title: Demographic, socioeconomic, and behavioral factors affecting patterns of tooth decay in the permanent dentition: principal components and factor analyses.
abstract: OBJECTIVE
  Dental caries of the permanent dentition is a multifactorial disease resulting from the complex interplay of endogenous and environmental risk factors. The disease is not easily quantitated due to the innumerable possible combinations of carious lesions across individual tooth surfaces of the permanent dentition. Global measures of decay, such as the DMFS index (which was developed for surveillance applications), may not be optimal for studying the epidemiology of dental caries because they ignore the distinct patterns of decay across the dentition. We hypothesize that specific risk factors may manifest their effects on specific tooth surfaces leading to patterns of decay that can be identified and studied. In this study, we utilized two statistical methods of extracting patterns of decay from surface-level caries data to create novel phenotypes with which to study the risk factors affecting dental caries.
  
  
  METHODS
  Intra-oral dental examinations were performed on 1068 participants aged 18-75 years to assess dental caries. The 128 tooth surfaces of the permanent dentition were scored as carious or not and used as input for principal components analysis (PCA) and factor analysis (FA), two methods of identifying underlying patterns without a priori knowledge of the patterns. Demographic (age, sex, birth year, race/ethnicity, and educational attainment), anthropometric (height, body mass index, waist circumference), endogenous (saliva flow), and environmental (tooth brushing frequency, home water source, and home water fluoride) risk factors were tested for association with the caries patterns identified by PCA and FA, as well as DMFS, for comparison. The ten strongest patterns (i.e. those that explain the most variation in the data set) extracted by PCA and FA were considered.
  
  
  RESULTS
  The three strongest patterns identified by PCA reflected (i) global extent of decay (i.e. comparable to DMFS index), (ii) pit and fissure surface caries and (iii) smooth surface caries, respectively. The two strongest patterns identified by FA corresponded to (i) pit and fissure surface caries and (ii) maxillary incisor caries. Age and birth year were significantly associated with several patterns of decay, including global decay/DMFS index. Sex, race, educational attainment, and tooth brushing were each associated with specific patterns of decay, but not with global decay/DMFS index.
  
  
  CONCLUSIONS
  Taken together, these results support the notion that caries experience is separable into patterns attributable to distinct risk factors. This study demonstrates the utility of such novel caries patterns as new outcomes for exploring the complex, multifactorial nature of dental caries.
authors.affiliation: Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA. jrs51@pitt.edu
authors.forename: John R
authors.initials: JR
authors.lastname: Shaffer
authors.forename: Deborah E
authors.initials: DE
authors.lastname: Polk
authors.forename: Eleanor
authors.initials: E
authors.lastname: Feingold
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Wang
authors.forename: Karen T
authors.initials: KT
authors.lastname: Cuenco
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Weeks
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: DeSensi
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Weyant
authors.forename: Richard
authors.initials: R
authors.lastname: Crout
authors.forename: Daniel W
authors.initials: DW
authors.lastname: McNeil
authors.forename: Mary L
authors.initials: ML
authors.lastname: Marazita
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001061:Appalachian Region / Q000453:epidemiology; D004245:DMF Index; D003731:Dental Caries / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D019229:Dentition, Permanent; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D025341:Principal Component Analysis; D012307:Risk Factors; D012959:Socioeconomic Factors
keywords: dental caries; factor analysis; permanent dentition; pit and fissure surfaces; principal components analysis; smooth surfaces; tooth brushing; tooth surfaces