Has the prevalence and severity of dental erosion in Norway changed during the last 30 years? -

Is dental erosion more frequent nowadays, the objective was to compare the prevalence and severity of dental erosion among 16–18 year-olds in Norway in 2012 with 15 year-olds in 1985.
Thirty years ago, the prevalence of dental erosion was in the same order as reported nowadays, but the condition seemed less severe.