model is varied among populations and also affects tooth structure.7 
 , 
 8 
 , 
 13 
 , 
 15 various studies have been carried out in different parts of the world on different races and used different methods.1 
 , 
 4 
 - 
 8 
 , 
 10 
 , 
 13 
 , 
 15 for this purpose , the present study was performed to estimate the existence of the second canal in mandibular canines in an iranian population . 
 

the researchers judgment in exploring the second canal can play a major role in the achieved results .
this bias can occur in studies using only radiography where one may interpret a radiolucent area as a second canal while others may not have the same judgment .
lambrianidis et al also stated that varied results can be due to the differences in genetic model and race in the studied population , sample size , techniques , classification systems and the researchers judgment and diagnosis . 


 the results of the present study revealed that 12% of mandibular canines  had two canals of which 5% were type ii and 7% were type iii .
these findings emphasize the importance of dentist s knowledge of variations in root canal morphology , since leaving a canal untreated is one of the main reasons of endodontic failures . when treating mandibular canines , the existence of a second canal should be taken into consideration . 

 background and aims 
 a perfect endodontic treatment necessitates proper understanding of the morphology of canal and pulpal variations . this in vitro study 
 was conducted to demonstrate the in - ternal anatomy of mandibular canine teeth in an iranian population . 
 
 materials and methods 
 the samples consisted of 100 extracted mandibular permanent canines . 
 the roots of the teeth were molded in acrylic boxes . 
 the crowns of the teeth were cut and 2 mm cross sections were made from cej to the apex . 
 sections were examined using stereomicroscope to reveal the number and location of root canals . 
 
 results 
 from 100 evaluated teeth , 12 ( 12% ) had 2 canals from which 5 had type ii canal configu - ration and 7 ( 7% ) had type iii . 
 88% of the specimens had one canal and none were seen to be of type iv . 
 
 conclusion the findings of this study emphasize the importance of dentist s knowledge of varia - tions in root canal morphology , since leaving a canal untreated is one of the main reasons of endodontic failures . 
 when treating mandibular canines , the existence of a second canal should be taken into consideration . 
Introduction
Materials and Methods
Results
Discussion
Conclusion