Photobiomodulation,Photomedicine,and Laser Surgery

Objective: The purpose of the present study is to call attention to well-established concepts in optics, which, however, are not necessarily known by medical laser users but may be important for interpretation of some data. Background Data: In reviewing some aspects of the physical concepts of wavelength, frequency, photon energy, and color, it was possible to establish, beyond doubt, the right conditions to use these terms to classify specific laser radiations. This may help in the correct interpretation of some low-level laser therapy (LLLT) experimental results. Materials and Methods: In order to achieve our objective - maintaining the reader's interest - we use the simplest physical concepts and equations necessary for nonphysicists to understand this subject. Results: The most important result pointed out through this study is the fact that the numerical value for wavelength, normally assigned to commercial lasers, should not be used to describe the light propagation inside the tissue. Conclusion: The knowledge of the relation among the magnitudes discussed in the present study and their effects, although it does not add much to the use of a laser merely as a cutting instrument, becomes of fundamental significance when used to determine the effects that depend on light propagation within biological tissue and that do not result only from absorption of light energy. This will certainly help in the understanding of phenomena whose causes are attributed to the electric and magnetic polarization of laser radiation, as seems to be the case observed in laser biostimulation.

Objective: The aim of the present study is to assess the clinical effectiveness of the artificial dermis. Background Data: We have previously observed prolonged postoperative pain and bleeding in patients receiving potassium titanyl phosphate (KTP) laser surgery for oral mucosal diseases. Materials and Methods: The artificial dermis was placed on the wound and fixed to the surrounding oral mucosa by silk suturing. The silicon sheet of the artificial dermis and the sutures were removed on the seventh postoperative day. Postoperative bleeding from the oral mucosa, duration of postoperative pain, and the period required for healing were all assessed clinically. The results were compared to those in a group of similar cases which were treated without the artificial dermis. In this retrospective review, we considered 20 cases of tongue lesion treated by KTP laser (10 leukoplakias, nine squamous cell carcinomas, and one metastatic renal cell carcinoma to the tongue), nine of which were followed by application of an artificial dermis to prevent postoperative pain and bleeding, and 11 of which were not. Results: No postoperative bleeding was observed in the group of cases treated with an artificial dermis, although it was observed in 45.5% in the group of cases treated without an artificial dermis. There was a statistical difference between these two groups (p < 0.03). Conclusion: It was concluded that use of artificial dermis prevented postoperative bleeding.

Objective: The purpose of this study was to determine the effects of prophylactic near-infrared light therapy from light-emitting diodes (LEDs) in pediatric bone marrow transplant (BMT) recipients.Background Data: Oral mucositis (OM) is a frequent side effect of chemotherapy that leads to increased morbidity. Near-infrared light has been shown to produce biostimulatory effects in tissues, and previous results using near-infrared lasers have shown improvement in OM indices. However, LEDs may hold greater potential for clinical applications. Materials and Methods: We recruited 32 consecutive pediatric patients undergoing myeloablative therapy in preparation for BMT. Patients were examined by two of three pediatric dentists trained in assessing the Schubert oral mucositis index (OMI) for left and right buccal and lateral tongue mucosal surfaces, while the patients were asked to rate their current left and right mouth pain, left and right xerostomia, and throat pain. LED therapy consisted of daily treatment at a fluence of 4 J/cm² using a 670-nm LED array held to the left extraoral epithelium starting on the day of transplant, with a concurrent sham treatment on the right. Patients were assessed before BMT and every 2-3 days through posttransplant day 14. Outcomes included the percentage of patients with ulcerative oral mucositis (UOM) compared to historical epidemiological controls, the comparison of left and right buccal pain to throat pain, and the comparison between sides of the buccal and lateral tongue OMI and buccal pain. Results: The incidence of UOM was 53%, compared to an expected rate of 70-90%. There was also a 48% and 39% reduction of treated left and right buccal pain, respectively, compared to untreated throat pain at about posttransplant day 7 (p < 0.05). There were no significant differences between sides in OMI or pain. Conclusion: Although more studies are needed, LED therapy appears useful in the prevention of OM in pediatric BMT patients.

Objective: To examine the effects of low-intensity laser therapy (LILT) on bacterial growth in vitro. Background Data: LILT is undergoing investigation as a treatment for accelerating healing of open wounds. The potential of coincident effects on wound bacteria has received little attention. Increased bacterial proliferation could further delay recovery; conversely inhibition could be beneficial.Materials and Methods: Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus were plated on agar and then irradiated with wavelengths of 630, 660, 810, and 905 nm (0.015 W/cm²) and radiant exposures of 1-50 J/cm². In addition, E. coli was irradiated with 810 nm at an irradiance of 0.03 W/cm² (1-50 J/cm²). Cells were counted after 20 h of incubation post LILT. Repeated measures ANOVA and Tukey adjusted post hoc tests were used for analysis. Results: There were interactions between wavelength and species (p = 0.0001) and between wavelength and radiant exposure (p = 0.007) in the overall effects on bacterial growth; therefore, individual wavelengths were analyzed. Over all types of bacteria, there were overall growth effects using 810- and 630-nm lasers, with species differences at 630 nm. Effects occurred at low radiant exposures (1-20 J/cm²). Overall effects were marginal using 660 nm and negative at 905 nm. Inhibition of P. aeruginosa followed irradiation using 810 nm at 5 J/cm² (-23%; p = 0.02). Irradiation using 630 nm at 1 J/cm² inhibited P. aeruginosa and E. coli (-27%). Irradiation using 810 nm(0.015 W/cm²) increased E. coli growth, but with increased irradiance (0.03 W/cm²) the growth was significant (p = 0.04), reaching 30% at 20 J/cm² (p = 0.01). S. aureus growth increased 27% following 905-nm irradiation at 50 J/cm². Conclusion: LILT applied to wounds, delivering commonly used wavelengths and radiant exposures in the range of 1-20 J/cm², could produce changes in bacterial growth of considerable importance for wound healing. A wavelength of 630 nm appeared to be most commonly associated with bacterial inhibition. The findings of this study might be useful as a basis for selecting LILT for infected wounds.

Objective: This paper describes five cases of macroscopic irregular CO₂ laser-beam ablation patterns that can generate below-surface complications during surgery. These five cases are related to curved reflected beams, curved craters generation with abnormal superficial thermal damage, and craters that show irregular wall contours. Although these alterations have been observed during irradiation in PMMA samples (polymethilmethacrylate), it is possible that similar unpredictable changes also happen in low-water-content, hard and uniform biological tissues such as compact bone, enamel, and dentin. This fact can predict severe impacts on the quality of the final surgical outcome, especially there where precision surgery techniques are required. A qualitative description about the possible causes of these effects and how to avoid them during surgery have been suggested too. Background Data: In the past decades, daily surgery and research studies have provided useful information about the interaction between medical CO₂ laser beams and animal, human, and other biological tissues. Several mathematical models describe with acceptable accuracy all the ablative properties of the 10.6 µm laser beam. Very few studies describe the presence and address the consequences of the ablative aberrations, which can frequently and randomly happen during laser surgery. The probability that these changes happen in below-surface, therefore invisible, parts of the biologic media under treatment makes the whole matter crucial, even in cases of traditional surgery. Where gross mass removals are considered, the presence of unpredictable and sudden deviations from the expected traditional cone-shaped patterns raise several questions about safety. The continuous need for properly engineered medical laser-beam devices, online laser-beam monitoring, and real-time control becomes mandatory in modern surgery. Materials and Methods: The equipment used in this study was provided by the National Cancer Institute of Milan, Milan, Italy, and by the Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel. A large TEM-mode laser-beam device (Valfivre, Italy) and TEM00 laser-beam device (Synrad, USA), both coupled to 2.5- and 5-inch focusing lenses, have been used to irradiate, at 10 Watts nominal output, on the focal spot, several PMMA blocks (3 × 2 × 4 × 2 × 2 cm) up to 10 sec CW. For one set of experiments, a metallic, well-polished mirror was placed against one surface of each sample to simulate possible internal beam reflections caused by generic metallic surgical instruments, such as conventional scalpels or clamps. Results: The experimental evidence of five major and unpredicted changes in the shape of craters produced by CO₂ laser beams in PMMA are shown in photos and discussed in a qualitative way. Several physical and thermodynamic phenomena are proposed to identify and therefore minimize or avoid the causes of these events. Conclusion: The results discussed in this paper show how important it is to constantly and carefully observe both the irradiated tissue's or media's structure and the beam's broadening under surface during the ablation process. Fume attenuation of the incoming laser beam, fume escape paths, internal beam interference phenomena, media's microstructural changes and, perhaps more importantly, their combination can offer good explanations of all the described phenomena. In summary, the presence of fumes in at least two out of the five reported cases plays a key role in aberrant crater generation processes. Therefore, the author recommends paying extra attention to them in order to provide a higher quality outcome in Surgery where CO₂ laser beams are deployed.

Objective: Noninvasive laser therapy is a treatment method employed in many disciplines. This review article points out instances when it appears to be effective to administer such therapy. Materials and Methods: Noninvasive laser therapy has a number of suitable applications that cause minimal damage to the patient. Many patients are not sent to institutions equipped with relevant instruments, since physicians are burdened by a number of contraindications, many of which are incorrect. The purpose of this article was to divide these contraindications into the following three groups: correct indications, indications doubtful under certain conditions, and incorrect indications. Discussion: We consider the following contraindications as correct: history of a histologically demonstrated malignant carcinoma; irradiation of the neck region in hyperthyreosis; epilepsy; exposure of the retina; and exposure of the abdomen during pregnancy. The contraindications that are doubtful under certain conditions are as follows: fever and infectious diseases; certain blood diseases; heavy blood losses; neuropathies; and irradiation in the region of gonads. The other contraindications reported in the literature are considered to be incorrect.