the first and second vertebrae ( atlas and axis , respectively ) are different from others with their function and anatomy . normally , the intervertebral disc is located between two vertebrae , but not located between atlas and axis . the most common cervical vertebrae anomalies ( cvas ) are fusion and posterior arch deficiency ( pad ) . the second ( c2 ) and third ( c3 ) cervical vertebrae are most commonly influenced by fusion . posterior arch anomalies occur probably the result of a locally decreased blood supply during fetal development . skeletal deviations in maxillofacial region , head and neck posture deformities , cervical inclination , and orthopedic findings can be associated with malocclusion . several studies declared the relation between the cervical vertebrae morphology and position of the mandible . cva is often asymptomatic , for this reason , patients may notice anomalies with decrease age or an injury the pathologic condition may reveal with the radiographic examination . although orthodontists do not have to be experts in cva these patients should be directed to the experts early as possible and prevents progressively degenerative neurologic defects . the present study is the first report to determine the frequency of cvas in orthodontic patients with dental malocclusions . the aims of this study were to investigate the distribution of cvas among angle class i , ii , and iii malocclusions in a turkish patient population and whether a correlation between cva and dental malocclusion ; thus , being the first series of cvas in our population described in the english literature . a power analysis conducted using the g*power version 3.1.7 . software ( franz faul , universitt kiel , germany ) indicated that a total sample size of 150 patients would give more than 80% power ( actual power = 0.8229 ) to detect significant differences with an effect size of 0.30 at an  = 0.05 level of significance ( critical  = 11.0705 ; noncentrality parameter  = 13.5000 ) . the study was performed on 318 patients clinical records ( case histories , lateral cephalometric radiographs , and study models ) which were taken in archive at the department of orthodontics , faculty of dentistry , kirikkale university . if an accurate diagnosis of the cva could not be made from these records , the subject was excluded from the study . exclusion criteria included the patients , who were less than 18 years of age , had records with poor quality radiographs , had craniofacial anomaly and systemic muscle or joint disorder and , wound , burns , or scarring in the head and neck . subjects were selected according to the following criteria : turkish with turkish grandparents , no history of trauma , and previous orthodontic treatment , study models including the first molars and standardized lateral cephalometric radiographs with the first five cervical vertebrae visible . a total of 341 subjects were included in the study , but 23 subjects with developmental anomalies were excluded . the radiographs of the patients were obtained with the teeth in occlusion , the lips in a relaxed position in a standardized head posture ( the frankfort plane parallel to the horizontal ) . the radiographs were taken by an experienced x - ray technician using an orthopantograph ( planmeca proline cc 2002 , helsinki , finland ) with a film - to - focus distance of 165 cm and a film - to - median plane distance of 15 cm . dental malocclusion groups observed through molar relationship in plaster models were divided into angle class i , ii , and iii according to angle 's classification . angle class i : normal relationship of the molars ( mesiobuccal cusp of the upper molar occludes in buccal groove of the lower molar ) , but a line of occlusion incorrect because of malposed teeth , rotation , or other causes . angle class ii : lower molar distally positioned relative to upper molar , a line of occlusion not specified . angle class iii : lower molar mesially positioned relative to upper molar , a line of occlusion not specified . cvas were categorized and recorded for all patients : fusion was defined as no intradiscal radiolucency or osseous continuities without complete separation between two cervical vertebrae . pad was defined as a uniform radio - opacity without an internal cortical outline at the posterior arch of the cervical vertebra . the lateral cephalograms were examined by an orthodontist ( h.k . ) and a dentomaxillofacial radiologist ( e.y . ) simultaneously . to determine errors in the methods , 20% of the subjects with or without cva were selected randomly.first , each radiograph was separately evaluated by authors , but a final examination was done together , so a sentence was made to decide . in addition , the same examiners twice reevaluated all of the radiographs after 4 weeks of the first evaluation . a paired t - test was applied to both the first set and a second set of measurements , and no significant difference was found between the two sets . intra - examiner reproducibility was found to be 90 and 92% , respectively , and the agreement between both investigators was 95% . the chi - square and fisher 's exact test were used to determine the potential differences in the distribution of dental malocclusions , and genders when stratified by cvas . pearson 's correlation test was used to determine the correlation between cvas and different parameters ( dental malocclusions and genders ) . all of the statistical analyzes were performed with the spss software package ( spss version 16.0 , spss inc . , 233 south wacker drive , 11 floor , chicago , il , usa ) . a p < 0.05 was considered statistically significant . the final sample of 318 patients was examined ( 170 females and 148 males , mean age ; 20  0.9 years from 18 and 29 years ) . of these 318 patients , 98 ( 30.81% ) had angle class i , 124 ( 38.99% ) had angle class ii , and 96 ( 30.18% ) had angle class iii malocclusion . cva was observed in 42 individuals ( of which 26 [ 8.1% ] had fusion and 16 [ 5.0% ] had pad ) , with a frequency of 13.2% . of the 26 fusion defect , 8 ( 30.8% ) had angle class i , 8 ( 30.8% ) had angle class ii , and 10 ( 38.4% ) had angle class iii malocclusion . of the 16 pad , 8 ( 50% ) had angle class i , 8 ( 50% ) had angle class ii but no patients with angle class iii malocclusion was observed . the distribution of dental malocclusions regarding cvas was not statistically significant ( p = 0.076 ) [ table 1 ] . the distribution of cvas according to dental malocclusions of these 42 individuals with cva , 52.3% ( 15 fusions and 7 pad ) were females and 47.7% ( 11 fusions and 9 pad ) were males . the cvas and the gender were also compared [ table 2 ] and no statistically significant differences were found ( p = 0.339 ) . as shown in table 3 , statistically significant negative correlation ( p = 0.025 ) was found among cvas and dental malocclusions , but no statistically significant correlation was found between cvas and genders . according to the sample size calculation for a power of 0.80 at  = 0.05 significant level , 150 subjects would be sufficient . at baseline , there were 341 subjects for this study group ; twenty - three subjects in the study group have been excluded from the study . at the end of the study , there were 318 patients for the study group . correlation between cva and vertebrae morphology , craniofacial malformations , and skeletal malocclusions were reported in the previous studies . the aims of our study were to identify the prevalence of cva in turkish population and also whether there is a correlation between cva and dental malocclusion . in our study , the prevalence of fusion and pad were found 8.1% and 5.0% , respectively [ table 1 ] . besides , a statistically significant correlation ( p = 0.025 ) was found among cva and dental malocclusions [ table 3 ] . the prevalence of cva was reported with a wide range of 0 - 61.4% in the literature . sonnesen and kjaer reported that the incidence of fusion ( 61.4% ) more common in skeletal class iii patients and skeletal horizontal overjet when compared with control group ( 14.3% ) . they revealed that if a skeletal horizontal overjet was caused by maxillary retrognathia , the decreased prevalence of fusion more likely seen . reported that the descending distribution of cva were determined in skeletal class i , ii , and iii malocclusion , respectively ( 17 ) . in addition , a higher prevalence of c1 level partial cleft and occipitalization was reported in their study . our study was designed to investigate dental malocclusion , but the previous studies were planned to examine skeletal anomalies . to the best of our knowledge , this is the first study evaluate the frequency and distribution of cvas in orthodontic patients with dental malocclusions . had stated that the angle of the cranial base and the head posture deviations were sexually dimorphic , females showing larger cervicohorizontal , and cranial base angles than males . in addition , they reported that the relation between the cervical column fusion and cranial base angle , the inclination of the upper cervical spine and cervical lordosis were determined in females . hence , it could be hypothesized that cervical column fusion has a dimorphic pattern in their occurrence . in contrast , some researchers affirmed that there was no significant relation between gender and the occurrence of cva in their studies . so that , our findings supports the studies showing no gender dimorphism [ table 2 ] . it is not clear why vertebral anomalies occur and why these anomalies occur in different craniofacial morphology groups and skeletal malocclusion traits . the genetic studies and insight of the early embryogenesis might be essential to understand the etiology of the cva . the recent studies affirmed that the notochord may be responsible to these anomalies . because the vertebral bodies were formed around the notochord in the prenatal period . besides , the jaws develop from the migration of the neural crest cells to the craniofacial area before the notochord is surrounded by bone tissue . however , the association between the precise signaling of notochord to the neural crest and the migration of the neural crest cells to the craniofacial area is still unknown . lateral cephalograms are usually used in orthodontic clinics to planning pretreatment and examined the postorthodontic treatment results . early diagnose of these pathologies on cephalograms can provide essential documentation to the patient due to symptoms , injury , aging , and progression of the degenerative process . however , two - dimensional radiographs may not be valid in the diagnosis of cva , because of the superimposition of the spine inclination and radiographic overlapping of the facets . for this reason , the suspectable sign of cva on cephalogram is reevaluated with three - dimensional imaging systems like cone beam computed tomography to prevent misdiagnose . the prevalence of fusion and pad were found 8.1% and 5.0% in turkish population , respectivelystatistically significant differences were found among the dental malocclusions , and no statistically significant correlation between cva and angle class i , ii , and iii malocclusionno statistically significant differences were also found between the genders , and no statistically significant correlation between cva and genders were found . 
  the prevalence of fusion and pad were found 8.1% and 5.0% in turkish population , respectively statistically significant differences were found among the dental malocclusions , and no statistically significant correlation between cva and angle class i , ii , and iii malocclusion no statistically significant differences were also found between the genders , and no statistically significant correlation between cva and genders were found .
aims : the aims of our study were to investigate the distribution of cervical vertebrae anomalies ( cvas ) among dental angle class i , ii , and iii malocclusions in turkish population and whether a correlation between cva and dental malocclusion.materials and methods : the study was performed on lateral cephalometric radiographs which were taken at the department of orthodontics , faculty of dentistry , kirikkale university . 
 the final sample of 318 orthodontic patients was included in the study . 
 dental malocclusions were performed according to angle classification . 
 cvas were categorized : ( 1 ) fusion and ( 2 ) posterior arch deficiency ( pad ) . 
 the chi - square test was used to the analysis of the potential differences among dental malocclusions.results:the final sample of 318 patients was examined . 
 cva was observed in 42 individuals ( of 26 [ 8.17% ] had fusion and 16 [ 5.03% ] had pad ) , with a frequency of 13.2% . 
 of the 26 fusion defect , 8 ( 30.7% ) had angle class i , 8 ( 30.7% ) had angle class ii , and 10 ( 38.4% ) had angle class iii malocclusion . 
 of the 16 pad , 8 ( 50% ) had angle class i , 8 ( 50% ) had angle class ii but no patients with angle class iii malocclusion was observed . 
 the distribution of dental malocclusions regarding cva was not statistically significant ( p = 0.076 ) . 
 of these 42 individuals with cva , 52.3% ( 15 fusions and 7 pad ) were females and 47.7% ( 11 fusions and 9 pad ) were males.conclusion:in our study , the prevalence of fusion and pad were found 8.1% and 5.0% in turkish population , respectively . besides , no statistically significant correlation between cva and angle class i , ii , and iii malocclusions were found . 
 our findings support the studies showing no gender dimorphism .