Effects of Nd: YAG laser, air-abrasion and acid-etching on human enamel and dentin

The effects of the Nd:YAG laser, air-abrasion and acid-etching systems on mineral content and surface morphology of cut dentin and enamel were examined in 10 extracted human teeth. Enamel specimens were lased for two seconds at a fluence of 0.75 J and a frequency of 15 Hz, air-abraded for two seconds with 50 micron Al-oxide and etched for 60 seconds with 37% ortho-phosphoric acid. Dentinal specimens were subjected to the same procedure for half the time. Untreated areas of the same specimens served as the control. Morphologically, the lased dentin showed an apparently melted surface with partial obstruction of the dentin tubules, as well as cracks along the lased surface. Air-abrasion created very irregular surfaces on enamel and dentin. Dentin tubules were observed on the acid-etched dentin samples but not the air-abraded surfaces. The Nd:YAG laser created the most surface irregularity on both enamel and dentin. Laser treatment appeared to alter the chemical structure and surface morphology of the dentin and enamel.