successful root canal therapy requires a comprehensive knowledge of the root and the root canal morphology .
there have been numerous studies assessing the root canal morphology over the years ; from the early work of hess and zurcher to the most recent technologically advanced studies demonstrating complexities of the root canal system , and all these have concluded that a single root canal ending in a single foramen is rare .
deviations in the anatomy of the root canal systems occur often and are not considered abnormal .
therefore , knowledge of the various root canal configurations aid the clinician to negotiate and debride the canals efficiently and thus provide a successful endodontic outcome .
a study by brescia in 1961 on human teeth reported that the mandibular first premolar displayed the most variable canal morphology .
the washington study also reported the mandibular first premolar had the highest rate of failure owing to the differences in the root canal morphology and inaccessibility of extra canals .
the occurrence of two or more root canals in the mandibular first and second premolars have been found to vary between 2.7% and 65% and 043% respectively .
most studies assessing the root canal morphology of mandibular first premolars were performed on individuals from the american , far - eastern , iranian , indian , and turkish population .
a study of the jordanian population in 2008 reported the high prevalence of multiple canals in the mandibular premolars in comparison to studies performed in populations of different origins .
a review of the literature by cleghorn et al . on the permanent mandibular first premolar have revealed that this tooth has both a complex root morphology as well as a complex internal canal morphology .
various techniques have been employed to evaluate canal morphology such as conventional and digital radiographic techniques , using cross - sections , cone - beam computed tomography ( ct ) , and peripheral quantitative computed tomographic imaging .
it has been shown that detailed information can be obtained ex vivo by demineralization and staining .
this clearing technique allows the form of the canal and all minute structures to be clearly visible , enabling the tooth to be preserved for a considerable amount of time with the use of readily available and inexpensive chemicals .
the purpose of this study was to investigate the root canal morphology of mandibular first premolars in an emirati subpopulation using decalcification and clearing method .
one hundred extracted permanent mandibular first premolar teeth were collected in the united arab emirates ( uae ) from an emirati subpopulation .
these teeth were acquired from the tooth bank of the oral surgery department of al tawam hospital , al ain , and uae from emirati patients who had undergone orthodontic treatment at the hospital .
the extracted permanent mandibular first premolars were collected in a separate container to avoid mixing with the second mandibular premolars .
teeth with large carious lesions , large metal restorations , teeth with fractures , and teeth with immature apices and those which were endodontically filled were discarded .
ethical approval for this study was obtained from the research and ethics committee , university of sharjah ( no .
the teeth samples were stored in 10% formalin . all the soft tissue and calculus attached on the tooth surface was removed using an ultrasonic scaler .
the tooth length was measured using vernier calipers from the tip of the crown to the apex of the root .
the teeth were then subject to the process of decalcification and clearing following the method explained by robertson et al .
2 round bur ( cavity access z set , dentsply , maillefer , usa ) , the root canal orifice was located , seen with the naked eye , and was photographed using the microscope at  12.8 ( zeiss , opmi proergo , germany ) .
following this , the teeth samples were kept in 3% sodium hypochlorite for 48 h and agitated manually to remove the pulp tissue .
india ink ( sanford rotring gmbh , hamburg , germany ) was injected into the pulp chamber using an endodontic irrigating syringe with a 27-gauge needle .
simultaneously , a suction tip was placed at the root apex to draw the ink through the root canal system .
the teeth samples were then placed in 5% nitric acid for 72 h. the acid in which the samples were soaked was changed every 24 h and was stirred once every 8 h. the decalcification was considered complete after verifying by periodic radiography .
the teeth were then washed in running water and dehydrated by immersing the samples in increasing concentrations of isopropyl alcohol ( 70% , 80% , 90% and 100% ) for 12 h consecutively .
the samples were then immersed in methyl salicylate ( 99% methyl salicylate , al nawras medilab , dubai , uae ) to make them transparent and were stored in this solution until examination .
the samples were observed with a  3 magnifying glass , and the canal configurations were categorized into the eight types according to vertucci 's classification .
location of the apex whether central or lateral and apical deltas , if the present was documented .
lateral canals ( lcs ) , which are branches of the main canal which arise along its length at right angles or obtuse angles to open onto the side of the root , were identified in reference to the coronal , middle or apical third of the root .
intercanal communications ( iccs ) , defined as complex canal ramifications that join the main canal but do not open onto the root surface , were also identified in reference to the coronal , middle or apical third of the root .
in the one hundred lower first premolar teeth collected , the average length was 19.93 mm ( standard deviation 2.084 ) .
all the teeth were single rooted , and 44% had mesial invaginations on the root surface .
various canal patterns seen in the present samples are shown in table 1 and figure 1 .
there were no teeth which displayed vertucci type vi , vii , and viii canal morphology .
they have been described as modification 1 and modification 2 [ figure 2a and b ] .
modification 1 is where two canals arise from the pulp chamber in the coronal third and one of these canals further divide into two in the middle third of the root .
modification 2 is where the main trunk of the root canal divides into four canals in the apical third of the root .
percentage of canal system types the canal patterns ( a ) type i , ( b ) type ii , ( c ) type iii , ( d ) type iv , and ( e ) type v alterations in canal morphology ( a ) modification 1 , ( b ) modification 2 forty - four percent of the teeth displayed mesial invaginations , of which the canal patterns were type iv ( 11% ) , type v ( 10% ) , 1% modification 1 and 2% modification 2 , and type i ( 20% ) .
lcs , when present , were seen typically in the coronal and middle third of the teeth [ figure 3 ] .
iccs , if present , were observed in the middle and apical third of the teeth [ figure 4 ] .
the shapes of the orifices photographed using the microscope are shown in figure 6a  d , and detailed percentages of various orifices observed in the present sample are given in table 2 .
intercanal communication canal orifices ( a ) c - shaped , ( b ) ribbon - shaped , ( c ) two orifices , and ( d ) dumbell - shaped root canal anatomy in mandibular 1 premolar teeth
evaluation of root canal morphology of first mandibular premolar teeth in an emirati subpopulation will unveil canal characters in this ethnic group .
the mean length of the first mandibular premolar teeth was 19.9 mm which is comparable to previous studies . in this study , although all teeth were single rooted , there were mesial invaginations in 44% of the teeth .
the presence of mesial invaginations should lead the clinician to suspect a possibility of multiple canals as observed in the present study .
lu et al . in their study on permanent mandibular first premolars showed that all permanent mandibular premolars that had an external concavity on the root surface showed a c - shaped configuration .
the c - shaped morphology was found in the apical 3 mm and or 6 mm cross sections with their coronal sections demonstrating a single oval or two canals in an oval - shaped root .
all the samples in the present study were single rooted yet 44% of them had mesial invaginations present .
furthermore , the samples in the present study were only viewed coronally , and the majority of the orifices were either oval - shaped ( 36% ) or round ( 25% ) .
using cross - sectional method also reported a 14% incidence of c - shaped canals in 106 permanent mandibular premolars in the united states population .
they noted that the c - shaped canals were associated predominantly with type iv canals .
therefore , it may be possible that many of the root canals could have a more complex configuration further deeper into the canal .
the presence of multiple canals in the apical 3 mm , as in the case of circumferential canal configurations , make complete debridement in this region difficult . as a consequence ,
when treating failed cases surgically , apicoectomies of more than 3 mm should be considered as an option and the resected end should be further examined using microscopes for viewing circumferential openings so that they can be sealed adequately .
the shape of the root canal orifices most commonly seen were the oval and round orifices .
ribbon - shaped canal orifices were seen in 14% of the teeth [ figure 6b ] .
the teeth with this type of orifice generally had a type i canal pattern , but the shape of the orifice should encourage the clinician to clear the canal of all residual pulp tissue and necrotic debris with thorough irrigation and adequate instrumentation .
love and jenkinson , in their study , showed that when bacteria are left behind in the dentinal tubules , they may cause infections following root canal therapy .
the thorough cleansing and shaping of canal irregularities is the most important factor considered when discussing endodontic treatment success .
the majority of teeth ( 65% ) displayed type i category of vertucci root canal pattern with a single canal from the orifice to the apex .
this is comparable with studies pertaining to mandibular first premolars reported among different populations , 69.3% american , 64% chinese , , 72% jordanian , and 76% indian .
the frequency of multiple canals in the mandibular first premolars was 35% in the present study .
previous studies in the frequency of multiple canals in the mandibular first premolars have reported different percentage value among different populations .
the values observed 23% jordanian , and 28% indian , 29% iranian , and a range of 1430% among americans . in the present sample
, type v canals were observed in 14% of the samples and type iv in 13% of the samples .
the finding is of clinical importance as one canal bifurcates in the lower two - thirds of the root .
significantly , two modifications in the canal system types were observed in this study . although the percentage of teeth with this modification was low , its presence in the emirati subpopulation is of clinical relevance .
it is very difficult to define the exact configuration of the middle and apical third of the canal by just assessing the coronal orifice morphology
. it would be easy to access the buccal canal , but the lingual canal can be negotiated only if the access cavity preparation is extended more lingually .
adequate access cavities to view the canals and locate individual canals that can be traced to the apex are of immense importance .
operating microscopes may aid in visualizing canal system branching off from the main canal in the middle third of the root .
fan et al . using micro - ct did detailed studies on the c - shaped canal systems and have shown that some of the isthmuses could be found dangerously close to the developmental groove on the root surface .
reported that in type iv canals , the majority of the secondary canals originate on buccal or lingual walls and exit the major canal at a sharp angle .
an experienced practitioner would be able to detect accessory canal systems with the help of a fine curved stainless steel file using his tactile sense .
the practitioner has to consider this tooth group as a complex one and rely on available diagnostic tools and technology and to ensure a successful outcome .
while taking radiographs , varying the horizontal angle of the x - ray projection could enhance the visualization of the superimposed canals .
however , the radiographs have their limitation in complex morphologies and more advanced techniques such as the cone - beam ct and spiral ct are presently being employed .
the apical foramen was located centrally in 77% of the teeth in the present sample , which is relatively higher when compared to the study conducted by sert and bayirli , while that of awawdeh and al - qudah was reported as 4451% and 49.6% , respectively .
however , the present finding is comparable to a study done in the indian population by velmurugan and sandhya on mandibular premolar teeth reporting a percentage of the centrally located foramen to be 83% .
the position of the apical foramen is of clinical significance in the working length determination while using radiographs .
when the foramen opens laterally , the working length may appear to be short on the radiograph .
lcs were seen in 40% of the teeth with the majority of these canals located in the coronal and middle third of the teeth .
the findings of the present study are comparable with that of vertucci in which he found 44.3% of lcs .
awawdeh and al - qudah identified 25.4% of lcs in the apical third of the root in the jordanian population . in comparison ,
sert and bayirli observed lcs in the middle and apical third in 22% of the samples .
the percentages in both these reports were lower than that observed in the present study .
the presence of lcs makes complete debridement of microorganisms from the canals almost impossible . hence biomechanical preparation , including the use of irrigating systems and intracanal medications should be considered in order to achieve a sterile field prior to obturation .
iccs were seen in 17% of the teeth , and the majority were found in the middle and apical one - third of the canals . this percentage stands lower than previous reports at 27.4% and 32% .
results obtained from studies among american 5.7% , turkish 16.9% , and jordanian 29.2% population are comparable to those of this present study . this varied range could be based on ethnic differences .
cleaning of the apical ramification is not easily achievable hence it remains a source of infection .
the samples in the present study showed diffusion of dye into the dentinal tubules which might have resulted in a smudged appearance of the samples .
this could be attributed to a limitation of the study method . henceforth using micro - ct in these types of studies
in one hundred mandibular first premolars examined the most common type of canal pattern detected was type i ( 65% ) . while 35% of the samples were those with multiple canals ( type ii , iii , iv , v , and modification 1 and 2 ) .
 objective : the purpose of this study was to determine the root canal anatomy of mandibular first premolar teeth in an emirati subpopulation using a decalcification and clearing method.materials and methods : one hundred permanent mandibular first premolar teeth extracted for orthodontic purposes from an emirati subpopulation from the united arab emirates were used for this study . 
 they were subjected to decalcification and clearing . 
 the tooth length , the canal orifice shape , mesial invagination , canal pattern , the location of apex , presence of lateral canals , and intercanal communications were determined.results:the most common canal pattern was the vertucci type i ( 65% ) followed by type v ( 14% ) and type iv ( 13% ) . 
 the most common type of canal orifice seen was the oval shape ( 36% ) followed by the round shape ( 25% ) . 
 mesial invaginations were seen in 44% of the teeth . 
 the mean tooth length was 19.9 mm , and apical deltas were seen in 24% of teeth.conclusion:the vertucci type i canal pattern was the most prevalent in the mandibular first premolars while the occurrence of multiple canals was noted in 35% of this population . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSION
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