The objectives of the present study were to evaluate the effects of soft laser irradiation for the proliferation and the differentiation of human bone cells and periodontal cells cultured on titanium plates and plastic dishes both derived from the identical donor. Bone cells derived from mandibular fragments and periodontal ligament (PDL) cells from mandibular first premolars were obtained simultaneously from the identical orthognathic patient. Both cells in the 6th passage were seeded (5×103 cells/well) in 24-well plastic culture dishes with or without titanium plates and incubation continued for 72 hours. During the incubation period, soft laser irradiation was performed none, once, twice, which were served as control, 1×laser, 2×laser, respectively. At the end of incubation period, both cells were used for the assays of DNA synthesis and alkaline phosphatase (ALP) activity. The following results were obtained: 1. Bone cells cultured on plastic dishes did not show any significant change of DNA contents and ALP activity by the various time periods of soft laser irradiation. On the other hand, bone cells cultured on titanium plates showed significant increases of DNA contents and ALP activity by the soft laser irradiation, especially by 1×10 minutes laser irradiation group. In this group, the level of DNA contents and ALP activity by titanium-cultured-bone cells were significantly greater than those by plastic-cultured-bone cells. 2. In case of PDL cells, the level of DNA contents and ALP activity were constant for any kind of groups with the exception of 2×10 minutes laser group which showed significant DNA increase as compared to control group, suggesting that the existance of titanium plates and/or the irradiation of soft laser were not effective for cultured PDL cells. These results suggest that the proliferation and the differentiation of bone cells cultured on titanium plates can be stimulated by the irradiation of soft laser in vitro.
The purpose of this study was to research the relation between different energy patterns on the same output power and wound healing by the pulsed Nd: YAG laser irradiation. Five hairless rats were used on this study. The pulsed Nd: YAG laser was irradiated with different energy patterns on the same output power (Group 1: 60 mJ, 100 pps. Group 2: 100 mJ, 60 pps. Group 3: 200 mJ, 30 pps. ; 6 W) in a duration 5 sec. in dorsal skin of rats. Wound healing process after the pulsed Nd: YAG laser irradiation were evaluated over a period of 28 days by clinical photographs and histological observation. In the early period of wound healing (0, 1, 3 days after the laser irradiation), wound size of Group 1 was narrow compared with Group 2 and 3 by clinical photographs and histological observation. Until 14 days of healing, a difference was found between the Group 1 and the other groups. In Group 2 and 3 of laser irradiation, a delay in wound healing was observed. After 21 days of healing, an extensive reduction of the wound size in each groups was observed. This report showed, even if the laser is irradiated on the dorsal skin at the same output power, the irradiated tissues receive a severe damage and a delay in wound healing would be observed in the high energy irradiation.
The aim of this study was to investigate Nd: YAG laser's capability of removing canal obstructions. Twenty four extracted single-human teeth were used in this experiment. After removing the tooth crown, they were randomly divided into three groups: dowel core, gutta-percha, and file removal groups. In the dowel core and gutta-percha removal groups, root canals were cleaned, shaped and obturated with laterally condensed gutta-percha and sealer. Then, in the dowel core removal group, post spaces 7.5 mm in length were created, and dowel cores were placed with glass ionomer cement. The dowel cores were made from an Au-Ag-Paalloy. In the file removal group, a tip of a K file, 3 mm long, was intentionally fractured between the middle and apical third of the root canal. Nd: YAG laser (output energy: 900mJ 10pps) irradiation with an optical fiber (∅=400μm) vwas performed in water to remove dowel cores, gutta-percha and K files from the root canal, and the laser irradiation time was counted. In addition, contact-micro-radiographs were taken before and after the laser irradiation, and the rate of postoperative increase in the root canal area was evaluated. The results were as follows: 1. Nd: YAG laser was able to remove dowel cores and gutta-percha from the root canal. In 5 out of 8 cases, files were successfully removed from the root canal in the file removal group. 2. The irradiation time of Nd: YAG laser in the dowel core, gutta-percha, and file removal groups was, 670 (±345), 19 (±8), and 317 (±220) sec, respectively. 3. The rate of postoperative increase in the canal area of the dowel core, gutta-percha, and file removal groups was, 28, 6, and 62%, respectively.
We have developed the fluorescence diagnostic apparatus of oral lesion. In this study, we analyzed autofluorescence of SCC and leukoplakia. Both cases of SCC and leuk oplakia, we found two fluorescence peaks. In case of SCC, a major peak was at 628 nm and a smaller peak was at 668 nm. As regard to intensity, the maximal intensity of SCC was 18 times stronger than that of normal oral mucosa. In case of leukoplakia, a major peak was at 658 nm and smaller peak was at 627 nm. The maximal intensity of leukoplakia was five times stronger than that of normal oral mucosa. The results suggested that the autofluorescence diagnosis of oral lesion would be possible by new fluorescence diagnostic apparatus.
We developed the new colorimetric analysis system with the KOITO white light laser. The KOITO white light laser is a hollow cathode He-Cd laser device that simultane ously oscillates three light laser beams of three primary colors (red, green, blue) from a single laser tube. These beams are formed into a white light laser. In addition, because the oscillation wavelengths of red (635.5 nm, 636 nm), green (533.7 nm, 537.8 nm), blue (441.6 nm) color light are very near the ideal three primary colors. This system has three character. First character is non-contact type without integral sphere. Second is using pen-type probe which contain the bundle type fiber. Third is recording the rate to three colors in the standard reflex light. We examined the efficacy of this colorimetric analysis system with experimental study and clinical cases. On the other hand, we improved this system in the diagnosis of oral malignant tumor. Using this system, we could measure the color disorders in the oral cavity non-invasively, easily, immediately, exactly. Moreover we performed spectral analysis in patients with an oral squamous cell carcinoma. We found that there were bimodal peak at 650 and 690 nm at the excitation wavelength of 441.6 nm and that this result is different from the normal autofluorescenc. We consider that this coloriometric analysis system is useful to measure the color disorders in the oral cavity and has possibility to be improved in the diagnosis of oral malignant tumor.
The purpose of this study is to research the change of mechanical properties of dental enamel around the laser irradiated area. CO2 laser and Er: YAG laser were irradiated bovine enamel at 23-161J/cm2, and the its fracture toughness was examined by means of indentation microfracture method. The fracture toughness of bovine enamel irradiated by CO2 laser was reduced compared with control at any irradiation energy. On the other hand Er: YAG laser irradiation at all energy condition did not cause the reduction of the fracture toughness. These result suggest that Er: YAG laser is useful in preparation of tooth without mechanical changes of enamel around irradiated area.
Many studies describing favorable effects of Nd: YAG Laser irradiation during treatment of hard tissue such as treatment and prevention of dental caries, treatment for hypersensitive dentin, root canal treatment, and root planing, etc., have been reported. Suguro has reported that the effect of removal of softened dentin was influenced strongly by special color mediators. The purpose of this study was to investigate the percent transmittance of various color mediators around wavelength in the near infra-red region and the effect of removal of softened dentin by Nd: YAG Laser irradiation associated with their transmittamce. In this study, 4 color mediators (Indialnk mediators: Black Indialnk, Red Indialnk Waterink mediators: Black Waterink, Blue Waterink) were carried out. Each mediator was diluted to 5, 25, 50 and 75% with distilled water and the degree of transmittamce was measured as a percentage under wavelength range of 800-1300nm. To obtain the softened dentin, bovine mandibular incisors (∅5mm×3mm) were treated with Plank-Rhychlo decalcified solution for 5 days, and stained with above color mediators for 30 minutes. They were then dried in a Vacuum Drying Oven prior to supply to the ablation test. The laser irradiations were carried out 10 seconds with a Nd: YAG laser (CW SLT Contact Laser) with a regulated power-range to 5 watts. The rate of ablation was analyzed by comparing the changes in weight before and after irradiation. Stereoscopic and SEM observation were performed on the irradiated surface of each specimens. The following results were obtained: 1) The percent transmittance of Black Indialnk around a wavelengthin the infra-red region was not detected (0.0%). The percent transmittance of other color mediators were increased by decreasing their density.2) The degree of ablation weight was obtained highest in un diluted solution, and decreased parallel with the diluted of their color mediators. 3) There are correlations between the percent transmittance of color mediators and this ablation in the case of Black Watetlnk, Blue WaterInk, Red Indialnk. 4) In stereoscopic and SEM observation, there were no change on the surface of specimens by Red Indialnk and Blue WaterInk, but it was observed deep defect by Black Indialnk, Black WaterInk. They were observed molten surface like a lava at the bottom of the defect in SEM observation.