This study reported on a mass media periodontal campaign in order to evaluate periodontal knowledge of Iranian adults. Overall, the campaign was well received and the study showed significant knowledge improvement among the adult population.
Similar findings have been observed previously: for instance, Mårtensson et al. showed improvement of the knowledge on periodontal disease after a mass media campaign among Swedish population . Similarly, in a survey conducted in Norway, knowledge of how to prevent periodontal diseases was also increased up to three years after a mass media periodontal campaign . Public awareness improvement regarding periodontal health and disease and slight improvement of oral health status has been reported following a periodontal awareness program in New Zealand .
Mass media has long being used an important tool for promoting public awareness in health issues. Evidence suggests that mass media campaigns can produce positive change in health knowledge, attitude and beliefs, and healthy behaviour across populations [24, 25] and for several health topics including smoking cessation, HIV testing and health services utilization [26–28]. Moreover, the existing literature indicates that oral health promotion campaigns using mass media can also increase the level of knowledge, stimulate an interest, correct the attitudes and facilitate behaviour changes [10, 13, 14, 21, 29]. It has been shown that mass media intervention is effective in promoting health especially in developing countries . A systematic review demonstrated a positive impact of the mass media on knowledge of HIV transmission and reduction in high-risk sexual behavior in developing countries . A mass media campaign was also effective in mothers' knowledge and behavior regarding timely initiation of breastfeeding . On the other hand in developed societies the effect might be weaker .
Females and participants aged 25–36 years showed more improvements on periodontal knowledge. These findings were in contrast to a similar study in Sweden where no statistically significant association was reported between knowledge improvement and gender or age . In addition participants with higher education demonstrated much better periodontal knowledge improvement. Similar results were found by Mårtensson et al. where higher education was associated with better periodontal knowledge after the mass media campaign . It seems that in designing similar campaigns the educational level of audiences is an important issue. Improvement in knowledge among those with higher education might imply that either we should choose easier messages for public or target audience based on segmentation.
We believe the findings from this study could be a good starting point in launching similar campaigns in Iran. The study used a rigorous methodology in several areas. The campaign used television for transferring oral health messages as the main route, method recently shown to be the main source of information in Iran . The campaign launched through four national and one local channels and the main message was repeated hundred times in ten days. A stratified, multistage random sampling method, covering all 22 districts of Tehran, was considered to increase the representativeness of the sample. To assess periodontal knowledge we used a valid and reliable instrument created previously . Data on the follow-up session was collected from the same subjects participated in the baseline interview. In order to increase responsiveness, interviewers continue data collection after the campaign to reach response rate of 70%, approximately three referrals for each subject. Additionally, dropout analysis was performed to compare characteristics of subjects who have been lost with respondents. No statistical difference was found between characteristics of the participants and non-participants in the follow-up session. At the population level this makes the dropout rate and conclusions reasonable.
The three questions may not completely capture periodontal knowledge, however, the method used was similar to studies using short questionnaire to evaluate periodontal awareness . In addition the nature of our study did not allow having a control group, however the individuals who did not see the campaign were considered as controls. In fact, we compared those who seen the campaign and who did not. Huhman et al. used a similar method for comparison where they evaluated the effects of a mass media campaign on the levels of physical activity among children 9 to 13 years of age in the USA . Furthermore having access to other sources of information rather than TV such as newspaper, books, etc. may influence people’s medical knowledge. Thus, one might argue that the results were contaminated with other sources of information out of our control. Although in general this is true, the interval between baseline and follow-up assessments was short and therefore it is less likely that in this short period of time any major changes have been occurred.
Health promotion campaigns through mass media are expensive and need a secure source of funding if they are to become routine. It is argued that such approaches in developing countries might work  particularly when those are in line with government policies. However, further evaluation of mass media oral health campaigns and their effects on behavior change is recommended.