Identification of factors in the natal and neonatal period influencing enamel development in the permanent first molars and incisors

Abstract

Molar-Incisor Hypomineralisation (MIH) is defined as hypomineralisation of one to four first permanent molars, frequently associated with affected permanent incisors. MIH refers to a qualitative enamel developmental defect of systemic origin clinically manifesting as demarcated discolouration that ranges from white-opaque to yellow-brown defects that are soft and fragile. The possible aetiology of MIH remains unclear and is thought to be acquired via multifactorial, systemic disturbances during amelogenesis. Some of the possible aetiologies that have been suggested to be associated with this condition are high fever, oxygen deficiency at birth, prenatal and perinatal sickness, respiratory infections in the first three years of life, or nephritic disease. MIH has also been suggested as being associated with toxins and antibiotic consumption, malnutrition, intestinal inflammation, diarrhoeas and hypoparathyroidism occurring during the critical period of enamel development.

The overall aim of the current study was to better understand the clinical features of MIH and to contribute to the knowledge of the aetiology of MIH. The specific objectives were to assess relationships of pregnancy, delivery history and birth complications in mothers of children identified with and without MIH. A matched case-control study was designed to further investigate and help to identify factors from perinatal and postnatal time periods that could influence enamel development in the first permanent molars and incisors related to MIH, through the assessment of medical birth records. The case group comprised of children who had been diagnosed with MIH selected from Paediatric Dentistry records at the University of Otago School of Dentistry. The control group was either volunteered by the case group or randomly selected from the Dental Therapy Clinic at the School of Dentistry. All study children received a clinical assessment that recorded developmental defects of enamel (DDE) and dental caries status. Mothers of these children completed questionnaires to record pregnancy history, delivery history and the child’s medical history in the first years of life after birth. Mothers’ and children’s medical birth records were assessed for further pregnancy and delivery history. Univariate and bivariate statistics were computed using SPSS version 19.0 and STATA version 10. The level of significance was set at P<0.05. The case group had similar sociodemographic characteristics to the control group. Statistically there was no significant difference in the ethnic variation between the case and the control groups. The prevalence of MIH defects were found to be higher in the first permanent molars than in the incisors. The prevalence of MIH defects was similar in the maxillary first permanent molars and mandibular first permanent molars, but were found to be higher in tooth 26 (93.5%), although this difference was not statistically significant. MIH defects were more common in the maxillary incisors than in the mandibular incisors. Children with MIH were diagnosed to have a higher overall caries experience in the deciduous and permanent dentitions than children without MIH. Children diagnosed with MIH had more medical problems related to birth, such as oxygen deprivation, one or more signs of foetal distress, premature births, low birth weight (LBW) and were born through assisted delivery. Mothers of children diagnosed with MIH had received more drugs such as nitrous oxide, pethidine and antibiotic(s) during delivery. No associations were found between the occurrence of MIH and medication(s) taken by mothers during pregnancy or medical problems during pregnancy. The findings from the current study do have clinical implications with higher number of medical problems related to birth having been demonstrated as an indicator for an increased prevalence of MIH.