Introduction and objective: Tooth caries is the most prevalent infectious disease in children. The purpose of this study was to assess carries experience indexes and related factors among 7-12 year-old school children in Yasuj, Iran, in 2014.

Materials and methods: In the present Cross-sectional and analytical study, using a two-stage random sampling, 460 students from primary schools of Yasuj city and surrounding villages were selected. The children were clinically examined at their school by a professional calibrated dentistry team. Their demographic and socioeconomic status, mouth health behaviors and teeth carries status and consumed nutritional materials were gathered by a questioner and a dental chart. The data were analyzed using inferential statistical methods. The SPSS software version 22 was used to extract the outputs and &alpha=0.05 was considered as the significant level.

Results: The dental caries prevalence of deciduous, permanent and total of  two type of dents were  75.2, 41.1 and  89.8 percent, respectively and the dmft, DMFT and dmft+DMFT indexes were 3.57, 0.87, and 4.44, respectively.. The caries prevalence of permanent teeth and DMFT in girls were significantly higher than boys (p=0.046), but the caries prevalence in total of dents in boys was significantly higher than girls ( p=0.32). Furthermore, the dental caries prevalence in permanent teeth and DMFT in children resident in rural areas were significantly higher than those in urban areas (p<0.0001). The DMFT had a direct association with the children’s age and the dmft + DMFT index had a significant adverse linear correlation with Body Mass Index (BMI) of children (p=0.004). Moreover, the output indicated that tooth caries experiences in children who used dental flossing was significantly lower (p=0.027). Correspondingly, in children who used tooth brushing, consumed dairy foods, whom their fathers being official employees and parents having higher education, dental caries prevalence was lower (p>0.1).

 Conclusions: Prevalence and severity score of dental caries among 7 - 12 year-old Yasuj students were higher than the WHO standards. The tooth caries experiences were more prevalent in boys and in children resident in rural areas, increased with age and decreased with BMI and less prevalent in children with higher family socioeconomic status. Tooth brushing and flossing and consuming dairy foods were protective agents in occurring tooth caries in primary school children in Yasuj, Iran.