The purpose of this study was to evaluate the pain relief effects of pulsed Nd: YAG laser irradiation with and without Chinese ink. Twenty mandibular canines and the mucogingival areas were examined in this study (10 males, 10 females; aged 25 to 30 years; the mean age, 26.5 years). The right areas were irradiation sites (with and without Chinese ink), and the left areas were control sites without irradiation. The conditions for irradiation were laser energy 1.5w, pulses per second 15pps, and irradiation time 60sec. And the laser was irradiated on mucogingival surfaces stained with and without Chinese ink. Also, pain relief effects were evaluated as to pulp thermal sensitivity and surface anesthetic effect. (1) Evaluation of pulp thermal sensitivity: The buccal surfaces of canines were heated to 65°C with the tip of a heat probe, and each subject reported an immediate response to pulp thermal sensitivity. And, the degree of pulp thermal sensitivity was measured by a pain thermometer on irradiation sites and control sites. (2) Evaluation of surface anesthetic effect: The mucobuccal folds were penetrated with a 30G cartridge needle, and each subject reportedan immediate response to needle penetration on the irradiation site and the control site. The pain was classified into the following three grades: grade 1, no pain; grade 2, slight pain; grade 3, pain. For these results of pain relief effects on pulp thermal sensitivity and surface anesthetic effects, there was a statistically significant difference in the pain relief effects between the irradiation site and the control site (P<0.05: Wilcoxon signed-ranks test). In the irradiation site, the pain relief effect of Nd: YAG laser irradiation with Chinese ink was significantly more effective than that without Chinese ink (P<0.001: Wilcoxon signed-ranks test). This study suggested that Nd: YAG laser irradiation with Chinese ink may be useful for pain relief.
To elucidate whether low-power laser irradiation stimulates activation of dental pulp, effects of low-power laser (Ga-Al-As) irradiation on cellular growth and alkaline phosphatase (ALPase) activity were examined, using five populations of human dental pulp-derived fibroblast-like cells (HDP 1-5). HDP were seeded into 96-well microplates and incubated in 10% FBS-containing a-MEM until confluency, for 3 days. After 24 h of serum starvation, a low-power laser (80 mW) was irradiated for 20 s, 1min, or 3min, once on day 5 (1 IR), or twice on days 5 and 6 (2 IR), respectively. Cellular growth of HDP 1, 4, and 5 was accelerated to 120% compared with controls, by 1 min or 3 min of laser irradiation. ALPase activity of HDP 1, 2, 4, and 5 was stimulated up to 120-170% compared with controls, by 1min or 3min of irradiation. The above HDP responses induced by laser irradiation did not depend on irradiation frequency. These results indicate that HDP responded to low-power laser irradiation, and the responses were effective on cellular differentiation rather than cellular growth.
The present study aimed to determine the clinical effect of Nd: YAG laser exposure to dentin hypersensitivity in relation to periodontal therapy. After laser irradiation, the dental pulp vitality and adverse effects were assessed long-term. Thirty-three patients with 96 sensitive teeth participated in this study and were followed up for from 3 months to 6 years and 11 months. Hypersensitivity occurred in 24 teeth after brushing procedure, in 39 teeth after scaling procedure, and in 21 teeth after periodontal surgery. And there were 12 unknown trigger teeth. It was observed that no hypersensitivity reaction was felt after irradiation in 89 out of 96 teeth. A one-time laser irradiation resulted in 66.7% and 51.3% success after brushing and scaling procedures, respectively. However, several time exposures were required to resolve hypersensitivity in postsurgiCal cases, and that finally there is no effect on the dentin hypersensitivity after periodontal surgery in 5 teeth and 3 teeth in the case of unknown group. In addition, an electric pulp tester was used to determine teeth vitality. Before and after laser exposure, teeth vitality scores were recorded. Results showed that there were no differences obtained, between before and after treatment, in 61.1% of all the teeth. And, lower and higher scores in comparison with before treatment were observed. This may suggest that a more precise re-evaluation is necessary.
We have already reported that dental pulp can be securely protected against Er: YAG laser irradiation during caries removal, because the related heat can be controlled by simultaneous cooling with a water spray. However, this water spray may reduce the cutting efficiency, if used excessively. The present study was carried out to determine the optimal amount of water spray during dentin cutting with Er: YAG laser irradiation. Temperature was measured under six different conditions, prepared by changing the amount of water spray (0, 1, 2, 4, 6 and 8ml/min) during Er: YAG laser irradiation, and the cut surface was observed by stereoscopic microscopy for morphological evaluation. The results were are as follows: 1. Temperature elevation by laser irradiation could be prevented with a small amount of water spray. 2. Thermal damage was observed on the irradiated surface under stereoscopic microscopy when the irradiation had been made without water spray, or with water spray at 1ml/min. 3. The depth of cavity was largest in the non-water spray group, and the cavity area tended to become shallower as the amount of water spray was increased. 4. Cutting decreased in efficiency if performed with watar spray at 6 and 8ml/min, as compared with cut volumes obtained with water spray at 1-4 ml/min. From these results, it is inferred that 2 to 4ml/min is an optimal amount of water spray during dentin cutting with Er: YAG laser irradiation.
The purpose of this study was to evaluate interstitial photodynamic therapy using the Microselectron ® Flexible implant tube (Nucletron B. V.) for advanced cancer. VX2 carcinoma was transplanted subcutaneously into the femur of Japanese white rabbits. When the cancer grew to the size of 60 mm, a dose of 10 mg/kg of porfimer sodium (Photofrin ®, Wyeth Lederle Japan Ltd.) was administered intravenously. Microselectron ® tubes were implanted into the tumor at intervals of 20mm in which the optic fiber was inserted. Then irradiation was performed under conditions of 4mJoul/pulse and a pulse repetition frequency of 80Hz. The total light dose along a tube was 100Joul/cm. At 5 days after irradiation, the tumors had flatted, due to necrotic change. We suggest that interstitial photodynamic therapy using the Microselectron ® tube is applicable for treatment of solid oral cancer.
The purpose of this study was to clarify the clinical usefulness of the Er: YAG laser for class V cavity preparation. A clinical evaluation using an Er: YAG laser (Erwin, Morita Co., Japan) was carried out on 708 subjects (1068 permanent teeth), aged between 7 and 92 years, having indications for dental caries or a wedge-shaped defect. Class V cavity preparation was carried out in all the teeth. In each tooth, tha cavity margin was beveled using the laser. The condition of laser irradiation was 70mJ/pulse to 200mJ/pulse, with a pulse repetition rate of 10 pps. The cavities prepared using the Er: YAG laser were restored with light-cured composite resin, following application of a bonding agent, but without acid etching by phosphoric acid or primer application. Most of the patients received no local anesthesia during the cavity preparation. After one year of observation, it was noted that only 13 composite resin restorations had fallen out of the cavities, (1.2% of the whole sample), out of which only one had shown secondary dental caries. The rest of the teeth showed no discoloration, no cracking of tooth substance, and no marginal breakdown. Therefore, the results of our study indicate that Er: YAG laser treatment may be effective for Class V cavity preparation with composite resin restoration without acid etching or primer application.
The purpose of this review is to provide information about the current and potential applications of laser technology in the treatment of periodontally-diseased root surfaces and periodontal pockets. Based on its various characteristics, such as ablation or vaporization, hemostasis, and sterilization effect, laser treatment has been expected to serve as an alternative or adjunctive therapy to conventional, mechanical periodontal therapy. Carbon dioxide (CO2) and neodymium: yttrium-alminum-garnet (Nd: YAG) lasers have been approved for soft tissue treatment in periodontics, because of their excellent ability for soft tissue ablation, accompanied by hemostatic and bactericidal effects. However, these laser irradiations showed insufficient ability to ablate dental hard tissues, due to major thermal side-effects, when high energy output was applied. Recently, the erbium: yttrium-aluminum-garnet (Er: YAG) laser has been developed in dentistry, and its excellent ability for ablation in both soft and hard tissues has enabled laser application to root surface debridement, as well as to dental caries removal. Currently, laser application into periodontal pocket has become a promising field in laser dentistry, and much interest has been focused in this area. Further basic and clinical studies are required in order to establish a base for clinical use of laser energy in periodontal therapy, and clinicians should follow the results of scientific investigations to obtain successful outcomes.