Temperature variation at the external root surface during 980-nm diode laser irradiation in the root canal

Abstract 

Objective

To assess the temperature variation in the cervical, middle and apical thirds of root external wall, caused by 980-nm diode laser irradiation with different parameters.

Methods

The roots of 90 canines, had their canals instrumented and were randomly distributed into 3 groups (n=30) according to the laser potency (1.5W, 3.0W and 5.0W). Each group was subdivided into 3 (n=10) according to the frequency (CM, 100Hz and 1000Hz), and each subgroup divided into 2 (n=5): dried canal or filled with distilled water. The maximum temperature values were collected by 3 thermocouples located at each third of the root external wall and recorded by digital thermometers.

Results

The groups irradiated in the continuous mode (CM) presented the highest values (11.82±5.78), regardless of the canals were dry or not, which were statistically different (p<0.01) from those obtained with 100Hz (6.22±3.64) and 1000Hz (6.00±3.36), which presented no statistical difference between them (p>0.01). The groups irradiated with 5.0W presented the greatest temperature variation (12.15±5.14), followed by 3.0W (7.88±3.92) and 1.5W (4.02±2.16), differing between them (p<0.01). The cervical third of the root presented the highest temperature rises (9.68±5.80), followed by the middle (7.66±4.87) and apical (6.70±4.23), with statistical difference among them (p<0.01). After 30s from the end of irradiation, all the specimens presented temperature variation lower than 10°C.

Conclusions

Application of 980-nm diode laser in the root, at 1.5W in all operating modes, and 3.0W, in the pulsed mode, for 20s, can safely be used in endodontic treatment, irrespective of the presence of humidity.

Keywords: Diode laser, Temperature increase, Intrapulpar irradiation, Endodontics