Removal of gutta-percha from root canals using an Nd:YAG laser.
OBJECTIVE
To examine the use of an Nd:YAG laser in removing gutta-percha fillings from root canals when used in conjunction with eucalyptol, dimethylformamide (DMF) or no solvent.


METHODS
Root-canal fillings (sealer and gutta-percha) were removed with laser irradiation of 20 Hz/1.5 W from 30 roots randomly divided in three groups. In group 1, the solvent was eucalyptol; in group 2, the solvent was DMF; and in group 3, no solvent was used. Laser irradiation was performed until the temperature measured on the root surface increased by 4 degrees C over room temperature. The treatment was deemed complete when the apical foramen was reached with the optical fibre and a reamer. The samples were split longitudinally, and the area of remaining gutta-percha on the root-canal walls was determined with the aid of a computer program. The total number of laser pulses to achieve length and the highest temperature recorded was determined for each tooth. The results were statistically analysed using Student's t-test (P < 0.05) for independent samples.


RESULTS
The average temperature increase in group 1 was 9.17 +/- 0.56 degrees C; in group 2, 9.56 +/- 0.28 degrees C; and in group 3, 8.29 +/- 0.41 degrees C. The shortest time to achieve length was in group 3 (6.4 +/- 0.49 min), then in group 1 (6.7 +/- 0.85 min) and group 2 (7.05 +/- 0.79 min). The area of remaining gutta-percha was the largest in group 2 (6.13 +/- 5.76%), whilst the smallest was for group 3 (4.69 +/- 4.03%), but the difference was not statistically significant. The number of pulses was not statistically significant between the groups.


CONCLUSIONS
Use of an Nd:YAG laser alone is capable of softening gutta-percha. The addition of solvents did not improve the retreatment, either in terms of the time required for the procedure or in terms of the area of remaining gutta-percha on root-canal walls.
D000538:Aluminum Silicates; D003511:Cyclohexanols / Q000627:therapeutic use; D003786:Dental Pulp Cavity / Q000528:radiation effects / Q000648:ultrastructure*; D004126:Dimethylformamide / Q000627:therapeutic use; D000077591:Eucalyptol; D005052:Eucalyptus; D006171:Gutta-Percha / Q000737:chemistry* / Q000528:radiation effects; D006244:Hardness; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007834:Lasers; D039821:Monoterpenes / Q000627:therapeutic use; D009354:Neodymium; D012387:Root Canal Filling Materials / Q000737:chemistry* / Q000528:radiation effects; D018915:Root Canal Preparation / Q000295:instrumentation; D012997:Solvents / Q000627:therapeutic use; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D015019:Yttrium
D000538:Aluminum Silicates; D003511:Cyclohexanols; D039821:Monoterpenes; D012387:Root Canal Filling Materials; D012997:Solvents; D009354:Neodymium; D015019:Yttrium; D004126:Dimethylformamide; D006171:Gutta-Percha; D000077591:Eucalyptol