title: Unification of the "burst" and "linear" theories of periodontal disease progression: a multilevel manifestation of the same phenomenon.
abstract: Previously, burst and linear theories for periodontal disease progression were proposed based on different but limited statistical methods of analysis. Multilevel modeling provides a new approach, yielding a more comprehensive model. Random coefficient models were used to analyze longitudinal periodontal data consisting of repeated measures (level 1), sites (level 2), teeth (level 3), and subjects (level 4). Large negative and highly significant correlations between random linear and quadratic time coefficients indicated that subjects and teeth with greater-than-average linear change experienced decelerated variation. Conversely, subjects and teeth with less-than-average linear change experienced accelerated variation. Change therefore exhibited a dynamic regression to the mean at the tooth and subject levels. Since no equilibrium was attained throughout the study, changes were cyclical. When considered as a multilevel system, the "linear" and "burst" theories of periodontal disease progression are a manifestation of the same phenomenon: Some sites improve while others progress, in a cyclical manner.
authors.affiliation: Biostatistics Unit, Academic Unit of Epidemiology and Health Services Research, Medical School, University of Leeds, 24 Hyde Terrace, Leeds, LS2 9LN, UK. m.s.gilthorpe@leeds.ac.uk
authors.forename: M S
authors.initials: MS
authors.lastname: Gilthorpe
authors.forename: A T
authors.initials: AT
authors.lastname: Zamzuri
authors.forename: G S
authors.initials: GS
authors.lastname: Griffiths
authors.forename: I H
authors.initials: IH
authors.lastname: Maddick
authors.forename: K A
authors.initials: KA
authors.lastname: Eaton
authors.forename: N W
authors.initials: NW
authors.lastname: Johnson
mesh_terms: D000293:Adolescent; D000328:Adult; D015986:Confounding Factors, Epidemiologic; D018450:Disease Progression; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D008889:Military Personnel; D008954:Models, Biological; D017622:Periodontal Attachment Loss / Q000473:pathology; D010510:Periodontal Diseases / Q000503:physiopathology*; D010512:Periodontal Index; D010514:Periodontal Pocket / Q000473:pathology; D012044:Regression Analysis; D012307:Risk Factors; D011795:Surveys and Questionnaires