Objective: To evaluate molar-incisor-hypomineralization (MIH) prevalence, clinical characteristics, and severity amongst school children in Riyadh, Saudi Arabia.

Subjects and Methods: Randomly selected, healthy third- and fourth-grade students (aged 8–10 years) attending elementary schools in Riyadh, and children of the same age attending dental clinics at the College of Dentistry, King Saud University, were examined for the presence of MIH, its clinical characteristics, and severity.

Results: The sample studied consisted of 924 children, 447 (48.4%) of whom were boys. There were 376 children, (199 females and 177 males), with at least 2 index teeth affected (prevalence = 40.7%). A total of 133 (35.4%) had only molar hypomineralization (MH), whereas 243 (64.6%) had molars and incisors involved (MIH). The mean number of affected teeth per child was 6.6 ±3.6 (3.3 for molars and 3.2 for incisors). The chi-Square test showed no association between the distribution of hypomineralization and age (P = 0.115). Children with severe hypomineralization predominated across all age groups, with the 10-year-old group having more severely affected children (71.9%)  compared to 8- and 9-year-old groups (P = 0.000).  Proportional t-test showed no statistically significant difference (P>0.05) between males and females in the occurrence of MH or MIH, and in the severity of the hypomineralization. Upper molars were more affected than lower molars, whilst upper incisors were more affected than lower incisors.

Conclusion: Enamel hypomineralization is a common feature in the dentition of 8–10-year-old children in Riyadh, Saudi Arabia. There is no association with age and no gender predilection.