An Incremental Effect of Acid Resistance and Remineralization on Incipient Caries of Enamel with Laser Irradiation

Abstract

The authors have demonstrated that a normal pulsed Nd: YAG laser was the most suitable among the lasers to produce resistance against acid decalcification of human tooth enamel, and a combined treatment of laser irradiation and fluoride application onto the enamel obtained most remarkale acid resistance.It is interest to determine whether the use of laser and fluoride in combination is a more effective procedure for incipient caries prevention.Artificial caries-like lesions were made on human enamel, and the enamel was then treated with laser irradiation and APF (acidulated phosphate fluoride). The laser used in this study was a normal pulsed Nd YAG laser which has 0.3 msec pulses with a pulse energy of 0.2 J/pulse. The tooth enamel was lased at a repitition rate of 20pps and total enegy density of 40J/cm2.The acid resistance of the enamel was determined by the amount of dissolved calcium from the enamel surface in the acidic solution. Fluoride uptake in the enamel was examined by mean of EPM (electron probe microanalyzer). Remineralization of the enamel was measured by microradiographic technique and microhardness test. The following results were obtained.1) An increment in acid resistance of enamel was caused by laser irradiation alone and also fluoride treatment after laser irradiation.2) In the case of fluoride treatment after laser irradiation, the fluoride uptake into the surface and subsurface enamel was higher than in the cases of fluoride treatment alone.3) The remineralization was remarkable in the cases of laser irradiation and fluoride treatment after laser irradiation groups. The extent of remineralization was seen from the surface to the bottom of the lesion area.