The aim of this study was to evaluate histologically the anti-inflammatory reaction following Nd: YAG laser irradi ation in surgical mandibular defects of rats. Fifteen rats were used in this study and the experimental period was one, three, or seven days. The rats were given a general anaethetic, and the mandibule was exposed using a skin-mucosal flap. In each animal, a surgical defect of 2×2 mm was created at the inferior border of the mandible bilaterally. In the experimental group (Exp), Nd: YAG laser was irradiated to the bone defect and the inside of the skin-mucosal flap under saline water (3.0 W, 30 seconds, 3 times). In the control group (Cont), no intervention was made following surgery. At day 1, 3 and 7, each group of 5 animals was sacrificed. Undecalcified sections were made, stained with tolidine blue, then subjected to histological analysis and planimetric measure ments. Histological observation revealed that the tissue component inside surgically created bone defects was fibrous connective tissue that was dense and almost regularly aligned in Exp, but the fibrous connective tissue was dense and irregularly aligned in Cont. In Exp, the connective tissue corresponding to the line considered both bone edges (irradiated skin-mucosal flap) was dense and irregularly aligned at day 1, but it was loose and almost regularly aligned at day 7. In Cont, it was loose and regularly aligned at day 1, but was dense and irregularly aligned at day 7. In Exp, the bone edges were observed to be convexo concave and a densely stained area but were not osteoclast and resorption cavity observed during the experimental period. However, in Cont, they were not observed to be convexo concave and densely stained area. The results of planimetric measurements indicated that there was no statistically significant difference in the areas of surgi cally created bone defects in both Exp and Cont (p>0.05). In addition, there was no statistically significant difference in the number of inflammatory cells in both Exp and Cont during the experimental period (p>0.05). This study suggested that the anti-inflammatory effect following Nd: YAG laser irradiation is not a quantitative change of the number of inflammatory cells but a qualitative change associated with a histological change caused by laser irradiation.
The bactericidal effects of Nd: YAG laser by using a reaction mediator of TiO2 were studied. Two strains of bacteria, Streptococcus mutans ATCC 25175 and Streptococcus soblinus ATCC 33478 were used for this experiment. Bacterial cell suspensions of each strain were divided into four groups: such as cell suspension alone, cell suspension with TiO2, and cell suspension with or without TiO2, which were irradiated with the Nd: YAG laser at 900 mJ-10pps, total energy of 1, 500 J under control of the temperature of the reaction mixture. After those treatments, the viable cell count was estimated in each group. The bactericidal effects of the Nd: YAG laser with TiO2 showed a significant reduction of viable cells of S. mutans and S. soblinus after laser irradiation with total energy of 1, 500 J. It might be possible that the bactericidal action revealed shock wave effects by Nd: YAG laser irradiation with TiO2 as a reaction mediator.
Recently, CO2 lasers, diodelasers, Nd: YAG lasers, Er: YAG lasers, and Ho: YAG lasers have been used in dental treatment. A new laser device, Er, Cr: YSGG laser, has been developed that can be used for hard tissue ablation and soft tissue incision. Moreover, since use of this laser device hardly causes any sharp pain to occur when making incisions in soft tissue, the operation using this laser can be performed without local anesthesia. The purpose of this clinical study was to examine the clinical evaluation of oral soft tissue diseases that were treated by incision using a surgical scalpel and an Er, Cr: YSGG laser device. Sixty patients (28 males; 32 females), with gingival hyperplasia (n=20), gingival polyp (n=20), or abnormalities of the frenum (n=20) were selected and randomly divided to a control group treated by incision with a surgical scalpel and a laser treatment group. The scores of the clinical evaluations were recorded before treatment and immediately, 1 week, 2 weeks, and 4 weeks after treatment. The total scores of each case in the control group and laser treatment group were calculated and divided into three categories (very effective: 100-80, effective: 79-60, and no effect: 59-0). All cases treated using the Er, Cr: YSGG laser device fall into the very effective category, and there were no complications or side effects during the follow-up period of this clinical study. In conclusion, these results suggest that the Er, Cr: YSGG laser device had equal efficiency and safety compared to use of a surgical scalpel in the treatment of oral soft tissue diseases. Moreover, since the Er, Cr: YSGG laser could be employed without the use of local anesthesia in many cases, it was deemed extremely suitable for use in treating elderly or hypertension patients.
Treatment regimens used in pain clinics include oral drugs, nerve blocks, and physical therapy. Recently, photo therapy, a noninvasive treatment with minimal side effects, has been used for pain management in elderly patients in whom nerve blocks cannot be performed because of concurrent disease. We used the rabbit ear chamber method under direct vision to examine changes in the arteriolar microcirculation after phototherapy. Low-power laser light (laser group) and linearly polarized near-infrared light (near-infrared group) were used to measure the luminal diameter, blood-flow velocity, and blood volume of the arterioles. As compared with the values before treatment (100%), the arteriolar diameter increased to 101.9%±5.9% in the control group, 130.1%±10.4% in the laser group, and 125.2%±16.9% in the near-infrared group. These increases in both the laser and near-infrared groups were significant as compared with the control value (p<0.05). Blood-flow velocity increased from a baseline value of 100% to 101.3%±3.6% in the control group, 126.3%±14.8% in the laser group, and 129.1%±16.8% in the near-infrared group. The increases in both the laser and near-infrared groups were significant as compared with that in the control group (p<0.05). Arteriolar blood volume showed a similar trend, and significantly increased after phototherapy (p<0.05). Phototherapy improved the microcirculation with minimal systemic and local side effects and can therefore be used as adjuvant therapy. Laser therapy is very often used in the field of pain management. Laser therapy alone or combined with other treatments such as nerve blocks and drug therapy has been shown to be effective. Previous basic research, including our study, has suggested that the mechanism by which laser therapy relieves pain involves factors such as the selective inhibition of peripheral-nerve conduction, relaxation of vascular smooth muscle, and arteriolar dilation due to the inhibition of sympathetic-nerve activity. In addition to relieving pain, laser therapy can reduce inflammation and promote wound healing. We describe our findings and the clinical usefulness of laser therapy in the field of pain management.
Since laser devices for medical treatment emit high-power laser light, even laser light that enters eyes indirectly due to reflection or scattering can cause damage. Furthermore, because emissions from most lasers for dental treatment are invisible, one can not notice, if the eyes are exposed to the laser light. Therefore, when using lasers for dental treatment, a laser controlled area should be set up with warnings, and all persons in the controlled area should wear protective glasses. Protective glasses must be adapted to the wavelength and output power of the laser to be used. On the other hand, since a high-voltage power supply is used in most laser devices, when using a laser, it is necessary to consider protection from not only laser light but also electric shock, so the equipment must be grounded. Optical components used in laser devices are weak against mechanical shock, and if deviation arises at the angle of the mirrors used for the laser resonator and so on due to vibration or shock, it may lead to a fall of laser power or malfunction. Therefore, it is important for laser devices to give neither vibration nor shock. Since mirrors, lenses, optical fibers, etc. which are used in laser devices deteriorate easily in a humid environment, it is desirable to use and keep the devices in a dehumidified environment. If dirt is adhered to the surfaces of a chip, optical fiber, and so on, it may cause damage or reduce the transmitted power, so it is necessary to perform checks and cleaning every time of use or every several months according to the directions of the maker. However, the parts and procedures of periodical checks and cleaning, and consumable parts and their exchange frequency differ for every model of laser. When two or more models of laser device are being used, the information for each model should not be confused.