We previously reported on the establishment of cloned human chondrocytes isolated from lesional area (Ch-8-OA) and non-lesional (normal surface) area (Ch-8) of osteoarthritis (OA) patient by introduction of SV40 early gene. In this study, the biological effects of various cytokines, including TNFα, and AlGaInP diode laser irradiation on the growth of these cells were examined. Cloned cells were exposed to cytokines and/or laser irradiation, and proliferation of these cells as well as production of TNFα was studied. When cells were treated with TNFα, the growth of CH-8-OA cells was significantly inhibited as compared with Ch-8 cells. Increased number of TUNEL positive cells and elevation of the activity of caspase 3 and 8 were observed by introduction of TNFα, indicating that TNFα induced the apoptotic change of these chondrocytes. Interestingly, inhibitory effect of TNFα on the growth of Ch-8-OA cells was diminished by AlGaInP diode laser irradiation. Similar phenomena were observed when primary cultured chondrocytes obtained from normal (fracture) or OA patients were treated with TNFα and/or AlGaInP diode laser irradiation. The novel established human chondrocytes displaying cartilage-specific modulation and can be used as a model for studying the biological effect of laser irradiation on human chondrocytes. And the fact that the laser irradiation stimulated the growth of chondrocytes may provide a basis for the clinical use of laser irradiation in OA patients.

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Our group recently developed a dual-wavelength laser capable of simultaneously irradiating at two wavelengths, 2.94μm and 1.67 μm, for the ablation of soft tissue and hard tissue. In this study we examined the pulp reaction when this dual-wavelength laser was applied to the dentin of 42 teeth from three adult dogs. After preparing dentin cavities using an air turbine hand piece with the animals placed under general anesthesia, a prototype dual wavelength laser with an optical parametric oscillator was irradiated on the dentin with water for 30 seconds. The irradiation conditions were established by mixing the wavelengths of 2.94μm (hereinafter, 3μm band) and 1.67μm (hereinafter, 2μm band) as follows:
1. 3μm band (1 W 40 Hz)
2. 3-2μm band (3μm band (50) and 2μm band (50%)) (1 W 40 Hz)
3. 2μm band (1 W 40 Hz)
4. 3-2μm MAX (3μm band (100%) and 2μm band (100%)) (2 W 40 Hz)
5. Control (cavity preparation by air turbine)
Once irradiated, the cavities were filled with a glass ionomer cement. The animals were sacrificed immediately after the procedure, on the 7th after the procedure, and on the 28th day. According to histopathological observation, the dentin was effectively ablated under irradiation with the 3μm band and completely unablated with the 2μm band. Some of the teeth in each group exhibited histopathological signs of hyperemia, but no teeth in any group showed signs of serious damage. These results suggest that dentin ablation by the dual-wavelength laser, especially at the 3μm band, may be effective and safe for the dental pulp.

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Vitiligo is an acquired disorder characterized by amelanotic macules. The efficacy of conservative therapy such as topical corticosteroids and PUVA is limited for many cases of vitiligo. Especially for segmental vitiligo, autologous epidermal grafting using the tops of suction blisters is used. We succesfully treated 15 patients of segmental vitiligo with this epidermal grafting technique with laser resurfacing using CO₂ laser (SurgiTouch: Lumenis Laser 30C^®) for the preparation of recipient site of vitiligo. CO₂ laser with computed scanning system is suited for treating vitiligous lesion prior to grafting because it can provide rapid, predictable de-epithelialization.

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Vbeam^®, 595nm-long pulsed dye laser with adjustable pulse duration (ALPDL), is a kind of pulsed dye laser with 595nm wave length with maximum energy fluences of 40J/cm². The pulse duration is adjustable from 0.45 ms through 40 ms and it is equipped dynamic cooling device^® which makes the surface of the targeted skin cooled with tetrafluoroethane gas (−26.1°C). The longer wavelength allows the laser beam to penetrate deeper in the skin, and the longer pulse duration with high-energy fluences is considered to be optimal for damaging larger caliber vessels with less side effects such as pigmentation or scarring. ALPDL has 5 different round spot sizes and 3×10mm rectangle spot. Pigmented lesion handpiece has been developed for pigmented skin diseases such as senile lentigo which allows the pigmented lesion to be eliminated without impacting underlying blood vessels.
ALPDL has been used to treat various skin diseases such as portwine stains, strawberry marks, teleangiectasia, senile lentigo, viral warts, acne, hypertrophic scar/ keloid, psoriasis, and photoaging, and proved to be effective for treatment of most of these diseases. We report here the efficacy and availabilities of ALPDL to these diseases.

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A study of histopathological changes of hair shaft and hair follicle tissue after irradiation with a long pulse alexandrite laser was performed. The tissue was from the head skin of a 27 year-old female. After she received the operation of her basal cell carcinoma of the head, the normal skin which was adjacent to basal cell carcinoma was used in this experiment. Long pulse alexandrite laser system was used Gentle LASE LE ^TM (Candela Corporation. Wayland. MA. USA) (wave length 755nm, pulse width 3m second, spot size 12mm) giving an output power of 30 Joule/cm² with dynamic cooling devices 40/20 m second. The vacuolar degeneration was recognized in hair shaft in the dermis and the degeneration was recognized in the inner root sheath and the outer root sheath in the dermis, while the epidermis was completely protected by the cooling device. The collapse of hair shaft into the fat tissue with destruction of hair root sheath was also recognized in the lower hair follicle. The degeneration in hair matrix was recognized in the fat tissue. The findings of the collapse of hair shaft were very interesting.

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There has been an increase in the clinical application of low-energy laser irradiation therapy for skin diseases.
Atopic dermatitis is a common inflammatory skin disease characterized by several clinical and immunological alteration. Because of side effect problem of steroid ointment, treatment of atopic dermatitis has been confusing.
The purpose of this review was to value the effect of low-energy laser irradiation on atopic dermatitis and herpes zoster.
Based on the many reports, laser therapy may be of theraptic benefit to atopic dermatitis and for pain treatment of herpes zoster.

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The carbon dioxide(CO₂) laser has an emission wavelength of 10,600nm. The laser is often used the treatments in dermatology and plastic surgery to absorb by its target of interaction water. The CO₂ laser can select and use the mode(single pulse, repeat pulse, continue, superpulse, scan). The defocused beam in used effectively in the treatment of small skin tumor , such as seborrheic keratosis, nevus pigmentosus, and syringoma. The CO₂ laser is common useful in these treatments. However, clinician should understand the mechanism of the laser system and side effect and informed to the patients that this therapy in sometimes painful, result in scarring and hyperpigmentation.

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The pulsed dye laser(SPLT-1, Candela) and Q-switched alexandlight laser (ALEX, Candela) were used in the treatment of nevus including congenital angiomas and dermal melanocytosis in 385 children under 15 years old, mainly babies and young children. The laser treatments of children are desirable not to depend on general anesthesia, but in local anesthesia used 7% lidocaine creem, triclofos sodium and chloral hydrate.
The dye laser treatments of portwine were effective so that age is young, and those in faces and trunks were more effective than those in extremities. Some of salmon patches, which is left throughout the life, could be almost removed by the first dye laser treatment. Strawberry mark of tumor type could be diminished earlier and the scars became minimum, if dye laser treatments were given within 1-2 months of age.
An excellent or good response was observed after the treatment by Q-switched alexandlight laser in babies or young children with aberrant mongolian spots or nevus of Ota. Recurrences were seen with about 80-90% in the laser treatments of congenital pigmented nevi or nevus spilus. But 10-20% of them were effective specially in the younger babies.

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In photodynamic therapy (PDT), the combination of a tumor-localizing photosensitizer and visible light induces photochemical reactions in malignant tumors, selectively destroying tumor cells.
In the dermatological field, this therapy has not been approved for health insurance. However, ALA-PDT, in which a porphyrin precursor, 5-aminolevulinic acid (ALA), is applied, is mainly performed, and is effective for actinic keratosis, Bowen's disease, and malignant superficial epithelial tumors of the skin, such as superficial basal cell carcinoma.
Using an excimer dye laser with a wavelength of 630 nm, we performed ALA-PDT to treat actinic keratosis, Bowen,s disease, malignant superficial tumors of the skin including superficial basal cell carcinoma, lymphoma of the skin, extramammary Paget,s disease in which surgery was considered difficult, hyperplasia of the sebaceous gland, recalcitrant wart, acne vulgaris, and sarcoidosis. In particular, we obtained good treatment results in a large number of patients with actinic keratosis and Bowen's disease.
Currently, the number of patients with malignant superficial tumors of the skin is increasing. ALA-PDT is a noninvasive procedure, and can be indicated for elderly patients, those with a poor general condition, and those refusing surgery.
The necessity of PDT, which can be repeatedly performed without systemic side effects, and is cosmetically advantageous, will increase in the future.
To allow the common use of PDT in the dermatological field, guidelines should be prepared.

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Improvement of facial pigmentation, wrinkles, and acne could be achieved by laser treatment. People's demands for better treatment of these conditions are now enlarging. Therefore, dermatologists are now required to understand the mechanisms of laser treatment and master the skill of these treatments. In this review article, these points were summarized.

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Q-switched lasers, with nanosecond-domain pulse-width, are useful for treatment of pigmented lesions except melasma, although transient postinflammatory hyperpigmentation usually develops during the following 3-4 months. However, cafe-au-lait macules respond variably to treatment. Therefore, accurate diagnosis is the key to success in the laser treatment. If the postinflammatory pigmentation does not disappear after one year, incontinentia pigmenti histologica is a possibility. The pulse-width of the vascular-specific lasers must be longer (microsecond-domain). Because the wavelength of the lasers for vascular lesions, however, cannot penetrate into the deep areas of the skin, not all vascular lesions can be treated. Hair removal by laser or light-assisted machines with millisecond-domain pulse-width offers an efficient way to permanently reduce excessive hair growth. Skin rejuvenation is also possible by these machines. Because these light sources, however, cause severe damage to the skin surface, the exposure energy must be reduced and the treatment must be combined with cooling devices. Therefore, the clinical results of light-assisted skin rejuvenation are not prominent. In conclusion, the pulse-width and wavelength of the laser light are critical parameters for laser treatments. If we obtain information about these parameters for specific lasers, we can expect the results of the treatment to be positive.

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