Third permanent molar agenesis in children with and without molar incisor hypomineralisation: an international investigation

To investigate whether children with molar incisor hypomineralisation (MIH) are more likely to have missing third permanent molars (TPMs) than unaffected peers. Additional objectives were to explore variation in TPM agenesis by sex, geographic region and hypodontia of other permanent teeth.

The study was conducted in specialist paediatric dentistry centres across 14 countries. Participants were children with or without MIH, aged between 10 and 17 years. Following informed consent, a validated MIH index was used to assess the presence/extent of any hypomineralised teeth and panoramic radiographs were viewed to record the number and location of any developing TPMs.

A total of 634 participants were recruited: 264 (41.6%) with MIH and 370 (58.4%) without this condition. Two hundred fifty-five (40.2%) of the overall study population had at least one missing TPM. Logistic regression analysis indicated that neither MIH status nor sex were associated with TPM agenesis. However, TPM agenesis was significantly more likely in participants with hypodontia of other permanent teeth (OR = 2.57, 95% CI 1.42, 4.66, p = 0.002). Geographical region was also statistically significantly associated with TPM agenesis with the lowest prevalence found in the African region (6.3%) and the highest found in the European region (55.9%).

Within the limitations of this study, children with MIH appear at no greater risk of TPM agenesis than their non-MIH peers; however, clinicians should be aware of marked differences between different geographical regions and the greater likelihood of TPM agenesis in children with hypodontia of other permanent teeth.