Bacterial bone resorption in advanced cases of human periodontitis

Metabolomic Status of The Oral Cavity in Chronic Periodontitis

Chronic periodontitis is an inflammatory disease of tooth-supporting tissues associated with Porphyromonas gingivalis. Expansion and invasion of this bacterium into the periodontium is associated with changes in the metabolome of the oral cavity.

MATERIALS AND METHODS

Metabolomics analysis of mouth washout and tongue swab samples based on proton nuclear magnetic resonance (¹H-NMR) method was employed to determine metabolic status of the oral cavity in chronic periodontal disease.

RESULTS

Mouth washout extracts contained a total of 23 metabolites and tongue swab extracts contained 17. Identified metabolites partially overlap with the content of saliva and gingival crevicular fluid. The colonization of the oral cavity of patients with periodontitis by bacteria was manifested in the change in levels of eight metabolites.

CONCLUSION

NMR-based metabolomics analysis is a potentially useful methodological approach for monitoring the pathological processes observed in the oral cavity in the course of periodontitis.

Porphyromonas gingivalis infection increases osteoclastic bone resorption and osteoblastic bone formation in a periodontitis mouse model

Background

Porphyromonas gingivalis has been shown to invade osteoblasts and inhibit their differentiation and mineralization in vitro. However, it is unclear if P. gingivalis can invade osteoblasts in vivo and how this would affect alveolar osteoblast/osteoclast dynamics. This study aims to answer these questions using a periodontitis mouse model under repetitive P. gingivalis inoculations.

Methods

For 3-month-old BALB/cByJ female mice, 10⁹ CFU of P. gingivalis were inoculated onto the gingival margin of maxillary molars 4 times at 2-day intervals. After 2 weeks, another 4 inoculations at 2-day intervals were applied. Calcein was injected 7 and 2 days before sacrificing animals to label the newly formed bone. Four weeks after final inoculation, mice were sacrificed and maxilla collected. Immunohistochemistry, micro-CT, and bone histomorphometry were performed on the specimens. Sham infection with only vehicle was the control.

Results

P. gingivalis was found to invade gingival epithelia, periodontal ligament fibroblasts, and alveolar osteoblasts. Micro-CT showed alveolar bone resorption and significant reduction of bone mineral density and content in the infected mice compared to the controls. Bone histomorphometry showed a decrease in osteoblasts, an increase in osteoclasts and bone resorption, and a surprisingly increased osteoblastic bone formation in the infected mice compared to the controls.

Conclusions

P. gingivalis invades alveolar osteoblasts in the periodontitis mouse model and cause alveolar bone loss. Although P. gingivalis appears to suppress osteoblast pool and enhance osteoclastic bone resorption, the bone formation capacity is temporarily elevated in the infected mice, possibly via some anti-microbial compensational mechanisms.

Integrin α5β1-fimbriae binding and actin rearrangement are essential for Porphyromonas gingivalis invasion of osteoblasts and subsequent activation of the JNK pathway

BACKGROUND

Chronic periodontitis is an infectious disease of the periodontium, which includes the gingival epithelium, periodontal ligament and alveolar bone. The signature clinical feature of periodontitis is resorption of alveolar bone and subsequent tooth loss. The Gram-negative oral anaerobe, Porphyromonas gingivalis, is strongly associated with periodontitis, and it has been shown previously that P. gingivalis is capable of invading osteoblasts in a dose- and time-dependent manner resulting in inhibition of osteoblast differentiation and mineralization in vitro. It is not yet clear which receptors and cytoskeletal components mediate the invasive process, nor how the signaling pathways and viability of osteoblasts are affected by bacterial internalization. This study aimed to investigate these issues using an in vitro model system involving the inoculation of P. gingivalis ATCC 33277 into primary osteoblast cultures.

RESULTS

It was found that binding between P. gingivalis fimbriae and integrin α5β1 on osteoblasts, and subsequent peripheral condensation of actin, are essential for entry of P. gingivalis into osteoblasts. The JNK pathway was activated in invaded osteoblasts, and apoptosis was induced by repeated infections.

CONCLUSIONS

These observations indicate that P. gingivalis manipulates osteoblast function to promote its initial intracellular persistence by prolonging the host cell life span prior to its intercellular dissemination via host cell lysis. The identification of molecules critical to the interaction between P. gingivalis and osteoblasts will facilitate the development of new therapeutic strategies for the prevention of periodontal bone loss.

An unusual presentation of peripheral buttressing bone in anterior maxilla: Case report and management

The phenomenon of buttressing bone formation is relatively uncommon in the alveolar bone, more so in the anterior maxilla. In our case, peripheral buttressing bone formation presented as an isolated hard gingival swelling with relation to 21 in a 14-year-old girl. Radiographic presentation was normal with no evidence of bone loss or altered bone density. Therefore explorative surgery was planned. Buttressing bone formation could be appreciated, which also was the cause for swelling clinically. Osteoplasty was done and bone graft placed in the defect. On a subsequent recall visit gingivoplasty was done to reduce gingival thickness to improve esthetics. We report the case for its unusual presentation, its management with follow-up.

Fimbriae of Porphyromonas gingivalis are important for initial invasion of osteoblasts, but not for inhibition of their differentiation and mineralization

BACKGROUND

Porphyromonas gingivalis is etiologically associated with chronic periodontitis. The major fimbriae of this periodontal pathogen mediate binding to host gingival epithelial cells and fibroblasts, a critical function in the initiation of periodontitis. However, the role of fimbriae in P. gingivalis-osteoblast interactions remains unknown. In the present study, the involvement of major fimbriae in the initial and long-term interactions between P. gingivalis and osteoblasts is investigated.

METHODS

Primary mouse calvarial osteoblast cultures were established and inoculated with P. gingivalis ATCC 33277 or YPF1, a major fimbriae-deficient mutant of P. gingivalis. Confocal microscopy images were acquired to assess bacterial invasion. DNA content measurement, real-time polymerase chain reaction, and alizarin red S staining and calcium content analysis were used to study the impact of bacteria on the proliferation, differentiation, and mineralization of osteoblasts, respectively.

RESULTS

Compared to the parent strain, YPF1 was significantly reduced in invasion of osteoblasts after 3 hours interaction. However, extended culture of infected osteoblasts did not reveal significant differences in persistence between the two strains. Proliferation of osteoblasts was not affected by either strain, and differentiation and mineralization of osteoblasts were inhibited by both strains to comparable levels.

CONCLUSION

This study reveals that major fimbriae are involved in the initial invasion of osteoblasts by P. gingivalis, but are not essential for the subsequent inhibition of osteoblast differentiation and mineralization in long-term culture.

Paxillin phosphorylation and integrin expression in osteoblasts infected by Porphyromonas gingivalis

OBJECTIVE

We investigated early biological events initiated by Porphyromonas gingivalis infection of human osteoblasts, focusing on tyrosine-phosphorylation and the expression of key components in focal adhesion and cell signalling.

DESIGN

Human primary osteoblasts were challenged for 1h with Porphyromonas gingivalis. Tyrosine-phosphorylation of paxillin and focal adhesion kinase (FAK) was examined by Western blotting. Changes in alpha3- and beta1-integrin mRNA expression were quantified by RT-PCR.

RESULTS

Tyrosine-phosphorylation of paxillin was proportional to the size of the Porphyromonas gingivalis inoculum. FAK, a potential kinase for paxillin, was not activated. The amount of alpha3- and beta1-integrins, determined by Western blotting, did not vary significantly, while the corresponding mRNA levels fell significantly when a large bacterial inoculum was used.

CONCLUSIONS

These results indicate that Porphyromonas gingivalis infection of osteoblasts in vitro triggers tyrosine-phosphorylation of paxillin but not FAK and modify alpha3- and beta1-integrin mRNA expression. This infection thus appears to have different effects on components with essential roles in focal adhesion (paxillin) and cell signalling (FAK and integrins).

Salivary antioxidants and periodontal disease status

Periodontal disease is a common chronic adult condition. The bacterium Porphyromonas gingivalis has been implicated in the aetiology of this disease, which causes destruction of the connective tissue and bone around the root area of the tooth. It has been observed that invading P. gingivalis bacteria trigger the release of cytokines such as interleukin 8 and tumour necrosis factor a, leading to elevated numbers and activity of polymorphonucleocytes (PMN). As a result of stimulation by bacterial antigens, PMN produce the reactive oxygen species (ROS) superoxide via the respiratory burst as part of the host response to infection. Patients with periodontal disease display increased PMN number and activity. It has been suggested that this proliferation results in a high degree of ROS release, culminating in heightened oxidative damage to gingival tissue, periodontal ligament and alveolar bone. Antioxidant constituents in plasma have been well-documented, being chiefly ascorbate, albumin and urate, and these are known to display sensitivity to dietary antioxidant intakes. The concentration of antioxidants in saliva does not appear to mirror those of plasma. The extent of dietary influence upon salivary antioxidant status is unclear. Urate is the predominant salivary antioxidant, with albumin and ascorbate providing minor contributions. Previous research has found reduced salivary antioxidant activity in patients suffering from periodontal disease. An improved understanding of the role antioxidants play in periodontitis, and the influence of nutrition on antioxidant status, may lead to a possible nutritional strategy for the treatment of periodontal disease.

Life below the gum line: pathogenic mechanisms of Porphyromonas gingivalis

Porphyromonas gingivalis, a gram-negative anaerobe, is a major etiological agent in the initiation and progression of severe forms of periodontal disease. An opportunistic pathogen, P. gingivalis can also exist in commensal harmony with the host, with disease episodes ensuing from a shift in the ecological balance within the complex periodontal microenvironment. Colonization of the subgingival region is facilitated by the ability to adhere to available substrates such as adsorbed salivary molecules, matrix proteins, epithelial cells, and bacteria that are already established as a biofilm on tooth and epithelial surfaces. Binding to all of these substrates may be mediated by various regions of P. gingivalis fimbrillin, the structural subunit of the major fimbriae. P. gingivalis is an asaccharolytic organism, with a requirement for hemin (as a source of iron) and peptides for growth. At least three hemagglutinins and five proteinases are produced to satisfy these requirements. The hemagglutinin and proteinase genes contain extensive regions of highly conserved sequences, with posttranslational processing of proteinase gene products contributing to the formation of multimeric surface protein-adhesin complexes. Many of the virulence properties of P. gingivalis appear to be consequent to its adaptations to obtain hemin and peptides. Thus, hemagglutinins participate in adherence interactions with host cells, while proteinases contribute to inactivation of the effector molecules of the immune response and to tissue destruction. In addition to direct assault on the periodontal tissues, P. gingivalis can modulate eucaryotic cell signal transduction pathways, directing its uptake by gingival epithelial cells. Within this privileged site, P. gingivalis can replicate and impinge upon components of the innate host defense. Although a variety of surface molecules stimulate production of cytokines and other participants in the immune response, P. gingivalis may also undertake a stealth role whereby pivotal immune mediators are selectively inactivated. In keeping with its strict metabolic requirements, regulation of gene expression in P. gingivalis can be controlled at the transcriptional level. Finally, although periodontal disease is localized to the tissues surrounding the tooth, evidence is accumulating that infection with P. gingivalis may predispose to more serious systemic conditions such as cardiovascular disease and to delivery of preterm infants.

Topographic distribution of subgingival plaque along root surfaces of human periodontally diseased teeth. A descriptive study

The purpose of this study was to characterize the topographical distribution and organization of subgingival plaque in periodontally diseased teeth. 26 extracted teeth were fixed and processed for undecalcified histological evaluation. The sections were cut perpendicular to the long axis of the tooth and analyzed by phase-contrast microscopy. The coronal portion of the analyzed roots showed a dense accumulation of filamentous forms, fusiform rods, coccoid forms and loosely aggregated spirochetes. The middle and apical portions showed a non-uniform distribution of the microflora, with microorganisms representing all the known morphotypes. Furthermore, plaque was detected below undisturbed periodontal fibers, indicating that plaque not only forms apically, but also in a lateral direction, penetrating and colonizing below areas where periodontal fibers are inserted into the root surface.

Human gingival crevicular fluid keratin at healthy, chronic gingivitis and chronic adult periodontitis sites

The present study was designed to determine, in a cross-sectional study, whether there was any relationship between the keratin-positive material in gingival crevicular fluid and the clinical periodontal status. Keratins were selected as putative indicators of degradation of epithelial cells cytoskeletal proteins. Keratin positive material was determined by enzyme-linked immunosorbent assay in 42 subjects exhibiting clinical sites of health, chronic gingivitis and chronic periodontitis. The concentration of keratin in parotid saliva was also measured for each subject. Keratin concentration in gingival crevicular fluid samples was significantly greater at sites exhibiting signs of gingivitis and periodontitis compared with healthy sites. No differences were detected between sites exhibiting gingivitis and periodontitis. No differences were found between the 3 groups for the saliva keratin-positive material which was significantly less than that detected in gingival crevicular fluid. These results suggest that gingival crevicular fluid keratin concentration may serve as a marker of gingival damage.

The significance of bone in periodontal disease

Although the connective tissue attachment represents the key issue in periodontal health or disease and in periodontal therapy, the assessment of alveolar bone changes renders valuable indirect evidence for periodontal stability, progression of disease, or repair mechanisms. In periodontal disease bacterial products trigger host cells to release mediators, which may imbalance the steady state between resorption of bone and apposition of osteoid. Modulation of the hosts prostaglandin or interleukin-I synthesis by drug therapy could support the antimicrobial concept of periodontal therapy. Cross-sectional and long-term assessments of alveolar bone have been used to estimate the progression rate of periodontal disease. Inherent limitations of bone assessments in radiographs have to be considered when drawing conclusions from measurements that represent remodeling in periodontal lesions after therapy. Both bone quantity and quality seem to be of secondary importance with respect to the progression of disease, as well as response to therapy. Other risk factors that affect the microbial ecology and/or the hosts immune system seem to be the primary determinants for the periodontal health status.

Virulence factors of Actinobacillus actinomycetemcomitans relevant to the pathogenesis of inflammatory periodontal diseases

There is strong evidence implicating Actinobacillus actinomycetemcomitans as the causative agent of localised juvenile periodontitis (LJP), a disease characterised by rapid destruction of the tooth-supporting tissues. This organism possesses a large number of virulence factors with a wide range of activities which enable it to colonise the oral cavity, invade periodontal tissues, evade host defences, initiate connective tissue destruction and interfere with tissue repair. Adhesion to epithelial and tooth surfaces is dependent on the presence of surface proteins and structures such as microvesicles and fimbriae. Invasion has been demonstrated in vivo and in vitro although the mechanisms involved are poorly understood. The organism has a number of means of evading host defences which include: (i) inhibiting poloymorphonuclear leukocyte (PMN) chemotaxis; (ii) killing PMNs and monocytes; (iii) producing immunosuppressive factors; (iv) secreting proteases capable of cleaving IgG; and (v) producing Fc-binding proteins. Surface components of A. actinomycetemcomitans are potent stimulators of bone resorption and can induce the release of a range of cytokines which can initiate tissue destruction. A number of surface components can also inhibit the proliferation of fibroblasts and their production of components of the extracellular matrix. Little is known, however, regarding the way in which these factors operate in vivo to produce the pathological features of the disease.

Cloning and expression of a neutral phosphatase gene from Treponema denticola

We have isolated and characterized a neutral phosphatase gene, phoN, from Treponema denticola ATCC 35405. The gene was isolated from a T. denticola clone bank constructed in the medium-copy-number plasmid vector pMCL19. Subcloning and nucleotide sequencing of the DNA insert from one phosphatase clone, pTph14, revealed that the activity corresponded to an open reading frame consisting of 1,027 bp coding for a 37.9-kDa protein. Hydrophobicity analysis indicated that the protein exhibits some hydrophobic regions. Indeed, partial purification of the phosphatase suggested that the enzyme was membrane associated both in T. denticola and in the Escherichia coli clone. The pH optimum of the enzyme, approximately pH 6.4, indicated that it corresponded to a neutral phosphatase activity from T. denticola. An examination of possible natural substrates for the enzyme suggested that this enzyme hydrolyzes nucleoside di- and triphosphates. Northern (RNA) blot analysis revealed that this phosphatase gene is not likely to be present in an operon structure.

Effect of outer membrane of Treponema denticola on bone resorption

The effect of the outer membrane (outer sheath) of Treponema denticola on bone resorption was studied. Bone resorption was measured by the release of previously incorporated 45Ca from the shafts of the radii and ulnae of 19-day fetal rats. A treated-over-control ratio (T/C ratio) significantly greater than 1 indicated the stimulation of bone resorption by the test substance. The addition of outer membrane of T. denticola increased the release of 45Ca from the assay bones. The minimum concentrations required to yield significant 45Ca release from the assay bones were 15, 22 and 75 micrograms protein/ml for serovars a, b and c, respectively. These protein values corresponded to estimated lipopolysaccharide contents of 0.6, 0.8 and 2.8 micrograms/ml, based on 3-deoxy-2-manno-octulosonate analysis. Heat treatment of outer membrane (60 degrees for 30 min) did not change the effect on 45Ca release. Parathyroid hormone or prostaglandin E2, known to act synergistically with lipopolysaccharides in bone resorption, was also added to the assay system. Neither prostaglandin E2 at 10(-7) M nor parathyroid hormone at 40 ng/ml, by itself, increased 45Ca release. However, in the presence of 10 micrograms protein/ml of outer membrane of serovar b at 120 h, the T/C ratio was increased to 1.31 +/- 0.07 and 1.58 +/- 0.118, respectively. These results suggest that a lipopolysaccharide-like material is present in the outer membrane of T. denticola that may be responsible for bone resorption in the in vitro system.

Effects of a streptococcal lipoteichoic acid on complement activation in vitro

This study describes activation of serum complement by lipoteichoic acid (LTA) from Streptococcus mutans OMZ 176, while in solution. Serum from 16 healthy students was taken. Test samples were incubated with increasing doses (1-5,000 micrograms/ml) of LTA or lipopolysaccharide (LPS) from Escherichia coli 0111:B4 for 1 h at 37 degrees C; then assayed for degradation of C3, C4 or factor B by crossed immunoelectrophoresis. Each preparation caused a significant (p < 0.05) dose-dependent conversion of C3. The response curves obtained were not statistically different. LPS was a stronger activator of the alternative pathway than LTA, as judged from analysis of C3 degradation in the presence of Mg2+/EGTA, and from their effects on factor B cleavage. LTA caused, however, pronounced alterations in the shape of C4 precipitation in the gels. Functional (hemolytic) assays showed that, when tested at 200 micrograms/ml, LTA and LPS triggered significant (p < 0.05) consumptions of both classical and alternative pathway proteins. LPS was a significantly (p < 0.05) stronger activator than LTA. Apparently, the C3 degradation found for this LTA involved the alternative pathway to a small extent; thus some other mechanism of fluid-phase C3 cleavage seemed also to be operative.

Longitudinal monitoring of humoral antibody in subjects with destructive periodontal diseases

Fifty-one subjects (16-61 years old) with evidence of prior destructive periodontal disease were monitored clinically and immunologically at bi-monthly intervals for up to 5 yr. Periodontal disease activity, determined as new attachment loss, was detected in 33 of these subjects. Only 4 of 51 subjects failed to show an elevated serum antibody level to any of the 18 subgingival species tested. The antibody level threshold established for periodontally healthy subjects was exceeded most often in diseased subjects with serum antibody to Actinobacillus sp., P. gingivalis, E. corrodens, C. concisus, F. nucleatum and P. intermedia in that order. In general, most serum antibody levels to subgingival species remained relatively consistent for periods as long as 5 yr. However, major increases and decreases in antibody could be detected to at most one or two species in individual subjects. In addition, prolonged, steady increases and decreases in antibody to specific species could be detected in certain subjects. These findings suggest that major changes occurring in serum antibody may reflect fluctuations in the nature of the infection. Differences were observed in the antibody level to specific species when subjects were divided into subsets on the basis of clinical criteria. These included high levels of antibody to A. actinomycetemcomitans Y4 in LJP and RPP subjects and to A. actinomycetemcomitans 29523 in LJP and GJP subjects.

Factors in virulence expression and their role in periodontal disease pathogenesis

The classic progression of the development of periodontitis with its associated formation of an inflammatory lesion is characterized by a highly reproducible microbiological progression of a Gram-positive microbiota to a highly pathogenic Gram-negative one. While this Gram-negative microbiota is estimated to consist of at least 300 different microbial species, it appears to consist of a very limited number of microbial species that are involved in the destruction of periodontal diseases. Among these "putative periodontopathic species" are members of the genera Porphyromonas, Bacteroides, Fusobacterium, Wolinella, Actinobacillus, Capnocytophaga, and Eikenella. While members of the genera Actinomyces and Streptococcus may not be directly involved in the microbial progression, these species do appear to be essential to the construction of the network of microbial species that comprise both the subgingival plaque matrix. The temporal fluctuation (emergence/disappearance) of members of this microbiota from the developing lesion appears to depend upon the physical interaction of the periodontal pocket inhabitants, as well as the utilization of the metabolic end-products of the respective species intimately involved in the disease progression. A concerted action of the end-products of prokaryotic metabolism and the destruction of host tissues through the action of a large number of excreted proteolytic enzymes from several of these periodontopathogens contribute directly to the periodontal disease process.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of histopathology in the diagnosis and prognosis of periodontal diseases

The histological evaluation of surgical biopsies from affected tissues is a standard way of assessing pathological change and determining treatment in many diseases. In most forms of periodontal disease, however, this approach finds limited application. Here, we review what uses the histopathological approach has in the study and evaluation of the periodontal diseases. Current understanding of the changes in epithelial anatomy during pocket formation, the cellular composition and dynamics of the inflammatory infiltrate and the mechanisms of bone resorption and repair are reviewed from the perspective of the information available from microscopical investigation, including the uses and potential application of modern immunocytochemical methods to these questions. The usefulness of histological study of biopsy material is reassessed in the light of advances made in immunohistochemical techniques and their application to gingival inflammatory infiltrates and epithelia. Such techniques offer immediately valuable research opportunities with potential for diagnostic applications, noteably the recognition of phases of destructive activity and their differentiation from periods of effective host defence.

Effect of infection with Eikenella corrodens on the progression of ligature-induced periodontitis in rats

The periodontopathic ability of Eikenella corrodens 1073-R (EcR) on ligature-induced periodontal defects in immunosuppressed and non-immunosuppressed rats was studied bacteriologically and histologically. Silk ligatures were placed around the maxillary second molars of rats, and the rats were divided into eight groups. Four groups received cyclophosphamide (CY), an immunosuppressive agent, the day after ligature placement. On days 3 and 4, the oral cavities of the rats in all four groups were inoculated with 8 x 10(8) cells of live EcR. Rats were sacrificed on d 1, 3, 5, 8, 11 and 18. Alveolar bone resorption of ligated rats was enhanced by the implantation of EcR, although the number of total cultivable bacterial cells from ligated sites was not changed by the implantation of EcR. CY suppressed the number of white blood cells, inflammatory cellular infiltrates in gingival tissue, and repair of periodontal tissue, and enhanced bone destruction. The implantation of EcR in the ligature- and CY-treated rats also enhanced osteoclastic bone resorption. Without ligatures, high doses of CY or EcR inoculum did not result in periodontal destruction. These results indicate that it is possible to establish EcR in conventional rat flora with a ligature and that EcR causes osteoclastic bone resorption in this model.

Purification and characterization of alkaline phosphatase of Bacteroides gingivalis 381

Cell-associated alkaline phosphatase (ALPase) of Bacteroides gingivalis 381 was found in the outer part of the periplasmic space by using an ultracytochemical procedure. Cell-associated ALPase was solubilized by extraction with 1% Triton X-100, and the solubilized enzyme was purified 904-fold with 5.6% recovery by using affinity column chromatography for mammalian intestinal-form ALPase. The purified enzyme gave a single protein band that corresponded to the enzyme activity band on polyacrylamide gel electrophoresis preparations. A single protein band at a molecular weight of 61,000 was observed on sodium dodecyl sulfate-polyacrylamide gel electrophoresis preparations. The molecular weight of the native enzyme was estimated to be 130,000 by gel filtration with TSK-gel G3000SW. These findings indicate that B. gingivalis ALPase is a homodimer. The optimal pH of the enzyme was between 9.1 and 9.3 in the absence of divalent metal ions and was between 10.1 and 10.3 in the presence of manganese or zinc ions. The apparent km for p-nitrophenylphosphate was 0.037 +/- 0.003 mM (mean +/- standard deviation) at pH 9.2 in the absence of divalent metal ions and 0.22 +/- 0.02 mM at pH 10.2 in the presence of 1 mM manganese ions. Under both of the conditions described above, the purified enzyme was able to hydrolyze casein and O-phosphoserine, suggesting that B. gingivalis ALPase can act as a phosphoprotein phosphatase. ALPase that immunologically cross-reacted with the purified enzyme was found in the extracellular soluble fraction. This means that ALPase is released from the periplasmic space into the culture supernatant as a soluble form.

Bacterial penetration of gingiva in the adult beagle dog with periodontitis

Invasion of gingival tissues by bacteria is thought to be a major factor in development of periodontal lesions. Morphologic studies have revealed bacteria within the pocket epithelium, gingival connective tissues, alveolar bone, and oral epithelium. The current studies are intended to determine whether they are present in healthy and diseased tissues and to identify the microbial source. Five beagle dogs with naturally occurring periodontitis were fed a soft diet. Two quadrants of the dentition of each dog were cleaned regularly and health maintained while others were allowed to develop further disease. After 4 weeks, samples of gingiva were removed both prior to and after the animals were sacrificed by perfusion fixation attempting not to introduce microorganisms. The identical samples were examined by light and scanning electron microscopy for numbers and location of organisms. Their numbers were greater in diseased than in healthy tissues. Furthermore, the quantity was greater in samples taken prior to perfusion fixation than after such treatment, especially in the oral epithelium. The results suggest that normally there are some microorganisms present within the periodontal tissues and that their numbers are greater in diseased tissues. However, the data also indicated that significant numbers may be introduced into the tissues during sampling of unfixed tissues.

Scanning electron microscopic examination of pocket wall epithelium and associated plaque in localized juvenile periodontitis

The purpose of this investigation was to describe the morphologic characteristics of epithelial-associated plaque in periodontal pockets of patients with localized juvenile periodontitis (LJP). 25 tissue specimens obtained from 10 adolescent patients were examined by scanning electron microscopy. Specimens were evaluated to determine the following specific features: (1) distribution of microbial colonies on the epithelial surface; (2) topographic features of pocket epithelium associated with microbial colonies; and (3) the predominante microbial morphologic types comprising the colonies. Observations made during this investigation revealed the following. (1) The surface epithelium in the coronal one-third of the pocket wall was essentially healthy in appearance and exhibited no distinct microbial colonies or unusual topographic features. (2) The surface epithelium in the middle one-third area featured randomly-dispersed microbial colonies consisting of 3 major morphotypes: cocci, bacilli and coccobacilli. Also in this zone, there was morphologic evidence of microbial penetration of the epithelial barrier along intercellular spaces. (4) The apical one-third zone was characterized by lymphocytic infiltration, epithelial cavitation and ulcerations, and singular organisms entrapped in fibrin meshworks. There were no distinct microbial colonies in this zone, although individual spirochetes, fusiforms, filamentous organisms, and short and long rods were observed.

Quantification of bacterial penetration in spontaneous periodontal disease in beagle dogs

The role of bacteria in the pathogenesis of periodontal disease is controversial. Although bacterial penetration has been demonstrated in human periodontitis, relationships of bacteria to varying levels of periodontal health in other animals has not been well documented. In this study of beagle dog periodontium, bacteria were counted within the various tissue regions of sites which exhibited periodontal health, gingivitis, or periodontitis. Affected sites within whole block sections from two aged beagle dogs were prepared for investigation by light (LM) and scanning electron microscopy (SEM), and bacterial counts were subjected to statistical analysis for differences. Periodontitis sites viewed with LM had more bacteria than healthy sites. Neither LM nor SEM observations yielded any other differences in bacterial counts between the levels of periodontal health. When viewed using SEM, the sulcular epithelium had more bacteria than the other tissue regions in diseased sites. Relative to the number of bacteria in plaque, however, counts from all microscopic observations were very low. These findings indicate that the presence of bacteria within the periodontium is of questionable significance in the pathogenesis of spontaneous periodontal disease in beagle dogs.

Bacterial invasion in root cementum and radicular dentin of periodontally diseased teeth in humans. A reservoir of periodontopathic bacteria

In this study the viability and the distribution of bacteria within the radicular dentin and pulp of periodontally diseased caries-free teeth were studied. Healthy teeth served as controls. Samples were obtained from the pulp tissue and from the radicular dentin. Dentin samples were taken from the interdental surfaces in the subgingival area. Starting from the pulpal side, three to five successive dentin layers of approximately 1 mm thickness were sampled. The samples were processed and cultured using an anaerobic technique. Bacterial growth was detected in 87% of the periodontally diseased teeth. In 83% of the teeth, bacteria were present in at least one of the dentin layers. Fifty-nine percent of the diseased teeth, from which the pulp tissue was cultured, contained bacteria in the pulp samples. The mean bacterial concentrations in the pulp and dentin layers ranged from 1,399 to 16,537 colony-forming units (CFU) per mg of tissue. These concentrations were 259 to 7,190 times greater than concentrations found in healthy teeth. It is suggested that the roots of periodontally diseased teeth could act as bacterial reservoirs from which recolonization of mechanically treated root surfaces can occur, as well as infection of the dental pulp. These findings might change current concepts concerning root surface debridement in periodontal therapy.

Lack of bacterial invasion in experimental periodontitis

The present study in the beagle dog was performed to analyze whether micro-organisms from a subgingival microbiota could be translocated into or had the potential to invade the pocket epithelium and the gingival connective tissue during a phase of rapid breakdown of the attachment apparatus. An attempt was also made to assess whether tetracycline therapy suppressed the subgingival microbiota and changed the size and quality of the lesions in the gingival tissue. 5 inbred beagle dogs were used. Throughout the period of experimentation, the animals were fed a soft diet permitting gross accumulation of plaque and calculus. No mechanical plaque control measures were performed during the course of the study. On day 0, a 120-day period of periodontal tissue breakdown was initiated at the right mandibular 3rd and 4th premolars by tying cotton floss ligatures around the neck of these teeth. The process of tissue breakdown at the mandibular left 3rd and 4th premolars was started 30 days later. The ligatures were replaced once every 2 weeks during the subsequent 4-month period. On experimental day 120, the first biopsy was performed and gingival tissue sections prepared for light and electron microscopic assessment of a series of histometric characteristics. On day 120, a 30-day period of tetracycline (per os) administration was initiated. Each dog was given a dose of 500 mg tetracycline twice daily. On day 150, the biopsy procedure was repeated in the mandibular left premolar regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue localization of Actinobacillus actinomycetemcomitans in human periodontitis. II. Correlation between immunofluorescence and culture techniques

Recent immunohistological studies have suggested that Actinobacillus actinomycetemcomitans is present in the gingival tissues in juvenile periodontitis lesions. The present study examined tissue bound A. actinomycetemcomitans by bacterial culture and immunohistological demonstration of antigen in tissue. A total of 14 periodontitis lesions were examined. Eleven biopsies were obtained from gingiva adjacent to A. actinomycetemcomitans infected pockets, while the remaining three control biopsies were obtained from gingiva adjacent to pockets where subgingival A. actinomycetemcomitans infection could not be detected. Each biopsy was hemisected, one half was used for immunofluorescence microscopic examination while the other half was processed for culture of A. actinomycetemcomitans. The latter section was surface-disinfected, repeatedly washed and then minced to release bacteria from within the tissues. Aliquots from the serial washings and the minced tissue suspension were cultured on medium selective for A. actinomycetemcomitans. Surface disinfection and serial washings gradually decreased cultivable A. actinomycetemcomitans in the washings aliquots. Following tissue disruption, an increase in colony-forming units of A. actinomycetemcomitans was seen from eight of the 11 test biopsies. This bacterium could not be detected in washings or minced tissue suspensions from the control biopsies obtained from lesions in which subgingival A. actinomycetemcomitans was previously not detected. A positive correlation was seen between the presence of A. actinomycetemcomitans antigens in the gingival biopsies and; (1) A. actinomycetemcomitans colony-forming units released from the minced tissues (r = 0.90, p = 0.000), as well as; (2) the colony-forming units from the periodontal pocket (r = 0.62, P = 0.017).(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue localization of Actinobacillus actinomycetemcomitans in human periodontitis. I. Light, immunofluorescence and electron microscopic studies

Invasion of periodontal tissues by different bacterial morphotypes has been reported in human periodontitis; however, limited information is available as to prevalence, localization and the bacterial species involved. The present study determined prevalence and gingival localization of Actinobacillus (Haemophilus) actinomycetemcomitans in periodontal lesions of juvenile periodontitis patients. Thirty-five gingival biopsies were obtained from 12 juvenile periodontitis patients at the time of periodontal therapy. One additional control biopsy was obtained from each of two adult periodontally healthy subjects, one adult periodontitis patient and one periodontally healthy monkey (Macaca fosibolius). The biopsies were carefully processed to avoid mechanical introduction of bacteria into the tissues and were examined using light and electron microscopy. Rabbit antisera specific for the three A. actinomycetemcomitans serotypes were used for immunofluorescence microscopic localization of A. actinomycetemcomitans antigens in the gingival sections. Immunofluorescence microscopy showed A. actinomycetemcomitans specific antigens in the gingival tissues of 11 of the 12 juvenile patients examined. None of the control specimens showed evidence of A. actinomycetemcomitans antigens in the gingival connective tissue. One specimen from a periodontally healthy subject and the monkey biopsy, however, showed A. actinomycetemcomitans antigens in bacterial plaque on the surface of the crevicular epithelium. Transmission electron microscopic examination showed microcolonies of small gram-negative rods in the connective tissue, as well as single bacterial cells between collagen fibers and in areas of cell debris. In addition to these extracellular bacterial cells, evidence of bacterial cells was also found within gingival connective tissue phagocytic cells. The data from the present study suggest that the gingival tissue in juvenile periodontitis lesions harbors A. actinomycetemcomitans.

Bacterial penetration of pocket soft tissues in chronic adult and juvenile periodontitis cases. An ultrastructural study

This study investigates bacterial invasion of the soft tissue walls of deep pockets from cases with adult (AP) and juvenile periodontitis (JP). Transmission electron microscopy was used to examine pocket soft tissue walls removed from extracted teeth from 5 patients with AP and 2 patients with JP. Bacteria were sparse throughout the epithelium and connective tissue, regardless of the level of tissue breakdown. However many inflammatory cells were seen, and these did appear to be located in regions of marked collagen loss. Accumulations of large numbers of bacteria were extremely rare and found only on the epithelial surface or in artefactual spaces within the deeper tissues. The findings indicate that the tissue destruction associated with periodontitis is not directly related to bacterial invasion. The sparse organisms within the pocket tissues probably result from passive entry rather than an invasive action. Under these circumstances, it would seem reasonable to suggest that bacterial metabolic products rather than the micro-organisms themselves penetrate the tissues in periodontitis.

Inflammatory cells and bacteria in pericoronal exudates from acute pericoronitis

The present work is one in a series of studies carried out to verify the relationship between bacteria and gingival tissues in pericoronitis. Exudates from 6 cases of acute pericoronitis were examined by light and electron microscopy, including ultrathin sections and negative staining. While bacterial phagocytosis was prevalent in all the exudates studied, spirochetes, which were the predominant microorganisms, were not observed being phagocytized by PMNs or macrophages. The presence of spirochetes in pericoronitis as compared with acute necrotizing ulcerative gingivitis is discussed.

Clinical and microbiological effects of sustained release chlorhexidine in periodontal pockets

Previous studies have shown that a 3-day exposure of the pocket flora to the sustained release of chlorhexidine significantly reduced the relative numbers of spirochetes and motile rods in periodontal pockets to negligible amounts. By 14 days post-treatment, their numbers had returned to pre-treatment levels. The present study extended the exposure time of the pocket flora to the sustained release of chlorhexidine in an attempt to prolong the suppression of the microbial flora for a clinically significant period of time. Clinical parameters were also studied. Sustained release devices (SRD) were inserted into 13 pockets from 8 patients. Pocket depth ranged between 5 and 8 mm. The SRD's were replaced every 3 days to give a total exposure of 9 days. Plaque index (PlI), bleeding on probing and pocket depth were measured, and bacterial samples taken for dark field microscopy and anaerobic culture. There was a marked decrease in the relative proportions of spirochetes and motile rods and the total anaerobic count post-treatment. Pocket depth was reduced in all 13 pockets. These results indicate that a prolonged exposure to chlorhexidine suppresses the pocket flora to negligible amounts and reduces pocket depth for up to 11 weeks post-treatment.

Pathogenesis of periodontitis

Periodontitis is an inflammatory disease of the periodontium which is characterized by a progressive destruction of the tissues supporting the tooth. Its primary etiology is an ill-defined series of microbial infections which may be composed of only some of the more than 300 species of bacteria currently recognized in the oral cavity. The disease is currently considered to progress as periodic, relatively short episodes of rapid tissue destruction followed by some repair, and prolonged intervening periods of disease remission. Despite the apparent random distribution of episodes of disease activity, the resulting tissue breakdown exhibits a symmetrical pattern of alveolar bone loss and pocket formation which is common to several forms of periodontitis, although the distribution of the most affected teeth and surfaces may vary among diseases (e.g., juvenile periodontitis versus adult periodontitis or rapidly progressive periodontitis). Several reports have indicated that bacterial cells can be found in the pocket wall of periodontitis lesions. The translocation of bacteria into the tissues from the pocket environment is quite common, as evidenced by the common occurrence of bacteremias in patients with periodontitis following relatively minor events such as chewing and oral hygiene procedures. However, it is important to distinguish between the passive introduction of bacteria into periodontal tissues and frank invasion as might occur in an acute infection, since the pathological implications may be quite different.

The alteration in gingival basement membrane antigens in chronic periodontitis

The gingival basement membrane antigens, Type IV collagen, bullous pemphigoid antigen and epidermolysis bullosa acquisita antigen were studied by indirect immunofluorescence in 11 gingival specimens from patients with periodontitis and 2 normal gingival specimens. In the normal control gingival specimens, the antigens were all present and stained with a continuous linear pattern. In periodontitis, alterations occurred in the gingival basement membrane antigens in the apical portion of the pockets. These included thinning, interruptions, partial or complete absence involving one or more rete pegs and fragmentation. These alterations may result form the disease process or play a role in the pathogenesis.

Microscopic monitoring of pathogens associated with periodontal diseases. A review

Microscopic monitoring of the subgingival microbiota to detect pathogens associated with periodontal diseases has been an active area of investigation. Researchers have demonstrated that plaque samples obtained at diseased sites contain more motile bacteria and less coccoid forms than healthy sites. Therapy at diseased locations has resulted in a shift in the microbiota to one that resembles healthy sites. However, the ability to predict disease activity based on morphotype counts still remains unverified. The current literature addressing chairside microscopic assessments as a diagnostic parameter is reviewed and discussed.

The colonization and establishment of invading bacteria in periodontium of ligature-treated immunosuppressed rats

The morphologic features and pattern of bacterial invasion of the periodontal tissue in ligature-induced periodontal defects of immunosuppressed rats were studied. Silk ligatures were placed circumferentially on the maxillary left second molar of 24 Sprague-Dawley rats. The treatment group (14 rats) received Cytoxan (75 mg/kg) the day after ligature placement and at Day 4. The control group (10 rats) received no medication. All animals were sacrificed on Day 8 and the maxillae processed for light and electron microscopy. Only ligated sites in immunosuppressed animals exhibited bacterial invasion. Invading bacteria consisted of microcolonies of Gram-negative and Gram-positive coccoid cells and rods located near the tissue surface. Each microcolony consisted of morphologically homogeneous microorganisms. The deeper sites revealed a diffuse invasion of Gram-negative rods which appeared morphologically similar. Other features associated with invasion were complete destruction of epithelial tissue next to the ligature and the lack of inflammatory cells in the gingival region. These findings, when compared to those of other reports of tissue penetration by bacteria, point to the necessity of differentiating between bacterial invasion of gingival tissues, associated with penetration of tissues by proliferating bacteria, and bacterial translocation, a situation in which bacteria are passively carried into the tissues, for example by mechanical manipulation immediately before or during biopsy taking, or possibly during processing for histology.

Actinobacillus actinomycetemcomitans in human periodontal disease

Recent evidence implicates Actinobacillus actinomycetemcomitans in the etiology of localized juvenile periodontitis. This paper reviews the morphological, biochemical and serological charcteristics of A. actinomycetemcomitans, evidence incriminating it as a periodontopathogen, its importance in human nonoral infections, and virulence factors which may be involved in the pathogenesis of A. actinomycetemcomitans infections. A. actinomycetemcomitans is a non-motile, gram-negative, capnophilic, fermentative coccobacillus which closely resembles several Haemophilus species but which does not require X or V growth factors. The organism has been categorized into 10 biotypes based on the variable fermentation of dextrin, maltose, mannitol, and xylose and into 3 serotypes on the basis of heat stable, cell surface antigens. A. actinomycetemcomitans' primary human ecologic niche is the oral cavity. It is found in dental plaque, in periodontal pockets, and buccal mucosa in up to 36% of the normal population. The organism can apparently seed from these sites to cause severe infections throughout the human body such as brain abscesses and endocarditis. There is a large body of evidence which implicates A. actinomycetemcomitans as an important micro-organism in the etiology of localized juvenile periodontitis including: (1) an increased prevalence of the organism in almost all localized juvenile periodontitis patients and their families compared to other patient groups; (2) the observation that localized juvenile periodontitis patients exhibit elevated antibody levels to A. actinomycetemcomitans in serum, saliva and gingival crevicular fluid; (3) the finding that localized juvenile periodontitis can be successfully treated by eliminating A. actinomycetemcomitans from periodontal pockets; (4) histopathologic investigations showing that A. actinomycetemcomitans invades the gingival connective tissue in localized juvenile periodontitis lesions; (5) the demonstration of several pathogenic products from A. actinomycetemcomitans including factors which may: (a) facilitate its adherence to mucosal surfaces such as capsular polysaccharides; (b) inhibit host defense mechanisms including leukotoxin, a polymorphonuclear leukocyte chemotaxis inhibiting factor, and a lymphocyte suppressing factor (c) cause tissue destruction such as lipopolysaccharide endotoxin, a bone resorption-inducing toxin, acid and alkaline phosphatases, collagenase, a fibroblast inhibiting factor and an epitheliotoxin.(ABSTRACT TRUNCATED AT 400 WORDS)

Bacterial invasion of periodontal tissues in advanced periodontitis in humans

Bacterial invasion of the pocket epithelium and underlying connective tissue was found in seven cases of advanced human periodontitis. Four cases showed invasion of the epithelium as well as the connective tissue while in the other three cases bacterial invasion was limited to the pocket epithelium. The microorganisms observed included cocci, rods, filaments, fusiforms and spirochetes and these were morphologically similar to those observed in the apical zone of the subgingival plaque. Most bacteria showed typical Gram-negative cell walls. Bacteria were seen in enlarged epithelial intercellular spaces and among debris of disintegrated epithelial cells. In the connective tissue the bacteria were seen among remnants of collagen fibers and degenerated fibroblasts. Identification of the invading microorganisms may assist in understanding the pathogenesis of chronic periodontitis.

Eubacterium brachy. Reactivity in in vitro bone resorptive bioassay

Recent studies have demonstrated an association of Eubacterium sp. with the subgingival microflora of patients with chronic periodontitis. One species, Eubacterium brachy, was evaluated to determine the possible mechanisms by which this microorganism may contribute to this disease. An extracellular antigen was identified in the culture supernatant which reacted with antibodies in human sera. This antigen was isolated by methanol precipitation and purified by gel filtration. The purified extracellular antigen was reacted in vitro with 45CaCl2-labeled fetal rat bone in a bone resorptive bioassay. This antigen was shown to have a molecular weight of 170,000, to share a line of identity with a sonicated preparation of E. brachy whole cells and to result in increased 45CaCl2 release from fetal rat bones when cultures were exposed to the purified extracellular antigen at concentrations of 10 to 53 micrograms/ml.

The bone-resorbing activities in tissue culture of lipopolysaccharides from the bacteria Actinobacillus actinomycetemcomitans, Bacteroides gingivalis and Capnocytophaga ochracea isolated from human mouths

The activities of lipopolysaccharides (LPS) were assessed by measuring the calcium release from mouse calvaria in vitro and compared to that of LPS from Salmonella typhimurium. Stimulation of bone resorption was maximal at an LPS concentration of 10 micrograms/ml and at this dose all oral LPS preparations showed similar levels of activity and less than that of LPS from S. typhimurium. Only S. typhimurium LPS and B. gingivalis LPS retained bone-resorbing activity at 0.1 microgram/ml. No bone-resorbing activity was observed against killed bone and histochemical observations of stable acid phosphatase activity indicated both mononuclear and multinuclear cells participating in bone removal. Addition of indomethacin to the culture medium did not inhibit calcium release from the bones by any of the LPS preparations except for that from A. actinomycetemcomitans. Fetal calf serum completely blocked the activities of all the LPS preparations whereas human serum did not inhibit the action of B. gingivalis LPS. Thus this particular LPS could be important in mediating bone loss in chronic periodontitis.

Middle zone of the root surface integument of human teeth affected by chronic periodontitis

This study has confirmed the presence on the root surface of teeth affected by chronic periodontitis of a zoned organic integument analogous to that on enamel. Measurements showed a highly significant correlation between the levels of the bounding structures of this zone, that is, the apical plaque border and the coronal border of residual periodontal ligament, for both shallow and deep pockets. The middle zone between these two was on average 1 mm wide.