Molar-Incisor Hypomineralization (MIH) is a poorly understood disorder attributed to disrupted ameloblastic function during the formation of the permanent dentition.


Teeth affected in MIH:

(1) It affects 1 to all 4 permanent first molars.

(2) It affects 0 to 8 of the permanent incisors (central and lateral, left and right, maxillary and mandibular).

(3) It does not affect other teeth (generalized opacities in all teeth excludes the diagnosis).


This a patient with MIH may have from 1 to 12 affected teeth. The severity of involvement tends to increase with age.


Affected teeth:

(1) have demarcated areas of defective enamel that appear as opacities (which may be white-cream or yellow-brownin color). These opacities have a distinct boundary to normal enamel.

(2) tend to develop caries in the areas of defective enamel.

(3) may be more fragile (post-eruptive breakdown).

(4) are at increased risk of being lost or requiring extraction.


Restorations in affected areas tend to be problematic. The defects that must be restored may show atypical sizes and shapes. The restorative material tends to show poor adhesion and the adjacent enamal may be fragile. Restorations may fail early and often.


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