bifid mandibular condyle is an uncommon anomaly with an unclear origin , which was first described in 1941 by hardlicka .
the condylar head is divided into two partially or completely separated lobes by a rift or a deep groove .
the separating groove can be oriented anteroposteriorly or mediolaterally to determine the spatial relationship of the heads .
several theories exist about the origin of bmc , mainly suggesting traumatic or developmental origin [ 24 ] .
if so , the broken condylar head will be displaced anteriorly due to the function of the lateral pterygoid muscle .
gradually , a new head will grow up over the mandibular neck , in response to the functional demands with an anteroposterior orientation between the two heads .
some believe that extended remaining of a fibro - vascular tissue over the developing condyles during the fetal period may result in bmc formation .
although the mediolateral type of bmc is considered to be developmentally formed , some exceptions with traumatic origin have been reported .
there is also a concept that only anteroposterior division of the condyles can be considered as a true bmc ; bmc is believed to play a role in some cases of temporomandibular joint disorder ( tmd ) , and joint symptom . on the other hand , radiographic appearance of bmc
can mimic vertical condylar fractures , which confuses the physicians in cases of trauma to the face .
thus , differential diagnosis is important in cases of trauma to the face and tmd .
most cases of bmc are discovered accidentally during routine dental radiographic examinations , more commonly on panoramic views taken for other dental purposes [ 2,3 , 10 ] .
there is still a need for more epidemiologic research on the incidence and probable role of bmc in general health .
considering the availability of only a few reports on bmc three - dimensionally , this study was designed to evaluate the incidence of bmc in a south iranian population using cbct since cbct typically imposes a lower dose to patients compared to conventional radiography and computed tomography .
this cross - sectional study was performed to assess the frequency of bmc and condylar head orientation on the transverse plane based on 425 cbct scans of paranasal sinuses in shiraz , iran .
these cbct scans had been ordered as part of preoperative records for patients seeking rhinoplasty in an otolaryngology clinic .
all cbct scans were obtained in upright position , using a newtom vgi scanner ( qr srl , verona , italy ) , in a 1515 field of view ( fov ) and standard resolution mode ( 0.3 mm voxel size ) .
presence of space occupying lesions within the tmj area and lack of demographic information were considered as the exclusion criteria .
only the cases in whom , both condyles were within the fov of cbct scans were included .
the cbct scans were reviewed in nnt station ( qr srl , verona , italy ) by an experienced oral and maxillofacial radiologist .
horizontal angulations of each condyle were determined by measuring the angle between the long axis of the condyle in the axial cross - section with the largest mediolateral dimension and an imaginary horizontal line ( fig .
the left and right condylar heads were evaluated for presence of bifidity separately in the axial , coronal and sagittal planes .
considering the condylar head orientation , true sagittal and coronal cross - sections were prepared at a thickness of 1 mm with 0.5 mm interval , over the largest mediolateral dimension of the condyle in the axial plane .
the ethics committee of shiraz university of medical sciences approved the study and informed consents were obtained of all the participants .
horizontal angle of a bifid left mandibular condyle on a transverse plane based on the axial cross - section .
ab : horizontal line ; ac : the long axis of condyle spss software version 17.0 ( chicago , il , usa ) was used for data analysis .
p - value less than 0.05 was considered statistically significant . frequency of bmc was compared between the left and right sides and between males and females using t - test .
spss software version 17.0 ( chicago , il , usa ) was used for data analysis .
p - value less than 0.05 was considered statistically significant . frequency of bmc was compared between the left and right sides and between males and females using t - test .
the cbct records of 309 patients including 170 females ( 55% ) and 139 males ( 45% ) with a mean age of 29.439.7 years were entered in the study .
the bmc was detected in 14 of them ( seven females and seven males ) , which comprised 4.53% of the total population ( figs . 2 and 3 ) .
coronal cross - sections ( 0.5 mm thickness ) of the cases with ( a ) unilateral and ( b ) bilateral bifid mandibular condyles ( a ) axial , ( b ) corrected coronal and ( c ) corrected sagittal cross - sections of a case with right condylar head bifidity there was no significant difference in the incidence of bmc between males and females .
eleven bmcs ( 3.56% of the population ) were unilateral , while bilateral condylar head bifidity was detected only in three cases .
five unilateral cases were detected on the right side and six in the left side .
the mean horizontal angulations of the condyles in normal individuals were calculated to be 22.66 versus 24.024.33 in bmc cases , implying no significant difference ( p=0.64 ) . similarly , there was no significant difference in the mean horizontal angulation values between men ( 23.25.8 ) and women ( 22.215.96 ) .
since bmc may play a role in tmds or be mistaken for a condylar fracture , its differential diagnosis is of great importance .
many epidemiologic studies have been conducted to estimate the real incidence of bmc all over the world , with a wide variability in results .
most of the researches on bmc incidence were conducted on panoramic views , since it is a wide - spread , low cost , relatively low radiation dose , and easy to access radiographic technique , which visualizes a large volume of dental and supporting structures , including the rami and condyles . besides
, a large number of people have already taken panoramic views for dental purposes , which can be used in epidemiologic studies as a pre - existing sample source .
unfortunately , there are some serious limitations with the panoramic technique in this regard . due to superimpositions
partial bmcs are hard to detect on panoramic views and mediolateral bmcs may be seen as anteroposterior ones , if the condyles horizontal angulations are large enough . the great discrepancy in the results of studies performed on panoramic views
cho and jung believed that panoramic views either under- or over - estimated the incidence of bifidity . on the other hand ,
there is no universally accepted protocol to diagnose bmc on panoramic views , and judgments are subjective . since the introduction of cbct , dental imaging improved by versatile abilities of this three - dimensional imaging modality . yet
, relatively low doses of radiation are delivered to patients and images are prepared in a really short time by a single rotation of the machine .
deleting superimpositions brings the chance to observe the anatomical structures of interest precisely , and multi - planar images enable the physician to evaluate the interested structure in proper plane . as the operator can observe the condyles conspicuously , the probability of false positive and false negative diagnoses is significantly reduced , although the need for a standard scale to classify the severity of separations of the heads still exists .
the cbct imaging is not used as widely as the panoramic views because of the nature of this technique .
thus , the existing source of cbct records is slightly different from the normal population compared with panoramic images .
the incidence of bmc in the current study was slightly higher than that in previous reports on the same population , but considering the advantages of three - dimensional imaging , it is negligible .
most researchers believe that the incidence of bmc is increasing , as more radiographic examinations of higher quality are becoming available [ 35,7 ] .
about 78% of cases were unilateral , and female to male ratio was 3 to 1 .
evaluated 10,200 panoramic views and reported an incidence of 0.3% for bmc in a turkish population .
reported the prevalence of bmc to be 0.52% in turkey , using panoramic radiographies as the screening tool .
later , employing ct scan images , they reported a higher rate of about 1.82% in the same population .
using cbct records , cho and jung compared the prevalence of bmc in asymptomatic and symptomatic subjects with tmj problems and no traumatic history and found no significant difference between them .
they concluded that the presence of bmc would not lead to any tmj symptoms or cause osseous changes .
we have already reported a high rate of bmc ( 3.5% ) in an iranian population   while in the current study , we found that 4.53% of cbct records revealed bmc in patients of the same population . the new rate ,
this difference can be attributed to the advantages of cbct that eliminates superimpositions in the images of the condyles .
this finding is in accordance with the results of sahman et al , who reported a higher rate for bmc in ct records compared to panoramic images in the same country .
it is worthy to mention that the lack of conspicuous criteria to diagnose bmc on panoramic images may be less important for cbct scans , because of higher reliability of multi - planar images provided by this modality .
similarly , we believe that this will improve the agreement between different observers , and reduces the need to employ multiple observers in such studies , which requires the inter - observer agreement to be in an acceptable level . in most studies ,
the ratio of unilateral cases of bmc to bilateral form is about 3 to 1 .
the results of the current study are compatible with this ratio , using a three - dimensional imaging modality ( nearly 4 to 1 ) .
our results ( seven females and seven males ) , are also in accordance with the afore - mentioned mean female to male ratio for bmc prevalence , which is about 1.3 to 1.0 .
however , menezes et al . reported a much higher prevalence in females ( 3.5 to 1.0 ) .
finally , we believe that panoramic views face some limitations in detection of bmcs although they provide opportunities for screening purposes .
oblique forms and partial bifid condyles are hard to discover using panoramic and other conventional imaging techniques .
should the angulations of the condyle in the transverse plane are large enough , the mediolateral form of bmc may be diagnosed as an anteroposterior type .
more advanced imaging techniques should be ordered , at least for symptomatic cases of bmcs or when treatment plans are to be conducted [ 3,4 , 7 ] .
last but not least , cbct imaging may be an invaluable modality , considering its low dose of radiation ( compared to ct scan ) , the short time needed ( compared to magnetic resonance imaging ) , and high reliability of the produced images .
the prevalence of bmc in the studied population was 4.53% , which was slightly higher than that in previous reports .
no significant difference was detected between males and females , sides and condylar horizontal angulations of patients with normal and bifid condyles .
 objectives : differential diagnosis of bifid mandibular condyle ( bmc ) is important , since it may play a role in temporomandibular joint ( tmj ) dysfunctions and joint symptoms . 
 in addition , radiographic appearance of bmc may mimic tumors and/or fractures . 
 the aim of this study was to evaluate the prevalence and orientation of bmc based on cone beam computed tomography ( cbct ) scans.materials and methods : this cross - sectional study was performed on cbct scans of paranasal sinuses of 425 patients . in a designated nnt station , all cbct scans were evaluated in the axial , coronal and sagittal planes to find the frequency of bmc . 
 the condylar head horizontal angulations were also determined in the transverse plane . 
 t - test was used to compare the frequency of bmc between the left and right sides and between males and females.results:totally , 309 patients with acceptable visibility of condyles on cbct scans were entered in the study consisting of 170 ( 55% ) females and 139 ( 45% ) males with a mean age of 39.439.7 years . 
 the bmc was detected in 14 cases ( 4.53% ) . 
 differences between males and females , sides and horizontal angulations of condyle of normal and bmc cases were not significant.conclusion:the prevalence of bmc in the studied population was 4.53% . no significant difference was observed between males and females , sides or horizontal angulations of the involved and uninvolved condyles . 
INTRODUCTION
MATERIALS AND METHODS
Statistical analysis:
RESULTS
DISCUSSION
CONCLUSION