One hundred and sixty-four articles were included in the review. There were 36 randomised controlled trials (RCTs; n=3,353), 80 quasi- experimental studies (i.e. non-randomised clinical trials), 33 single-group pre-test post-test studies, 7 multiple baseline and 6 mass media studies; the number of participants for the other study designs was not reported.
RCTs (n=7): 4 RCTs reported a small non significant effect on the level of caries. Almost all of the oral health promotion initiatives which looked at caries involved the use of fluoride. The meta-analysis showed that the mean intervention effect was a caries reduction of 1.8 surfaces (95% CI: 0.38, 3.26).
Quasi-experimental studies (n=11): these studies indicated that the levels of caries could be reduced by daily brushing with a fluoridated toothpaste. The size of the intervention effect was dependent on the length of time that elapsed between the introduction and evaluation of the programme. Greater reductions in caries were observed in the longer-term studies. There was no evidence that the levels of caries were affected by interventions that did not involve daily brushing.
Single-group studies (n=3): these were poor studies and no conclusions could be drawn.
RCTs (n=23): the majority of studies used plaque levels in the participants' mouths as the outcome measure. The conclusions drawn in each individual study varied according to the follow-up period.
The majority of studies with short follow-up showed significant improvements in plaque levels, whilst studies with long periods of follow-up suggested that instruction and education about plaque control were not effective in the long term. The more elaborate and theoretically based interventions appeared to be no more successful in reducing plaque levels than the more simple approaches. A meta-analysis showed that the mean intervention effect was a 0.316 reduction in the plaque index (95% CI: -0.063, 0.695).
Quasi-experimental studies (n=33): there was no convincing evidence that school-based education programmes had any effect on the plaque levels in the participants' mouths, even when daily brushing at school was part of the programme. School-based programmes, whether run by dental professionals, teachers, or older pupils teaching younger pupils, have not been demonstrated to affect oral hygiene. In clinic- and work-based interventions, some experimental plaque control programmes with adults demonstrated dramatic reductions in plaque levels. Educating the parents about plaque control in their young children was effective.
Single-group studies (n=22): these were poor studies and no conclusions could be drawn.
Sugar consumption. Study designs not reported (n=8): the outcomes reported by these studies were behavioural intentions or reported behaviour. Thus, it was difficult to draw definitive conclusions from these studies.
Knowledge, attitudes and behaviours. Study designs not reported (n=37): these studies indicated that knowledge levels were invariably altered by the interventions described. Complex and technical educative methods added little benefit, and simple provision of information was sufficient to increase knowledge levels. However, the studies that included other outcome measures also suggested that alterations in knowledge, attitudes and beliefs were not related to changes in behaviour or health.
Mass media. Study designs not reported (n=7): these studies suggested that oral health promotion via the mass media was ineffective for promoting both knowledge and behaviour change. However, the authors stated that the evaluation methodologies in these studies were inadequate and, therefore, no specific conclusion regarding the role of mass media could be drawn.