Effects of Nd:YAG Laser Irradiation on Root Canal Dentin Wall: A Scanning Electron Microscopic Study

Abstract

Objective: The purpose of this study was to evaluate, by scanning electron microscopy (SEM), the effects of Nd:YAG laser irradiation applied perpendicular or parallel to the root canal dentin wall. Methods: Thirty human teeth were divided into two groups: Group A (20 roots), laser application with circular movements, parallel to the dentin root surface; and Group B (10 roots), roots cut longitudinally and laser applied perpendicular to the root surface. Group A was subdivided into A1 (10 roots), laser application with 100 mJ, 15 Hz and 1.5 W; and A2 (10 roots) with 160 mJ, 15 Hz, and 2.4 W. Group B was subdivided into B1 (10 hemisections) and B2 (10 hemi-sections) with parameters similar to A1 and A2. Four applications of 7-sec duration were performed, with a total exposure of 28 sec. SEM evaluations were made in the cervical, middle, and apical thirds, with 500؋ and 2000؋ magnifications. Morphological changes scores were attributed, and the results were submitted to Kruskal Wallis statistical test (5%). Results: Significant statistical differences were found between groups A and B (p = 0.001). In groups A1 and A2, few areas of dentin melting were observed. In groups B1 and B2, areas of melting dentin covering dentin surface were observed. Conclusions: It was concluded that intracanal laser application with circular movements (parallel to the surface) produces limited morphological changes in root canal dentin wall.

Adaptation and penetration of resin-based root canal sealers in root canals irradiated with high-intensity lasers

“…Several studies demonstrated its efficacy in cleanliness and disinfection. 8,9,[11][12][13][14][15] Few studies have compared the resin-based sealers that were investigated in the present study and the influence of high-intensity laser irradiation on the adaptation and penetration into dentin tubules of these sealers. 3,5,6 Therefore, the hypothesis of this study is that the treatment of dentin prior to obturation using high intensity laser irradiation interferes with the quality of the apical seal when using resin-based sealers was accepted.…”

“…These results concur with other reports in the literature. 9,[15][16][17][18][19] On the other hand, Er: YAG laser irradiation caused ablation of the dentin surface, which was more evident in the intertubular than the peritubular dentin. This resulted in more exposed dentinal tubules as previously reported.…”

“…Teeth in Group Neodymium had the root canals irradiated with a 1064-nm Nd:YAG laser (Pulse Master 1000; American Dental Technologies, Southfield, Michigan) operated at 1.5 W, 100 mJ, 15 Hz, and 124;34 J∕cm 2 , in pulsed mode. 9,11,16 Group diode was irradiated with an 808-nm diode laser (Zap Softlase; Zap Lasers Ltd., Pleasant Hill, California) with a setting of 2.5 W in continuous mode. 5,6,19,20 In the fourth group (Erbium), the root canals were irradiated with a 2940 nm Er:YAG laser (KavoKey laser 2; KaVo Co., Biberach, Germany) operated at 1 W, 100 mJ, 10 Hz, and 38;03 J∕cm 2 in pulsed mode.…”

“…[2][3][4][5][6][7] As an adjunct in endodontic treatment, the use of high intensity laser devices has demonstrated significant intracanal disinfection and morphological changes of the dentin surface that interfere with dentin permeability and root canal sealing. 5,6,[8][9][10][11][12][13][14][15][16] The interaction between laser wavelengths and irradiated tissues will assume the level of energy absorbed by the latter and therefore the intensity of tissue alteration. 3,9,11-,15-18 Wavelengths between 800 and 1100 nm (i.e., diode and Nd:YAG lasers) have poor interaction with dental hard tissues like enamel and dentin.…”

“…These lasers can melt their surfaces, creating a new pattern and occluding dentinal tubules. 9,11,13,[15][16][17][18][19] On the other hand, wavelengths in the range of 2700 and 3000 nm (Er, Cr:YSGG and Er:YAG lasers) have an optimal interaction with water and hydroxyapatite, and therefore the laser energy is highly absorbed by dental structures causing surface ablation. 3,10,12,13,18 Despite the favorable properties of the methacrylate resinbased sealers and high intensity laser irradiation, it is not well understood if the association of these two resources improves the root canal seal, and therefore might enhance the success of root canal treatment.…”