Canines are affected in 16-year-olds with molar-incisor hypomineralisation (MIH): an epidemiological study based on the Tromso study: "Fit Futures".

AIM: This was to determine the prevalence, distribution of affected teeth and severity of MIH in adolescents from Northern Norway. METHODS: It was part of a cross-sectional health survey Fit Futures including 16-year-olds from two neighbouring municipalities, Tromso and Balsfjord. RESULTS: The prevalence of MIH was 13.9% (110 of 794). The maxillary first permanent molars (FPMs) were 1.6 times more frequently affected than in the mandible (P < 0.001). The FPMs on the right side were 1.2 times more often affected than the FPMs on the left side (P = 0.038). The maxillary incisors were 2.5 times more often affected than the incisors in the mandible (P < 0.001). The proportions of participants whose canines and incisors were involved were 22.8 and 41.8%, respectively. Altogether 201 FPMs were affected; 54.0% of these had opacities only, 24.3% had posteruptive breakdown (PEB), 18.8% had atypical restorations, and 3.0% had been extracted due to MIH. The buccal surfaces were most often affected in FPMs. More severe lesions were found in the mandibular FPMs compared with the maxillary FPMs (P = 0.002). In the lower canines, only opacities were recorded, while in the upper jaw 13.0% of the affected canines showed PEBs. The distribution of MIH in the dentition was not symmetrical. CONCLUSION: The prevalence of MIH (13.9%) in the study population of 16-year-olds from Northern Norway is consistent with previous Scandinavian reports. The distribution pattern shows that one participant in four with MIH had at least one affected canine. Further studies are needed to describe the localisation of defects on the enamel surface and to relate these findings to enamel thickness and the duration of amelogenesis.