The Pathogenesis and Aetiology of MIH: More Questions Than Answers

Demarcated hypomineralized lesions of enamel, pathognomonic of MIH, are caused by the process of amelogenesis being altered or interrupted, most likely during the maturation phase. Increased protein concentrations are present in the lesion, primarily from serum, although some proteins involved in amelogenesis, such as amelogenin, have also been identified. The result of this disruption is enamel with decreased mineral density, decreased hardness and increased porosity and crystalline impurities, making it prone to demineralization and physical breakdown. The cause of enamel defects included in MIH and similar conditions including hypomineralized second primary molars is yet to be determined. Several hypotheses have been proposed, including childhood illness and genetic influences and a putative individual threshold of susceptibility; however, there is still conjecture on what the causative factors are.