Introduction: Dental caries is the most prevalent chronic disease among schoolchildren. We aimed to investigate the association between dental caries index and socio-demographic status in schoolchildren by using a multilevel hurdle model. Materials and Methods: A cross-sectional epidemiological study was carried out on 906 primary school pupils in Kerman, Iran in 2012. The subjects were selected through a stratified cluster random sampling. At first, the whole target area was stratified according to two geographic areas, the north and south area. Then each area was stratified according to gender. In the next step, several schools were considered as clusters, which were selected randomly in each geographic area and gender strata. All the schoolchildren in these schools were included in this study as samples. Twelve-year-old pupils were examined for dental caries. The dependent variable in this study was the dmft/DMFT index. Eight variables, including socio-demographic information, were collected. Multilevel negative binomial hurdle model was employed for data analysis. Results: The prevalence of caries-free pupils was 30.1% and the mean dmft/DMFT was 3.6 ± 2.2. Negative binomial part of the adjusted model showed that the dmft/DMFT adjusted rate for females was 1.36 (95% CI: 1.10-1.79) times higher than males. Also, the dmft/DMFT adjusted rate for overweight pupils was 0.86 (95% CI: 0.74-0.98) times lower than those with normal weight. Logistic part of the adjusted model showed that the posibility of caries-free state in overweight pupils was 1.95 (95% CI: 1.22-3.11) times higher than those with normal weight. In addition, pupils whose fathers and mothers were workers and housewives, respectively, and those with a high maternal age were at a greater risk for caries experience than others (p < 0.05). Conclusion: BMI, gender, parent’s job and mother’s age at delivery were factors effecting on dental caries in schoolchildren. These pupils need more attention to dental care.
 Petersen, P.E., Bourgeois, D., Ogawa, H., Estupinan-Day, S. and Ndiaye, C. (2005) The global burden of oral diseases and risks to oral health. Bulletin of the World Health Organization, 83, 661-669.
 Kopycka-Kedzierawski, D.T., Auinger, P., Billings, R.J. and Weitzman, M. (2008) Caries status and overweight in 2-to 18-year-old US children: Findings from national surveys. Community Dentistry and Oral Epidemiology, 36, 157-167. doi:10.1111/j.1600-0528.2007.00384.x
 Kazerouni, K., Mohammadi, N., Ansari, G. and Kamali, Z. (2005) The effects of socio-economic status on dental caries incidence in a group of primary school children, Tehran-2000. Journal of Dental School, 22, 51-59.
 Motlagh, M.G., Khanik, G.R.J. and Adiban, H. (2007) Investigation of dental caries prevalence among 6 -12 year old elementary school children in Andimeshk, Iran. Journal of Medical Sciences, 7, 116-120. doi:10.3923/jms.2007.116.120
 Momeni, A., Mardi, M. and Pieper, K. (2006) Caries prevalence and treatment needs of 12-year-old children in the Islamic Republic of Iran. Medical Principles and Practice, 15, 24-28. doi:10.1159/000089381
 Saied-Moallemi, Z., Virtanen, J.I., Tehranchi, A. and Murtomaa, H. (2006) Disparities in oral health of children in Tehran, Iran. European Archives of Paediatric Dentistry, 7, 262-264. doi:10.1007/BF03262563
 Solinas, G., Campus, G., Maida, C., Sotgiu, G., Cagetti, M.G. and Lesaffre, E. (2009) What statistical method should be used to evaluate risk factors associated with dmfs index? Evidence from the national pathfinder survey of 4-year-old Italian children. Community Dentistry and Oral Epidemiology, 37, 539-546. doi:10.1111/j.1600-0528.2009.00500.x
 Amanlou, M., Jafari, S., Afzalianmand, N., Omrany, Z.B., Farsam, H. and Nabati, F. (2011) Association of saliva fluoride level and socioeconomic factors with dental caries in 3 -6 years old children in Tehran-Iran. Iranian Journal of Pharmaceutical Research, 10, 159-166.
 Sanchez-Perez, L., Irigoyen, M.E. and Zepeda, M. (2010) Dental caries, tooth eruption timing and obesity: A longitudinal study in a group of Mexican schoolchildren. Acta Odontologica Scandinavica, 68, 57-64. doi:10.3109/00016350903449367
 Norberg, C., Stalin, U.H., Matsson, L., Thorngren-Jerneck, K. and Klingberg, G. (2012) Body mass index (BMI) and dental caries in 5-year-old children from southern Sweden. Community Dentistry and Oral Epidemiology, 40, 315-322. doi:10.1111/j.1600-0528.2012.00686.x
 Moghimbeigi, A., Eshraghian, M.R., Mohammad, K. and McArdle, B. (2008) Multilevel zero-inflated negative binomial regression modeling for over-dispersed count data with extra zeros. Journal of Applied Statistics, 35, 1193-1202. doi:10.1080/02664760802273203
 Medina-Solis, C.E., Maupome, G., del Socorro, H.M., Perez-Nunez, R., Avila-Burgos, L. and Lamadrid-Figueroa, H. (2008) Dental health services utilization and associated factors in children 6 to 12 years old in a low-income country. Journal of Public Health Dentistry, 68, 39-45. doi:10.1111/j.1752-7325.2007.00056.x
 Preisser, J.S., Stamm, J.W., Long, D.L. and Kincade, M.E. (2012) Review and recommendations for zero-inflated count regression modeling of dental caries indices in epidemiological studies. Caries Research, 46, 413-423. doi:10.1159/000338992
 Lewsey, J.D. and Thomson, W.M. (2004) The utility of the zero-inflated poisson and zero-inflated negative binomial models: A case study of cross-sectional and longitudinal DMF data examining the effect of socio-economic status. Community Dentistry and Oral Epidemiology, 32, 183-189. doi:10.1111/j.1600-0528.2004.00155.x
 Mohammadi, T.M., Hossienian, Z. and Bakhteyar, M. (2012) The association of body mass index with dental caries in an Iranian sample of children. Journal of Oral Health and Oral Epidemiology, 1, 29-35.
 Elias-Boneta, A.R., Psoter, W., Elias-Viera, A.E., Jimenez, P. and Toro, C. (2006) Relationship between dental caries experience (DMFS) and dental fluorosis in 12-year-old Puerto Ricans. Community Dental Health, 23, 244-250.
 Wedl, J.S., Danias, S., Schmelzle, R. and Friedrich, R.E. (2005) Eruption times of permanent teeth in children and young adolescents in Athens (Greece). Clinical Oral Investigations, 9, 131-134. doi:10.1007/s00784-004-0295-y
 Namal, N., Vehit, H.E. and Can, G. (2005) Risk factors for dental caries in Turkish preschool children. Journal of Indian Society of Pedodontics and Preventive Dentistry, 23, 115-118. doi:10.4103/0970-4388.16881
 Boitor, C.G., Fratila, A., Stanciu, L., Pitic, A. and Acu, A.M. (2011) Socio-economic factors and hygienic food-illness involved in determining dental caries of 12-year- old children in rural and urban area. Review of Research and Social Intervention, 33, 167-177.