Dental service rates: age, period, and cohort effects

Objective 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. Th e aim of the study was to examine the operation of age. period, and cohort factors on variation in service rates. Basic research design Data were coll ected by a mailed survey of a random sample of 10% of male and 40% of femal e dentists from each state/territory of Australia in 1983-84, 1988-89, and 1993-94 with response rates of 73, 75 and 74% respectively. Main outcome me asures Data on main areas of service were obtained from a log of service it ems provided on a typical day. Results Poisson regressions of rates fur the 10 main areas of service over time showed increased rates over the study p eriod for diagnostic, preventive, endodontic. crown and bridge, general/ mi scellaneous and orthodontic services. and decreased rates of prosthodontic services. Goodness-of-fit tests indicated that models For periodontal and e ndodontic services had a good fit. However, only endodontic services were r eadily interpretable in terms of descriptive trends. While the age-period-c ohort model was preferred. age-period and age-cohort models were also exami ned because of problems of identification with age-period-cohort models. En dodontic rates were higher among younger dentist birth cohorts, and increas ed over the 10-year study period for most cohorts of dentists. Conclusions If these effects for dentist cohorts were extrapolated over the next 10-yea r interval, the distribution of services would alter, with endodontic servi ces emerging as a dominant area behind restorative. diagnostic, and prevent ive services.