Changes in periodontitis prevalence over two decades in New Zealand: evidence from the 1988 and 2009 national surveys.

Objectives: To determine whether the prevalence of periodontitis in New Zealand adults changed between 1988 and 2009, and, if changes did occur, to determine the nature of any sex differences in those changes.

Design: Secondary analysis of data from national oral health surveys conducted in 1988 and 2009.

Methods: Computation of CPITN-equivalent estimates from the 2009 data, in order to enable direct comparison with the 1988 estimates. The statistical significance of any observed changes was determined by examining for overlapping 95% confidence intervals.

Results: For CPITN scores 3 and 4 ("any pocketing"), there was no change in the 20-24 age group, but significant decreases in the 35-44 and 65-74 age groups were observed. Among males, there was a slight increase in the 20-24 age group, and substantial decreases in the 35-44 and 65-74 age groups. Among females, there was a slight increase in the 20-24 age group, and substantial, statistically significant decreases in the 35-44 and 65-74 age groups.

Conclusions: There have been significant reductions in the prevalence of periodontitis among people aged 35-44 and 65-74 years over two decades in New Zealand (and most notably among women), but no such reductions were observed among those aged 20-24 years.