Vascular leakage resulting from topical application of endotoxin to the gingiva of the beagle dog

DNA from periodontopathogenic bacteria is immunostimulatory for mouse and human immune cells

Although bacterial DNA (bDNA) containing unmethylated CpG motifs stimulates innate immune cells through Toll-like receptor 9 (TLR-9), its precise role in the pathophysiology of diseases is still equivocal. Here we examined the immunostimulatory effects of DNA extracted from periodontopathogenic bacteria. A major role in the etiology of periodontal diseases has been attributed to Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Peptostreptococcus micros. We therefore isolated DNA from these bacteria and stimulated murine macrophages and human gingival fibroblasts (HGF) in vitro. Furthermore, HEK 293 cells transfected with human TLR-9 were also stimulated with these DNA preparations. We observed that DNA from these pathogens stimulates macrophages and gingival fibroblasts to produce tumor necrosis factor alpha and interleukin-6 in a dose-dependent manner. Methylation of the CpG motifs abolished the observed effects. Activation of HEK 293 cells expressing TLR-9 which were responsive to bDNA but not to lipopolysaccharide confirmed that immunostimulation was achieved by bDNA. In addition, the examined bDNA differed in the ability to stimulate murine macrophages, HGF, and TLR-9-transfected cells. DNA from A. actinomycetemcomitans elicited a potent cytokine response, while DNA from P. gingivalis and P. micros showed lower immunostimulatory activity. Taken together, the results strongly suggest that DNA from A. actinomycetemcomitans, P. gingivalis, and P. micros possesses immunostimulatory properties in regard to cytokine secretion by macrophages and fibroblasts. These stimulatory effects are due to unmethylated CpG motifs within bDNA and differ between distinct periodontopathogenic bacteria strains. Hence, immunostimulation by DNA from A. actinomycetemcomitans, P. gingivalis, and P. micros could contribute to the pathogenesis of periodontal diseases.

Relationship between hydroxy fatty acids and prostaglandin E2 in gingival tissue

Bacterial hydroxy fatty acids and alpha-hydroxy fatty acids have been demonstrated in complex lipid extracts of subgingival plaque and gingival tissue. However, little is known about the relationship between these hydroxy fatty acids in plaque and gingival tissues or the significance of these complex lipids in promoting inflammatory periodontal disease. The present study determined the percentages of ester-linked and amide-linked hydroxy fatty acids in complex lipids recovered from plaque and gingival tissue samples and the relationship between bacterial hydroxy fatty acids and alpha-hydroxy fatty acids in the lipid extracts. To evaluate a potential role for these hydroxy fatty acids in inflammatory periodontal disease, gingival tissue samples were examined for a relationship between prostaglandin E2 (PGE2) and hydroxy fatty acids recovered in gingival lipid. This investigation demonstrated that alpha-hydroxy fatty acids are only ester linked in plaque lipids but are largely amide linked in gingival tissue lipids. Furthermore, the level of alpha-hydroxy fatty acid in gingival lipid is directly related to the level of the bacterial hydroxy fatty acid 3-OH iso-branched C17:0 (3-OH iC17:0) in the same lipid extract. However, the relationship between hydroxy fatty acids in gingival lipids does not parallel the fatty acid relationship observed in plaque lipids. Finally, alpha-hydroxy fatty acid levels in gingival tissue lipids correlate directly with the recovery of PGE2 in the same tissue samples. These results demonstrate that alpha-hydroxy fatty acid levels in gingival lipids are directly related to both 3-OH iC17:0 bacterial lipid levels and PGE2 levels. These results indicate that in periodontal tissues there are unusual host-parasite interactions involving penetration of bacterial lipid in association with an altered gingival lipid metabolism and prostaglandin synthesis.

Reactive change in proliferative activity of the junctional epithelium after topical application of lipopolysaccharide

IT IS WELL ESTABLISHED THAT apical migration of junctional epithelium (JE) along a root surface is an important factor in periodontal pocket formation and deepening. However, the exact mechanism and, more specifically, the role of inflammatory products in influencing the activity of cells within the JE is not known. To address this issue lipopolysaccharide (LPS) was applied topically into rat molar gingival sulcus and then tissues evaluated immunohistochemically for expression of proliferating cell nuclear antigen (PCNA). Tissues were prepared for histological analysis at designated times. Histologically, infiltration of neutrophils with associated edema was noted in JE and gingival connective tissues 6 hours after LPS application and was prominent at 12 hours. These inflammatory changes persisted in the 2- and 3-day specimens, and disappeared at 5 days. In normal gingiva, before the LPS application, the JE showed few PCNA positive cells, while almost all cells in the basal and suprabasal cell layers of the oral gingival epithelium and the oral sulcular epithelium were PCNA positive. No increase in the number of PCNA positive cells in the JE beyond zero time was observed at 6 and 12 hours after LPS application. One day after LPS application, PCNA positive cells appeared in the basal cell layer of the JE, with a continued increase number of PCNA positive cells in the JE continued at 2 and 3 days. By day 5 the number of PCNA positive cells were decreasing with return to a normal range by 7 days. These results showed that 1) under normal physiological conditions, cells within the JE have minimal mitotic activity and 2) the JE cells can enter the proliferating cell cycle when exposed to LPS, and suggest that the enhanced proliferating activity in the JE is an important factor for the deepening of the periodontal pocket, if the connective tissue attachment is broken down.

Effect of Campylobacter rectus LPS on plasminogen activator-plasmin system in human gingival fibroblast cells

The plasminogen activator (PA)-plasmin system is implicated in the degradation of the extracellular matrix in inflammation through activation of metalloproteases and prekallikrein. We examined the activation of the PA-plasmin system in human gingival fibroblast cells (Gin-1 cells) following treatment with lipopolysaccharide (LPS) from Campylobacter rectus, which is frequently detected at sites of periodontal disease. The C. rectus LPS stimulated the plasmin activity in the conditioned medium of Gin-1 cells in a time- and dose-dependent manner, and C. rectus LPS also stimulated the PA activity in the conditioned medium. The PA produced by Gin-1 cells was determined to be urokinase PA (uPA), as preincubation of Gin-1 conditioned medium with anti-uPA antiserum completely inhibited the PA activity while that with anti-tPA antiserum had no inhibitory effect. The concentration of PA inhibitor-1 (PAI-1) in the conditioned medium was decreased by the addition of C. rectus LPS. Therefore, the enhancement of plasmin activity in the conditioned medium was dependent on increased uPA activity via the decrease of the PAI-1 level of Gin-1 cells treated with C. rectus LPS. Furthermore, the conditioned medium of Gin-1 cells treated with C. rectus LPS showed significantly increased kallikrein activity, indicating the conversion of prekallikrein to kallikrein, which converts kininogen into kinin. These findings suggest that C. rectus LPS is a potent stimulator of inflammation of gingival tissue which acts through stimulation of the PA-plasmin system.

Distribution of 3-hydroxy iC17:0 in subgingival plaque and gingival tissue samples: relationship to adult periodontitis

Gram-negative organisms incorporate hydroxy fatty acids into the lipid A moiety of lipopolysaccharide (LPS), and in the case of some members of the family Enterobacteriaceae, hydroxy fatty acids are incorporated exclusively into lipid A. However, a limited number of Bacteroides species have been shown to incorporate several classes of 3-hydroxy fatty acids, particularly 3-hydroxy iC17:0, into constitutive lipids as well as LPS. The present study examined the distribution of hydroxy fatty acids in two periodontal pathogens, Prevotella intermedia and Porphyromonas gingivalis, by employing a phospholipid extraction procedure (E. G. Bligh and W. J. Dyer, Can. J. Biochem. Physiol. 37:911-917, 1959) which partitioned constitutive lipids into the organic solvent phase and LPS into the aqueous phase. The distribution of hydroxy fatty acids within organic solvent and aqueous extracts of these bacterial species was then compared with the distribution in subgingival plaque samples isolated from either gingivitis or severe periodontitis sites as well as the distribution in gingival tissue samples. The organic solvent and aqueous extracts were hydrolyzed under strong alkaline conditions, and the free fatty acids were treated to form pentafluorobenzyl-ester, trimethylsilyl-ether derivatives. Hydroxy fatty acid levels were quantified by using gas chromatography-negative-ion chemical ionization-mass spectrometry. By using this approach, the mean values of the 3-hydroxy iC17:0 recovered within organic solvent extracts of P. gingivalis strains ranged from 56 to 63% of total 3-hydroxy iC17:0. Substantially less 3-hydroxy iC17:0 (< 5%) was recovered in organic solvent extracts of P. intermedia. By comparison, 75% of the 3-hydroxy iC17:0 in periodontitis subgingival plaque samples was recovered in organic solvent extracts, while only 43% of the 3-hydroxy iC17:0 in gingivitis plaque samples from the same patients was recovered in organic solvent extracts. However, 3-hydroxy iC17:0 was recovered essentially only in organic solvent extracts of both healthy or mildly inflamed and periodontitis gingival tissue samples. The preferential recovery of 3-hydroxy iC17:0 in tissue lipids indicates that gingival tissues do not harbor significant levels of subgingival plaque organisms which contain 3-hydroxy iC17:0. Furthermore, these results indicate that LPS from these organisms is not prevalent in gingival tissues. Finally, these results indicate either selective penetration of certain bacterial lipids into gingival tissues or that 3-hydroxy iC17:0 is metabolically transferred from bacterial lipids into gingival tissue lipids.

The secretion of PGE2, IL-1 beta, IL-6, and TNF alpha by adherent mononuclear cells from early onset periodontitis patients

The secretion of prostaglandin E2 (PGE2), tumor necrosis factor alpha (TNF alpha), interleukin 1 beta (IL-1 beta), and interleukin 6 (IL-6) by adherent mononuclear cells (AMNC) from 28 patients with early-onset periodontitis was studied. The early onset-periodontitis patients consisted of 12 patients with localized juvenile periodontitis (LJP) and 16 patients with severe generalized periodontitis (SGP). The AMNC responses to different concentrations of lipopolysaccharide (LPS) (E. coli) were determined in these 28 patients and compared to 14 healthy controls. Mediator levels in the supernatant were measured using radioimmunoassays for PGE2, IL-1 beta, and IL-6 determination and an enzyme linked immunosorbent assay for TNF alpha levels. The mean age of the patients was 19.9 years for the LJP group, 30.4 years for SGP, and 28.0 years for the controls. The mean number of teeth per patient with attachment loss of > 6 mm was 4.75 in the LJP patients and 17.3 in the SGP group. In the absence of LPS, LJP AMNC secreted significantly more PGE2 than unstimulated control or SGP AMNC, while similar baseline amounts of IL-1 beta, IL-6, and TNF alpha were secreted by AMNC from the 3 patient groups. LPS stimulation resulted in the dose-dependent secretion of significantly higher levels of PGE2 by LJP AMNC compared to SGP AMNC which in turn secreted significantly more than controls. TNF alpha secretion by LJP monocytes was significantly greater than the SGP and the control groups while IL-1 beta secretion by the SGP AMNC was depressed compared to the other two patient groups.(ABSTRACT TRUNCATED AT 250 WORDS)

A stereomicroscopic and immunohistochemical study of vasculature in gingiva bleeding after probing

This study investigated the stereomicroscopic appearance of gingival sulcular surfaces and the histologic alterations of subepithelial vasculature of gingiva bleeding after probing. Sixty-four pairs of gingival biopsies from 49 patients were obtained and the results of stereomicroscopically visible vasculature were observed in half of the specimens. The number of biopsies showing that the vasculature of bleeding gingiva was significantly greater than those of non-bleeding gingiva. The immunohistochemical marker UEA-1 was used to identify endothelial cells on the vascular walls of 34 gingival biopsies from 15 patients. Following stereomicroscopic examination, tissue preparation with routine and UEA-1 stainings was performed. Volumetric and numerical analyses of vasculature in 6 divided portions of subepithelial connective tissue were measured. The results showed that significantly greater numbers of UEA-1 staining vessels were found within the apico-superficial portion of bleeding gingiva than those of non-bleeding gingiva. However, there was no specific correlation between the UEA-1 positive vessels within gingival tissue and stereomicroscopic visibility of vasculature on the surface appearance. It is suggested that increased vascularity in gingiva may be responsible for bleeding on clinical probing.

Endotoxin levels in periodontally healthy and diseased sites: correlation with levels of gram-negative bacteria

This study investigated the correlation between endotoxin levels and the percentage of Gram-negative bacteria in healthy sites and in periodontitis sites. Twelve healthy adults participated. Each subject provided 3 periodontitis sites with 5 to 8 mm probing depths that bled on gentle probing and 3 healthy sites with sulcus depths of 1 to 3 mm that did not bleed. Clinical examinations and sterile paper point sampling of all study sites were conducted on days 0, 7, and 14, and site-specific endotoxin levels and percentage of Gram-negative bacteria were determined. There were significant differences in both endotoxin levels and percentage Gram-negative bacteria between healthy and periodontitis sites across all 3 sampling periods, but no difference across sampling periods in the healthy sites and the periodontitis sites, respectively. Correlation coefficients revealed a high degree of correlation between site-specific endotoxin levels and percentage of Gram-negative organisms. Using a sample dilution of 1 x 10(4), endotoxin levels differentiated healthy from periodontitis sites with a specificity of approximately 91% and a sensitivity of approximately 90%.

LPS-elicited secretory responses in monocytes: altered release of PGE2 but not IL-1 beta in patients with adult periodontitis

Lipopolysaccharide responsiveness in human subjects was assessed through the examination of LPS-stimulated PGE2 and IL-1 beta release from counterflow isolated monocytes from patients with varying levels of periodontal destruction. This study was performed in order to investigate a possible relationship between LPS-mediated secretory responses in monocytes and susceptibility to periodontal destruction in humans. Subjects were chosen based on apparent resistance or susceptibility to disease as measured by little or no periodontal destruction versus generalized severe destruction, respectively. Because IFN-gamma can influence LPS-stimulated responses, the effect of IFN-gamma on the LPS-stimulated release of PGE2 and IL-1 beta was also assessed. Peripheral blood monocytes were separated by counterflow centrifugation and cultured (10(6)/ml/well) with control medium or medium containing LPS from Bacteroides gingivalis, B. intermedius, Actinobacillus actinomycetemcomitans, or Salmonella typhimurium, with or without 10 Units/ml recombinant IFN-gamma. Media were exchanged at 24 and 48 hours and culture supernatants assayed for both PGE2 and IL-1 beta by RIA. Patients classified as Susceptible to periodontitis demonstrated 2- to 3-fold greater PGE2 release than Resistant patients. This difference was observed with all LPS preparations over both the 0-24 hour and 24-48 h culture periods. IL-1 beta release, however, was not significantly different between patient groups. IFN-gamma did not affect the LPS-stimulated release of PGE2 but significantly enhanced the release of IL-1 beta. The IFN-gamma effects were similar for both patient groups. These findings indicate that LPS-stimulated PGE2 release from peripheral blood monocytes may correlate with susceptibility to periodontitis in human subjects.

Effect of lipopolysaccharide on proteoglycan synthesis by adult human gingival fibroblasts in vitro

The effect of lipopolysaccharide preparations from Salmonella enteritidis, Bacteroides gingivalis, and Actinobacillus actinomycetemcomitans on human gingival fibroblasts was studied. Lipopolysaccharide from all sources inhibited fibroblast proliferation in the concentration range of 0.5 to 50 micrograms/ml, with the lipopolysaccharide from A. actinomycetemcomitans having the strongest inhibitory effect. Assessment of the effect of lipopolysaccharide on gingival fibroblast metabolism indicated both total protein and proteoglycan synthesis to be inhibited with increasing concentrations of lipopolysaccharide. As for the antiproliferative effect, lipopolysaccharide from A. actinomycetemcomitans had the greatest inhibitory effect on cell synthetic activity. This inhibitory effect was determined by pulse-chase experiments to be a true depression in synthesis. Furthermore, the effect was independent of lipopolysaccharide-induced changes in cell proliferation and prostaglandin synthesis. This study confirmed the toxic effect of lipopolysaccharide on fibroblasts and, in particular, indicated that various lipopolysaccharide preparations vary in their potency to influence cell proliferation and extracellular matrix synthesis.

Kinin generation in the gingival inflammatory response to topically applied bacterial lipopolysaccharides

A water-soluble lipopolysaccharide from Salmonella enteritidis and a phenol-soluble lipopolysaccharide from Leptotrichia buccalis were applied topically to the healthy marginal gingivae of beagle dogs. Saline was applied to contralateral areas as an internal control. Increases in vascular permeability were monitored by measurement of gingival fluid, and the collected gingival fluid samples were assayed for kininogenase and kinin activities. Both lipopolysaccharides induced an inflammatory response, as indicated by increased gingival fluid flow. Kininogenase-kinin activities paralleled the increases in gingival fluid flow, with the highest values being associated with peak increases in gingival fluid. The results indicate that both lipopolysaccharides, although different in lipid solubility, penetrate healthy sulcular epithelium and initiate an inflammatory response which is mediated in part by the kallikrein-kinin system. Interrelationships between this system and other inflammatory mediators suggest that kinin generation not only plays a role in the early phases of acute gingival inflammation, but may also contribute to the activation of other mediators appearing later in the response and in chronic inflammatory lesions.

Mitogen-induced hyperproliferation response of peripheral blood mononuclear cells from patients with severe generalized periodontitis: lack of correlation with proportions of T cells and T-cell subsets

Severe generalized periodontitis (SGP) is a localized inflammatory disease which differs clinically from common periodontitis in that it leads to remarkable extensive alveolar bone loss in relatively young adults. There is evidence that B-cell responses to bacterial substances may play a major role in the pathogenesis of this disease. In the present report, we show that a B-cell mitogen from Actinomyces viscosus (AVIS) bacteria provokes a hyperproliferation response of peripheral blood mononuclear cells (PBMNC) from these patients. In addition, AVIS-stimulated PBMNC from SGP patients proliferate for longer periods in culture than do PBMNC from control subjects. There were, however, no differences between patients and controls in the numbers of immunoglobulin-secreting cells in these cultures as determined by an indirect plaque-forming cell assay. The possibility that differences in numerical proportions of regulatory T-cell subsets may play a role in the mitogen-induced hyperproliferation phenomenon is examined. PBMNC were stained with fluorescein isothiocyanate-conjugated monoclonal antibodies OKT3, OKT4, and OKT8 in order to identify, respectively, total T cells, helper/inducer, and suppressor/cytotoxic subsets. Flow cytometric analysis of such specifically stained cell preparations from 14 control subjects and 14 SGP patients did not reveal any significant differences between the proportions of total T cells or T-cell subsets of the two groups. Furthermore, there were no statistically significant correlations between the magnitude of proliferation responses and the proportions of total T cells or either of the T-cell subsets.

Human immune responses to oral microorganisms. II. Serum antibody responses to antigens from Actinobacillus actinomycetemcomitans and the correlation with localized juvenile periodontitis

Human serum antibody responses to antigens from a suspected oral pathogen, Actinobacillus actinomycetemcomitans (Aa), were studied. IgG and IgM isotype antibodies to four antigen preparations, sonicate antigen (SA), leukotoxin (LT), group carbohydrate (LG), and lipopolysaccharide (LPS), were determined using an ELISA. An ELISA inhibition technique was developed to show that human serum antibodies reacting with the LT, LG, or LPS materials were binding to different antigenic moieties in each preparation. Cross-sectional studies of serum IgG antibodies showed that patients with localized juvenile periodontitis (LJP) had a greater frequency of occurrence and a higher level of antibodies to the SA (82%), LT (70%), and LG (62%) antigens compared to all other diseased (11-46%) or normal (4-13%) groups. Serum IgM antibodies to LPS were increased in LJP, generalized juvenile periodontitis, and adult periodontitis patients compared to all other groups. Therefore, while both IgG and IgM antibodies were found against various Aa antigens, the detection of IgG antibodies was most clearly associated with the specific disease classification of LJP. Blocking studies suggested that the human serum responses were specific for the Aa antigens and that the LT, LG, and LPS comprise major antigenic determinants on the organisms to which human serum antibody reacts.

Effect of peptide extracted from skeletal muscles of the fur seal on periodontal diseases

It has been confirmed previously that a physiologically active peptide extracted from the skeletal muscles of fur seals exhibits excellent dermal absorption and has peripheral vasodilating properties. These properties were postulated to be beneficial to inflamed periodontal tissues. To test this, a dentifrice containing the peptide was prepared and utilized in a double-blind test. Significant improvement in the gingiva conditions was observed when a 0.1% or more concentration of peptide was used. As time progressed, distinct clinical improvement in redness, swelling, drainage, bleeding and pocket depth was noted. No significant side effects were noted although there were seen increased salivation and gingival blanching. It is believed, as a result of this and other studies, that the clinical efficacy of this peptide is due to its vasodilating action on the venules, thus reducing the internal pressure in the vascular beds.

Bacterial endotoxin: a role in chronic inflammatory periodontal disease?

A review of current information was undertaken examining suggested roles for bacterial endotoxin in periodontal disease. Evidence for the presence of endotoxin in plaque, gingival crevicular fluid and periodontally involved cementum is discussed. The biological effects of endotoxin are numerous, and its abilities to induce tissue inflammation, resorb rat foetal bone, activate the complement pathway, stimulate macrophages and activate immune responses are examined in relation to the suggestion that endotoxin is an important factor in the pathogenesis of periodontal disease.

Vascular morphology in noninflamed healed gingiva of dogs

The objective of this study was to determine if the regular vascular network previously reported as occurring in noninflamed marginal gingiva would become re-established following plaque control and treatment of gingiva by gingivectomy and scaling. Gingivectomies were performed on dogs with and without pre-experimental gingivitis in order to obtain gingival specimens healed for 4, 8 and 12 weeks. Plaque was controlled using toothbrushing and topical applications of 0.2% chlorhexidine gluconate. After 12 weeks, the animals were perfused via the carotid arteries with glutaraldehyde and Microfil latex compound. Specimens were processed for either routine histology or examination of vascular morphology in methyl salicylate cleared tissues. The absence of inflammation in healed gingiva was evaluated clinically, using the Gingival and Plaque Indices, and histologically. Results showed that in healed clinically and histologically noninflamed gingiva, the vascular morphology was established as a series of looped vessels which could readily be distinguished from the regular network of vessels described by Hock (1975) in marginal gingiva that had neither been inflamed nor resected.

Morphological features and functional properties of human fibroblasts exposed to Actinomyces viscosus substances

Connective tissue fibroblasts undergo cytopathic degenerative changes during certain long-term inflammatory diseases such as rheumatoid arthritis and periodontitis. The failure of inflamed tissues to repair properly may result from functional alterations of fibroblasts within the affected tissues. Numerous previous studies indicate that direct cytotoxicity by bacterial or other substances may be responsible for the cellular alterations observed in vivo. We have tested this hypothesis by exposing cultures of human diploid fibroblasts to homogenates of Actinomyces viscosus (a microorganism associated with periodontitis and capable of causing other chronic inflammatory diseases) and analyzing the effects on cell viability, morphology, and function. The cells bind and subsequently engulf relatively large quantities of the bacterial substances. These substances do not appear to be toxic to fibroblasts as determined by 51Cr release and microcytotoxicity assays, although there is a slight but significant decrease in protein synthesis (P less than 0.01) as measured by the incorporation of [14C]proline. However, collagen production was not altered, and the cytopathic alterations observed in diseased tissues in vivo did not occur in the exposed cells. These findings suggest that A. viscosus substances do not directly cause injury to connective tissue fibroblasts in periodontal disease but may, through cell-surface binding, mark these cells for subsequent immune-mediated damage.

The effect of endotoxins and enzymes in vitro on the release of gingival histamine

Gingival samples removed from fifteen Beagle dogs were sectioned into small pieces, parts of which served as the uncultured piece; the remaining pieces were organ cultured for four hours at 37 degrees C in MEM control, compound 48/80, endotoxins, protease, collagenase, hyaluronidase, trypsin and chymotrypin media. Uncultured and cultured tissues and spent media were analyzed spectrofluorometrically for histamine content. The uncultured gingiva contained a mean of 2.80 mug histamine/g of tissue and was considered to contain 100% total histamine available for release. The percentages of histamine released into the medium were 5.4% for culture control, 57.3% for compound 48/80, 5.4% for endotoxins, 77.3% for protease, 16.1% for hyaluronidase, 24 for collagenase, 39.3% for trypsin, and 36.5% for chymotrypsin. When compared to the culture control, all test substances showed statistically significant histamine release (P less than 0.005 to P less than 0.0005) except for the endotoxins and for hyaluronidase (P greater than 0.05). The results demonstrate (1) that gingiva contains a potential source or reservoir of histamine, presumably in mast cells, and when appropriately challenged in vitro can release this histamine; (2) no direct effect of endotoxins on histamine release in vitro, (3) that all enzymes tested except hyaluronidase resulted in significant histamine release. The results of this in vitro study support a thesis that enzymes are active in the early events of gingival inflammation.

Effect of soluble plaque factors on inflammatory reactions in the dental pulp

The present investigation was undertaken to determine whether soluble factors from human dental plaque are capable of inducing or mediating pathological alterations in the dental pulp. The experiment was performed in three monkeys and involved 40 teeth in all: 20 test and 20 control teeth. Class V cavities were prepared on the buccal surface close to the marginal gingiva. In the test cavities an extract of human dental plaque was applied once very 5 min during an 8-h period. The cavities of the contralateral teeth were treated in an identical manner but with Ringer's solution. The animals were sacrificed 10 or 32 h after the initiation of the test. Two hours prior to sacrifice the animals were injected with colloidal carbon and then perfused with 10% neutral buffered formalin. Histologic examination demonstrates that the pulp tissue response to topical application of a plaque extract was characterized by (1) increased degree of carbon retention - indicative of vascular exudation and (2) enhanced rate of emigration of neutrophils and monocytes.

Gingival vasculature around erupting deciduous teeth of dogs and cats

The presence of plaque and of overt inflammation, occurring with eruption of deciduous teeth in dogs and cats 2-14 weeks old, were related to the concomitant gingival vascular morphology, using vital microscopy, perfusion and histological techniques. Although localised, acute inflammation accompanied plaque formation at the time of weaning, it seldom developed into chronic inflammation. The onset of overt chronic inflammation was not related to tooth eruption or to events associated with formation of the gingiva. Infiltration of gingival tissue by chronic inflammatory cells occurred in only a few specimens and was associated with increased plaque and replacement of the gingival vessel network by loop paterns.