The adherence of oral bacteria to host cells and to restorative materials is considered to be an important first step in the development of periodontal tissue destruction. Bacterial fimbriae are one of the major cell structures for this adherence. Since bacterial adherence to these materials is mediated by specific molecules in the saliva, it is very important to investigate substances that modulate fimbria-mediated binding to saliva-coated materials and to determine the mechanism of action. Porphyromonas gingivalis is one of the predominant pathogen in adult periodontitis. Fimbriae are an important cell structure that involved in the adherence of the organism to host cells. In this study, we examined the involvement of fibronectin in saliva for P. gingivalis fimbria-mediated adherence to the restorative materials.
Three different highly filler-filled resin-composite materials, self-cured acrylic resin (RTPR) and a cast 20 K gold alloy were tested. P. gingivalis adherence to the restorative materials was measured by an enzyme-linked immunosorbent assay (ELISA) with its monoclonal antibody. The adherence to the restorative materials was dramatically inhibited by monoclonal antibody against its fimbriae. The fimbriamediated adherence increased when the materials were pretreated with human parotid saliva. This increase in the bacterial adherence to saliva-pretreated materials was inhibited by pretreatment with fibronectin antibody. Purified human fibronectin pretreatment significantly increased the fimbria-mediated adherence to the restorative materials. The present study demonstrates that P. gingivalis fimbria-mediated adherence to the restorative materials is regulated by fibronectin in saliva. J. Jpn. Soc. Periodontol., 42: 235-246, 2000.

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The purpose of this study was to examine the effects of rhBMP-2 applied dentin on alkaline phosphatase (ALP) activity and mineralized nodule formation in gingival fibroblasts in vitro with a view toward developing periodontal regenerative therapy inducing hard tissue to form on the root surface by gingival connective tissue in vivo.
Dentin blocks were demineralized with EDTA, divided into 5 groups, then labeled based on the treatment, i. e., groups 0, 1, 5, and 10 with 0, 1, 5, and 10. μg/ml rhBMP-2 applied and group PL treated with only DMEM.
Human gingival fibroblasts (HGF) were seeded on each dentin block in groups 0, 1, 5, and 10 and human periodontal ligament cells (HPLC) on those of group PL. ALP activity and protein concentration of attached cells were assessed on days 1, 3, and 7.
Dentin blocks in each group were then placed over the confluent HGC and HPLC monolayers and incubated in a-MEM supplemented with β-glycerophosphate. The area of mineralized nodules around dentin blocks was stained by the Von Kossa method and measured on days 5, 7, and 10.
On day 1, the attached HGF in groups 0, 1, 5, and 10 showed lower ALP activity than that in group PL. On day 3, groups 1, 5, and 10 had about 6 times higher ALP activity than group 0 (p<0.01), and almost the same level as group PL (p>0.05). On day 7, ALP activity in groups 1 and 5 decreased, whereas that in group 10 showed no significant difference compared to the PL group (p>0.05). The amount of mineralized nodule in groups 1, 5, and 10 was about 2.5 times higher than that in group 0 (p<0.05), and was not significant compared to the PL group on day 7 (p>0.05). RhBMP-2 applied dentin thus enhanced ALP activity and mineralized nodule formation in HGF to the level in HPLC. These results suggest that the application of rhBMP-2 may induce hard tissue formation on the root surface by gingival connective tissue. J. Jpn. Soc. Periodontol., 42: 247-254, 2000.

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We studied the process of periodontal destruction after vertical root fracture involving 56 upper and lower premolars of 4 beagls. After separation, the root was vertically fractured with a chisel and mallet. Gingival index (GI), probing depth (PD) and probing attachment loss (PAL) were examined clinically. Animals were sacrificed 3 days or 1, 2, or 4 weeks after fracture and radiographs were taken. Epithelial downgrowth, bone resorption, and root resorption were measured histometrically.
After 3 days or 1 week, PD and PAL increased slightly. Epithelial downgrowth did not occur and bacteria accumulated slightly in the root canal. Inflammation of periodontal ligament was very minimal. After 2 weeks, PD was 4.6±1.7 mm, PAL 3.0±1.6 mm, and epithelial downgrowth 0.2±0.2 mm. Bacteria accumulated in the root canal and on the fracture surface. The periodontal ligament was inflamed and bone and root had resorbed slightly at the fracture site. After 4 weeks, PD was 5.5±1.4 mm, PAL 4.6±1.3 mm, and epithelial downgrowth 0.5±0.3 mm. Plaque had accumulated on root surface, the periodontal ligament was increasingly inflamed and fiber disappeared. Resorption of bone and root had deteriorated and radiography revealed wedge-shaped bone defect.
These results showed that attachment loss was minimal in the early fracture stage even if probing depth was considerable, and irritants such as bacteria in the root canal induced inflammation of periodontal tissues. Attachment was later lost along the fracture site and periodontal destruction progressed with plaque accumulating on root surfaces. J. Jpn. Soc. Periodontol., 42: 255-266, 2000.

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We studied the influence of Bisphosphonate (Incadronate) administration onbone resorption in rapidly progressive experimental periodontitis caused by bacterial and traumatic factors in rats. Subjects were 53 10-week-old male Wistar rats, 5 of which were categorized in a normal group (N), 24 in a periodontitis group (P), and 24 rats in a periodontitis and Bisphosphonateadministration group (PB).
In groups P and PB, experimental periodontitis was induced by ligature wire (diameter: 0.25 mm) tied around the contact between the first and second maxillary molars. Bisphosphonate (Incadronate) solution was administered to group PB rats intraperitoneally every 24 hours (1.0 mg/kg/day). Histological and histometrical examinations were conducted before wire tying (Group N) and 1, 2, 3, 5, and 7 days after tying (Group P, PB). Group P showed gingival inflammation and attachment loss, with osteoclast appearing and bone resorption increasingly. Group PB evidenced the suppression of osteoclast appearing and bone resorption, and significantly decreased bone resorption 7 days after tyingcompared to group P.
Some osteoclasts on group PB specimens showed extraordinary numbers of nuclei, loss of the brushborder, nuclear degeneration such as vacuolization or condensation, and apoptosis. No damaged osteocytes or osteoblasts were seen in group PB. These results suggest that Bisphosphonate (Incadronate) administration suppresses rapid alveolar bone resorption by reducing the number of osteoclasts and their activity in experimental periodontitis caused by bacterial and traumatic factors inrats. J. Jpn. Soc. Periodontol., 42: 267-281, 2000.

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The relationship between periodontitis progression andocclusal trauma is not clearly understood in detail. We studied the effects of periodontal marginal inflammation and occlusal trauma on the healing of angular bony defects treated by root planing.
Subjects were 5 Japanese monkeys, initially, the first mandibular molars or second premolars were extracted. After healing, 3-wall bone defects were createdon adjacent teeth, notches were made at the bottom of defects, and plastic braids were inserted in defects. Braids were removed after 4 weeks and teeth root-planed. Experimental teeth were divided into 4 subgroups: in Group C, both inflammation and occlusal trauma were controlled; in Group I, inflammation persisted but occlusal trauma was controlled; in Group T, inflammation was controlled, but occlusal trauma was applied; and in Group IT, both inflammation and occlusal trauma were applied. Inflammation was evoked by suspended teeth cleaning, cotton ligature insertion around the neck of the tooth, and soft diets, controlled by teeth cleaning, root planing and hard diets. Occlusal trauma was induced by placing high onlays and applying orthodontic power chains. Sites were observed for 10 weeks clinically and radiographically with standardized radiography Pathological observations and histometrical analysis were also conducted.
In Group C, angular bony defects, probing pocket depth (PD), and clinical attachment level (CAL) improved. In Group I, angular bony defects tended to decrease, but PD and CAL worsened.
In Group T, PD and CAL improved but angular bony defects persisted. In Group IT, angular bony defects remained or worsened and PD and CAL worsened.
This suggests that when angular bony defects were treated by root planing, postoperative controls of inflammation and occlusal trauma are important, i. e., postoperative control of inflammation influenced the improvement of CAL and the control of occlusal trauma influenced the improvement of angular bony defects. J. Jpn. Soc. Periodontol., 42: 282-297, 2000.

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We studied rat and human teeth by light and transmission electron microscopy (TEM) to clarify the structure and origin of the intermediate cementum and the Hopewell-Smith hyaline layer. Undemineralized ground sections and demineralized paraffin sections of developing and completely developed human teeth and rat molars were observed by light microscopy. Demineralized and undemineralized sections of developing rat molars were observed by TEM. The intermediate cementum and Hopewell-Smith hyaline layer belonged to the mantle dentin in human and rat teeth based on the original definition, meaning these 2 structures originate in the dentin. The entire mantle dentin showed delayed mineralization in developing human teeth, while only a 1-μm-thick, fibril-poor, superficial layer of mantle dentin showed delayed mineralization in developing rat molars. It was confirmed previously that the fibril-poor layer develops into the cemento-dentinal junction. The fibril-poor layer is often referred to as the intermediate cementum or hyaline layer, because this nomenclature is often more convenient than the original definition. At the same time, however, these differences in nomenclature have confused the original definition. In conclusion, we propose that (1) the Hopewell-Smith hyaline layer be equated with mantle dentin, (2) the term intermediate cernentum nut be applied to any particular structure, and (3) the fibril-poor layer he referred to as the intervening adhesive layer. J. Jpn. Soc. Periodontol., 42: 298-306, 2000.

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Some 180, 000 patients are currently undergoing renal dialysis in Japan. Dialysis does not, however, compensate for all kidney functions, e. g., erythropoietin production and vitamin D₃ activation, which are very important reactions in the human body, are both inhibited. Osteoporotic disorder resulting from these functional deficiencies is a prominent side effect in renal dialysis patients. We suspect chronic renal failure to be a risk factor in periodontal disease. To determine the relationship between periodontitis and renal failure, we studied periodontal conditions in 38 subjects undergoing renal dialysis, together with a control group of 42 similar-aged healthy subjects. Community periodontal index of treatment needs (CPITN) assessment showed that dialysis patients, at 2.4±0.1, scored higher than controls, at 1.9±0.1 (p<0.05). No difference was seen between groups in the simplified calculus index (CI-S) score. The number of missing teeth, at 6.1±1.3, was 2.2 times greater in dialysis patients than in controls, at 2.8±0.8 (p<0.05). When patients were divided into 4 groups by dialysis duration, no significant difference was observed in any index. No correlation was seen between blood concentration of parathyroid hormone (PTH) and alveolar bone height or between PTH and CPITN. Of the 38 dialysis patients, 7 suffered fromdiabetic nephropathy, and most suffered from severe periodontitis. Compared to the other 31 patients, those having diabetic nephropathy showed an increase in missing teeth, from 3.9±1.1 to 15.9±3.6 (p<0.05), and a decrease in alveolar bone height from 79±1% to 58±6% (p<0.05). When the 31 nondiabetic dialysis patients were compared to controls, these patients, at 2.3±0.1, scored a higher CPITN than controls, at 1.9±0.1 (p< 0.05), indicating that nondiabetic patients suffered more from periodontitis than healthy subjects. This suggests that patients with chronic renal failure undergoing dialysis are at risk for periodontitis and that those with diabetic nephropathy suffer more from severe periodontitis. J.Jpn. Soc. Periodontol., 42: 307-313, 2000.

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To clarify changes in cell proliferation and the mechanism behind phenytoin (PHT) -induced gingival overgrowth, representative medication-induced gingival overgrowth, we immunohistochemically studied gingival tissues from patients with PHT gingival overgrowth (PHT-GO), comparing them to those with proliferative gingivitis secondary to the presence of dental plaque (ND) and clinically healthy gingiva (controls). Five patients from each of the above types ofgingiva were selected randomly and biopsies obtained during periodontal surgery or tooth extraction, processed routinely in paraffin wax, and serially sectioned. These specimens were immunostained using mouse antiproliferating cell nuclear antigen (PCNA) monoclonal antibody. Fibroblasts and epithelial cells in each group contained immunoreactive products. Many PCNA-positive cells were recognized in the PHT-GO group, but few positive cells appeared in elongated rete pegs. The number of total fibroblasts per unit area of connective tissue adjacent to the oral epithelium was significantly greater in the PHT-GO group than in other groups (p<0.01), with no statistical significance seen between ND and controls. The density of PCNA-positive fibroblasts was highest in PHT-GO and declined in ND and controls. Statistically significant differences were found between PIIT GO and ND groups (p<0.05), PHT-GO and controls (p<0.01), and ND and controls (p< 0.01). Comparisons of frequency in PCNA-positive fibroblasts between highly and poorly inflammatory cell-infiltrated areas in connective tissues showed no significant difference in PHT-GO and ND. These findings suggest the possibility of enhancement in proliferation of fibroblasts in PHT-GO. The number of infiltrated inflammatory cells was not related, however, to that of proliferating fibroblasts. In summary, the mechanism behind the appearance of PHT-induced gingival overgrowth appears to be the increase in PCNA-positive fibroblasts resulting in an increase in gingival fibroblasts. J. Jpn. Soc. Periodontol., 42: 314-322, 2000.

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