Methods: Thirty-two bovine enamel blocks were prepared and placed on delrin blocks. One set of blocks (n=15) was divided into five windows and two of those windows were ablated by the CO2-laser. One of those two windows was etched (37.5% H3PO4). One of the remaining windows was covered with acid resistance varnish, another window was acid-etched and the last window was untreated. The samples were subsequently exposed to an acid-dissolution model. The remaining blocks (n=17) were divided into eight windows that were laser-irradiated at a fluence of 20J/cm2 and acid-etched for various time periods before exposure to the acid-dissolution model. Automated methods of analysis were employed to calculate the depth and severity of the subsurface lesions after scanning with Polarization-Sensitive OCT. Sample groups were statistically analyzed (ANOVA, Tukey’s, p<0.05).
Results: PS-OCT imaging indicated that acid-etching significantly increased the dissolution rate of laser-irradiated and non-irradiated enamel surfaces compared to non-etched group (p<0.05). The outer layer of enamel modified by the laser was rapidly etched away after 5-10 seconds.
Conclusion: This study suggests that the thermally modified enamel layer is rapidly removed by phosphoric acid etching after 5-10s and such etching also significantly accelerates the formation of subsurface lesions on both laser-ablated and non-laser irradiated surfaces.
Keywords: Acid etch, Demineralization, Enamel, Lasers and PS-OCT