Table 2: Definitions of the criteria used for diagnosing MIH (Weerheijm et al 2001a)

Criteria		Definitions
Opacity		A defect involving an alteration in the translucency of the enamel, variable in degree. The defective enamel is of normal thickness with a smooth surface and can be white, yellow or brown in color. The border of the lesions is demarcated.
PEB		A defect that indicated deficiency of the surface after eruption of the tooth. This may be caused by such factors as trauma and attrition.
Atypical restoration		Size and shape of restoration do not conform to typical restorative characteristics. In most cases, restorations will be extended to the buccal or the palatinal smooth surface. At the border of the restoration, opacity may be noticed.
Extraction due to MIH		Absence of a molar should be related to the other teeth of the dentition. Absence of a first permanent molar in a sound dentition is suspected to have been an MIH molar.