KTP/532 and holmium: YAG (Ho: YAG) lasers newly developed have been applied to the field of rhinology. We report new aspects of application of both lasers to endoscopoic sinus surgery. Eighty patients with chronic sinusitis and mucoceles underwent KTP/532 laser under endoscopic sinus surgery. KTP/532 laser was demonstrated to provide efficient results with reduction of postoperative polyps and granulation tissues around the enlarged maxillary sinus ostium and an enhanced healing of the extensive polypoid degeneration of the maxillary sinus in patients with chronic sinusitis. However, no significant result was obtained in the postoperative care of the enlarged opening of mucoceles. We applied Ho: YAG laser to endoscopic sinus surgery in view of a characteristic property of efficient ablation to bone tissue. The inferior turbinectomy, marsupialization of paranasal sinus mucoceles, and dacryocystorhinostomy using Ho: YAG laser led successful and satisfactory results. Both KTP/532 and Ho: YAG lasers are concluded to be promising tools for endoscopic sinus surgery.

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With the advantage of less bleeding and our accumulated experience of using the Nd: YAG laser for head and neck surgery, we applied the laser assisted uvulo palatoplasty (LAUP). Between February 1994 and September 1994, 241 patients, 184 male and 57 female, with the problem of snoring or sleep apnea consulted our department. Eighty seven patients were operated by LAUP. Among them, 42 patients were operated by LAUP type 1 method and 45 by LAUP type 2 method. The apnea index and loudness of snoring were significantly diminished after surgery but no serious complications such as significant bleeding or postoperative episode of asphyxia or nasopharyngeal stenosis, nasal regurgitation were observed. This new operation method was effective especially as a day care surgery.
Obstructive sleep apnea is a disorder characterized by a wide range of severity of subjective symptoms including but not limited to daytime hypersomnolence, headache, altered mentation, and snoring. While medical management of the disorder had been unpredictable, Fujita et al (1) developed the uvulo palatopharyngoplasty operation in 1981. With the advantage of less bleeding and our accumulated experience with using the Nd: YAG laser for surgery of head and neck region (2, 3), we applied the laser assisted uvulo palatoplasty (LAUP) by the contact Nd: YAG laser system as a day care surgery.

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We have presented the laser treatment for bone under the present condition and future. 1) The study on the effects of diode laser on cultured osteoblastic cells. This study was carried out to clarify the effects of low-energy laser, diode laser (wavelength: 890nm, output power: 0.339mW) irradiation on osteoblastic cell activity In addition, we investigated the influence of presence of the implant body on osteoblastic cells.
We used the human osteoblastic cells (HU09, 09N2, YT-48). These cells were cultured in a RPMI-1640 medium supplemented with 2mM ascorbic acid, 2mM α-glycerophosphate and 10% fetal calf serum. Irradiation time (density) were 1 min(0.6mJ/cm²), 3min (1.8mJ/cm²), 5min (3.0mJ/cm²), 7min (4.2mJ/cm²), 10min (6.0mJ/cm²), 12 (7.2mJ/cm²), 15min (9.0mJ/cm²).
As the result, proliferation of these cell were not stimulated by the laser irradiation, but the presence of the implant body were not inhibited them. Alkaline phosphatase activity of HU09 and 09N2 were decreased by laser irradiation (irradiation density, more than 6.0mJ/cm²). But YT-48 was not inhibited. 2) Development of laser bone scalpel using an eximer laser
The laser bone scalpel consists of a monitor system, which allows surgeons to control the depth of the incision during operation, a flexible manipulator which guides the ultraviolet laser beam, detachable laser hand pieces which are fitted to operations in various affected areas, and a laser safety system for the excimer laser. These elements result in a safe, easier-to-use laser scalpel for bone surgery.

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The purpose of the present study is to evaluate the effects of low power laser on bone formation.
In the in vivo study, artificial bone defects in the mandible of the dogs were used to investigate the effect of laser irradiation on the process of healing. The number of cellular elements in bone marrow, including osteoclasts in Howship's Iacnae, increased on the laser-irradiation side at 3 days after the operation. At 7 days, the mass of newly formed bone around the defect on the laser-irradiation side was apparently more than that on the control side. In the later days, however, there were no differences between the two groups. In the in vitro study, osteoblastic cells (UMR 106) were used to investigate the effect of laser irradiation on their function. Laser irradiation increased DNA synthesis in the cells at a logarithmic phase without effect on their morphology. To exert this stimulatory effect, more than 3 min/day laser irradiation was necessary in the presence of more than 5% (v/v) Fics. In both PTH- and PGE 2 -treated cells, however, laser irradiation had no significant effect on DNA synthesis. In addition, laser irradiation increased alkaline phosphatase activity (per protein).
These findings suggest that low power laser may stimulate the osteoblast-mediated bone formation.

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In order to clarify the effects of soft laser under the cell culture in vitro, we observed cell growth, differentiation and calcification of osteogenic cells. As compared with the non-irradiated group, the irradiated group well proliferated. Especially F mode irradiated group showed significantly great values, and cell irradiated in F mode (F-cell) for 4 min x 3 times/day multiplied by cell division 24 hours later. The structure of F-cell due to the fluorescent antibody method of FITC phalloidin showed a long axis arrangement and strong fluorescence of stress fiber. The SEM findings showed a high density and a good adhesion of substrates. The microvilli in the differentiation demonstrated a slight protrusion in the cell surface after irradiation 12 days and an increase in the number, length and density in F-cell. With ALP and von Kossa staining, F-cell were intensely more positive than those of the others.
It is well known that the F-mode is available for bone cell diseases. It was identified that the cell proliferation and differentiation are accelelated by the F-mode. Therefore, the soft laser has biological effects against cells.

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The three dimensional measuring and modeling apparatus with semiconductor laser was applied for oral and maxillofacial surgery in our department.
The apparatus is composed of measuring, analysing and modeling machines (VOXELAN NKV-300DS^® NK EXA, 3D-SPHINX ^® MEDIC ENGINEERING, PCNC-4300 ^® CLIMB PRODUCTS). The measuring machine is mounted semiconductor laser. The measuring time is about ten seconds. Not only model(plaster, metal and wood etc.) even though living bodies can be measured. The facial forms of soft tissue in nine mandibular prognathism patients, who were operated by sagittal splitting method, were analysed. The average of setback distance was 10,9mm(min.9~max. 16) in the right side and 10.8mm(min.9~max. 13.5) in the left side. The difference of setback distance between right and left was less than 3mm. The facial forms of pre and post operation were compared; (1) the changes of facial forms were showed from mental region to mandibular body and in the upper lip area, (2) the simulated facial form was similar to the real facial form of post operation.

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Recently, the clinical treatment with Nd-YAG laser was carried out on 150 cases. 107 cases were treated with high power laser containing 44 tumors, 35 leukoplakia, 10 lichen planus and others. 43 cases were treated with low power laser containing 10 trigeminal neuralgia, 6 glossalgia, 4 nerve palsy, 4 oral psychosomatic diseases and others. The aim of this study was to evaluate the clinical effects of Nd-YAG laser for oral and maxillofacial lesions.
The Nd-YAG laser surgery with high power controlled benign tumors, i. e., fibroma, papilloma, granuloma, and haemangioma which is smaller than 10 mm in diameter. However we were not able to contrail two cases with haemangioma, almost all cases of lichen planus and some cases with leukoplakia.
In regard to low power therapy, relief of pain was obtained in all patients of trigeminal neuralgia except one patient, but was not obtained in all patients of glossalgia. The ulcer in oral cavity was covered by a pseudomembrane immediately after irradiation and completely healed. Nerve regeneration was obtained in three cases with facial nerve palsy (Bell's palsy) and a case with trigeminal nerve palsy.
Based on these results, we believe that the Nd-YAG laser surgery by high power is useful for excision of benign tumor, and for vaporization of haemangioma and leukoplakia. With low power, it is useful for trigeminal neuralgia, facial and trigeminal nerve palsy, and ulcer of oral mucosa.

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High frequency krypton fluoride excimer laser irradiation on the bone was studied as to whether it enables bone cut faster and the thermal damages to the bone become severe to delay the wound healing as the frequency becomes higher. The femur of the cow was used as an experimental material. After being irradiated with different frequencies between 40Hz and 200Hz, the bone was observed macroscopically and microscopically. The incised surface of the bone was also studied with a scanning electron microscopy.
Incised depth of the bone deepened proportionally to the increase of the frequency of the laser. Char was not found in any bone cut macroscopically. A very narrow zone adjacent to the bone cut was stained with hematoxylin. The width of the zone did not relate the increase of the frequency but scanning electron microscopy revealed that the ball-like structures became prominent as the frequency increased. At fourth week after the bone cut of the rabbit mandible, the wounds healed well and there was no difference of the wound healing among 60Hz, 120Hz and 160Hz laser osteotomies and a rotary bur osteotomy.

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Erbium: YAG (Er: YAG) laser has a characteristic of higher absorbability in water. The purpose of the present study was to determine whether this laser would be applicable for use on treatment of root dental caries lesion. Thirty-five extracted human teeth with cervical root caries were used. Each root caries lesion was divided into two areas axially. A divided half was treated with Er: YAG laser, and the other was removed with a round steel bur mounted on an electronic engine or was non treated control. Er: YAG laser irradiation was performed at 160mJ/pulse (56.5J/cm²) and 10 pps under water spray using a fiber delivery system with a contact probe. With both methods, the removal of the infected dentin layer was checked by using a cariesdisclosing agent (Caries Detector^TM), and the time required for caries removal was determined. Furthermore, SEM observation and hardness measurement of cavity floor dentin, and histological observation of the decalcified serial sections of the specimens were conducted.
As a result, obvious remnant lesion was not observed at the laser-treated site. SEM observation of the laser-treated site revealed interesting features which could not be observed with the conventional methods. The removal of carious dentin using the Er: YAG laser with water spray could be possible in vitro.
It seemed that the Er: YAG laser treatment diminished unpleasant sound and vibration, compared with the conventional methods. However, it is noticed that careful laser irradiation was necessary to remove infected dentin layer completely.

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This paper reports our experience in the otorhinolaryngological field with the KTP/532 laser. Since 1993, we have employed the KTP/532 laser in 31 cases with ORL problems. The KTP/532 laser was applied with both a transmitting flexible quartz fiber (Microstats) and a micromanipulator (Microbeam). Application with a transmitting quartz fiber facilitates cutting with the contact mode and coagulation with the noncontact mode simultaneously. It cuts faster than the Nd: YAG laser and coagulates much better than the CO₂ laser. In endonasal surgery, penetration of the bony wall is easily achieved with the contact KTP/532 laser. With an operating microscope, although the KTP/532 laser is not suitable to perform defocused vaporization in a superficially limited disease in cases such as carcinoma in situ of the vocal fold, a sharp cutting with Microbeam was extremely effective to incise mass lesion.

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Current situation of corneal refractive surgery and clinical results of photorefractive keratectomy (PRK) by excimer laser were discussed. The surgical methods to correct refractive error have been developed and their main object is cornea which has the largest refractive power in the optical system of the eye. The change of corneal shape can change refractive power. But cornea has very peculiar tissue characteristics to maintain its optical specificity. Any surgical attempts involve possibilities to damage its characteristics. Radial keratotomy of the peripheral cornea may cause weakning of the cornea and postoperative various unfavourable visual complaints. Recently developed cold laser, excimer laser with 193 nm wave length can remove corneal tissue and was applied to refractive surgery. The method is to ablade center of the cornea in optically designed lens shape by computer-assisted manipulation. This PRK method enables us to have a better predictability and less tissue damage than the other methods. However, PRK has still problems such as postoperative transient ocular pain, long standing corneal haze and fractuation of visual acuity in some cases.

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