Photobiomodulation,Photomedicine,and Laser Surgery

Objective: The authors carried out an experimental study to evaluate the histological alterations after irradiation of cartilage using Holmium:YAG (Ho:YAG) laser VersaPulse Select 60 watts and Infra Tome Delivery Systems 30° Handpiece (spot size at fiber tip 0.4 mm; Coherent Medical, Palo Alto, CA). Background Data: Recently, some authors reported cases with articular cartilage damage following arthroscopic laser surgery in the knee joint for the treatment of articular cartilage or meniscal pathology. Materials and Methods: The cartilage specimens immersed in saline were exposed to Ho:YAG laser irradiation. The laser wavelength was 2.1 μm, and pulse duration was 250 μsec. Power settings were 0.2-1 joules per pulse and 10-15 Hz. Total laser energy used in these procedures was 1.5 K joules. During the procedures, the handpiece was used at an angle of 30° and at a distance of 1 mm. Results: Electron microscopic evaluation demonstrated that the ultrastructure of the cartilage is preserved in both experiment and control groups. Conclusion: When Ho:YAG laser is used in optimal dosage (optimal joule and Hertz) with optimal technique (keeping the handpiece at an appropriate angle and distance) and avoiding overtreatment, it does not cause cartilage damage.

Objective: The purpose of this study was to examine the morphological changes and temperature increases of the titanium after Er:YAG laser irradiation, and also to investigate the effect of this laser on debridement of contaminated healing abutments. Background Data: Mechanical instruments have been used for the cleaning of implant abutment surfaces, however, most of them are not appropriate for the application to titanium surface. Recently, the Er:YAG laser has been expected to have a promising ability for the debridement of implant surface. Materials and Methods: Experiments were composed of three parts. At first, ten titanium round plates were exposed to the Er:YAG laser irradiation at 30-200 mJ/pulse and the surface changes were observed by stereomicroscope and scanning electron microscope. Secondly, the surface temperature changes of 60 titanium plates during and after Er:YAG laser irradiation at 30 and 50 mJ/pulse were measured by thermographic equipment. At last, calculus on the surface of six contaminated healing abutments was removed by Er:YAG laser or ultrasonic scaler, and the treated surfaces were examined by stereomicroscope. Results: Under 50 mJ/pulse, distinct morphological changes were not observed and the elevation of surface temperature was minimal, especially in the use of water-cooling. The Er:YAG laser at 30 mJ/pulse and 30 Hz with water spray was capable of effectively removing plaque and calculus on the implant abutments without injuring their surfaces. Conclusion: This study indicates that the Er:YAG laser can be a novel technical modality for the debridement of implant abutment surface.

Objective: To investigate the influence of linearly polarized near-infrared irradiation using the Super Lizer™ on deformability of human erythrocytes. Background Data: Not only low-powered laser but also linearly polarized near-infrared beams have some biostimulation effects on various tissues. There were some reports of erythrocyte deformability improved by low-powered He-Ne laser irradiation.Materials and Methods: Human erythrocyte samples stored for three weeks were adjusted to 30% hematocrit. Erythrocyte deformability presented as the filter filtration rate was measured. Results: There was no difference of the filter filtration rate between control group without irradiation and the group of 125 mJ/cm² exposure level at a wavelength of 830 nm. However, the groups of 625 and 1,250 mJ/cm² exposure levels at a wavelength of 830 nm showed higher filter filtration rates compared to the control group. Conclusion: Linearly polarized near-infrared irradiation in a range of 625-1,250 mJ/cm² exposure level at a wavelength of 830 nm improved deformability of human stored erythrocytes.

Objective: This study was conducted to evaluate the synergistic effect of cisplatin and interstitial KTP laser theapy induced hyperthermia in vitro and in vivo (interstitial laser chemotherapy, ILCT). Methods: In vitro study: human hypopharyngeal squamous carcinoma cell line (SNU-1041) was incubated in 1 mL of media containing various concentrations (0, 1, 2, 5, 10, 20, 50, 100 ng/mL) of cisplatin in 37° and 43°C for 2 hours. The viability of the cell was evaluated by MTT assay. In vivo study: human squamous cell carcinoma tumors were grown as subcutaneous transplants in nude mice and injected into tumor with cisplatin-epigel 100 μg, followed by interstitial laser therapy (ILT) via 0.6-mm diffuser fiber tips (532 nm, 1.0J/mm³). Results: In vitro study: the viability of tumor cells incubated with 10 ng/mL of cisplatin was 62% and 28% in 37°C and 43°C, respectively (p = 0.02). In vivo study: the tumor volume in 4 weeks after treatment was 179 mm³ in ILT group and 27 mm³ in ILCT group. The ILCT group showed 8 (80%) complete remission of tumors at 4 weeks follow up, while tumor remission occurred in only 3 (30%) in ILT group (p < 0.05). Conclusion: These results suggest ILCT may become an effective treatment for head and neck carcinoma with minimal functional deficit.

Objective: This present study was performed to compare the compositional changes of human dentin and, Knoop hardness of the cavity floor prepared by Er:YAG laser irradiation with that of the conventional bur cavity. Background Data: There are still no reports on the compositional changes of dental hard tissues and microhardness of the cavity floor prepared by Er:YAG laser irradiation. Materials and Methods: Fifteen laser and 15 bur cavities were cross-sectioned, and subjected to atomic analysis by SEM-EDX and knoop hardness testing. Statistical analyses were performed using the Mann-WhitneyU test; a value of p < 0.01 was considered significant. Cross sections of the remaining five laser and five bur cavities were examined by light microscopy and then by SEM. Results: The results showed that the quantities of Ca (Ca weight %) and P (P weight %) were increased significantly in the laser cavities, but no significant differences were found between the Ca/P ratio and Knoop hardness number of laser and bur cavities. The results of SEM observation revealed that the lased cavity surface was irregular, and there was also the absence of a smear layer; the orifice of dentinal tubules was exposed. Conclusion: Er:YAG laser device produces minimal thermal induced changes of dental hard tissue compositions; Ca/P ratio and Knoop hardness of the lased cavity floor was almost similar to the bur cavities.

Objective: The purpose of this study was an objective consideration of possible benefits of phototherapy implemented with therapeutic laser or possibly polarized light in treating episiotomy, which is the most frequent obstetric intervention. Materials and Methods: In the present study, the authors treated a total of 2,436 women. The light sources were as follows: a laser of a wave length 670 nm, power 20 mW, with continuous alternations of frequencies 10 Hz, 25 Hz, and 50 Hz, a polarized light source of a 400-2,000 nm wavelength in an interval of power 20 mW and frequency 100 Hz and a monochromatic light source of a 660 nm wavelength and power 40 mW, with simultaneous application of a magnetic field at an induction 8 mT. Results: The work demonstrated high healing effects with minimum secondary complications in the treatment of episiotomies using a therapeutic laser at an energy density of 2 J/cm². The application of polarized light at an energy density of 5 J/cm² also exerted favorable therapeutic effects.

Objective: The purpose of this study was to investigate the changes of hardness and elastic modulus of human dentin after Nd:YAG laser irradiation. Background Data: The application of Nd:YAG laser in dental hard tissues has been widely studied. However, little information is available about the mechanical properties of teeth after Nd:YAG laser irradiation. Methods: The human dentin was irradiated by Nd:YAG laser through a 400-µm optic bare fiber. The parameters in laser delivery were 100 mJ/pulse - 10 pps - 4 sec and 150 mJ/pulse - 10 pps - 4 sec. Both the hardness and elastic modulus were obtained using an Instron microhardness tester and Vickers indenter. The indentations were then examined under a scanning electron microscope. Results: The hardness and elastic modulus of irradiated human dentin in the energy of 100 mJ/pulse - 10 pps - 4 sec and 150 mJ/pulse - 10 pps - 4 sec were 44.7 kg/mm² and 22.8 GPa, and 46.9 kg/mm² and 21.4 GPa, respectively. These values were significantly lower than that of non-irradiated dentin by the Student's t test. Conclusion: Our study demonstrated that Nd:YAG laser irradiation would reduce the hardness and elastic modulus of human dentin.