Molar-incisor hypomineralization : observations from groups of Finnish children and a treatment practice survey among Finnish dentists

Molar-Incisor Hypomineralization (MIH) is a developmental enamel defect affecting 1-4 of the first permanent molars (FPM) and frequently also permanent incisors. Clinical appearance varies from small, opaque defects in enamel to extensive enamel breakdown. This doctoral thesis investigated the background and effects of MIH in groups of Finnish children, as well as Finnish dentists’ treatment practices concerning symptomatic, severely hypomineralized FPMs. The Study I population was a convenience sample of 818 children aged 7–13 years from different regions of Finland. Their teeth were examined for MIH. The possible associations with factors related to the family’s socio-economic status (SES) and the child’s living environment were assessed using the parent-filled questionnaire. Analyses did not show any significant association between MIH and the studied factors. However, the prevalence of MIH varied regionally, and the difference was greatest between Jalasjärvi (8.0%) and Lappeenranta (25.2%). Study II investigated the association between MIH and childhood illnesses and antibiotics. Patient records of 287 children from two locations, Lammi and Jalasjärvi, were obtained from the local health centers. Occurence of illnesses and exposure to antibiotics during the child’s first three years of life were investigated and the data was combined with the information of the dental examination. The children who were diagnosed with acute otitis media and the children who were prescribed penicillin, amoxicillin, or macrolide antibiotics had increased risk for hypomineralization in FPMs and permanent incisors. In a subset of the patients (Study III) whose caries experience had also been recorded (n = 636), MIH was found to be associated with the occurrence of caries in FPMs (DMFT > 0) as well as with the number of decayed or filled FPMs. MIH was a greater risk factor for caries than low SES. Study IV was a treatment practice survey among Finnish dentists (n = 765). The most common choice for symptomatic, severely affected FPM was restoration with composite resin (45.0%). Pediatric dentists preferred stainless-steel crowns. In addition, treatment practices varied from one area to another, and in the Helsinki-Uusimaa area it was more common than in other areas to refer an MIH patient forward. In summary, the prevalence of MIH seems to vary between regions for a reason that remains unknown. This thesis suggests a potential harmful effect of childhood illness or antibiotics on enamel development. This finding is waiting to be confirmed with further, prospective studies. In addition, MIH is a significant caries risk factor, especially in a low-caries population. However, unsolved issues related to the development and diagnosis of MIH need to be addressed in order to clarify the etiology.