A new photosensitizer Hematoporphyrin Oligomers (HpO) based photodynamic therapy (PDT) on mouse squamous cell carcinoma was studied.
Morphological changes of the tumor after PDT was investigated by a transmission electron microscopy. One hour after PDT, bullous mitochondria were seen with irregular shaped inner cristae. After six hours, the inner cristae and outer membrane of mitochondria disappeared. Endonucleus vesicles appeared. Heterochromatin increased in the nucleus. Forty-eight hours later, mitochondria had no longer its original feature. The outer layer of plasma membrane vanished away.
Our study concludes that target organ HpO based PDT seems to be mitochondria.

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This study was performed in order to evaluate the irradiative effect of Nd: YAG laser on surface anesthesia. Eleven students at Tsurumi University School of Dental Medicine participated in this study as subjects. Experimental sites were gingivobuccal areas of mandibular canines. The right area was irradiation site, and the left area was control site without irradiation. A pulsed Nd: YAG laser was applied to the areas coated with indian ink, twice for 30 seconds, using 120mJ pulses at 10pps. The judgement of the effect was made through the measurement of the penetrating distance of 30G catridge needle, and the measurement was performed immediately after the irradiation and after a week. The efficasy of pain was assessed by Visual Analogue Scale (VAS). The mean penetrating distance of needle at the irradiation sites revealed 3.8±1.4mm (Mean±SD) at immediately after the irradiation compared to the control sites 1.7±0.9mm, and in 6 cases needle was inserted into periosteum without pain. There was a significant difference (p<0.01) between the irradiation sites and the control sites. The VAS value revealed 2.7±2.9 at the irradiation sites, and 4.2±2.6 at the control sites. The penetrating distance of needle at the irradiation site after a week revealed 0.6 ± 0.4mm, and at the control sites of 1.6±1.0mm. The anesthetic effect of the irradiation of Nd: YAG laser was lost after a week. It was suggested that the irradiation of Nd: YAG laser has anesthesic effect on gingival surface, and that the effect will disappear within 1 week.

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Recently, the Er: YAG laser has been applied to some kinds of dental treatments. The aim of this study was to observe the surface changes of the restorative alloys irradiated by the Er: YAG laser. The specimens (8mm ∅×4mm high) were prepared from 5 alloys. [G;Type II gold alloy (CASTING GOLD M.C. TYPE II GC, Tokyo, Japan), 12% gold-silver-palladium alloy (PD; KINPARA S12% ISHIHUKU, Tokyo, Japan), silver alloy (S;MIRO 3, GC, Tokyo, Japan), amalgam (AM;SPHERICAL-D CAPSULE, SHOFU, Tokyo, Japan), gallium alloy (GA;Galliumalloy GF, Tokuriki, Tokyo, Japan)]. The specimens of G, PD and S were polished with silicon carbite paper to #1500. For AM and GA, two type of specimens were prepared [polished to #1500 (poAM, poGA), un-polished (noAM, noGA)]. The Er: YAG laser (KaVo K.E.Y. Laser) was irradiated to following 6 conditions: energy; 300mJ, pulse frequency; 1Hz, focal distance; 12mm, fine water mist; with/without, total pulse; 1, 3, 10 shots. The irradiated surface of specimens were observed using OPTIPHOTO (Nikon, Tokyo, Japan) and EPMA (Shimadzu, Kyoto, Japan). The results were as follows: 1. The Er: YAG laser irradiation did not affect G and PD. 2. S, poAM, noAM, poGA, noGA were melted by the Er: YAG laser irradiation. The surface of S was like beegum.
The surface of poAM and noAM was crater form. The surface of poGA and noGA was like a thin film. 3. In cases of 10 shots irradiation to S, poAM, noAM, poGA, noGA and 3 shots irradiation to S and noGA, irradiation with the fine water mist spray caused more effect than irradiation without the fine water mist. In the other cases, the effects of fine water mist spray were little.

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The purpose of this in vitro study was to determine if Er: YAG laser was capable of preparing retrograde cavities. The root canals of 40 extracted single-rooted human teeth were prepared to size 45 apically and obturated with laterally condensed gutta percha and sealer. Root ends were resected at 90 degrees 3mm from the apex. Then, the roots were randomly divided into two groups.
Retrograde cavities were prepared with Er: YAG laser (output energy: 70mJ10pps) or an ultrasonic retro tip. Working time was counted and the rate of increase in the root canal area at the resected surface measured, and they were statistically analyzed. In addition, retrograde cavity surfaces were evaluated with scanning electron microscopy. On the other hand, retrograde cavities of 7 roots in each group were filled with EBA cement. The root surfaces were sealed with nail polish and all samples were placed into 0.1% methylene blue dye for 3 days. Finally, they were split and the dye penetration length was measured and statistically analyzed.
The results were as follows:
1. Working time of the Er: YAG laser group and ultrasonic group was 52 (±27) and 176 (±62) sec., respectively. Er: YAG laser could prepare the retrograde cavity significantly quicker than ultrasonics. (Mann-Whitney U-test, P<0.0001)
2. The rate of postoperative increase in the roof canal area of the Er: YAG laser group and ultrasonic group was 212 (±72) and 198 (±58) %, respectively. There was no significant difference between the two groups (t-test, P=0.338).
3. There were no debris, gutta percha or sealer left on the retrograde cavity surface prepared by Er: YAG laser. The shape of the retrograde cavity was spread and irregular at the resected surface. On the other hand, debris and sealer were observed at cavity surfaces cut by ultrasonics and the cavity was cylindrical in shape.
4. Dye penetration length from the resected surface in the Er: YAG laser group and ultrasonic group was 1.01 (±0.18) and 1.30 (±10.61) mm, respectively. There was no significant difference between the two groups. (t-test, P=0.253)

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The purpose of this study is to evaluate after-loading interstitial photodynamic therapy using Microselectron ^® tube for advanced cancer. Materials and Methods: VX2 carcinoma was transplanted into the dorsal surface of Japanese white rabbits. When the cancer grows up to the size of 32×20×20mm, a dose of 5mg/kg of the photosensitizer, Hematoporphyrin derivative made by the QUENTRON OPTICS company was administered intravenously. Microselectron ^® tube was implanted into the tumor 24 hours after the administration in which the optic fiber was inserted and rotated. The irradiation conditions were 40.8mm/min, 17.5R.P.M., a pulse repetition frequency of 80Hz and 5mJ/pulse. The total light doses along a tube were 150J/cm. Result: No significant change of tumor temperature by laser beam was observed. The tumor around the tube was destroyed up to the extent of 28mm in diameter. We suggest that after-loading interstitial photodynamic therapy using Microselectron ^® tube is applicable for treatment of advanced cancer.

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It is generally recognized that the lower power Nd: YAG laser provides some therapeutic effects on tissue without irreversible changes. On the other hand, high power laser causes irreversible changes. The criterion about low and high power laser is, however, not established. The aim of this study is to verify the effect of lower and high power laser on wound healing of rat skin by measuring blood flow and histomorphologic findings with HE and SEM. Each laser were irradiated to the center of 6mm round full-thickness skin defect at the back of the rat at either (1) 300mW×3min, (2) 500mW×3min, (3) 700mW×3min, (4) 300mW×20min, (5) 500mw×20min, (6) 700mW×20min.
The results obtained are as follows;
1) The histological findings showed that irradiation time caused more tissue damage in the deeper layer, whereas irradiation power caused more damage to the surrounding tissue.
2) Small craters were starred on the bottom of the damaged tissue by laser irradiation at 700 mW x 20min. The formation of these craters was related to the absorption of laser irradiation.
3) On the irradiated area, blood volume decreased significantly as irradiation power increased. However, both blood flow and tissue damage increased as irradiation time increased. As for the surrounding tissue, the findings showed an increase in the blood flow and tissue damage as irra diation power increased.
4) High power laser at 700mW caused tissue damage regardless of irradiation time. On the other hand, 500mW irradiation power caused minimum damage to the tissue. Therefore, the range between 300 to 500mW and the irraditation time over 3min to less than 20min are classified as a lower power laser.

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Many studies were achieved on the application of Er: YAG laser to periodontal disease. We irradiated Er: YAG laser with the energies of 30mJ at 10 pulse per second (pps) with enough to water and air into the periodontal pockets and measured the changes of temperature of the laser irradiated tissues and followed up the four chronic periodontitis patients. The temperature of both irradiated and non-irradiated was measured before, on and recovery. The temperature of chronic lesions which was lower than the neighboring sound lesions before the irradiation, raised after the irradiation. After recovery temperature of irradiated lesions was same as sound lesions. It was suggested that the temperature of the periodontal lesions raises as recovery.

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In order to apply high power semiconductor laser scalpel in oral and maxillofacial surgery, we studied the wound healing process on abdominal skin of five japanese white rabbits, being incised by contact high power semicondactor laser scalpels (10W, 15W, 20W). We compared and discussed the results with those obtained when using the referetial Nd: YAG laser scalpel (10W, 15W, 20W) and electric scalpel (75W, 100W).
Optically no bleeding was observed when using a high power semicandactor laser scalpel and Nd: YAG laser scalpel, and partial bleeding spots were observed when using an electric scalpel. The wound healing process using the hish power semicondactor laser scalpel and Nd-YAG laser scalpel were almost same in recovery and were better than when using an electric scalpel. Spreding tendency of the surgical wound was observed when using an electric scalpel. Histologically, normal wound healing was observed when using any scalpels.
These experimental results revealed that high power semiconductor laser scalpel had effective prevention for post-incisional bleeding and no organic effect on the circumferential tissues as a result of the irradiation.

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We have already reported the promising ability of the Er: YAG laser to ablate subgingival calculus in vitro. The purpose of this study was to examine the features of the laser-scaled root surface in comparison with the ultrasonic scaling. Twenty-four periodontally involved human extracted teeth with a band of subgingival calculus were used. The teeth were randomly divided into two groups for laser scaling and ultrasonic scaling. An Er: YAG Laser ML22 (Erwin^®;HOYA Co. and J. Morita Mfg. Co., Japan) and an ultrasonic scaler (SOLFY^®; J. Morita Mfg. Co., Japan) were used in this study. Laser scaling was performed carefully in the contact and non-contact mode at the energy output of 40mJ/pulse (14.2J/cm²/pulse) and 10 pps under water spray, keeping the contact probe obliquely to the root surface. Ultrasonic scaling was performed at power 4 which is a standard power for clinical use. The features of the scaled site were observed by optical microscope or scanning electron microscope (SEM). The laser scaling was capable of removing subgingival calculus effectively. The laser-scaled area showed a slightly rough appearance macroscopically. Histologically, a thin thermally-damaged layer was observed on the lased root surface. The SEM examination of the lased root surface revealed a characteristic microroughness. This study suggests that the Er: YAG laser could be clinically applicable for the debridement of the periodontally diseased root surfaces. Further studies are required on the evaluation of the attachment of the periodontal tissue to the lased root surface and the necessity of the treatment for removing the superficial layer of the lased root surface.

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The purpose of this study was to examine the depth into penetration of the tissue and the circulatory structure of the microvasculature after irradiation the Nd: YAG laser on the lingual dorsum of a 9-week-old male wistar rat. The Nd: YAG laser was irradiated against differential position on the lingual dorsum of a rat under the 3Watt for 1.0 second.
Wounds of tongue dorsum were observed macroscopically, microscopically and also examined by SEM.
The following results were obtained;Microscopical findings: The penetration of left tongue dorsum anterior group was observed still the musculi longitudinalis superior. The penetration of right margo linguae group was observed still the musculi longitudinalis superior. The penetration of tongue dorsum posterior group was observed still the musculi tranversus linguae superior.
SEM findings: left tongue dorsum anterior group disappeared to the circulatory structure of the microvasculature. Right margo linguae group disappeared to the circulatory structure of the microvas culature. Right tongue dorsum posterior group disappeared to the lamina propria arteriolar and venular networks, arterioles and venulea were exposed.
Irradiation power of the Nd: YAG laser need to change by differential position on the lingual dorsum of the rat.

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