This study conducted to determine the status of DMFT among 12-year-old students in Gonabad and Bajnestan, two desert districts and its association with their individual and family characteristics in 2016. The total mean (SD) of the students’ DMFT was 1.47 ± 1.82 (in boys and girls 0.98 ± 1.47 and 1.91 ± 1.98, respectively). Also, based on the results of multiple logistic regression analysis, DMFT index had a significant relationship with the subjects’ sex, parents’ education, birth rank, and place of residence, but not with dental health behaviors of the students.
In our study, the students’ DMFT was 1.47 which was less than in Iran, as a whole (1.84) as well as in Khorasan Razavi province (1.71), based on the latest national oral and dental health survey (10). This was also less than some similar studies in Iran (25, 26), Saudi Arabia (27), Eritrea (23), Korea (28), and Libya (29); while more than that of some studies in India, China and Sudan (7, 22, 30). This discrepancies in various studies conducted in different geographical areas with different climate situations indicate that oral and dental health, rather than being affected by climate condition, are more affected by factors such as cultural, racial, access to dental services, nutritional habits, lifestyle, and the students’ status of education for dental health and providing preventive dental health services to them (23, 31, 32).
There was statistically significant difference between DMFT of the girls and boys in our study; so that the odds of caries in the girls was 2.69 times of the boys. This was consistent with the results of Zhang et al.(33) and Huew et al. (29) Yousefi et al. (34) and Gorgi et al. (14) ; but not to the results of study by Al-Akwa et al. (3) and Andegiorgish et al (23) and Toomarian et al (35). The high DMFT index in girls may be due to the earlier onset of permanent teeth, which makes their teeth longer exposed to rot; though, this measure, probably in the long run, become equivalent in both sexes (23, 27).
The results of this study showed that there is a significant association between the students’ DMFT and their residency location which means the students living in urban areas had higher odds of caries than those in rural areas (OR = 1.48). This is comparable with the results of d Al-Akwa et al. studies (3), while our result is not similar to Giacaman et al (36) study results. One of the potential explanation for this difference is that the urban students have probably more access to sugary foods and beverages, snacks (i.e. puff and chips), and fast food than rural students (3). These edibles could increase the risk of dental caries. Differences in Fluoride drinking water between urban and rural areas could be another reason for this discrepancy. Besides, because of lower student population in rural areas, better implementation of and more success in dental health programs such as using sodium fluoride mouthwash by students, varnish Fluoride therapy and fissure Sealant for Students would be a potential outcome. Although more studies need to evaluate this probability.
Our results showed that there is a significant relationship between the students’ DMFT and their mother level of education, which means that with the increase of mothers' education, the chance of dental caries in students is higher. Although the results of many studies in many countries such as Iran (37–39), China (40), and Greece (41) are not similar to our findings, some studies have not reported a meaningful statistical relationship between parents' education and dental caries. Of their children (42, 43). Even a Norwegian study showed that the chances of dental decay in children with one or both parents with low level of education are two and three times higher than children who have parents with high education level, respectively (44). Possible reasons for the difference in outcome may be due to differences in the age of the subjects, consideration of the parents' employment status, cultural and socioeconomic status of the children, and statistical methods used in various studies.
In our study, there was a direct association between the subjects’ DMFT and their birth rank. Indeed, the odds of dental caries of the students increased with their birth ranks. This was comparable with other studies (45, 46). This result is due to the fact that the increase in the number of children in the family is likely to reduce the parental attention of children. In addition, the number of children increase, the household expense increase; therefore, the possibility of receiving dental health care for children decrease and, subsequently, the probability of their dental caries increase (46).
In our study, there was no significant association between the students’ DMFT and their oral hygiene behavior such as using dental floss and brushing. Besides, there was no meaningful relationship between DMFT and using sodium fluoride mouthwash by the students. Our findings are similar to the results of QUAN and colleagues (40) in China, but inconsistent with Al-Akwa et al study results (3). It seems quality of dental floss use and brushing plays an important role in the prevention of dental caries. Meanwhile, the results of various studies have shown that the presence of standard fluoride in drinking water (3), as well as in mouthwashes and toothpastes, would be one of the effective factors on reducing dental decay (47). Therefore, since the fluoride is not added to drinking water in Iran, use of sodium fluoride mouthwash and fluoride-containing toothpastes, if used correctly and adequately, is recommended as routine intervention to reduce tooth decay.
There are some strengths in our study. Determining the oral health status by the dentist, using country program data, and entering the entire target population are some of the strengths of the study. One of the potential limitations is the use of more than one dentist in the Oral Health Program of Gonabad and Bajestan Students. This may have led to an inaccuracy of the gathered data due to inter-personal variation. To control this concern, all dentists were initially trained on how to implement the national plan, and they used the same checklist during the implementation of the plan. Moreover, the required data were extracted from the checklists used in the national program for oral health; so, the probability of inaccuracy in completing them would be another limitation of the present study.