Surface morphology of sound enamel after argon laser irradiation: an in vitro scanning electron microscopic study

Argon laser irradiation (ALI) at relatively low fluences (energy densities) enhances the caries resistance of sound enamel. The purpose of this SEM study was to compare the effects of argon laser irradiation at relatively low fluences (11.5 Joules/cm2 and 100 Joules/cm2) on enamel surface morphology. Following a fluoride-free prophylaxis, 12 extracted caries-free human molars were sectioned into tooth quarters. Tooth quarters were treated as follows: 1) Mesiobuccal-ALI at 11.5 J/J/cm2 for 10; 2) Distobuccal-Control; 3) Mesiolingual-ALI at 100 J/J/cm2 for 10; and 4) Distolingual-Control. Enamel surface morphology was compared among the two argon laser irradiation groups and matched non-treated control enamel surfaces by SEM. Argon laser treatment resulted in considerable alterations in the surface morphology compared with matched controls. Control enamel surfaces showed relatively smooth contours with occasional termination of enamel prisms at the surface. Both argon laser treatment groups had intact enamel surfaces lacking prism end markings and cratering of the enamel surface. A discontinuous granular surface permeated by numerous microporosities of < 1.0 micron in diameter was created with both argon laser treatment groups. Globular deposits of approximately 0.5 to 2 microns in maximum dimension composed the surface coatings. These deposits were admixed with areas of fine microporosities. Argon laser irradiation at relatively low fluences produces surface coatings which may act as reservoirs for mineral phases during an acidogenic attach of the enamel and may provide a certain degree of protection against a cariogenic challenge.