In vivo study of the Nd:YAP laser in persistent periapical lesion.

OBJECTIVE: The aim of this study was to evaluate the therapeutic effect of ND:YAP laser in persistent lesions through signs and symptoms such as the presence of fistulas and pain, respectively. BACKGROUND DATA: Periapical lesions with bacterial invasion, giving origin to bacterial infections, appear many times during the endodontic treatment, which aims at preparing and disinfecting the root canal system, in canals with mortified pulp. The endodontic treatment aim at eliminating infections and reinfection prevention; however, sometimes re-treatment is necessary, and it can be complemented with paraendodontic surgery due to reinfection, which can also persist. METHODS: Our study group consisted of six clinical cases (endodontic treatment), with the introduction of a 300-microm optic fiber through the fistula channel, where three applications were carried out with an interval of 15 sec, each with a discharge of 300 mJ of energy and frequency of 30 Hz. RESULTS: After a 7-day interval, the signs and symptoms were absent, even after a follow-up of 18 months. It was also observed, through a microbiological study, the decrease of the local microbiota. CONCLUSIONS: Our results supported the use of Nd:YAP laser, in part since it created an unfavorable environment for the continuing development of microorganisms.

Er:YAG laser: antimicrobial effects in the root canals of dogs' teeth with pulp necrosis and chronic periapical lesions.

OBJECTIVE: Our goal in this study was to evaluate the antimicrobial effect of Er:YAG laser applied after biomechanical preparation of the root canals of dog's teeth with apical periodontitis. BACKGROUND DATA: Various in vitro studies have reported effective bacterial reduction in infected root canals using Er:YAG laser. However, there is no in vivo research to support these results. METHODS: Forty root canals of dogs' premolar teeth with pulp necrosis and chronic periapical lesions were used. An initial microbiological sample was taken, and after biomechanical preparation was carried out, a second microbiological sample was taken. The teeth were divided into two groups: Group I-biomechanical preparation was taken of root canals without Er:YAG laser application; Group II-biomechanical preparation was taken of root canals with Er:YAG laser application using 140-mJ input, 63-mJ output/15 Hz. After coronal sealing, the root canals were left empty for 7 days at which time a third microbiological sample was taken. The collected material was removed from the root canal with a #40 K file and placed in transport media. It was serially diluted and seeded on culture dishes selective for anaerobes, aerobes, and total streptococci. Colony-forming units per milliliter (CFU/mL) were counted. RESULTS: Groups I and II showed an increase of CFU/mL for all microorganisms 7 days after treatment, being statistically significant for anaerobes in Group I and for anaerobes and total streptococci in Group II. When comparing CFU/mL of Groups I and II, there was a statistically significant increase after 7 d for total streptococci in Group II. CONCLUSION: Er:YAG laser applied after biomechanical preparation did not reduce microorganisms in the root canal system.