title: In vivo study of the Nd:YAP laser in persistent periapical lesion.
abstract: 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
  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.
authors.affiliation: School of Dentistry Universidade de São Paulo, Brazil. anaricardo@uol.com.br
authors.forename: Ana Lucia Franco
authors.initials: AL
authors.lastname: Ricardo
authors.forename: Maria Leticia Borges
authors.initials: ML
authors.lastname: Britto
authors.forename: Walter João
authors.initials: WJ
authors.lastname: Genovese
mesh_terms: D001047:Apicoectomy; D003751:Dental Fistula / Q000532:radiotherapy; D006801:Humans; D053685:Laser Therapy; D010482:Periapical Abscess / Q000382:microbiology / Q000532:radiotherapy*; D012184:Retrograde Obturation