Application of the erbium:YAG laser on hard dental tissues: Measurement of the temperature changes and depths of cut

Abstract

The 2.94 um Erbium:YAG laser was evaluated for drilling teeth, in view of the fact that the tissue coefficient of absorption at 2.94 um is almost 10 times greater than at 10.60 um, the wavelength of the CO2 laser.Thermocouple wires were inserted through cavities prepared on lingual surfaces of 29 freshly extracted teeth. The cavities were prepared such that the thermocouples were (A) in the enamel in 4 teeth, (B) within the labial wall dentine in 4 others, and (C) touching the labial wall of the pulp cavity in the remaining teeth. 3 carious teeth were similarly prepared. The teeth were exposed to pulsed erbium lasers, wavelength 2.94 um, pulse duration 250 us, power 2.2 W, frequency 6 HZ for 4 secs.; the energy density was 1.7 J/sq. cm..The mean rise in temperature in (A) was 16.1°F, in (B) 8.9°F and in (C), 7.8°F. Smaller spot sizes of the laser beam (0.25-0.5 mm) produced clean circular holes, 1 - 2.5 mm deep, with no cracking and chalkiness and slight to no charring. With spot sizes 0.75 - 1 mm, the cuts were shallower, 250 um, with white chalky bases, and again, no charring or cracking. On a carious occlusal surface pit, the laser produced a clean, sharp cut, 1 mm deep.The thickness of tissue between the exposed surface and thermocouple was measured from labio-lingual sections.The low energy density used and non-injurious pulpal temperatures obtained, promise important potentials of the ER:YAG laser in dentistry, especially since zirconium fluoride fibres have been developed to transmit the 2.94 um radiation.The 2.94 um Erbium:YAG laser was evaluated for drilling teeth, in view of the fact that the tissue coefficient of absorption at 2.94 um is almost 10 times greater than at 10.60 um, the wavelength of the CO2 laser.Thermocouple wires were inserted through cavities prepared on lingual surfaces of 29 freshly extracted teeth. The cavities were prepared such that the thermocouples were (A) in the enamel in 4 teeth, (B) within the labial wall dentine in 4 others, and (C) touching the labial wall of the pulp cavity in the remaining teeth. 3 carious teeth were similarly prepared. The teeth were exposed to pulsed erbium lasers, wavelength 2.94 um, pulse duration 250 us, power 2.2 W, frequency 6 HZ for 4 secs.; the energy density was 1.7 J/sq. cm..The mean rise in temperature in (A) was 16.1°F, in (B) 8.9°F and in (C), 7.8°F. Smaller spot sizes of the laser beam (0.25-0.5 mm) produced clean circular holes, 1 - 2.5 mm deep, with no cracking and chalkiness and slight to no charring. With spot sizes 0.75 - 1 mm, the cu...