title: Longitudinal changes in dental services provided by Australian dentists.
abstract: OBJECTIVE
  To estimate the longitudinal change in number of patients per year (PPY) per dentist by age and sex of dentists in Australia.
  
  
  METHODS
  Dentists were selected randomly from Australian dental registers, the baseline collection was in 1983 and repeated approximately every 5 years until 2009. Dentist's practice activity was collected by mailed questionnaire. Number of PPY was calculated from work hours and number of patients per week per dentist. Mixed-effects regression was applied to estimate both individual random effects and population averaged fixed effects for the number of PPY provided by age, time, and sex.
  
  
  RESULTS
  A total of 1,449 dentists completed 2,822 questionnaires from six waves of data collection (1983 to 2010). The average PPY decreased over the time of the study. The rate of change in PPY accelerated during younger ages and reached a peak when they moved into 50 years old (B = 86.04, P < 0.0001), and then decelerated (B = -0.90, P = 0.0002) across time. The mean number of PPY was higher in male dentists than female dentists in the same 10-year age group. The pattern of PPY change with aging was an inverted U-shape for male dentists. In contrast, there was a U-shape for female dentists.
  
  
  CONCLUSIONS
  The longitudinal change in PPY with aging was an inverted U-shape, which accelerated during younger age, and decelerated after reaching a peak at 50 years old. Males had higher PPY than female dentists at the same age. The pattern of PPY was different between male and female dentists.
authors.affiliation: Australian Research Centre for Population Oral Health (ARCPOH), The University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Xiangqun
authors.initials: X
authors.lastname: Ju
authors.affiliation: Australian Research Centre for Population Oral Health (ARCPOH), The University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: David S
authors.initials: DS
authors.lastname: Brennan
authors.affiliation: Australian Research Centre for Population Oral Health (ARCPOH), The University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: A John
authors.initials: AJ
authors.lastname: Spencer
authors.affiliation: Australian Research Centre for Population Oral Health (ARCPOH), The University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Dana N
authors.initials: DN
authors.lastname: Teusner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001315:Australia; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D019239:Practice Patterns, Dentists' / Q000706:statistics & numerical data*; D011795:Surveys and Questionnaires
keywords: longitudinal study; mixed-effects models; patient visits