Background Enamel hypoplasia occurs due to inherent and non-inherent factors. Researchers noted occurrence of non-inherent based enamel hypoplasia happens due to malnutrition of children or foreign infl uence to teeth while they are on their formation stage (Groshikov 1985). According to studies of N.A. Belova, a researcher, in 1976, an examination conducted on 200 children between the ages of 2.5-3 in Moscow area and resulted 20.5% of the children were affected with EH. Results from Asian countries such as in Beijing, China the prevalence rate was 22.5% (Lee et all, 1995) among 1344 children who were 8-15 years of age and had premature weight at birth, and in Deli, India 30% (Agarwal K.N et aii, 1999-2001) among 280 children who were 0-1 year of age and had substitute provision. Prevalence rate was 32.7% in Iranian cities of Yazd and Hadi among 1223 elementary school children (A.R.Daneshkazemi, DDS, MS; A. Davari, DDS, MS). Inherent based EH or Amelogenesis Imperfecta is an abnormal development of enamel. It is formed due to genetic mutation (Aldred, 2003). Prevalence of inherent EH differs from countries to countries and the variation was 1:718-1:14000 (Seow, 1993). Its genetic inheritance pattern can be autosomal dominant, autosomal recessive or XLinked (Shafer, 1987, Seow, 1993). The basis for this study work on risk factors of EH was due to lack of similar studies among the youth of our county. Objective The aim of the research work was to study the pathogenesis and etiology of enamel hypoplasia, Methodology We have conducted clinical examination up among 296 (12-year-old) children, and surveyed with a specially designed questionnaire those who are affected with enamel hypoplasia followed illustrations of their genetic chart. Result Of those who were involved in the research, 11.8% were affected with EH, and 10.4% had non-genetic infl uence factors, 1.01% had genetic infl uence factors and 0.34% had genetic syndrome. Statistical analysis was conducted to determine non-genetic infl uence factors among 62 children were free of EH (DMFT 1.70.14) and 31 children who had genetically infl uenced EH. While, 71% of the children who had EH had normal birth weight and 29% had miniature weight, 87% of the healthy children had normal birth weight and 13% had miniature birth weight (OR = 2.761 [CI 95percentage 0.944-8.08]).While 58% of the children with EH were breastfed, 16% had mixed milk, 8% had substitute milk only, 87% of the healthy children were breastfed, 8% had mixed milk, and 5% had substitute milk only(OR=5.0 [CI 95% 1.085-23.034]). Where as 31% of the healthy children had vitamin D defi ciency, 46% percent had digestion problems, 8% had some type of infectious disease, and 58% had respiratory infection while they were 0-1 year old, 25% of the children with EH had vitamin D defi ciency, 25% had digestion problems, 13% had some type infectious disease, and 58% had respiratory infection while they were 0-1 year old. Looking at the result digestion illness raises (OR = 5.895 [CI 95percentage 1.944-17.879]) the risk of having EH than any other infectious diseases (OR=1.356 [CI 95percentage 0.215-8.571]). 19% of the mother of the 31 children who had EH had early pregnancy sickness, 26% had late pregnancy sickness. However, 10% of the healthy 62 children had early, and 16% had late pregnancy sickness (OR=2.761 [CI 95percentage 0.944-8.08]). While 74% of the mothers of the children with EH were delivered on time and 26% premature delivery, 86% of the mothers of the healthy children were delivered on time and 11% had premature delivery(OR=2.733; CI95% 0.887-8.419). Genetic factor infl uence is due to X linked dominant chromosome on two occurrences, and one occurrence is due to Y chromosome. One occurrence of genetic syndrome has been diagnosed as Acrofacial syndrome Nagera. Conclusion. Late pregnancy sickness among other had the highest probability of causing EH. Premature delivery, miniature weight had the highest probability of causing EH. Babies breastfed mixed milk for age 0-1 had the highest probability of causing EH among other illnesses that causes EH. Digestion illness had the highest probability of causing EH among other illnesses that causes EH. Infectious diseases had relevant risk factor. Genetic factor infl uence on EH is due to X linked dominant chromosome, and Y chromosome. One sign of genetic syndrome has been detected as due to Acrofacial syndrome Nagera.