December 2016 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)

Cobb and Charles1 write an interesting article discussing the problems with laser research in the periodontal space. The comments apply to laser research generally and the abstract is reproduced in full.

Despite a quarter of a century of laser research, there is a persistent debate regarding the efficacy of dental lasers in the treatment of periodontitis or periodontal maintenance therapy. There are many claims and much hyperbole surrounding the use of lasers, either as a monotherapy or adjunctive to scaling and root planning, to treat periodontitis. There is little evidence that using a diode or neodymium:yttrium-aluminum-garnet laser adds clinical value over and above conventional non-surgical or surgical periodontal treatment. There is a significant need for better designed human clinical trials. Data from such trials should be analyzed according to initial probing depth and characteristics of the treated sites, such as non-molar, molar flat surfaces, and molar furcations, and evaluated for long-term post-treatment results.

Matos et al2 assed the effect of laser photobiomodulation (LPBM) at lambda808 nm and lambda660 nm and of storage media on the periodontal repair process of replanted teeth in rats and found that the LPBM protocol at lambda808 nm and lambda660 nm as well as whole milk and soy milk favored the periodontal repair process of replanted teeth in rats.

Frentzen et al3 published a paper describing a novel blue light diode laser (445 nm) for dental application showing improved cutting performance at a lower power level while retaining the advantages of the use of diode lasers for treatment of oral soft tissue.

Harris and coworkers4 published a paper on selective killing of pathogens by laser. Given the worries with rapidly expanding resistance of pathogens to antibiotics, the use of lasers for this purpose is to be welcomed. The abstract is reproduced in full.

Selective killing of pathogens by laser is possible due to the difference in absorption of photon energy by pathogens and host tissues. The optical properties of pathogenic microorganisms are used along with the known optical properties of soft tissues in calculations of the laser-induced thermal response of pathogen colonies embedded in a tissue model. The objective is to define the laser parameters that optimize pathogen destruction and depth of the bactericidal effect .MATERIALS AND METHODS: The virtual periodontium is a computational model of the optical and time-dependent thermal properties of infected periodontal tissues. The model simulates the periodontal procedure: Laser Sulcular Debridement.(1) Virtual pathogen colonies are placed at different depths in the virtual periodontium to determine the depth for effective bactericidal effects given various laser parameters (wavelength, peak power, pulse duration, scan rate, fluence rate) and differences in pathogen sensitivities . RESULTS: Accumulated background heat from multiple passes increases the depth of the bactericidal effect. In visible and near-IR wavelengths the large difference in absorption between normal soft tissue and Porphyromonas gingivalis (Pg) and Prevotella intermedia (Pi) results in selective destruction. Diode laser (810nm) efficacy and depth of the bactericidal effect are variable and dependent on hemin availability. Both pulsed-Nd:YAG and the 810nm diode lasers achieve a 2-3mm deep damage zone for pigmented Pg and Pi in soft tissue without surface damage (selective photoantisepsis). The model predicts no selectivity for the Er:YAG laser (2,940nm). Depth of the bactericidal effect is highly dependent on pathogen absorption coefficient. Highly sensitive pathogens may be destroyed as deep as 5-6mm in soft tissue. Short pulse durations enable confinement of the thermal event to the target. Temporal selectivity is achieved by adjusting pulse duration based on target size. CONCLUSION: The scatter-limited phototherapy model of the infected periodontium is applied to develop a proper dosimetry for selective photoantisepsis. Dosimetry planning is essential to the development of a new treatment modality.

Fornaini et al5 compared the effects of four different diode lasers on soft tissue and the abstract is reproduced in full.

The introduction of diode lasers in dentistry had several advantages, principally consisting on the reduced size, reduced cost and possibility to beam delivering by optical fibers. Up today only the wavelengths around 810 and 980 nm were the most utilized in oral surgery but recently more different lasers had been proposed. The aim of this study was to compare the efficacy of four diode laser wavelengths (810, 980, 1470 and 1950 nm) for the ablation of soft tissues. Material and methods: Specimens were surgically collected from the dorsal surface of four bovine tongues and irradiated by four different diode wavelengths. Thermal increase was measured by two thermocouples, the first at a depth of 0.5 mm, and the second at a depth of 2 mm. Initial and final surface temperatures were recorded by IR thermometer. Epithelial changes, connective tissue modifications, presence of vascular modification and incision morphology were histologically evaluated by two blind pathologists. Results: The time necessary to perform the excision varied between 271 seconds (808 nm, 2W) and 112 seconds (1950 nm, 4W). Temperature increase superficial level varied from 16.3° (980 nm, 4W) and 9.2° (1950 nm, 2 W). The most significant deep temperature increase was recorded by 980 nm, 4 W (17.3°) and the lowest by 1950 nm, 2 W (9.7°). The width of epithelial tissue injuries varied between 74 pm from 1950 nm diode laser at 2 W to 540 pm for 1470 nm diode laser at 4 W. Conclusion: The quality of incision was better and the width of overall tissue injuries was minor in the specimens obtained with higher wavelength (1950 nm) at lower power (2W).

Giannelli et al6 in an in vitro study examined the effects of diode laser on Staphylococcus aureus biofilm and Escherichia coli lipopolysaccharide adherent to titanium oxide surface of dental implants. They concluded that the lambda 808-nm diode laser was a valuable tool for decontamination/detoxification of the titanium implant surface and may be used in the treatment of peri-implantitis.

Yaneva and coworkers7 assessed temperature changes at specified time intervals during Er:YAG laser scaling and root planning of surfaces with dental calculus and concluded that the Er:YAG laser does not increase the temperature inside the pulp chamber.

Bizhang et al8 compared the ability of the pen-type laser fluorescence device (LF pen) to detect approximal carious lesions with that of bitewing radiographs and found that dentinal caries in approximal surfaces could be detected equally well using the LF pen.

Soares and coworkers9 compared the efficacy of neodymium-doped yttrium-aluminum-garnet (Nd:YAG) laser, gallium-aluminum-arsenide (GaAlAs) laser, and 2% neutral fluoride gel in the treatment of dentinal hypersensitivity and found that laser treatment resulted in significantly greater reductions in pain intensity.

References

1. Cobb, Charles M. Commentary: Is There Clinical Benefit From Using a Diode or Neodymium:Yttrium-Aluminum-Garnet Laser in the Treatment of Periodontitis? Journal of periodontology, 87 (10):1117-31; 10.1902/jop.2016.160134 2016-Oct.
2. Matos, Felipe de Souza; Godolphim, Fernanda de Jesus; Correia, Ayla Macyelle de Oliveira; de Albuquerque Junior, Ricardo Luiz Cavalcanti; Paranhos, Luiz Renato; Rode, Sigmar de Mello; Ribeiro, Maria Amalia Gonzaga. Effect of laser photobiomodulation on the periodontal repair process of replanted teeth. Dental traumatology : official publication of International Association for Dental Traumatology, 32 (5):402-8; 10.1111/edt.12276 2016-Oct.
3. Frentzen M, Kraus D, Reichelt J, Engelbach C, Dehn C, Meister J. A novel blue light diode laser (445nm) for dental application, Biomedical testing and clinical aspects. Laser international magazine of laser dentistry. Vol 8, issue 3/2016, pp3 6-8.
4. Harris, David M; Reinisch, Lou. Selective photoantisepsis. Lasers in surgery and medicine, 10.1002/lsm.22568 2016-Oct-10.
5. Fornaini, Carlo; Merigo, Elisabetta; Sozzi, Michele; Rocca, Jean-Paul; Poli, Federica; Selleri, Stefano; Cucinotta, Annamaria. Four different diode lasers comparison on soft tissues surgery: a preliminary ex vivo study. Laser therapy, 25 (2):105-114; 2016-Jun-29.
6. Giannelli, Marco; Landini, Giulia; Materassi, Fabrizio; Chellini, Flaminia; Antonelli, Alberto; Tani, Alessia; Zecchi-Orlandini, Sandra; Rossolini, Gian Maria; Bani, Daniele. The effects of diode laser on Staphylococcus aureus biofilm and Escherichia coli lipopolysaccharide adherent to titanium oxide surface of dental implants. An in vitro study. Lasers in medical science, 31 (8):1613-1619; 2016-Nov.
7. Yaneva, Blagovesta K; Zagorchev, Plamen I; Firkova, Elena I; Glavinkov, Ivan T. In Vitro Study of Temperature Changes in Pulp Chamber During Root Planing Procedure Using Er:YAG Laser. Folia medica, 58 (3):206-210; 10.1515/folmed-2016-0022 2016-Sep-1.
8. Bizhang, M; Wollenweber, N; Singh-Husgen, P; Danesh, G; Zimmer, S. Pen-type laser fluorescence device versus bitewing radiographs for caries detection on approximal surfaces. Head & face medicine, 12 (1):30; 2016 Nov 04.
9. Soares, Marilia De Lima; Porciuncula, Geane Bandeira; Lucena, Mara Ilka
Holanda Medeiros De; Gueiros, Luiz Alcino Monteiro; Leao, Jair Carneiro;
Carvalho, Alessandra De Albuquerque Tavares. Efficacy of Nd:YAG and GaAlAs lasers in comparison to 2% fluoride gel for the treatment of dentinal hypersensitivity. General dentistry, 64 (6):66-70; 2016 Nov-Dec..

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