Temperature Response in the Pulpal Chamber of Primary Human Teeth Exposed to Nd:YAG Laser Using a Picosecond Pulsed Regime

Objective: This study was conducted to analyze temperature variation in the pulpal chamber using the (Nd:YAG) picosecond-pulsed laser to promote ablation in enamel and dentin of primary teeth.

Background Data: Several previous studies reported the temperature rise in pulpal chamber during laser irradiation. Since there are no reports about pulp chamber temperature changes during irradiation with picosecond-pulsed laser, the purpose of our investigation is to quantify the intrapulpal temperature changes following picosecond-pulsed Nd:YAG laser irradiation of enamel and dentin of primary teeth.

Methods: In this study, we used 10 intact primary exfoliated teeth: five molars and five incisors. We used a commercial neodymium:- yttrium-aluminum-garnet continuous-wave (CW)-pumped Q-switched and mode-locked Nd:YAG laser, with varying power levels (200, 300, and 350 mW) operating with 100-psec pulsed duration.

Results: Typical plots show differences between heating and cooling of enamel and dentin of anterior and posterior teeth. Whereas for enamel the time evolution curves are dependent on power used for the investigated range (200-350 mW), for dentin the differences are not so evident. Observing temperature enhancement for each power, we were able to analyze operational conditions where temperature changes do not exceed 5.5 degrees C. Power-time-temperature (PTT) diagrams for clinical operations were determined based on varying power level and exposition time. Through the heating-cooling cycle, we could extract conventional heating and cooling times for enamel and dentin.

Conclusion: We have shown that the Nd:YAG picosecond-pulsed laser is a safe tool for ablation of primary teeth in a broad range of operational parameters.