title: Prevalence of and factors affecting malocclusion in primary dentition among children in Xi'an, China.
abstract: BACKGROUND
  This study aimed to investigate the prevalence and associated factors of malocclusion among children with primary dentition in Xi'an, China.
  
  
  METHODS
  A total of 2,974 subjects were selected from local schools in Xi'an city using a stratified cluster sampling method from January to September 2015. After screening samples according to the inclusion criteria, the final sample size comprised 2,235 pre-school children, with a mean age of 4.82 (SD, 1.76; range, 2.63-6.12) years. Malocclusion traits were assessed by trained clinicians followed by the evaluation of associated factors through clinical examination and a precisely designed questionnaire including data regarding gender, birth place, parental education level, monthly familial income, parental attitude toward the problem of malocclusion, feeding methods of the children, feeding postures, pacifier use, and delivery methods. Data were analyzed using the Chi-square test and logistic regression analysis.
  
  
  RESULTS
  The most common type of malocclusion was increased overjet (34.99 %) in the sagittal direction, deep overbite (37.58 %), and midline deviation (25.32 %) in the vertical and transverse directions, respectively. The prevalence of posterior crossbite, anterior crossbite, and anterior open bite was 7.56, 6.80 and 6.98 %, respectively. The prevalence of the anterior edge-to-edge occlusion was the lowest (2.46 %). The variables associated with malocclusion (P < 0.05) were birth place (odds ratio [OR] = 1.741 with 95 % CI of 1.384-2.162), insufficient abrasion of primary canines (OR = 1.465; 95 % CI of 1.153-1.894), caries in primary teeth (OR = 2.045; 95 % CI of 1.665-2.539), tongue thrusting (OR = 2.833; 95 % CI of 1.640-3.649), mandibular prognathism (OR = 2.621; 95 % CI of 1.574-3.689), and finger sucking (OR = 1.573 with 95 % CI of 1.098-2.014). The feeding methods (OR = 3.614 with 95 % CI of 3.087-4.596) along with the method of delivery (OR = 1.847 with 95 % CI of 1.323-2.451) have been observed to play an important role in the morbidity of malocclusion (P < 0.05).
  
  
  CONCLUSIONS
  The prevalence of malocclusion among pre-school children in Xi'an is higher compared to that in other geographical parts of China. Therefore, early attention to the development of occlusion and necessary interventions toward the associated factors are important to reduce its prevalence and further adverse effects.
authors: State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Diseases, Department of Pediatric Dentistry, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China.
authors: Zhifei
authors: Z
authors: Zhou
authors: State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Diseases, Department of Pediatric Dentistry, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China.|Department of Oral Medicine, Northwest Women's and Children's Hospital, Xi'an, People's Republic of China.
authors: Fen
authors: F
authors: Liu
authors: State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Diseases, Department of Pediatric Dentistry, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China.|Department of Oral Medicine, PLA 261 Hospital, Beijing, People's Republic of China.
authors: Shuning
authors: S
authors: Shen
authors: State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Diseases, Department of Pediatric Dentistry, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China.|Department of Pediatric Dentistry, Foshan Stomatological Hospital, Foshan, People's Republic of China.
authors: Linjuan
authors: L
authors: Shang
authors: Department of Health Statistics, School of Public Health, Fourth Military Medical University, Xi'an, People's Republic of China. shanglei@fmmu.edu.cn.
authors: Lei
authors: L
authors: Shang
authors: State Key Laboratory of Military Stomatology, National Clinical Research Center for Oral Diseases, Department of Pediatric Dentistry, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China. wxjingpd@hotmail.com.
authors: Xiaojing
authors: http://orcid.org/0000-0001-5485-750X
authors: X
authors: Wang
mesh_terms: D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D005386:Fingersucking; D006801:Humans; D008297:Male; D008310:Malocclusion / Q000453:epidemiology*; D015995:Prevalence; D014094:Tooth, Deciduous
keywords: Cross-sectional study; Epidemiology; Malocclusion; Prevalence; Primary dentition