Enamel hypomineralization in permanent first molars. A clinical, histo-morphological and biochemical study.

Hypomineralization in the permanent first molars was common in a group of 516 Swedish 8-year-old children. Ninety-five children (18.4%) had at least one molar with demarcated opacity. The incisors frequently displayed opacities concomitantly. The mean number of hypomineralized teeth of the affected children was 3.2 (SD 1.8), of which 2.4 were first molars. Six and a half percent of the children had severe defects, 5% had moderate defects, while 7% had only mildly hypomineralized teeth. Fifteen percent had more than one tooth affected, indicating systemic causation. The affected children, especially the boys, were reported to have had more health problems, asthma in particular (but only 4 cases), during the first year of life. Breast feeding history was similar in children with and without enamel defects. The children with severely defected enamel had undergone dental treatment of their first molars nearly ten times as often as the children in the healthy control group at the age of nine. Behavior management problems and dental fear and anxiety were common compared to the controls. Undemineralized sections from 73 permanent first molars, extracted due to severe hypomineralization of the enamel, were examined in polarized light. The hypomineralized areas extended from the cusps cervically comprising about half of the buccal and lingual sides. The cervical border to normal enamel was well defined and mainly followed the lines of Hunter-Schreger. The hypomineralized zones were covered by thin well-mineralized enamel. The concentration gradients for F, Cl, Na, Mg, K and Sr in hypomineralized enamel were analyzed by means of Secondary Ion Mass Spectrometry (SIMS), and completed with an analysis of the main matrix elements O, P and Ca by means of X-ray microanalysis (XRMA). Hypomineralized enamel had a higher content of C. Ca and P concentration were lower compared with normal enamel. The mean Ca/P ratio in hypomineralized areas was significantly lower (1.4) than the mean Ca/P ratio in the adjacent normal enamel (1.8).