Safety Instruction on the use of medical devices is an important factor in dental treatment. Although many dentists use various kinds of laser equipment in daily dental treatment, the importance of safety instruction on their use is not effectively conveyed in dental schools. We have been including laser irradiation practice to the current practice of operative dentistry for fourth grade students since 2005. Due to the lack of safety education and training on laser equipment, since last year we have included this topic as part of education. The aim of this study was to clarify the effectiveness of education on the safe usage of a carbon-dioxide laser for fourth grade dental students. The fourth grade students in 2010 and 2011 were divided into nine groups and completed a pre-practice questionnaire. Each group then received basic lectures on the principles and safe usage of the carbon dioxide laser, and was shown how to handle the laser instruments prior to laser irradiation practice. Each student irradiated white meat with the carbon dioxide laser, and then completed a post-practice questionnaire. Additionally, the same post-practice questionnaire, with the emphasis on safety, was completed by the fifth grade students of 2011 to confirm their knowledge retention of laser devices. Comparison of pre- and post-practice questionnaire results indicated the following: In the pre-practice questionnaire, many students showed some interest in laser dentistry. However, knowledge about laser equipment including safe usage was poor. In the post-practice questionnaire, almost all students understood the importance of protecting the eyes from laser light by wearing safety goggles. This knowledge was well retained one year after laser irradiation practice. The lecture and laser irradiation practice apparently stimulated the students' interest and their curiosity and gave them an incentive to study the mechanics of the carbon-dioxide laser. These results suggest that safety education carried out before clinical practice is very important, stimulates motivation, and is educationally effective.
One important goal of root canal treatment is the elimination of bacteria from the root canal. The disinfection of root canals involves mechanical enlargement using reamers and files, and chemical cleaning with irrigants such as sodium hypochlorite (NaClO) and ethylene diaminetetra-acetic acid (EDTA). Following that, intracanal medicaments such as formalin cresol and calcium hydroxide are applied in the root canal. However, it is very difficult to completely eliminate bacteria from the root canal due to bacterial invasion of the dentinal tubules, biofilm formation in the accessory canals, bifurcation, and the anatomical complexity of root canal systems such as isthmus and fin. Recently, applications of an Er:YAG laser, including its antibacterial effects, for use in root canal preparation, and in retrograde cavity preparation, have been investigated in endodontics. The effects of an Er:YAG laser on bacteria in the root canal are not known in detail. The purpose of this study was to evaluate the effects of 2.94-μm Er:YAG laser radiation on bacteria and lipopolysaccharides (LPS). An Er:YAG laser with an R200T irradiation tip was used to irradiate root canals containing suspensions of S. mutans, E. faecalis, or C. albicans and root dentin which LPS penetrates. The output energy was standardized at 30 mJ, and the pulse frequency was 25 pps. We evaluated the bactericidal effects based on the morphological changes of bacteria and the reduction rates of viable bacterial numbers. To confirm the bactericidal effects of the Er:YAG laser, live and dead bacteria invading the root dentin were stained with the LIVE/DEAD® stain method and observed by fluorescence microscopy. The effects of Er:YAG laser irradiation on LPS-invaded root dentin were evaluated. All statistical evaluations were performed using Student's t-test or two-way ANOVA. The denaturation of proteins and the destruction of bacteria due to laser irradiation were observed by scanning electron microscopy. The reduction rates of viable bacterial numbers were about 97.4 to 100% for the three bacterial species. A red layer indicating dead bacteria with the LIVE/DEAD® stain method was observed at 400 μm from the inner dentin surface. The LPS content was significantly lower in the samples from the pulpal surface to 100 μm (p < 0.05). These results indicate that Er:YAG laser irradiation may be an effective method for intracanal disinfection.
In 2010, The Committee of Clinical Training Program in Japanese Society for Laser Dentistry held the third educational seminar for safety management in clinical laser dentistry at the 22nd annual meeting of Japanese Society of Laser Dentistry. The purpose of this questionnaire study was to investigate the current status of dental laser applications as well as in clinic safety management. The data was taken from 53 attendants including 45 dentists and 8 dental hygienists. The participants of the seminar showed a high level of satisfaction with the contents of the seminar and expressed their in interests in participating in the future seminar. Sixty-nine percent of the dentists frequently use lasers in clinic, 31% checked lasers before usage and 82% used lasers approved by the ministry of Health, Labor and Welfare of Japan. The types of lasers used were the Er:YAG (24%), CO2 (23%), Diode (16%), Nd:YAG (16%), low-power laser (11%) and Er, Cr:YSGG (7%). The laser was applied to the treatment of hypersensitive dentin, soft tissue surgery, stomatitis, periodontal pocket, dental caries and temporomandibular joint disorders. These results suggested the necessity to hold this kind of seminar periodically.
Gingival hyperpigmentation can cause esthetic problems and embarrassment. Although melanin pigmentation of the oral tissues does not present a medical problem, patients complain they feel “ugly”. Therefore, various methods of depigmentation including surgery and laser irradiation have been reported. Many methods of removing gingival hyperpigmentation have been reported, but there are few reports evaluating the effect of each method. Therefore, in this study we evaluated and compared the effects of Er:YAG and CO2 laser treatment with surgical abrasion for gingival depigmentation. Depigmentation treatment was performed for one patient who complained of dark-brown gingival hyperpigmentation and who provided informed consent for this clinical comparative study. This patient was a smoker. The area of hyperpigmentation was divided into 4 parts and each area of the gingiva was treated differently as follows—Er:YAG laser: maxillary, left side, central incisor–cuspid, CO2 laser: mandibular, right side, central incisor–cuspid, abrasion surgery with carborundum points: maxillary, right side, central incisor–cuspid, and untreated control area: mandibular, left side, central incisor–cuspid. Laser irradiation was performed according to the manufacturer's recommendations for the treatment of hyperpigmentation. After treatment, depigmentation effects were evaluated using Image J (ver1.43, NIH, Bethesda, MD) for all methods. The results achieved were considered satisfactory by both the patient and the operator. Er:YAG laser treatment was performed 10 times until the patient was satisfied; however, the patient felt slight pain during the procedure. CO2 laser treatment was also performed 10 times to achieve a satisfactory outcome, but the CO2 laser did not cause any intraoperative pain. Abrasion surgery using a carborundum point was the most effective with regard to the degree of depigmentation, but it entailed a lot of pain after the procedure. The effect of depigmentation was highest with the abrasion surgery using a carborundum point, when evaluated by image analysis. Both Er:YAG and CO2 laser treatments achieved a satisfactory effect, with both methods producing almost equal results in terms of the degree of depigmentation. CO2 laser treatment provided an adequate depigmentation effect without pain, and there was no difference in the degree of depigmentation between Er:YAG laser and CO2 laser treatment.