A Microradiographic Interpretation of Abnormal Enamel Formation Induced by Subcutaneous Sodium Fluoride

¹ Department of Histology, College of Dentistry, University of Illinois, Chicago, Illinois

The subcutaneous injection of sodium fluoride causes an alteration in enamel-matrix formation. Using decalcified material, Schour and Smith¹ originally described this alteration as a light staining line found buried in the matrix parallel to the incremental surface of the enamel. In our study we evaluated this response using histochemical and microradiographic methods on undemineralized material.

The light staining line of Schour and Smith was found by microradiographic methods to contain little or no mineral. The absence of any staining reaction in this area suggested that there was a decrease or absence of matrix. We have postulated that the radiolucent component was formed by the inhibition of matrix deposition in Tomes' process.

In addition, microradiograms revealed a hypermineralized band on the dentinal side of the radiolucent component. This was seen only in developing enamel as it mineralized as densely as the surrounding matrix during maturation. This hypermineralization could be caused by a longer exposure of the incremental surface to the tissue fluids or some alteration in the matrix that rendered it more readily mineralized.