Aims: In 2007, Finnish authorities gave a national recommendation that schools should not sell sweet products. This study aimed to determine the effects of the national recommendation on school-level intermediary determinants (factors related to oral health inequalities) and if the changes were different according to school-level socio-economic position (SEP). Methods: This ecological and longitudinal study combined school-level data from two independent studies from Finnish upper comprehensive schools (N = 970): the School Health Promotion study (SHPS) and the School Sweet Selling survey (SSSS). The baseline data (SHPS from 2006-2007 and SSSS from 2007) and the post-intervention data (SHPS and SSSS from 2008-2009) were combined into a longitudinal school-level data set (n = 360 and response rate = 37%). The intermediary determinants were: attitudes and access to intoxicants, school health services, school environment, home environment, schools' health-promoting actions (including sweet product selling) and pupils' eating habits. Three equal-sized school-level SEP group - slow, middle and high - were formed. The changes in the intermediary determinants were analysed using Wilcoxon Signed Ranks test. Differences between school SEP groups were analysed the using Kruskal-Wallis test. Longitudinal linear mixed modelling was used to determine the contribution of intermediary determinants to the changes in pupils' eating habits. Results: The national recommendation was effective in decreasing sweet product selling at schools and the effect was equal in each school-level SEP group. Intermediary determinants contributed differently to eating habits in the three SEP groups. Conclusions: A national recommendation seems to be an effective tool in making the school environment healthier without increasing inequalities.
Keywords: Diet; health promotion; inequalities; longitudinal study; oral health behaviour; school oral health policy; schools; socio-economic factors.