GPR68 and amelogenesis imperfecta: The link between OGR1 and aberrant enamel formation was first established in 2016 [61] when three families with amelogenesis imperfecta type IIA6 (i.e. amelogenesis imperfecta caused by hypomineralisation) were shown to have homozygous genetic variants of OGR1 that resulted in loss of function of OGR1 protein.