Effect of Surface Alteration on the Permeability of Enamel to a Lactate Buffer

¹ Department of Research, Tufts University School of Dental Medicine, Boston, Massachusetts

The purpose of this investigation was to evaluate the influence of mechanical alteration of the surface of enamel sections through scratching, polishing, and grinding on the rate of subsurface penetration by a lactate buffer. The effect of topical applications of sodium fluoride solutions in the presence and absence of saliva was also studied. Sixty-six sections were imbedded between glass slides with only the outer edges exposed to a 1 molar, pH 5, lactate buffer. Transparencies were taken at 32 times magnification with the section between crossed Polaroids. The degree of penetration was measured by ruler after projection of the transparencies at a total magnification of 250 times. Color changes disclosed the migration of the decalcification front to the nearest micron. Roughening of the enamel surface produced a 27 per cent increase in the rate of penetration of the buffer; polishing of the roughened surface with sandpaper reduced the penetration rate to within 10 per cent of the original penetration rate. The sections that were treated with sodium fluoride showed greater resistance to penetration up to 96 hours' immersion in buffer, but the total penetration was practically the same after 264 hours. Sections treated with saliva showed slightly less penetration than did the control which had been treated with water.