Use of Howe’s ammoniacal silver-nitrate solution for some years, solely at first as a disclosing solution, developed the following observations and conclusions : (1) Occurrence of unsuspected, almost universal, proximal caries was revealed. (2) Incipient proximal caries is invisible to the eye, both aided and unaided, and in the best x-ray picture. (3) This period of invisibility may continue for from two years to ten or more—until enamel surface is broken. (4) As continuity of enamel surface is lost, the carious area becomes increasingly visible, both to the eye and in the x-ray picture. (5) The first damage to the smooth surface is only very superficial etching, which may be definitely disclosed by drying, applying Howe’s solution, and reducing with eugenol. (A radiolucent area indicates that enamel surface has been broken, i.e., a cavity has been produced. Simple etchings are never radiolucent—surface continuity has not been lost.) (6) Howe’s solution penetrates the interstitial spaces in an etching, and leaves a black residue that sharply defines the affected area—and the residue, being insoluble, neither fades nor wears or washes away. (7) To insure passage of Howe’s solution into all interstitial spaces in an etched surface, the solution must be ” frictioned in ” by rubbing the affected area with silk floss, after which reduction with eugenol is completed. (8) To be most effective, Howe’s solution should be applied before an etching has been converted into a cavity.
By these treatments, four times a year, the carious process has been arrested for at least eight and one-half years (maximum observation period) on all areas where enamel-surface continuity remained. The treatment, owing to the resultant black stain, is contraindicated where enamel surface is broken in front teeth. Proximal caries, the most destructive type, may be controlled, if this treatment is applied before enamel-surface continuity is lost.
Reference: J. Am. Den. Assoc., 24, 1950, 1937.