title: 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 (1.5 W, 3.0 W and 5.0 W). Each group was subdivided into 3 (n=10) according to the frequency (CM, 100 Hz and 1000 Hz), 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 100 Hz (6.22+/-3.64) and 1000 Hz (6.00+/-3.36), which presented no statistical difference between them (p>0.01). The groups irradiated with 5.0 W presented the greatest temperature variation (12.15+/-5.14), followed by 3.0 W (7.88+/-3.92) and 1.5 W (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 degrees C.
  
  
  CONCLUSIONS
  Application of 980-nm diode laser in the root, at 1.5 W in all operating modes, and 3.0 W, in the pulsed mode, for 20s, can safely be used in endodontic treatment, irrespective of the presence of humidity.
authors.affiliation: School of Dentistry, University of Ribeirão Preto (UNAERP), Ribeirão Preto, SP, Brazil.
authors.forename: E
authors.initials: E
authors.lastname: Alfredo
authors.forename: M A
authors.initials: MA
authors.lastname: Marchesan
authors.forename: M D
authors.initials: MD
authors.lastname: Sousa-Neto
authors.forename: A
authors.initials: A
authors.lastname: Brugnera-Júnior
authors.forename: Y T C
authors.initials: YT
authors.lastname: Silva-Sousa
mesh_terms: D001831:Body Temperature / Q000528:radiation effects*; D003481:Cuspid / Q000528:radiation effects; D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000528:radiation effects*; D003804:Dentin / Q000033:anatomy & histology / Q000528:radiation effects; D006801:Humans; D054023:Lasers, Semiconductor; D011829:Radiation Dosage; D018915:Root Canal Preparation; D013821:Thermometers; D019227:Tooth Apex / Q000528:radiation effects; D019237:Tooth Cervix / Q000528:radiation effects; D014092:Tooth Root / Q000528:radiation effects*; D014867:Water
chemical_list: D014867:Water