Actinobacillus actinomycetemcomitans is a pathogen of localized juvenile periodontitis and adult periodontitis. Immunomodulating activity is generally thought to be important in colonization by such pathogenic bacteria. Among the proteins possessing these activities, a 14kDa immunosuppressive factor of A.actinomycetemcomitans has been reported by Kurita-Ochiai and Ochiai (Infect Immun 64: 50-54, 1996). To evaluate this factor, we cloned and characterized the gene encoding it. The immunosuppressive factor was screened from a genomic library of A.actinomycetemcomitans using an oligonucleotide probe based on the amino acid sequence of the factor. The clone obtained, pHI13, contained a 1.5kbp fragment. The immunosuppressive factor located in its center. Southern blot analysis showed that this factor is common among A.actinomycetemcomitans strains. The open reading frame consisted of 324bp coding for 107 amino acid residues. The relative molecular mass of the deduced amino acid sequence was calculated to be 11,595. BLAST analysis indicated that the amino acid sequence is highly homologous with those of thioredoxins from Haemophilus influenzae (76.6%), Neisseria meningitidis (67.3%), and Pseudomonas aeruginosa (59.3%). These results suggest that the 14kDa immunosuppressive factor characterized in this study is a thioredoxin.

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The purpose of this study was to clarify the relationship between lip seal and malocclusion in Japanese children. Fifty-three patients aged 7 to 14 years (mean 10.24±1.93) were selected randomly, and compared with 20 subjects with normal occlusion aged 7 to 14 years (mean 10.50±2.56). The subjects were divided into a good lip seal group and poor lip seal group by observing the distance between the upper and lower lip at rest. The variables that were analyzed for morphological evaluation included model analysis and cephalometric analysis. Noted for functional evaluation were tongue position, the size of the tonsils and adenoids and the oral muscle force measured by button pulling. In the evaluation of the degree of lip seal, there was no statistical difference between subjects with malocclusion and those with normal occlusion. Within the group with malocclusions, however, there were significant differences in overbite (p<0.01), overjet (p<0.01), and oral muscle force by button pulling (p<0.05) between the good lip seal and poor lip seal groups. These results suggest that there is a need not only to correct malocclusion but also to be aware of lip sealing so that it may be improved in Japanese children.

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Plaque control during the course of orthodontic treatment is not an easy task, and dental caries are not an unlikely complication. We examined the possibility of controlling dental caries with Nd-YAG laser irradiation in orthodontic patients. As a preliminary experiment, we used the Nd-YAG laser to irradiate an extracted tooth and then left it to soak in lactic acid. The decay of the tooth was evaluated with a scanning electron microscope (SEM); tooth decay was inhibited by the action of the laser. Twenty patients undergoing orthodontic treatment for early decalcification of the teeth (white spot lesions) were selected, and photographs were taken of their oral cavities. White spot lesions on the four incisors and two canines of the maxilla were traced on tracing paper, and their areas were calculated by computer. Ten of the patients received laser treatment and acidulated phosphate fluoride solution (APF); the other ten acted as the control group. Between 11 and 12 months later, we photographed the oral cavity as we had previously; the white spot lesions were again traced and their areas calculated. The changes in the areas of the white spots of the laser-irradiated and control groups showed the following increases: laserirradiated group, 1.41 times; controls, 2.87 times. The difference was statistically significant. These results demonstrate that Nd-YAG laser irradiation with application of APF acts as an effective method of caries control during orthodontic treatment.

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The purpose of this study was to investigate the treatment of 190 cases of ameloblastoma in our department from 1966 to 1994. The statistical results with regard to age, sex and region agreed with those of other investigators. Thirty-five of 43 (81.4%) cases underwent enucleation in 1960s, but the sixteen of 27 (59.3%) cases underwent partial resection of mandible in 1990s. The defect of mandible was reconstructed with iliac bone grafting since 1968, grafts with a mixture of iliac blocked bone and PCBM (particulate cancellous bone and marrow) have been used since 1975. Grafting of the inferior alveolar nerve with the great auricular nerve to the defect has been performed in our department since 1977. Recently, technique involving pull-through of the inferior alveolar nerve bundle has been used in our department. When the reconstruction method for the mandible and nerve has been established, it becomes possible to operate radically and positively. Recurrence occurred in 17 cases after the primary enucleation. It is thought that the primary treatment of ameloblastoma must be as radical as possible. It appears to be necessary to observe progress and perform follow-up in cases of ameloblastoma for more than ten years, because there was one recurrence at 9 years and 4 months after the first operation. In fact, three quarters of our cases were lost to follow-up. Such losses can problems in confirming recurrence and responding rapidly.

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The ions generated by weak electric current may be used for removal of dental plaque. Also, it has been judged from changes in the viable bacterial cell count and the amount of adenosine triphosphate (ATP) in the saliva that the passage of such a current also has a bactericidal effect on the oral microflora. We confirmed in vitro that 0.5 and 1.0mA currents that passed for 10min through phosphate buffered saline containing salivary bacteria were effective in killing the bacteria.

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