Aim: This was to describe the distributions of affected first permanent molars (FPMs) in a sample of children with molarincisor- hypomineralisation (MIH) and molar hypomineralisation (MH), and to examine their perinatal and medical histories for putative associations with molar hypomineralisation.
Study design: A sample of 416 children aged 6-14 years with MIH or MH was identified from a specialist paediatric dental practice in Melbourne, Australia.
Methods: A questionnaire regarding perinatal and medical histories was sent to their parents/guardians; 182 (44%) useable questionnaires were returned and the dental records of these children were reviewed.
Results: The 182 dentitions were distributed as: MIH: 104; MH: 65; MIH* (permanent incisors unerupted): 13. These dentitions contained 720 FPMs; 429 FPMs were hypomineralised, distributed as: MIH: 282 FPMs; MH: 124 FPMs; MIH*: 23 FPMs. The 282 affected FPMs occurred in dentitions with MIH as: 1 FPM: 27%; 2 FPMs: 15%; 3 FPMs: 17%; 4 FPMs: 40% (mean 2.7 +/- 1.3 FPMs/dentition). The 124 affected FPMs occurred in dentitions with MH as: 1 FPM: 49%; 2 FPMs: 28%; 3 FPMs: 6%; 4 FPMs: 17% (mean 1.9 +/- 1.1 FPMs/dentition). The distribution of moderate to severe hypomineralisation in FPMs was: MIH: 89%; MH: 73%. Affected FPMs were similarly distributed between gender, quadrants and arches. At least one condition putatively associated with MIH/MH was seen in histories of 166 children (91%); ear infections, fevers, and perinatal conditions occurred in 53-66% of children. Frequent condition combinations were: ear infections + fevers (40% of children); antibiotics + ear infections (54%); antibiotics + other illnesses (56%).
Conclusions: All four FPMs in a given dentition were more likely to be affected and to differing extents in MIH than in MH. Putative associations appear to exist between MIH/MH and combinations of antibiotic use, ear infections, fevers, perinatal conditions, and other illnesses in the child's first 3 years. It is proposed that MIH is a more severe form of the hypomineralisation condition than MH, forming an MIH spectrum.