Indiana University-Purdue University Indianapolis (IUPUI) / Molar Hypomineralization (MH) of the first permanent molars (FPMs) and the second primary molars (SPMs) is a common developmental defect of enamel, with global prevalence of 14% and 5% respectively. Children with MH represent a special pediatric population because their affected molars have extreme susceptibility to enamel breakdown, decay and tooth sensitivity. Although the problem of MH has been described almost twenty years ago mainly through reports from Europe, there is very little information about the problem from the USA. In this dissertation, MH was explored both from the perspectives of pediatric dentists’ (PDs) and at population level. The majority of the survey respondents perceived MH prevalence to be <10% in their clinical practice (62%). The most cited clinical challenge in managing MH teeth was “long-term success of restorations” (79%). When analyzed individually, responses differed significantly for different demographics and educational characteristics of the respondents (p<0.05). At population level, MH of the FPMs (Molar Incisor Hypomineralization (MIH) cohort: 337 schoolchildren, average age 9 years) and of the SPMs (Hypomineralized Second Primary Molar (HSPM) cohort: 423 schoolchildren, average age 7 years) had prevalence estimates of 13% and 6% respectively. In the MIH cohort, water fluoridation or non-Hispanic Black race/ethnicity was significantly associated with higher collective prevalence of enamel defect (EDs) (P<0.05), but not with the prevalence of MH of the FPMs. In the HSPM cohort, race/ethnicity was significantly associated with higher overall prevalence of EDs of SPMs, but not with the HSPM prevalence. Older age group (>10 years), living in central Indiana, and water fluoridation were significantly associated with higher overall prevalence of EDs (P<0.01), but not with the HSPM prevalence. Caries experience was significantly higher in children with MH of FPMs and/or SPMs than in the group without MH. We concluded that USA pediatric dentists’ respondents were well aware of the MH problem, but demonstrated discrepancies in different aspects of the MH problem. At population level, MIH and HSPM were common presentation with prevalence estimates similar to the global figures. Certain demographic characteristics were significantly associated with the overall prevalence of the enamel defects of the examined teeth.