We looked into the complicating disease after the medical treatment for childhood dermal melanocytosis with two types of Q-switched laser. This research indicated that Q-switched ruby laser is more likely to cause complications significantly, compared with Q-switched Nd:YAG laser. Hypopigmentation is the most common complication. Such complications occur with high frequently in aberrant mongolian spot rather than nevus of Ota.

Postinflammatory hyperpigmentation (PIH) is one of the most undesirable complications after Q-switched laser treatment of senile lentigines. We conducted a retrospective study to examine the occurrence of postinflammatory hyperpigmentation after treatment of 158 cases of senile lentigines, comparing with Q-switched Ruby laser (694 nm) and with Q-switched frequency doubled Nd:YAG laser (532 nm). PIH was more frequently found after Q-switched Ruby laser treatment (64.1%), compared to Q-switched frequency doubled Nd:YAG laser treatment (47.0%) with statistically significance. Especially for the cases of the following factors as melasma, Fitzpatrick scale IV, female, darker lentigines and larger lentigines, Q-switched frequency doubled Nd:YAG laser had significantly low occurrence of PIH. Therefore, Q-switched frequency doubled Nd:YAG laser is recommended for these cases.

As ectopic Mongolian spots often lighten spontaneously, it is important to minimize treatment-related complications and reduce a psychological burden on patients, when laser treatment is applied. Therefore fewer number of laser treatments is desirable. To investigate the influencing factor on number of treatment to achieve a desired therapeutic effect, we analyzed the patients treated with Q-switched Ruby laser. The result is that significant factors influencing number of laser treatments are age, interval of time between laser irradiation, and overall treatment time. It is suggested that the laser treatment for ectopic Mongolian spots should be started in early childhood and repeated at long intervals.

Apical periodontitis is defined as a local inflammatory disease due to infection of pathogenic bacteria in the root canal system, and endodontic treatment aims to eliminate the intracanal pathogens and prevent reinfection. In our department, basic research on the application of lasers to endodontic treatment has been conducted since 1985. In particular, Er:YAG laser has been proven useful because of its ability to cut dentin without significant thermal damage to the surrounding tissue and sterilization effect. The purpose of this article is to summarize current problems in endodontic treatment, and then review the results obtained from our recent basic and clinical research on the application of lasers to endodontics.

The Er:YAG laser (ErL) is effectively used in daily clinical practice for periodontal treatment because of its excellent ability to ablate both soft and hard tissues. During initial periodontal treatment, ErL laser can be used to perform scaling and root planning with minimum damage to the underlying cementum. In surgical therapy, degranulation in bone defects can be safely performed using the ErL. Recently, we developed a novel procedure for periodontal regenerative surgery applying ErL irradiation for thorough debridement in bone defects as well as blood coagulation following autogenous bone grafting and observed excellent bone regeneration in severe bone defects in which favorable bone healing cannot be expected with conventional treatment modalities. The Er:YAG laser is currently applied as a useful device in periodontal therapy. In this paper, the effects of ErL in periodontal therapy and its recent applications in clinical practice are discussed based on scientific evidence.

Lasers are widely used in the oral and maxillofacial region surgeries. The CO₂ laser has been used in the treatment of diseases that occur in soft tissue because of its excellent incision and hemostatic abilities, and good results have been obtained. The Nd:YAG and KTP lasers have an affinity for pigmented tissues and penetrate soft tissues deeply. Using these characteristics, vascular malformations (hemangiomas) can be treated by photocoagulation with these lasers. In this paper, current status of oral and maxillofacial laser surgery is reported with some case presentations.

Recently, promising results have been obtained for large deep vascular lesions by intralesional photocoagulation (ILP) treatment using Nd:YAG laser (wavelength 1064 nm). This technique allows laser energy to be delivered directly into deep lesions via a bare fiber delivery system. Thirty three cases of oral vascular lesions were treated by ILP using a Nd:YAG laser. Twenty eight cases, which accomplished treatment schedule, showed marked regression after the treatment, and the treatment outcome was aesthetically and functionally satisfactory. There were no serious complications, such as obstruction or invasive infection.

We conclude that ILP with a laser is a promising technique for less-invasive and effective treatment of a vascular lesions in the oral cavity.

Orthodontic treatment is to reconstruct the jaws and teeth of malocclusion patients, and is re-establishing normal function and morphology and aesthetics of the oral cavity and face, however, there are some demerits. In order to improve the demerits of orthodontic treatment, we have conducted a series of studies that the bio-stimulatory effects of soft laser irradiation on orthodontic treatment. The results of those studies were that soft laser irradiation could accelerate bone regeneration in a mid-palatal suture during rapid palatal expansion, tooth movement during orthodontic tooth movement, and stability of orthodontic anchor screws through surrounding bone formation. Furthermore, the mechanism of accelerated bone formation was found to be due to increased expression of bone formation-related factors such as IGF-1 and BMPs by means of a laser irradiation.

On the other hand, as an application of hard laser, ceramic orthodontic brackets were bonded to bovine incisors using bonding materials containing thermal expansion microcapsules and the bond strength were measured after CO₂ laser irradiation. After laser irradiation for 5 or 6 s, the bond strengths of the adhesive containing 40 wt% microcapsules were significantly decreased to 0.4-0.48-fold (4.6-5.5 MPa) compared with the non-laser groups. The mean temperature rise of the pulp chamber was 4.3°C with laser irradiation for 6 s, which was less than that required to induce pulp damage. Based on these results, it is concluded that the combined use of a CO₂ laser and adhesive containing microcapsules could be effective and safe for de-bonding ceramic brackets with less enamel damage or tooth pain.

Thus, by applying the soft and hard laser in the orthodontic treatment, it is likely that it is possible to provide shorter orthodontic treatment period and better quality of treatment.

Currently, many laser processing machines for dental use are commercially available, and used in the fabrication of dental prostheses. Laser welding is the popular technique in dental prosthesis. Laser welding is advantageous in the fabrication of prosthetic devices for features such as short working time, narrow heat-affected zone and welding of similar composition metals. On the other hand, it is necessary to pay attention to the welding deformation, cracking and porosity generation. Selective laser melting has also been attracting attention as a new fabrication technology. Development of the use of laser to the fabrication of dental prosthesis should continue.

Acceleration of the bone healing period is important in clinical situations such as implant and periodontal treatments. Recently, it has been demonstrated that mechanical stimuli including ultrasound and microwaves are potentially powerful treatments for bone regeneration and the acceleration of bone healing. Moreover, laser irradiation has been shown to stimulate bone formation. However, there are few reports describing the histological changes in bone following laser irradiation. The aim of this study was to examine the effect of diode laser (λ=910 nm) irradiation on histological changes during bone healing in rats. Two groups of rats with bone defects in the tibiae were subjected to laser irradiation at 0, 40, 80, and 120 J; group 1 was irradiated daily with each dose for a total of 14 days, and group 2 was irradiated at 120 J for 7 days and subsequently evaluated for up to 14 days post-irradiation. Tibiae were removed at 3, 7, 14, and 21 days, and subjected to serial sectioning. Morphological examination of bone formation was conducted using hematoxylin-eosin staining and calcein labeling of sections. In group 1, bone formation was stimulated by laser irradiation, and at day 7 the effect was found to be energy-dependent. However, at day 14, bone volume was decreased in a energy-dependent manner. In group 2, the laser-irradiated tibiae showed a greater volume of bone formation than that of the control on day 14. However, no differences in bone volume were observed in the treatment groups on day 21. These results indicated that diode laser irradiation induced marked bone formation in the early phase of the bone healing process and the effects depended on the irradiation energy; however, a longer period of high-power laser irradiation inhibited bone formation. This study suggests that diode lasers can be utilized for bone regeneration, taking into consideration the irradiation period and energy.

We evaluated the efficacy of supplements treatment (L-carnitine and melatonin) and low reactive level laser therapy (LLLT) and the integrated medicine program for IVF failures. After L-carnitine treatment blastocyst rate was significantly increased (37.0 % vs 60.8 %, P<0.01). After melatonin treatment good embryo rate (45.2 % vs 63.0 %, P<0.01), blastocyst rate (28.3 % vs 54.4 %, P<0.01) and good blastocyst rate (29.4 % vs 67.7 %, P<0.05) were significantly increased. After LLLT, the numbers of MII oocytes (1.7 vs 2.0, P<0.05) and the numbers of fertilized oocytes (1.6 vs 1.8, P<0.05) were significantly increased. Good embryo rate was significantly increased (64.0 % vs 79.0 %, P<0.05). In hormone supplemented frozen thawed ET cycles, pregnancy rate of day 3 embryos was significantly increased (6.7 % vs 17.8 %, P<0.05) after LLLT. And after the integrated medicine program, pregnancy rate was significantly increased (12.0 % vs 23.7 %, P<0.01).

In the embryos made by assisted reproductive technology (ART), the hatching has been frequently inhibited by the hardening of the zona pellucida due to the in vitro culture. Assisted hatching (AH) is a technique to promote the hatching of embryo by breaching a part of zona pellucida using mechanical or chemical method. Laser technologies became increasingly common for zona manipulation. Laser assisted hatching (LAH) is an important technique to support the ART.

Recently, low-reactive level laser therapy (LLLT) has been used to the infertile patients in area of reproductive medicine. This therapy is proposed to be effective and impressive results to improve the pregnancy rate. However, the mechanism of the improvement of ovarian function by LLLT has been unclear in detail. Our results showed that VEGF is induced by LLLT through mechanisms involving MAPK in human granulosa cells. LLLT would promote various ovulatory phenomena as well as follicular growth.

Fetoscopic laser photocoagulation which ablates placental vascular anastomoses is an effective first-line treatment option for twin-twin transfusion syndrome. Fetoscopic laser photocoagulation is a successful application of laser therapy for perinatal medicine.

The activities of Social Insurance Committee of the Japan Society for Laser Surgery and Medicine for current medical fee revision and the results were described. In addition, the summary of the laser equipment that have been approved by government and the present insurance coverage for laser treatment were described in detail.