A total of 22 patients who had a superficial tongue cancer which was limited to the submucosal layer underwent partial glossectomy by laser surgery at the Department of Oral and Maxillofacial Surgery, Kobe University Graduate School of Medicine, between 1981 and 2002. They consisted of 18 patients of T1 and four of T2. Thirteen of the 22 patients were males and nine were females. The mean age was 60.7 years, ranging from 31 to 76 years. Laser surgery was able to control hemorrhaging and to remove lesions accurately, because unlike an electrotome, it does not show electrocontractility during the operation. The surgery was also able to reduce postoperative pain and edema because of minimal damage to adjacent tissue, thus keeping functional disorders to a minimum. Of the 22 patients, recurrence and regional lymph node metastasis were observed in 2 (9.1%) and 1 (4.5%), respectively. Two patients who had recurrence were both T1 cases showing erosive type and white plaque type in clinical characteristics. One of the two patients who had recurrence had regional lymph node metastasis, and the patient died from regional lymph node metastasis. It is suggested that partial glossectomy by laser surgery is correctly indicated in any superficial tongue cancer leaving no postoperative dysfunction irrespective of T classification.

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This study evaluated the acid resistance of CO₂ laser irradiation and fluoride application for hydroxyapatite (HA) granules.
HA granules samples were divided into the following four groups. Specimens of group L were irradiated vertically by CO2 laser (10.6μm) with 1W (46.2J/cm²) output power at a repeated pulse mode (pulse length 0.5 second). Those of group F were treated with acidulated phosphate fluoride (APF) solution for 30 minutes. Those of group L-F were treated with APF solution after CO₂ laser irradiation. Those of group C were not treated and were used as a control.
All specimens were individually immersed in 5ml acetate buffer solution (0.2M, pH4.2) at 37°C for 2 hours, then each specimen was centrifuged (1500 rpm, 10 minutes). The calcium content of the supernatant was measured using the ortho-cresolphthalein complexone method, and its fluoride content was measured using an ion meter for groups F and L-F.
The calcium elution rates of groups L, F, and L-F were significantly lower than that of group C (ANOVA; scheffe: p<0.01). The fluoride content of group L-F was significantly lower than that of group F (Student's t-test: p<0.01).
It was suggested that CO₂ laser irradiation (group L), APF solution treatment (group F), and combination of CO₂ laser irradiation and APF solution treatment (group L-F) are effective for acid resistance. The results suggest that this study model is useful for the evaluation of acid resistance.

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This study evaluated the pain relief effects at clamp placement after Nd: YAG laser irradiation. Eleven adult volunteers (6 males and 5 females, mean age of 24.5 years), who had consented to this study, participated in the study.
Both sides of healthy mandible canines were selected as experimental sites: the right side for irradiation, and the left side as the control without irradiation.
On the control side, pulp thermal sensitivity was measured by an electrothermal stimulator, the probe tip of which could be heated from 29°C to 65°C.
The clamp (Ivory #210) was then placed into cervical undercuts on the canine.
The severity of pain was evaluated by Visual Analogue Scale (VAS).
On the irradiation side, the pulsed Nd: YAG laser was applied to the cervical area of the canine coated with Chinese ink, twice for 30 seconds each, using 100 mJ pulses at 15 pps.
After the irradiation, pulp thermal sensitivity was measured, and also the severity of pain was evaluated by Visual Analogue Scale (VAS) after clamp placement.
There was a statistically significant difference in the pain relief effects on pulp thermal sensitivity between the irradiation side and the control side (p<0.05: Piared t-test).
There was also a significant difference in the sensitivity of pain by VAS at clamp placement between them (p<0.05: Wilcoxon signed-ranks test).
These results suggest that Nd: YAG laser irradiation before rubber-dam placement is very useful for pain relief. Nd: YAG laser irradiation appears effective for analgesia, and might be useful for clinical application.

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n recent years, a remarkable change has occurred in the concept of the treatment of dental caries, which is one of the two major diseases in dentistry, because of the progress of cariology and the use of laser.
Laser irradiation onto the tooth surface in the early stages of caries shows effects such as sterilization of oral micro-organisms, increase of acid resistivity of the tooth, incresae of fluoride uptake, and remineralization of caries lesion, and enables the minimal invasive treatment of hard tissue surrounding of the affected tooth through selective evaporation by laser irradiation. Thus, the laser has an important role for the maximal protection of tooth structure against caries invasion. In order to evaluate the laser effects, we used the DIAGNOdent instrument (Ka Vo Co. Biberach, Germany) which can numerically evaluate the organic substances with fluorescence in decayed lesions. The high peak pulse type (Power Pulse) Nd: YAG laser (SLT japan Co., Tokyo) was used for caries treatment upon approximately 800 teeth of patients with incipient and also advanced caries. The affected and softened hard tissue of the lesion was easily removed by means of shrinkage and evaporation after the laser irradiation.
The treated area was then remineralized with topical application of fluoride. This procedure was repeated until the infected lesion was completely removed. As this treatment was restricted only to the infected lesions, dental pulp did not suffer from inflammation, and pulpectomy was prevented.
Although ordinary drilling devices for cutting teeth irreversibly removed the tooth structure, the laser treatment demonstrated promising ability in maintaining oral health without destroying the tooth structure.

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r the initial reports of the effects of Er: YAG laser on dental hard tissue by Keller and Hibst, the Er: YAG laser has been recognized as a new tool developed for cavity preparation. The Er: YAG laser has a wavelength of 2.94μm and, by virtue of its highly efficient absorption in water, can efficiently ablate dental hard tissue with almost no thermal effect on the pulp. Moreover, the Er: YAG laser produces minimal vibration and noise during cavity preparation and the need for local anesthesia is none or minimal, so the Er: YAG laser does not cause a fear or discomfort to the patient in comparison to the conventional methods of cavity preparation. Futhermore, the patient feels less pain or none during laser ablation of dental hard tissue. However, it takes time to master the practical skill of Er: YAG laser irradiation on dental hard tissue, because it is difficult to control the power of the Er: YAG laser to ensure efficient ablation without side effects, cracking of tooth substance, heat damage to the pulp or causing pain to the patient. Moreover, both the method and mode of irradiation are very different for each type of Er: YAG laser apparatus. Therefore, training on irradiation skills based on the results of practical laser treatment is needed when applying the Er: YAG laser on dental hard tissue, and skills should be improved together with the development of Er: YAG laser apparatus.

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