Many dentists and researchers have carried out applied medical research to develop and promote laser dentistry. To ensure a systematic understanding, it is essential to compare research results consistently, and to summarize experimental results using important laser parameters to enable other researchers to correctly compare their results. This paper is intended for less experienced researchers who are engaged in medical and/or dental fields, describes the fundamentals of lasers (such as laser oscillation, laser instruments, laser parameters, and laser-tissue interactions), and summarizes experimental results of laser processing and/or laser dentistry.
In the last twenty years, treatments and care for dental caries by using various lasers have been established. Lasers can offer pain relief and/or faster healing not possible with ordinary treatment, and thus various high-quality treatments and services can be provided to the public. Laser dentistry is expected to continue to develop. The present paper reviews the following topics on the basis of a series of studies by the authors on laser dentistry: laser application in the examination and diagnosis of dental caries, preventive cure for the modification of tooth structures such as enhancing acid resistance, uptake of fluorides, and fusing nano-apatite crystals, and surgical intervention for removing dental caries and subsequent adhesive restorative treatment. The paper describes the current status and future development of laser dentistry for dental hard tissue.
Selective caries removal is one of the most required applications of lasers in dentistry. The objective of this study was to regulate the laser irradiation effect precisely and to develop a technique for selectively removing carious dentin for the next laser dentistry using the specific absorption in the 6 μm wavelength range. To prepare a carious dentin model, a bovine dentin disc was soaked in lactic acid solution to demineralize the surface of the disc. A nanosecond pulsed laser with a wavelength of 6.02 μm, which corresponds to the absorption band called amide I, was used as the light source for treatment. The pulse width and repetition rate were 5 ns and 10 Hz. At average power densities below 15 W/cm2, removal of sound dentin was not observed. For demineralized dentin, tissue removal was observed at the average power density of 15 W/cm2 from the irradiation time of 1 s. The removal continued to the surface of sound dentin, and stopped at the boundary between the sound dentin and demineralized dentin. Our group has estimated that the major cause of the selective removal shown in this study is the difference of mechanical properties between sound and demineralized dentin, due to the difference in hydroxyapatite (HAP) content rate. In conclusion, 6.02 μm is a promising laser wavelength for selective caries removal without serious side effects on sound dentin. In the near future, the development of extremely-compact laser devices will pave the way for minimal invasive laser treatment in dental clinics.
Background and Objective: In recent years, there has been growing interest in the use of dental lasers for treatment of periodontal diseases. The purpose of this clinical trial was to evaluate the effects of antimicrobial photodynamic therapy (aPDT) with indocyanine green (ICG) loaded nanospheres as photosensitizer for periodontal treatment. Material and Methods: Seventeen patients (56.1 ± 10.3 years of age) participated in this study. Intended sites were taken from periodontally involved sites with a probing depth of ≥ 5 mm totaling 51 sites. These sites were divided into three groups at random. The laser with nanospheres group consisted of 17 sites irradiated with a diode laser at 0.5 W for 90 sec per site after injecting nanospheres into the periodontal pocket. The optical fiber was inserted into the periodontal pocket 1 mm less than the probing depth with surface anesthesia and moved up and down in order to irradiate the root surface as evenly as possible. The laser group consisted of 17 sites that were irradiated with the diode laser at 0.5 W for 90 sec per site. The sham group consisted of 17 sites that were not irradiated, but the fiber was only inserted into the periodontal pockets and moved up and down. Each subject was monitored clinically at baseline, 1 month, and 3 months. Clinical parameters such as probing pocket depth (PPD), clinical attainment level (CAL), and bleeding on probing (BOP) were measured at each site with a stent. Results: The mean value of the PPD significantly decreased in the laser with nanospheres group from 5.23 ± 0.75 to 3.71 ± 0.92 after 3 months (P < 0.001), in the laser group from 5.35 ± 0.61 to 4.24 ± 1.39 after 3 months (P < 0.01), and in the sham group from 5.53 ± 1.01 to 5.47 ± 1.18 after 3 months (NS). The mean value of CAL significantly decreased in the laser with nanospheres group from 6.00 ± 1.62 to 4.82 ± 1.55 after 3 months (P < 0.05), in the laser group from 5.88 ± 0.93 to 5.24 ± 1.30 after 3 months (NS), and in the sham group from 6.29 ± 2.14 to 6.17 ± 1.67 after 3 months (NS). BOP decreased for the laser with nanospheres group (P < 0.01) at 1 month and 3 months after treatment. Conclusion: The results of this study show that the adjunctive application of aPDT is appropriate to improve periodontal clinical parameters.