Laser Literature Review Compiled by Dr Igor Cernavin, Prosthodontist, Honorary Senior Fellow University of Melbourne School of Medicine, Dentistry and Health Sciences



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Laser Literature Review
Compiled by Dr Igor Cernavin, Prosthodontist, Honorary Senior Fellow University of Melbourne School of Medicine, Dentistry and Health Sciences, Director and Cofounder of the Asia Pacific Institute of Dental Education and Research (AIDER), Australian representative of World Federation of Laser Dentistry (WFLD)

This study aimed to clarify pulpal responses to gallium-aluminum-arsenide (GaAlAs) laser irradiation. Maxillary first molars of 8-week-old rats were irradiated at an output power of 0.5 or 1.5 W for 180 seconds, and the samples were collected at intervals of 0 to 14 days. The authors found that the output energy determined pulpal healing patterns after GaAlAs laser irradiation; the higher energy induced the apoptosis in the affected dental pulp including odontoblasts followed by active cell proliferation in the intense HSP-25-immunoreactive areas surrounding the degenerative tissue, resulting in abundant tertiary dentin formation. Thus, the optimal GaAlAs laser irradiation elicited intentional tertiary dentin formation in the dental pulp.1


This in vivo study aimed to evaluate the performance of 2 fluorescence-based methods in detecting occlusal caries lesions in primary teeth, compared with the performance of visual inspection and radiographic methods Their conclusion was that both fluorescence-based methods presented similar performance in detecting occlusal dentine caries lesions in primary teeth, but they usually gave more false-positive results than did the visual and radiographic methods2.
A study examining the effects of ultramorphological changes on adhesion to lased dentin concluded that laser irradiation interacts with the dental hard tissue resulting in a specific morphological pattern of dentin and collagen fibrils that negatively affected the bond strength to composite resin3.
A study comparing the effects of different lasers, LED irradiation protocols and chlorhexidine treatment for deactivation of bacterial lopopolysaccharide to titanium surfaces found that laser and LED irradiation are capable of effectively reducing the inflammatory response to LPS adherent to titanium surface.
An interesting in vitro study examined the effect of diode laser irradiation on dentin as a preventive measure against dental erosion and found that dentin irradiation, using a diode laser with levels set at 60 J/cm(2), may induce inhibitory effects on root dentin demineralization without causing any harmful thermal effects. However, the exact mechanism of the action of the laser remains  unclear5.
Liu et al6 examined the pulsed Nd:YAG laser on the bond strength of self-adhesive resin cement to dentin and found that using the pulsed Nd:YAG laser(0.8W,10Hz) for 25s the shear bond strength in the control group and laser group was (9.481.80)MPa and (11.151.71)MPa, respectively, the difference was statistically significant(P<0.05).Most of the fractured surfaces were due to adhesive failure modes in the two groups. SEM observation of the cement-dentin interface in the two groups showed good adaptation, but resin tags were not observed. Their conclusion was that the pulsed Nd: YAG laser (0.8W, 10Hz) can increase the bond strength of self-adhesive resin cement to dentine.
Boehm and coworkers7 examined the effect of indocyanine green on periodontal pathogens and concluded that ICG combined with an 810 nm diode laser may be useful as a photodynamic adjunct for reduction of bacterial load in periodontal pockets. The abstract is reproduced in full below.
Commercially available photodynamic therapy for periodontal diseases utilizes methylene blue as a photosensitizer. Here we propose a novel photosensitizer dye, indocyanine green (ICG), because it can be readily activated by commercially available dental 810 nm diode lasers and has an established safety record as an intravascular agent in cardiac imaging and ophthalmologic photodynamic therapy. Therefore, we aim to characterize ICG uptake and killing of key periodontal pathogens to explore its potential as a periodontal photodynamic therapy agent. We tested ICG uptake by spectroscopy in Porphyromonas gingivalis 381 and Aggregatibacter actinomycetemcomitans, in addition to Escherichia coli DH5alpha and a human gingival epithelial cell line, HepG, in relation to ICG dose and exposure time. We then measured killing of bacteria by determining viable bacteria counts before and after exposure to ICG and 810 nm diode laser light (0-0.5 W output settings, 0-5 seconds). ICG was also applied to extracted, restored teeth, and the teeth inspected visually for staining after rinsing with saline. We found rapid and significant uptake of indocyanine green into P. gingivalis 381 and A. actinomycetemcomitans 67, compared to E. coli DH5alpha and HepG gingival cell line. This correlated with significant killing of strains 381 and 67 compared to E.coli, with less than 10% survival. ICG does not appear to stain tooth surfaces and materials except calculus.
Tsurumaki et al8 examined the effect of instrumentation using curettes, piezoelectric ultrasonic scaler and Er,Cr:YSGG laser on the morphology and adhesion of blood components on root surfaces and found that no statistically significant differences (p>0.05) among groups were found as to the adhesion of blood components on root surface. Ultrasonic instrumentation and Er,Cr:YSGG irradiation produced rougher root surfaces than the use of curettes, but there were no differences among treatments with respect to the adhesion of blood components.
Geminiani working with George Romanos whom you might remember from a recent tour down under9 , examined the temperature increase during CO2 and Er:YAG irradiation on implant surfaces and found that the CO2 laser in continuous mode generated a temperature increase of 10 degrees C after only 36 seconds. The Er: YAG laser in continuous mode produced a more rapid temperature increase and took only 10 seconds to reach the critical threshold. Moral of the story: be very careful when using the Er laser around implants.
References


  1. GaAlAs Laser Irradiation Induces Active Tertiary Dentin Formation after Pulpal Apoptosis and Cell Proliferation in Rat Molars. Copyright  2011 American Association of Endodontists. Published by Elsevier Inc

  2. Clinical performance of two fluorescence-based methods in detecting occlusal caries lesions in primary teeth. Copyright  2011 S. Karger AG, Basel.

  3. Effects of ultramorphological changes on adhesion to lased dentin-Scanning electron microscopy and transmission electron microscopy analysis. Microsc. Res. Tech., 2011.  2010 Wiley-Liss, Inc. Copyright  2010 Wiley-Liss, Inc.

  4. Comparative in Vitro Study Among the Effects of Different Laser and LED Irradiation Protocols and Conventional Chlorhexidine Treatment for Deactivation of Bacterial Lipopolysaccharide Adherent to Titanium Surface.

  5. The effect of diode laser irradiation on dentin as a preventive measure against dental erosion: an in vitro study.

  6. Liu, Kun; Deng, Jing; Zhang, Hui-Min; Yao, Li-Xia. Effect of pulse Nd: YAG laser on the bond strength of self-adhesive resin cement to dentin. Shanghai kou qiang yi xue = Shanghai journal of stomatology 20 (4): 381-4 2011-Aug.

  7. Boehm, Tobias K; Ciancio, Sebastian G. Diode laser activated indocyanine green selectively kills bacteria. Journal of the International Academy of Periodontology 13 (2): 58-63 2011-Jul.

  8. Tsurumaki, Jackeline do Nascimento; Souto, Braulio Henrique Marques; Oliveira, Guilherme Jose Pimentel Lopes de; Sampaio, Jose Eduardo Cezar; Marcantonio Junior, Elcio; Marcantonio, Rosemary Adriana Chierici. Effect of instrumentation using curettes, piezoelectric ultrasonic scaler and Er,Cr: YSGG laser on the morphology and adhesion of blood components on root surfaces: a SEM study. Brazilian dental journal 22 (3): 185-92 2011.

  9. Geminiani, Alessandro; Caton, Jack G; Romanos, Georgios E. Temperature Increase During CO2 and Er:YAG Irradiation on Implant Surfaces. Implant dentistry 20 (5): 379-82 2011-Oct.


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