Dentist age, period and cohort effects on provision of dental services in Australia: 1983-84 to 2009-10.

OBJECTIVE: To examine age, period and cohort factors of dentists in relation to diagnostic, preventive and total dental services over time in Australia.

METHOD: The Longitudinal Study of Dentists' Practice Activity (LSDPA) was designed to monitor dental practice activity and service provision in Australia. Participating dentists were sampled randomly from the dental registers in Australia from 1983 to 1984, and dental services provision was collected by mailed questionnaire with a log of dental services provided over one or two typical days. The data collection has been repeated every 5 years until 2009-2010. Sample supplementation of newly registered dentists occurred at successive waves. This study focused on diagnostic, preventive and total services. The time trends in the mean rates of the services were described using a standard cohort table, and negative binomial regression was applied to estimate age, period and cohort effects.

RESULTS: The response rates were 73%, 75%, 74%, 71%, 76% and 67% in 1983, 1988, 1993, 1998, 2003 and 2009, respectively. The mean rates of diagnostic, preventive and total services increased between 1983 and 2009 across all age groups. The period effect showed a higher rate of diagnostic (rate ratios [RR]: 1.21 in 1993 to 1.80 in 2009), preventive (RR: 1.19 in 1988 to 1.85 in 2009) and the total service (RR: 1.08 in 1988 to 1.39 in 2009) over time, compared with the reference group of 1983. Older cohorts had a lower rate, and the younger cohorts had a higher rate of diagnostic, preventive and the total number of services over the study period. The highest rate of diagnostic (RR=2.53), preventive (RR=2.44) and the total service (RR=1.52) was in those aged 25-29 years in 1983 compared with the reference group of 30-34 years in 1983.

CONCLUSIONS: Trends in dental services provision can be associated with age, period and cohort effects. The study found the rate of diagnostic, preventive and total services increased over time. Meanwhile, an increasing rate of diagnostic, preventive and the total services was observed when moving from older cohorts to younger cohorts among Australian dentists suggesting a sustained shift towards these services into the future.