Intrapulpal temperature during preparation with the Er : YAG laser: An in vitro study

Objective: This investigation evaluated the variation of the intrapulpal temperature when dentine was irradiated by the Er:YAG laser. Background Data: The effect of preparation with the Er:YAG laser on the intrapulpal temperature is probably the biggest problem in using the laser for preparation of dental hard tissue. Materials and Methods: Seventy-two bovine incisors were studied that had the enamel and dentine of the buccal surface polished to a thickness of 2.0 mm. The teeth were divided into three groups, according to the repetition rate used (Group I = 2 Hz, Group II = 4 Hz, and Group III = 6 Hz), and irradiated, with or without water cooling, using 250, 300, and 350 mJ of energy per pulse. Thermocouples were introduced inside the pulp chamber through the palatine opening of the samples and fixed to the vestibular wall of the pulp chamber using a thermal paste. Results: It was verified that there was a decrease of the intrapulpal temperature for all of the parameters in the Group I irradiated with water cooling and for the parameters of 350 mJ/4 Hz with water cooling. The other irradiations showed an increase of the intrapulpal temperature, varying from 0.03 degrees to 2.5 degrees C. Conclusion: We conclude that the use of the Er:YAG laser promoted acceptable temperature increases inside the pulp chamber. However, we do not recommend this procedure without water cooling because macroscopic observations of the dentine irradiated without water cooling showed dark lesions, suggesting carbonization of this tissue.o TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE AGOSTO DE 2015.23218218

Frequency doubled neodymium:yttrium-aluminum-garnet and diode laser-activated power bleaching-pH, environmental scanning electron microscopy, and colorimetric in vitro evaluations

Corrosiveness of enamel surfaces of SmartbleachA (R), Opus WhiteA (R), Opalescense Xtra BoostA (R) and a gel containing titanium dioxide (TiO2) particles, activated either by a frequency doubled neodymium: yttrium-aluminum-garnet (Nd:YAG) laser (532 nm) or a diode laser (810 nm) was evaluated by environmental scanning electron microscopy (ESEM). Changes in teeth color shades and the pH were also evaluated. Each bleaching agent was laser activated for 30 s and removed after 1 min or 10 min. This procedure was repeated up to four times, the bleaching agent receiving a maximum application time of 40 min, with total irradiation times of 0.5 min to 2 min of laser activation. The results of the pH measurements showed that only SmartbleachA (R) was in the alkaline pH range, whereas the other three were acidic. The surface effects were unrelated to the pH of the bleaching agents. With the exception of Opus WhiteA (R), no severe alterations on the enamel surface were detected. Although short application times were chosen, improved changes in brightness of up to ten steps on the VitapanA (R) classical shade guide were detected