third molar impaction is the most commonly observed tooth impaction in modern communities , as the third molars are the last teeth to erupt .
third molars have been reported to account for 18 - 32% of impactions . while most studies have reported no gender differences in caucasians ,
the purpose of this study was to investigate the prevalence , distribution , position , and depth of impacted third molars ( itms ) in turkish orthodontic patients from a single academic institution .
we retrospectively reviewed the panoramic radiographs , intraoral photographs , and dental casts of 207 patients ( 62 men and 145 women ; age , 20 - 39 years ; mean age , 22.7  3.29 years ) who had undergone orthodontic treatment .
patients with conditions such as cleidocranial dysplasia , and down 's syndrome were excluded from the study . if an itm was present , its angle and depth of impaction were recorded .
if the third molar was not fully erupted to its normal functional position or the eruption process was not complete with regard to angular position or lack of space , then it was deemed as impacted .
the angulation of impaction was measured with reference to the angle formed between the intersected longitudinal axes of the second and third molars .
the following classification system was adopted : 0-10 , vertical ; 11-79 , mesioangular or distoangular ; 80-100 , horizontal , and the remaining cases were classified as cases of inverted or buccolingual impaction .
the level of impaction was considered in relation to alveolar bone and the cementoenamel junction of the itm : level a , not buried in bone ; level b , partially buried in bone ( if any part of the cementoenamel junction was lower than the bone level , the tooth was considered to be partially buried in bone ) ; and level c , completely buried in bone .
statistical analysis was performed using ncss ( number cruncher statistical system ) 2007 statistical software ( utah , usa ) .
groups were compared using pearson 's chi - square test and fisher 's exact test .
in our orthodontic patient population , itms were evident in 112 patients ( 54.1% ) .
prevalence of itm was not found to be significantly different between men and women ( 61.3% , n = 38 vs. 51.0% , n = 74 , respectively ) , ( p = 0.23 ) .
the proportion of itms was approximately equally represented in the maxilla and the mandible for both genders . of the 300 itms ,
there was no significant difference between the distribution of maxillary and mandibular itms in men and women ( p = 0.97 ) .
in addition , there was no significant difference in the frequency of third molar impaction between the right and left sides within each arch ( p > 0.05 ) .
the distribution of itms on the right and left sides was equal ( 50% ) in the mandible . in the maxilla , the distribution was 51.35% for the right side and 48.65% for the left side .
distribution of itms by arch and gender the distribution of patients by number of itms is shown in table 2 .
the most common type was impaction of all 4 third molars and 2 third molars .
there were no significant differences between the distribution of the number of itms in male and female patients ( p > 0.05 ) .
distribution of patients by total number of itms the occurrence of the different angulations of impaction in the mandible is shown in table 3 , and their occurrence in the maxilla is shown in table 4 .
the most common angulations were mesioangular ( 65.1% ) and horizontal ( 25.7% ) in the mandible , while they were distoangular ( 64.2% ) and vertical ( 23.6% ) in the maxilla .
the distribution of the mesioangular and horizontal angulations of impaction in the mandible were significantly different between the men and women ( p < 0.05 ) [ table 3 ] . in the mandible , the mesioangular position was more common among women than among men , while this association was vice versa with respect to horizontal position .
on the other hand , there was no significant difference in the frequency of different angulation types of impaction between the sexes in the maxilla .
distribution of angulations of mandibular itms distribution of angulations of maxillary itms the distribution of impaction levels is shown in table 5
there were no significant differences between level b and level c impactions in the maxilla ( p = 0.75 ) , or in the mandible ( p = 0.79 ) in men and women .
the relative proportion of the different levels of impaction was significantly different between the 2 arches .
there was significantly more level c impaction in the maxilla ( 46% ) than in the mandible ( 32% ) ( p = 0.02 ) .
there was no significant difference between level b and level c impactions in the maxilla or the mandible , in men ( p = 0.45 ) , or women ( p = 0.21 ) .
distribution of levels of impacted third molars in the maxilla and mandible in our patient population , 86 patients presented with bilateral impaction ( 76.8% of all subjects with itms ) [ table 6 ] . the frequencies of maxillary and mandibular bilateral impaction were similar ( 30.2% , and 24.4% , respectively ) .
seventy - one percent of the mandibular bilateral impaction cases and 82% of the maxillary bilateral impaction cases presented with the same angle classification and the same level of impaction [ table 7 ] .
bilateral impaction with the same angulation ( 82% ) was significantly more frequent than bilateral impaction with different angulation ( 30% ) at the same level of impaction in the maxilla ( p = 0.00 ) .
there was no significant relationship between the impaction levels with regard to mandibular bilateral impactions ( p = 0.12 ) .
there was also no significant relationship between the bilateral impaction angulations in the maxilla and the mandible ( p = 0.38 ) .
distribution of bilateral impaction by arch distribution of bilateral impaction by angulation and level in the maxilla and mandible
to achieve more reliable results in this study , 20 years was deemed to be the lower age limit on the basis of literature regarding the growth and eruption time of the third molars .
in addition , due to possible angulation changes of third molars even after 30 years of age , the upper age limit was 39 in our patient population .
although all of the patient records and file information were carefully investigated , it is still possible that some third molars may have been extracted . for determination of the angular position of an itm ,
this useful system has also been used before by other researchers . in many other studies ,
the angulation of itms was usually determined using visual impression based on winter 's classification . due to ethnic variations
, differences in diet , and genetic heredity , variations in jaw - tooth sizes and facial growth can occur .
thus , some differences are evident in the prevalence of itms in studies of different populations . in addition
, differences in diagnostic criteria , sample sizes , and statistical methods may also lead to differences in results . in our study ,
many other studies have reported much lower frequencies of itms . in another turkish population study ,
it was concluded that the prevalence of itms was 35.9% , and this proportion was lower than was observed in our study . on the other hand , saglam and
tuzum reported the frequency of lower third molar impaction to be 42.4% and that of upper third molar impaction to be 40.5% in a sample of turkish patients aged between 16 and 75 .
there were some methodological differences between these studies with regard to factors such as age limits .
some other prevalence studies have also reported higher itm frequencies , between 65.6% and 76.0% , in american , chinese , indian , and swedish populations .
we observed no significant gender differences with regard to the frequency of third molar impactions ( p = 0.23 ) .
however , some other studies , including another investigating a turkish orthodontic patient population , have reported a significantly greater frequency of itms in women ( p < 0.05 ) . in our study , the proportions of impacted mandibular ( 50.7% ) and maxillary ( 49.3% ) third molars were almost equal .
in contrast , in most other studies , itms were observed more frequently in the mandible than in the maxilla , although some studies have also indicated the opposite .
because of the different classification systems used in different studies , including classification determined solely by visual impression alone , it is difficult to make reliable comparisons of the reported itm angulations . in this study
, we found that mesioangular impaction of mandibular third molar and distoangular impaction of maxillary third molar were the most common ( 65.1% , and 64.2% , respectively ) .
most other researchers have also reported that mesioangular inclination was the most common , in the mandible . however , hugoson and kugelberg reported vertical impaction to be the most common ( 50.0% ) in the mandible . in their study ,
in which they used a different classification system , celikoglu et al . reported that in a turkish population vertical impaction was the most common in the maxilla ( 58.9% ) . in our research ,
study result , and they used the same criteria in their study ( level b , 80% ) .
however , they included all third molars , impacted or otherwise , in their study .
thus , our result is not directly comparable to that reported by hugoson and kugelberg , or other study results . in this study , we only evaluated impacted third molars , and our reference was the amount of crown buried in bone .
the frequency of level a impaction was reported as only 5% by quek et al . in our research
however , level a was observed in only 1 patient and thus was not analysed statistically .
there was significantly more level c impaction in the maxilla ( 46% ) than in the mandible ( 32% ) ( p = 0.02 ) and this result is comparable with that of quek et al .
dachi and howel have indicated that the prevalence of unilateral and bilateral impaction of third molars was almost the same .
have reported that bilateral occurrence of third molar impaction was more common than unilateral impactions .
our study also showed that bilateral impaction of itms was more frequent . in this study
however , quek et al . indicated that the majority of bilateral third molar impactions were in the mandible .
they also reported that half of the bilateral impactions presented with the same classification of angle and level of impaction in the mandible , while this percentage was 71% in our research .
our study showed that third molar impaction was present in 54.1% of a group of turkish orthodontic patients aged between 20 and 39 years , with no significant gender differences , and this frequency is the highest , thus far , to be reported in a turkish population .
mesioangular and distoangular inclinations were the most common in the mandible and the maxilla , respectively . of all itms ,
 objective : we aimed to investigate the prevalence , distribution , angular position , and depth of third molar impaction in a turkish orthodontic patient population.materials and methods : we retrospectively reviewed the panoramic radiographs , intraoral photographs , and dental casts of 207 patients ( 62 men and 145 women ; age 20 - 39 years ) who had undergone orthodontic treatment at a university department of orthodontics for impacted third molars ( itms ) . 
 a comprehensive chart review of all subjects was conducted . 
 patient and treatment - related data were recorded in a digital database for comparative analysis.results:the prevalence of itms was 54.1% , and no statistically significant gender differences were evident ( 61.3% in men and 51.0% in women ; p = 0.23 ) . 
 the frequency of maxillary itms was 49.3% ( 148 of 300 teeth ) while that of mandibular itms was 50.7% ( 152 of 300 teeth ) . the most frequently observed angulations of impaction were mesioangular for the mandible ( 65.1% ) , and distoangular for the maxilla ( 64.2% ) . 
 of all the itms analysed , 61% were partially buried in bone and 39% were completely buried.conclusions:third molar impaction was evident in 54.1% of a group of turkish orthodontic patients aged 20 - 39 years , and there was no statistically significant gender bias . 
 mesioangular and distoangular inclinations were the most common in the mandible and the maxilla , respectively . 