Dental service rates: age, period, and cohort effects

Variation in dental service provision over time has been related to changes in factors such as oral health and demographics. Dentist factors such as age and cohort effects are also potential sources of influence. The aim of the study was to examine the operation of age, period, and cohort factors on variation in service rates.

data were collected by a mailed survey of a random sample of 10% of male and 40% of female dentists from each state/territory of Australia in 1983-84, 1988-89. and 1993-94 with response rates of 73, 75 and 74% respectively.

Data on main areas of service were obtained from a log of service items provided on a typical day.

Poisson regressions of rates for the 10 main areas of service over time showed increased rates over the study period for diagnostic, preventive, endodontic, crown and bridge, general/miscellaneous and orthodontic services, and decreased rates of prosthodontic services. Goodness-of-fit tests indicated that models for periodontal and endodontic services had a good fit. However, only endodontic services were readily interpretable in terms of descriptive trends. While the age-period-cohort model was preferred, age-period and age-cohort models were also examined because of problems of identification with age-period-cohort models. Endodontic rates were higher among younger dentist birth cohorts, and increased over the 10-year study period for most cohorts of dentists.

If these effects for dentist cohorts were extrapolated over the next 10-year interval, the distribution of services would alter, with endodontic services emerging as a dominant area behind restorative, diagnostic, and preventive services.