Porphyromonas gingivalis, a gramnegative anaerobe, is one of the major causative agents of periodontal disease. In this study, the effects of chlorhexidine digluconate and hydrogen peroxide on the hemin binding of P. gingivalis and coaggregation of this bacterium with oral streptococci were examined. The pretreatment of P. gingivalis W50 and 381 with chlorhexidine digluconate and hydrogen peroxide increased the hemin binding of these bacteria. The hemin binding of P. gingivalis was increased by the subminimal inhibitory concentration (MIC) of chlorhexidine digluconate. However, concentrations of hydrogen peroxide below the MIC had no effect on the hemin binding of P. gingivalis W50 and 381. Coaggregation of P. gingivalis 381 with Streptococcus oralis ATCC 9811 and Streptococcus gordonii DL1 was diminished by chlorhexidine digluconate. The coaggregation-inhibitory effect was concentrationdependent. Hydrogen peroxide also showed inhibitory effects on the coaggregation of P. gingivalis 381 with S. oralis 9811 and S. gordonii DL1 at concentrations below that used clinically. Concentrations of chlorhexidine digluconate below the MIC inhibited coaggregation. However, concentrations of hydrogen peroxide below the MIC were not effective in reducing the coaggregation of P. gingivalis with oral streptococci. These observations show that chlorhexidine digluconateand hydrogen peroxide could confer variable effects on P. gingivalis hemin binding and coaggregation of this bacterium with oral streptococci. (J. Oral Sci. 43, 1-7, 2001)

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It is reported in the European and American literature that salivary duct cysts constitute about 10 % of all cysts of the salivary glands, although they appear to be rare in Japan. Between 1975 and 1999, only 3 (0.5 %) of 586 salivary gland cysts were diagnosed as salivary duct cysts at the Division of Clinical Pathology, Iwate Medical University Hospital. Histologically, two cases appeared as a unilocular lesion lined by double- and multi-layered epithelium. The other case showed marked, intraluminar and intramural adenomatous proliferation of the epithelial lining, suggesting that the lesion was a benign tumor. A review of the literature yielded only two cases of tumors arising in pre-existing salivary duct cysts. (J. Oral Sci. 43, 9-13, 2001)

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Stainless steel wrought wires used as clasp arms for removable partial dentures in Thailand were compared with those used in some other countries (in the as-received condition) in terms of flexibility, Vickers microhardness and composition. The results showed that there were significant differences (P≤0.05) among the wires. A Japanese stainless steel wire (SK) was obviously different from the others. It had the lowest proportional limit and microhardness, but its flexibility was almost the same. The chemical composition of each wire was not greatly different. The wires were about 18-20 wt% chromium and 8-9 wt% nickel, except for the SK wire, which had about 12 wt% nickel. (J. Oral Sci. 43, 15-19, 2001)

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Juvenile xanthogranuloma (JXG) is a dermatological condition of unknown etiology that rarely affects the oral mucosa. There are conflicting reports suggesting that it may represent a reactive virally-induced lesion associated with cytomegalovirus (CMV) infection. The present paper reports an additional case of oral JXG and discusses its possible association with CMV infection. The biotin-streptavidin system was used to detect early and late CMV antigens. Positive immunolabelling for both antigens was demonstrated in some histiocytes in the lesion. These findings suggest that JXG may be associated with CMV infection. (J. Oral Sci. 43, 21-25, 2001)

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To examine whether the surface reaction layer of titanium castings can be reduced by lowering the mold temperature during casting, we cast titanium at three mold temperatures, including an ultra-low temperature produced by cooling the mold with liquid nitrogen, then measured the tensile strength and elongation of the castings. The titanium was cast using a centrifugal casting machine, and the molds were incinerated according to the manufacturers' instructions. Castings were then made with the molds at 200°C, 600°C, and an ultra-low temperature (-196°C). The castability of titanium cast in the mold at the ultra-low temperature was good. The Vickers hardness near the surface layer of castings decreased as the mold temperature decreased. (J. Oral Sci. 43, 27-33, 2001)

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A study was conducted to investigate the influence of temperature and relative humidity (RH) on the bond strengths of several recently developed dentin bonding systems. Six environmental conditions, (A) 25±0.5°C, 50±5% RH, (B) 25±0.5°C, 80±5% RH, (C) 25±0.5°C, 95±5% RH, (D) 37±0.5°C, 50 ±5% RH, (E) 37±0.5°C, 80±5% RH, (F) 37±0.5°C, 95±5% RH were used. Bovine mandibular incisors were mounted in self-curing resin and the facial surfaces were ground on wet #600 SiC paper to expose the dentin. After the tooth surface had been treated according to each manufacturer's instructions, adhesives were applied, followed by condensation of resin composites into a mold placed on the dentin surface. Fifteen specimens per group were stored in distilled water at 37°C for 24 h, and then shear-tested at a cross-head speed of 1.0 mm/min. Statistical analysis was carried out with two-way ANOVA followed by Tukey's test (P<0.05). Dentin bond strengths decreased with increasing relative humidity but were not influenced by environmental temperature. Even though one-bottle adhesive systems require a wet dentin surface, their bond strengths are affected by an increase in environmental humidity. (J. Oral Sci.43, 35-40, 2001)

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To evaluate the possible effect of sampling technique and sequential sampling on gingival crevicular fluid (GCF) volume and myeloperoxidase (MPO) activity, 14 patients presenting at least two symmetrical maxillary sites with mild/moderate periodontitis were selected. Two sites in each individual were sequentially sampled using either the deep-intracrevicular or orifice technique. Spectrophotometrically determined MPO levels were presented either as total MPO activity or MPO concentration. Although the clinical periodontal status of the 20 sampling sites were similar, the deep-intracrevicular technique regularly provided larger GCF volumes. With both techniques, the last samples contained the highest GCF volume. During sequential orifice sampling, GCF volume was relatively more stable. In general, a depletion of MPO activity was observed with sequential sampling performed with either of the techniques. Depletion of MPO did not replenish to baseline levels at the end of the 10-min sequential sampling. Although MPO activity showed a general reduction during sequential orifice sampling with both modes of data presentation, total MPO activity and MPO concentration did not match with the deep-intracrevicular technique. Due to the potential of affecting GCF volume/composition, the selection of sampling technique seems to be a critical methodological decision in GCF-profile studies, primarily during sequential sampling. In GCF-profile studies, mode of data presentation should also be considered. (J. Oral Sci. 43, 41-48, 2001)

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The purpose of this study was to examine oral health attitudes/behavior and gingival self-care levels of Korean dental hygiene students (n=271). A questionnaire known as HU-DBI (Korean version) was administered to each class. Higher scores of the HU-DBI indicate better oral health attitudes/behavior. The student's gingival self-care level was scored as excellent (+2), good (+1), questionable (0), poor (-1), or very poor (-2) according to the criteria of the Oral Rating Index (ORI) for youth. The mean score of the HU-DBI was 6.40, and that of the ORI was +0.12. Most samples scored 0 or +1. The mean HU-DBI scores of year-2 and year-3 students (7.06, and 7.61 respectively) were significantly greater than that of year-1 students (5.23) (P< 0.001). Twenty-three percent of the students reported a belief that they may eventually require false teeth. Half stated that they put off going to the dentist until they had toothache. Year-1 students were more likely to have this attitude compared to year-3 students. HU-DBI scores were significantly associated with ORI scores (r = 0.315; P< 0.001). The differences in the HU-DBI and ORI scores across the level of education were highly significant. (J. Oral Sci. 43, 49-53, 2001)

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Although low-power laser irradiation provides many anabolic effects such as acceleration of bone formation, the effects of different pulse frequencies used during laser irradiation on bone formation have not been elucidated. Osteoblastic cells isolated from fetal rat calvariae were irradiated once with a low-power GaAl-As laser (830 nm, 500 mW) in two different irradiation modes; continuous irradiation (CI), and 1 Hz pulsed irradiation (PI). We then investigated the effects on cellular proliferation, bone nodule formation, alkaline phosphatase (ALP) activity, and ALP gene expression. Laser irradiation in both groups significantly stimulated cellular proliferation, bone nodule formation, ALP activity, and ALP gene expression, as compared with the nonirradiation group. Notably, PI markedly stimulated these factors, when compared with the CI group. Since 1 Hz pulsed laser irradiation significantly stimulates bone formation in vitro, it is most likely that pulse frequency is an important factor affecting biological responses in bone formation. (J. Oral Sci. 43, 55-60, 2001)

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The purpose of this study was to evaluate the effects of guided bone regeneration (GBR) with either a non-resorbable (ePTFE) or bioabsorbable barrier membrane (RSLT) on osseointegration and extent of bone formation around hydroxyapatite-coated (HA) and uncoated threaded titanium (Ti) dental implants placed into surgically-created dehiscence type defects in rabbit tibia. A dehiscence type bone defect, approximately 3 mm in width and height was surgically created on the outer surface of the bone in each tibia of 9 rabbits. For the conventional group, either a HA or a Ti implant was then placed at this site. After the same procedure was performed as in the conventional group, the implant site of the GBR group was covered with either an ePTFE or a RSLT. After 4 months, the rabbits were sacrificed. Specimens were prepared and examined histometrically. It was found that the mean percentage of osseointegration tended to increase in HA compared to Ti implants, both with and without membranes. There was a tendency that the extent of newly regenerated bone was higher in the GBR group than that in the conventional group. (J. Oral Sci. 43, 61-67, 2001)

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Two cases of double lip malformation, an uncommon oral anomaly, are presented, and the factors involved in the development, pathogenesis, diagnosis, and treatment of these uncommon lesions are reviewed. Double lip is usually associated with Ascher's syndrome, which is a rare disease with three more or less consistently associated abnormalities : double upper lip, blepharochalasis and enlargement of the thyroid. Two cases of double lip are reported; one of which was related with Ascher's syndrome, while the other had a traumatic origin. (J. Oral Sci. 43, 69-72, 2001)

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