Study design and Population
This cross-sectional study carried out among adults aged 18 to 65 years old between May and October 2016 in Tabriz (Iran). A population-based household survey was conducted in order to recruit a representative sample of adults from the community. Only adults who were living in the study area and who were at home at the time of data collection were included in the study. Written informed consent was obtained from each participant. Those with mental and cognitive disorders were excluded. The Ethics Committee in the Tabriz Medical University approved the present study. Participants approved to participate in this study by giving informed consent.
Sampling and sample size
The sample size was calculated using based on the level of oral health status in adult population of Tabriz. To estimate the oral health status of 46% , with a 95% confidence and an error of 3%, 2310 the sample size was estimated.
The population of Tabriz was estimated to be 980,000 (aged 18-65) in 2016 . The study population was sampled using multi-stage cluster sampling design. The first sampling stage, four health care centers (HCCs) was randomly selected from 16 HCCs. In the next stage, 25% of blocks in the area of HCCs were selected. Then, every 11th household of each block was identified for the recruitments of the study participant. Finally, in each household eligible individual were asked to participate in the study. Sampling in the blocks was continued to reach the required sample size specified for that block.
Data Collection and questionnaire
The WHO’s oral health questionnaire (WHO’s OHQ) for adults was used for measuring oral health status and oral health behavior . WHO’s OHQ is comprised of the first six items assessing oral health status that consist of “ How many natural teeth do you have?”, “ How often during the past 12 months did you have toothache or feel discomfort due to your teeth?”, “Do you have any removable dentures?”, and “ How would you describe the state of your teeth and gums? Is it “excellent”, “very good”, “good”, “average”, “poor”, or “very poor”?. The second three items assessing oral health related behaviors including “how often do you clean your teeth”, “which tools do you use to clean your teeth?”, “do you use toothpaste to clean your teeth”, and “do you use toothpaste that contains fluoride?”
Two next questions were about “how long is it since you last saw a dentist?” and “what was the reason of your last visit to the dentist?” The next question assessed “dental problems experienced during the past 12 months” for example “difficulty in biting food” or “difficulty in chewing food” or “felt embarrassed due to appearance of teeth”, each of which had five possible answers (0= don’t know, 1= no, 2= sometimes, 3=fairly often, 4=very often).
The next question examined eating or drinking behaviors that consist of nine items; for example “eating fresh fruits” or “Biscuits and cream cakes” or “ drinking tea with sugar”, each items had six possible answers (1=never/seldom, 2=several times a month, 3= once a week, 4= several times a week, 5= every day, and 6=several times a day).
The next item assess tobacco using behaviors with five items (cigarettes, pipe, cigar, chewing tobacco and use snuff), each items had six possible answers (1=never/seldom, 2=several times a month, 3= once a week, 4= several times a week, 5= every day, and 6=several times a day). The last question assessed alcohol drinking behavior during the past 30 days with six possible answer (0=less than 1 drink to 5= 5 or more drinks).
Finally, all participants also responded to socio-demographic questions about age, gender, education, and marital status.
Validity and reliability of the WHO’s OHQ was assessed based on standardized cross-cultural translation guidelines project . English version of WHO’s OHQ was translated into Persian. The translation was done by two independent native Persian translators. Both translators agreed on a common translation. Then, the questionnaire was back translated from Persian to English by two professional translators. The translators and researchers checked and agreed on the final Persian version. Content validity was conducted in a pilot study on 20 targeted populations .
Cronbakh alpha coefficients ranged from 0.65 to 0.78. The Persian version of WHO’s OHQ had satisfactory validity and reliability among pilot population.
Statistical analyses were performed with Statistical Package for Social Science (SPSS 18 for windows, SPSS Inc.® headquarter, Chicago, USA). Normality of data was analyzed by Kolmogorov-Smirnov test. Discrete variables are presented with number and percentage. Chi-square analyses were used to test the difference between biochemical variables between two groups. Results were considered statistically significant at p < 0.05.