Sample and procedures
A randomized controlled trial was conducted in elementary school children and their parents seen between May and August 2017 in a dental clinic located in a middle class socioeconomic area of Tehran, Iran. Children were recruited from a public dental clinic that provides dental care services mostly to those covered by health insurance. The majority of services in this clinic are free or at low cost to patients. A convenience sample fulfilling inclusion and exclusion criteria was recruited to participate in the study. Sample size was determined using a formula suggested by Chow et al. [33] to estimate the number of participants necessary to identify at least a moderate effect size of 0.55 for behavior change [34] with a type I error rate of 0.05 and type II error rate of 0.20 for a one unit change in standard deviation. With an estimated attrition rate of 5 percent, it was determined that 112 participants would be necessary to include in the study. Therefore, this number of participants was identified and randomly assigned to either the intervention or control group using a random numbers table with an allocation ratio of 1:1. Simple randomization was performed using a shuffled deck of cards. Sequentially numbered cards were used to perform determine the random allocation sequence. Enrolling participants and random assignment to intervention or control groups was carried out anonymously by individuals on the research team. Because of the nature of intervention (education), there was no possibility of blinding examiners, who knew which group participants were in. Only statistical analyses were performed blinded to treatment group. Inclusion criteria were age 6–12 years (elementary school children), participation of at least one parent (either father or mother), being a permanent resident in the enrollment area, having a medical record in the dental clinic, and being able to speak and understand Persian. Children with advanced oral diseases or other serious medical conditions or disabilities, those routinely using anti-inflammatory agents, those who had used antibiotics within the past two weeks, children with illiterate parents or parents whose job was related to dentistry, and those receiving ongoing orthodontic treatments were excluded. The main outcome was oral health status as measured by DMFT score, gingival health index, and constructs of the HBM and related behaviors. The dentist who performed the clinical examination was first educated on the study’s aims and the nature of intervention. She then, accompanied by an oral health educator, conducted the examination and answered any queries regarding the scale. The training was done based on WHO guidelines [35, 36] however, no calibration was performed to calculate Kappa correlation index for caries examination.
The study protocol was approved by the institutional review board committee of Baqiyatallah University of Medical Sciences (#BMSU.1395.63789). The study was also retrospectively registered on 08/11/2021 in the clinicaltrials.gov under this identifier: NCT05112224. Children and their parents were informed about the study and provided written informed consent to participate (written consent from parents and oral consent from children). Administrative staff in the dental clinic, after being informed on study qualifications, directed potential participants to researchers, who provided further information about the study and obtained consent. Those who met inclusion criteria then completed questionnaires and underwent a dental examination to be described later. The dental examination was conducted by a trained dentist. Questionnaires were distributed and explained by a qualified health educator. Parents completed the demographic and HBM-related questionnaires. The CONSORT flow diagram of the study has been included in the Fig. 1.
Measures
Demographic information on child and parent age, academic grade, parent education, parent job, family income level, and coverage for dental services by health insurance was obtained from parents.
Papillary bleeding index (PBI)
The PBI was used for gingival assessment. This scale, developed by Muhlemann (1977), was used to evaluate different areas of gingiva in terms of bleeding when probed [37]. This was conducted by entering a probe into the base of papilla and then moving it to the tip of the papilla. The distal aspect of the papilla was also assessed in this way. PBI ratings consist of 5 grades. Grade 0 indicates no bleeding on probing, whereas grade 4 indicates profuse bleeding that spreads to the marginal gingiva. The scale has been used in previous studies in Iranian populations and demonstrated acceptable psychometric properties in diagnosing gingivitis and periodontal problems.
Decayed, missing, and filled teeth (DMFT)
DMFT is a traditional oral health index developed in 1930s and is still used as the primary measure of dental health around the world, especially for epidemiological purposes. The index provides the sum of decayed, missing, and filled teeth that an individual has, and ranges from 0 to 28 in adults, with higher scores indicating poorer oral health status. When a person is caries free, the DMFT score is 0. Number of decayed, missing and filled teeth may also be calculated separately, with the proportion of decayed teeth (D/DMFT) indicating unmet treatment need and the proportion of filled teeth (F/DMFT) indicating access to dental services. DMFT score is also one of the common oral health indices used in young Iranians, especially among school-age children. The DMFT score in 12-yer-old children is one of the standard measures of oral health used by WHO to compare oral health between regions and countries [36]. To measure DMFT score the study examiner (dentist) must be trained using guidelines provided by the WHO that have been manualized [36]. The DMFT scale has been used in several experimental studies to measure changes related to oral health [21].
Health belief model questionnaire (HBMQ)
The HBMQ developed by Kasmaei et al. (2014) addresses six aspects of HBM, including subscales assessing perceived susceptibility (3 items), perceived severity (7 items), perceived benefits (3 items), perceived barriers (7 items), self-efficacy (5 items), cues to action (3 items), and behavior (3 items). Responses to items on all subscales, except the behavior subscale, range from completely disagree (0) to completely agree (4), asking participants to rate sentences representing their beliefs concerning each of these six domains. The behavior subscale asks about frequency of behaviors such as use of mouth wash, teeth brushing, and teeth flossing from never (0) to always (4). The score of each subscale is computed by summing the score of all items belonged to that subscale and for the total score, summing scores on all subscales with the exception of the perceived barriers subscale. Higher subscale and total scores indicate more positive attitudes/beliefs. For the perceived barriers subscale, lower scores indicate that the person believes they have the capacity to overcome barriers related to improvement of his/her oral health status. The HBMQ was originally developed as a part of a doctoral thesis in Iran to measure HBM constructs on oral health in Iranian elementary school children and their parents, and has well-established psychometric properties in this population [38].
Educational intervention
Those in the test group received an educational intervention as described below, while those in the control group received only the routine educational program provided by the dental clinic. The routine educational program for control group consisted of a weekly face-to-face sessions on the importance of oral health for children and related preventive behaviors such as brushing and flossing. This education was provided by an oral health technician over a time period of approximately one hour, which is largely repetitive from session to session. The educational program for the test group was scheduled in five consecutive weekly sessions based on HBM principles. HBM principles including perceived susceptibility, perceived severity, perceived benefits and barriers, cues to action, and self-efficacy were used to design the intervention program. The intervention was applied by an oral health educator (expert both on oral health and health education). The conceptual theoretical approach for this intervention was adapted from Glanz et al. (2015) [29]. Each session lasted approximately one hour, and all of sessions were held between 9:00 and 11:00AM. Participants in the intervention group (children and one of their parents) were divided into groups consisting of 12–15 members in whom the educational program was administered. As noted above, the trained health educator skilled in oral health education facilitated all of the sessions.
In the first session, focus was placed on perceived susceptibility. For this session, a short lecture (20 min) was first provided that described statistics on oral health diseases especially for dental caries in school-age children. Next, participants in the group were asked to explain how much they thought they might be at risks of such problems and why. Both children and parent were encouraged to participate in this discussion. In the second session, the focus was on perceived severity. This session began by describing a story on outcomes related to oral health problems. In this story, the experiences of a 10-year-old boy regarding health problems due to dental caries were described, thereby illustrating problems that may develop for children who failed to engage in preventive strategies and early treatment of dental problems. At the end of this session participants were encouraged to share first-hand or second-hand experiences that may have been similar to the case presented. The third session emphasized oral disease prevention skills and their perceived benefits. The behaviors most strongly emphasized were teeth brushing, flossing, and use of mouthwash, illustrated on a model of teeth. Information regarding the timing and frequency of such behaviors was also provided. Participants were then asked to prepare a list of all potential benefits regarding the demonstrated behaviors and then to discuss these benefits with the overall group. The fourth session focused on perceived barriers to performing oral health behaviors. Participants were asked to bring up and discuss attitudes or beliefs that might prevent them from carrying out the behaviors correctly. The facilitator, with contribution from other participants in the group, then corrected wrong beliefs and provided strategies for overcoming the barriers. In the fifth and last session, the health educator discussed how to increase self-efficacy with regard to oral health behaviors. First, an educational video was played showing a healthy role model, i.e., a child correctly performing behaviors such as brushing and flossing. Participants were then asked how much they trusted themselves to correctly perform these behaviors and if there were any questions on the proper ways to do so. Competing behaviors or stressors that might impede participants from performing the health-related behaviors were also asked about and suggestions on how to overcome those barriers were provided. Finally, to address the cues to action dimension of the HBM, the cell phone number of parents was obtained and a text message reminder was sent every two weeks for three months after the intervention on the importance of oral health behaviors.
Data analysis
Descriptive data were reported by means (M) (with standard deviation) for quantitative measures or numbers (N) (with percent) for categorical variables. To examine between-group differences at baseline, the Chi-square test or Fisher’s exact test (if applicable) was used for categorical variables. Normal distributions were examined using the Shapiro–Wilk test. If the p value for this test is greater than 0.05, then the data distribution is considered normal. The Student’s t-test was also used to examine between-group differences before and after the intervention for continuous variables. The Levene’s test was used to assess the homogeneity of variances between groups when using the t-test. If the resulting p value on this test is greater than 0.05, then no significant difference between groups is considered present in terms of variances. The paired t-test was used to assess within-group differences from baseline to follow up. Means and 95% confidence intervals (CI) were used in reporting between-group and within-group differences. To adjust for baseline differences between groups, analysis of covariance test (ANCOVA) was used. In the model, baseline variables were entered as covariates with group as a fixed factor (independent variable) and follow-up data on dependent variables. Homoscedasticity was assessed before using ANCOVA by producing a scatter plot of residuals compared to predicted values. For significant results, the alpha level was set at less than 0.05. All statistical analyses were performed using SPSS version 24 for Windows (IBM statistics, Armonk, NY).