Prevalence and Predictors of Molar Incisor Hypomineralization (MIH) among Rural Children in Northern Iran

Molar incisor hypomineralization (MIH) is an enamel defect in permanent first molar and inci-sor teeth. The defects may vary from white, to yellow-brown demarcated opacities that may easily break (post-eruptive breakdown) and results in extensive caries or early extraction of the teeth. The unaesthetic appearance of anterior teeth, sensitivity, pain, and difficulties in achieving local anesthesia, and providing proper restorations are of MIH complications (1). The MIH prevalence varies from 2.4% to 40.2% globally (2). The eti-ology is not clear. However, it seems as a multi-factorial entity caused by several etiologic factors of systemic origin that intensify each other. First permanent molar, the most important functional unit of mastication, has a calcification window from 20 wk in utero to three yr of life. The upper and lower incisors, and to a lesser degree canines have some synchrony in hard tissue formation with first molar. Hence, pre, peri, and post-natal complication during this critical period in hard tissue formation, may cause temporary or permanent damages to the ameloblasts, the responsible cells for enamel formation, and induce enamel defects (3, 4). There is a lack of enough information on MIH among Iranian children especially in rural populations. The aim of the present study was to determine the prevalence and potential predisposing factors of MIH in 6-13-yr-old children living in rural areas of Masal and Shanderman, Guilan, an almost restricted and unspoiled community, in Northern Iran. The study population consisted of 553 children aged 6-13-yrs old recruited from the schools. The socioeconomic status was almost similar and rated low moderate according to parental education and occupation. A cluster sampling method was used in this study (schools as clusters). All dental examinations conducted in the schools using a headlight, and flat dental mirrors. After cleaning the teeth with gauze, the wet teeth were examined by a calibrated examiner (D.A). The European Academy of Paediatric Dentistry (EAPD) 2003 criteria used for diagnosis (5). During calibration sessions, a kappa value of 91% reached by the examiner (D.A). The prevalence was determined first. In the next stage, the data on probable predicting factors gathered by questionnaire and interview with mothers in a case-control design. One hundred and two subjects (18.4%) diagnosed as MIH, included 47.1% males and 52.9% females. The mean number of affected teeth per child was 6.5 including 3.7 molars and 2.8 inci