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

Er:YAG laser therapy for peri-implant infection: a histological study

The purpose of this study was to evaluate the effects of Er:YAG laser on degranulation and implant surface debridement in peri-implant infection. The peri-implant infection was experimentally induced in dogs, and the treatment was performed using an Er:YAG laser or a plastic curet. Animals were sacrificed after 24 weeks, and undecalcified histological sections were prepared and analyzed. Degranulation and implant surface debridement were obtained effectively and safely by Er:YAG laser. Histologically, a favorable formation of new bone was observed on the laser-treated implant surface, and the laser group showed a tendency to produce greater bone-to-implant contact than the curet group. These results indicate that the Er:YAG laser therapy has promise in the treatment of peri-implantitis.

Periodontal tissue healing following flap surgery using an Er:YAG laser in dogs

BACKGROUND AND OBJECTIVES

The purpose of this study was to compare periodontal tissue healing following flap surgery using an Er:YAG laser with that of conventional surgery.

STUDY DESIGN/MATERIALS AND METHODS

Bilateral premolars with experimentally induced periodontitis in six dogs were treated by periodontal flap surgery. Degranulation and root debridement in the furcation were performed using an Er:YAG laser or curet. At 3 months postsurgery, animals were sacrificed and decalcified specimens were prepared for histological and histometric analysis.

RESULTS

Degranulation and root debridement were effectively performed with an Er:YAG laser without major thermal damage and significantly faster than with a curet. Histologically, the amount of newly formed bone was significantly greater in the laser group than in the curet group, although both groups showed similar amounts of cementum formation and connective tissue attachment.

CONCLUSIONS

The Er:YAG laser irradiation can be safely and effectively utilized in periodontal flap surgery, and has the potential to promote new bone formation.

Bacterial adhesion to sulcular epithelium in periodontitis

The purpose of this study was to investigate, by electron microscopy, the type of bacterial attachment to the sulcular epithelium in periodontitis. Gingiva biopsies were observed in a transmission electron microscope using cytochemical staining with ruthenium red for glycocalyx visualisation. In addition, subgingival plaque samples and biopsies from the sulcular epithelium in periodontitis from the patients were estimated microbiologically. Aerobic bacteria only were estimated in the subgingival plaque and both aerobic and anaerobic bacteria in the gingival biopsies. No bacterial internalisation could be observed. Fimbria-mediated adhesion as the only type of bacterial attachment and a large diversity of bacterial glycocalyces were detected. As the fimbrial adhesins of putative periodontal pathogens are able in vitro to induce inflammation and bone resorption via stimulation of the proinflammatory cytokine production, the demonstrated fimbrial adhesins suggest the significant role of bacterial adhesion to sulcular epithelium in periodontitis.

The intra-oral translocation of periodontopathogens jeopardises the outcome of periodontal therapy

BACKGROUND

Although periodontitis has a multi-factorial aetiology, the success of its therapy mainly focuses on the eradication/reduction of the exogenous/endogenous periodontopathogens. Most of the species colonise several niches within the oral cavity (e.g. the mucosae, the tongue, the saliva, the periodontal pockets and all intra-oral hard surfaces) and even in the oro-pharyngeal area (e.g., the sinus and the tonsils).

METHODS

This review article discusses the intra-oral transmission of periodontopathogens between these niches and analyses clinical studies that support the idea and importance of such an intra-oral translocation.

RESULTS AND CONCLUSIONS

Based on the literature, the oro-pharyngeal area should indeed be considered as a microbiological entity. Because untreated pockets jeopardise the healing of recently instrumented sites, the treatment of periodontitis should involve "a one stage approach" of all pathologic pockets (1-stage full-mouth disinfection) or should at least consider the use of antiseptics during the intervals between consecutive instrumentations, in order to prevent a microbial translocation of periodontopathogens during the healing period. For the same reason, regeneration procedures or the local application of antibiotics should be postponed until a maximal improvement has been obtained in the remaining dentition. This more global approach offers significant additional clinical and microbiological benefits.

A novel factor isolated from Actinobacillus actinomycetemcomitans stimulates mouse B cells and human peripheral blood mononuclear cells

A novel immunostimulating factor (ISTF) of Actinobacillus actinomycetemcomitans ATCC 29522 was isolated and characterized as inducing proliferation of mouse B cells and human peripheral blood mononuclear cells. This factor was isolated from the bacterial culture medium and purified by size exclusion chromatography, dye-ligand affinity chromatography, immunoaffinity chromatography using monoclonal antibodies, and preparative electrophoresis. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the purified ISTF migrated as a single band corresponding to a molecular mass of 13 kDa. ISTF was a proteinaceous material distinct from lipopolysaccharide; it directly induced the proliferation of B lymphocytes but had no effect on the proliferation of T lymphocytes, even in the presence of antigen-presenting cells. A B-lymphocyte-mitogenic activity of ISTF was also shown by flow cytometric analysis of responding cell subpopulations. Immunoblot analysis revealed that ISTF was a component of the outer membranes of bacteria, could exist as a soluble form, and was released by growing and/or lysed bacteria. These results suggest that ISTF produced by A. actinomycetemcomitans may play an important role in immunopathologic changes associated with A. actinomycetemcomitans infections.

Bone resorption caused by three periodontal pathogens in vivo in mice is mediated in part by prostaglandin

Gingival inflammation, bacterial infection, alveolar bone destruction, and subsequent tooth loss are characteristic features of periodontal disease, but the precise mechanisms of bone loss are poorly understood. Most animal models of the disease require injury to gingival tissues or teeth, and the effects of microorganisms are thus complicated by host responses to tissue destruction. To determine whether three putative periodontal pathogens, Porphyromonas gingivalis, Campylobacter rectus, and Fusobacterium nucleatum, could cause localized bone resorption in vivo in the absence of tissue injury, we injected live or heat-killed preparations of these microorganisms into the subcutaneous tissues overlying the calvaria of normal mice once daily for 6 days and then examined the bones histologically. We found that all three microorganisms (both live and heat killed) stimulated bone resorption and that the strain of F. nucleatum used appeared to be the strongest inducer of osteoclast activity. Treatment of the mice concomitantly with indomethacin reduced but did not completely inhibit bone resorption by these microorganisms, suggesting that their effects were mediated, in part, by arachidonic acid metabolites (e.g., prostaglandins). Our findings indicate that these potential pathogens can stimulate bone resorption locally when placed beside a bone surface in vivo in the absence of prior tissue injury and support a role for them in the pathogenesis of bone loss around teeth in periodontitis.

Periodontal therapeutics--a viable option?

Research in recent years in periodontology has seen a shift from surgery towards medicine. While surgery, particularly regenerative, and including implants, continues to form an important element of periodontal treatment, the volume of treatment required and the results of recent and ongoing non-surgical studies clearly show that most future periodontics will be based on a physician-type approach. Improved diagnostics based on more precise periodontal disease classification, simplification of mechanical oral hygiene equipment and procedures, and the development of conventional and non-conventional chemical and physical adjuncts may be expected to reduce the rate of common periodontal disease advance, resulting in less complex treatments, and more of the latter coming to lie within the competence of the generalist and the hygienist working together. The rationale for non-surgical adjunctive therapy is extensive, far beyond the usual antimicrobial logic. It will also be important to control the oral microflora for systemic reasons, since increasingly strong links are being established between focal infection of oral origin, much of it periodontal, and a range of systemic diseases, including coronary heart disease, stroke, gastrointestinal disorders, and low birth weight, apart from severe, overt systemic infections. All these developments derive from a greatly improved understanding of the fundamentally ecological nature of the natural microbial biofilm that is dental plaque, and of its interactions with its human host.

Occurrence of invading bacteria in radicular dentin of periodontally diseased teeth: microbiological findings

Bacterial invasion in roots of periodontally diseased teeth, which has been recently documented using cultural and microscopic techniques, may be important in the pathogenesis of periodontal disease. The purpose of this investigation was to determine the occurrence and the species of invading bacteria in radicular dentin of periodontally diseased teeth. Samples were taken from the middle layer of radicular dentin of 26 periodontally diseased teeth. 14 healthy teeth were used as controls. Dentin samples were cultured anaerobically. The chosen methodology allowed the determination of the numbers of bacteria present in both deeper and outer part of dentinal tubules, and the bacterial concentration in dentin samples, expressed as colony forming units per mg of tissue (CFU/mg). Invading bacteria was detected in 14 (53.8%) samples from periodontally diseased teeth. The bacterial concentration ranged from 831.84 to 11971.3 CFU/mg (mean+/-standard deviation: 3043.15+/-2763.13). Micro-organisms identified included putative periodontal pathogens such as Prevotella intermedia, Porphyromonas gingivalis, Fusobacterium nucleatum, Bacteroides forsythus, Peptostreptococcus micros and Streptococcus intermedius. These findings suggest that radicular dentin could act as bacterial reservoir from which periodontal pathogens can recolonize treated periodontal pockets, contributing to the failure of therapy and recurrence of disease.

Surface-associated material from the bacterium Actinobacillus actinomycetemcomitans contains a peptide which, in contrast to lipopolysaccharide, directly stimulates fibroblast interleukin-6 gene transcription

The oral commensal Gram-negative bacterium Actinobacillus actinomycetemcomitans is believed to be the causative organism of localized juvenile periodontitis, a disease in which there is rapid loss of alveolar bone supporting the teeth. Previously, we have reported that gentle saline extraction of this bacterium removed a loosely adherent proteinaceous fraction from the cell surface of the bacterium, which we have termed surface-associated material. This material contained potent bone-resorbing activity. We now report that surface-associated material is also a potent stimulator of cytokines, and in particular, interleukin-6 (IL-6) synthesis, while the lipopolysaccharide from this bacterium is only a weak stimulator of IL-6 synthesis by fibroblasts and monocytes. In contrast to enteric lipopolysaccharide (LPS), which induces fibroblast IL-1, IL-6 and tumour necrosis factor (TNF) alpha synthesis, surface-associated material stimulated gingival fibroblasts to synthesize only IL-6, with no induction of IL-1 or TNF (the normal inducers of IL-6 synthesis). Reverse transcriptase PCR also failed to detect mRNA for IL-1 or TNF in surface-associated-material-stimulated fibroblasts, although both mRNAs were present in Escherichia coli LPS-stimulated cells. Neutralizing antibodies to IL-1 and/or TNF or the natural IL-1 receptor antagonist (IL-1ra) inhibited enteric LPS-induced IL-6 synthesis, but did not inhibit surface-associated-material-induced synthesis. In addition, dexamethasone, which completely suppressed LPS-induced IL-6 synthesis, only inhibited surface-associated-material-induced IL-6 synthesis by 50%. This suggests that the active constituent in the surface-associated material stimulates IL-6 gene transcription by a transcriptional control mechanism distinct to that of E. coli LPS. The IL-6 stimulating activity of the surface-associated material is inhibited by both heat and trypsin, suggesting that it is proteinaceous. The activity has been isolated using anion-exchange, reverse-phase and size-exclusion HPLC. The active moiety is a peptide of molecular mass 2kDa which may be the product of a bacterial short open reading frame.

The potent bone-resorbing mediator of Actinobacillus actinomycetemcomitans is homologous to the molecular chaperone GroEL

Actinobacillus actinomycetemcomitans is a Gram-negative bacterium implicated in the pathology of localized juvenile periodontitis, a condition involving rapid destruction of alveolar bone. We have established that gentle extraction of this bacterium in saline releases a proteinaceous fraction (which we have termed surface-associated material [SAM] which has potent osteolytic activity in the murine calvarial bone resorption assay. Fractionation of the SAM has now revealed that activity is associated with a 62-kD protein. This bone-resorbing activity can be blocked by a monoclonal antibody (raised to the whole bacterium) that is claimed to recognize a protein homologous to the Escherichia coli molecular chaperone GroEL. Purification of this bone-resorbing protein to homogeneity has been achieved by a combination of anion exchange, gel filtration, and ATP-affinity chromatography and the NH2-terminal sequence shows > 95% homology to E. coli GroEL. This GroEL homologue is found in the SAM of A. actinomycetemcomitans but is not found in the osteolytically active SAM from other Gram-negative or Gram-positive bacteria. The GroEL protein from E. coli, but not from Mycobacterium tuberculosis and Mycobacterium leprae, also showed activity in the bone resorption assay. We believe this to be the first observation that a molecular chaperone has the capacity to stimulate the breakdown of connective tissue.

Comparison of the osteolytic activity of surface-associated proteins of bacteria implicated in periodontal disease

OBJECTIVES

To compare the osteolytic activity of surface-associated material (SAM) and lipid A-associated proteins (LAPs) from periodontopathogenic bacteria.

MATERIALS AND METHODS

Surface-associated material was extracted from the surface and LAPs from the cell walls of a range of periodontopathic bacteria including Actinobacillus actinomycetemcomitans and Eikenella corrodens. These bacterial fractions were assayed to determine their composition and their capacity to induce bone resorption was determined by use of the neonatal murine calvarial bone resorption assay.

RESULTS

The SAMs from E. corrodens and A. actinomycetemcomitans demonstrated bone-resorbing capacity at concentrations as low as 1 ng ml-1 which, given the molecular weights of the active components, is in the picomolar range of activity. In contrast, the SAMs from the other three bacteria were significantly less potent and showed a lower efficacy. The LAPs all showed significant, and similar, capacities to induce bone breakdown.

CONCLUSIONS

This is the first demonstration that LAP from periodontopathic bacteria can stimulate bone degradation. The LAPs from diverse bacteria all produced similar levels of bone-resorbing activity. In contrast, the SAM showed significant differences in potency and in efficacy (maximal stimulation). This may mean that in vivo certain periodontopathic bacteria have significantly more bone-resorbing capacity than others and should be therapeutic targets.

The influence of surface roughness and surface-free energy on supra- and subgingival plaque formation in man. A review of the literature

In the oral cavity, an open growth system, bacterial adhesion to the non-shedding surfaces is for most bacteria the only way to survive. This adhesion occurs in 4 phases: the transport of the bacterium to the surface, the initial adhesion with a reversible and irreversible stage, the attachment by specific interactions, and finally the colonization in order to form a biofilm. Different hard surfaces are available in the oral cavity (teeth, filling materials, dental implants, or prostheses), all with different surface characteristics. In a healthy situation, a dynamic equilibrium exists on these surfaces between the forces of retention and those of removal. However, an increased bacterial accumulation often results in a shift toward disease. 2 mechanisms favour the retention of dental plaque: adhesion and stagnation. The aim of this review is to examine the influence of the surface roughness and the surface free energy in the adhesion process. Both in vitro and in vivo studies underline the importance of both variables in supragingival plaque formation. Rough surfaces will promote plaque formation and maturation, and high-energy surfaces are known to collect more plaque, to bind the plaque more strongly and to select specific bacteria. Although both variables interact with each other, the influence of surface roughness overrules that of the surface free energy. For the subgingival environment, with more facilities for microorganisms to survive, the importance of surface characteristics dramatically decreases. However, the influence of surface roughness and surface-free energy on supragingival plaque justifies the demand for smooth surfaces with a low surface-free energy in order to minimise plaque formation, thereby reducing the occurrence of caries and periodontitis.

The periodontally-involved root surface

Recent years have seen much research on the periodontally-involved root surface. Many of these studies have produced results which suggest that plaque contaminants of the root surface are only superficially placed, and capable of being removed by gentle means. Further research has attested to the difficulties in rendering periodontally-involved root surfaces free of calculus deposits by instrumentation, yet clinical studies show that periodontal disease can be managed by root planing. It is concluded that root surface debridement is best assessed on the basis of the healing response and that it should aim to disrupt plaque on and remove plaque from the periodontally-involved root surface rather than to remove part of the root surface itself.

Periodontics and prosthodontics: goals, objectives, and clinical reality

Prosthodontics and periodontics are collaborative disciplines. A successful prosthesis depends on a healthy periodontal environment, and periodontal health depends on the continued integrity of the prosthodontic restoration. To facilitate this collaboration, prosthodontists should not only appreciate the periodontic implications of gingival displacement procedures and tooth preparation, but should be knowledgeable about the types of gingival tissues, osseous topography, occlusal effects, and their implications for abutment choice. Working as a team, the periodontist can identify for the prosthodontist a patient's periodontal strengths and limitations. In that way, the prosthodontist can then assume responsibility for a given treatment plan based on a mutual understanding of the critical factors involved.

Immunodominant antigens of Actinobacillus actinomycetemcomitans serotypes a and c in high-responder patients

This study was undertaken to examine the characteristics of the immunodominant antigens of Actinobacillus actinomycetemcomitans serotypes a and c. The top responders for A. actinomycetemcomitans serotypes a and c were selected (19 for serotype a and 21 for serotype c) from 150 clinically characterized patients. Competition assays revealed that 9 of 19 of these patients were reacting specifically to serotype a and 12 of 21 for serotype c. Limiting dilution analysis on Western blots revealed that most antigen bands apparent at low dilution disappeared as the patient's serum was diluted. The antigen band(s) remaining at the endpoint or the dilution corresponding to the antibody titer were defined as immunodominant. For serotype a there were several different immunodominant antigens but none was present in more than half of the subjects. For serotype c the immunodominant antigens included a number of discrete bands and a diffuse smeared polysaccharide band. Only 2 of these antigens were present in the majority of the high-responders: 92% had the smeared antigen and 67% had a 15 kDa antigen. The 15 kDa band was a protein common to all A. actinomycetemcomitans serotypes. The smeared antigen was unaffected by protease K treatment and gave a reaction of identity with the serotype c specific rabbit antiserum. This rabbit antiserum is specific for a mannan carbohydrate and does not react with LPS (23). Therefore, the smeared immunodominant antigen appears to be a polysaccharide containing mannan.

Microscopic characterization of root surface-associated microbial plaque in localized juvenile periodontitis

The purpose of this investigation was to characterize by scanning electron microscopy, the microbial morphotypes associated with the roots of teeth from patients exhibiting localized juvenile periodontitis (LJP). Eighteen teeth were examined from 10 adolescent patients who satisfied the standard clinical diagnostic criteria for LJP. The microscopic evaluation was facilitated by dividing that portion of the root exposed to the periodontal pocket into coronal, middle, and apical one-thirds. Controls consisted of an equal number of teeth matched as to pocket depth and anatomical type obtained from patients exhibiting adult periodontitis (AP). All specimens were coded and examiners were unaware of their origins. Results of the SEM evaluation revealed little difference in microbial morphotypes comprising the root associated plaque in the coronal one-third of LJP specimens when compared to the AP controls. The dominant microbial morphotypes were cocci, short and long rods, filamentous microorganisms, and spirochetes. However, microbial plaque located in the middle and apical one-third root zones of LJP specimens was distinctly different than that of AP specimens. In the deeper pocket zones the dominant microbial morphotypes in LJP specimens were limited to cocci, short rods, coccobacilli, and various sized spirochetes. In contrast, AP specimens exhibited a collection of microbial morphotypes consisting of cocci, short rods, long rods, filamentous organisms and spirochetes. Calculus was found on the root surfaces of all specimens regardless of disease category although, as a group, the LJP specimens featured lesser amounts. Although areas of root resorption were common in both LJP and AP groups, they were more frequently observed in LJP specimens, likely associated with the generally less confluent deposits of calculus and plaque.

Direct and immune-cell-mediated effects of Bacteroides gingivalis on bone metabolism in vitro

We investigated direct and immune-cell-mediated effects of Bacteroides gingivalis on bone metabolism in vitro. Fetal mouse long-bone rudiments were cultured under aerobic conditions in the presence of (a) intact bacteria, (b) low molecular weight (MW less than 1000) metabolic products of the bacteria, or (c) conditioned media of mouse spleen cells activated by whole bacteria. A suspension of intact bacteria, added directly to the bone culture, had no effect on bone resorption or bone formation. Low molecular weight (MW less than 1000) excretion products of the bacteria inhibited bone resorption and transiently reduced mineralization of the diaphysis, while the growth in length of the bones was not affected. However, conditioned media of bacteria-activated spleen cells strongly enhanced bone resorption and increased osteoclast numbers in the bone culture, while inhibiting mineral formation in the diaphysis. This led to a strongly negative mineral balance. These data do not support a direct effect of either bacteria or bacterial products on bone tissue as a likely explanation for bone loss in periodontal disease. Rather, they favour the concept that the loss of bone in this disease is an indirect effect of the host response, resulting from the contact of immune cells with the bacteria. This implies that bacterial invasion of the connective tissue of the gingiva may not be a prerequisite for alveolar bone loss.

Immunodominant antigen of Actinobacillus actinomycetemcomitans Y4 in high-responder patients

This study was undertaken to look for characteristics of the immunodominant antigen(s) of Actinobacillus actinomycetemcomitans Y4 that might help explain the high antibody titers in periodontitis patients. Radioimmunoassays (RIA) were performed on sera from 481 patients; sera from the 32 patients with the highest anti-Y4 titers (above 128,000 RIA U/ml) were further analyzed. Y4 antigen was boiled for 45 min or treated with papain, and antibody responses were analyzed by RIA and Western blotting (immunoblotting). In addition, carbohydrate was purified from Y4 and examined by Western blotting. The results indicated that the immunodominant antigen of Y4 in high responders was stable after papain treatment or boiling for 45 min. Papain or boiling eliminated protein bands but a large diffuse band persisted on Western blots. With increasing dilutions of sera, bands on Western blots corresponding to protein antigens disappeared, while the large diffuse band resembling that of carbohydrate persisted. Partially purified Y4 carbohydrate contained the large diffuse band. Double-immunodiffusion analysis indicated that rabbit serotype b-specific antiserum and patient sera recognized the same antigen. When the carbohydrate extract was passed over a lipid A-binding column to remove lipopolysaccharide, the smear corresponding to the immunodominant antigen was still present on Western blots. The immunodominant antigen of Y4 in high-responder individuals appears to be a carbohydrate and is possibly the capsular polysaccharide.

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.

Comparison of scanning and transmission electron microscopy of the epithelial pocket wall in juvenile and adult periodontitis

Using scanning (SEM) and transmission (TEM) electron microscopy, this study compared fine structural features of the pocket walls in both juvenile and adult periodontitis (JP and AP, respectively) in 40 cases. Gingiva was also obtained from a control group consisting of periodontally noninvolved teeth. Clinical parameters were assessed in both JP and AP patients as well as in controls. Clinical findings showed low plaque accumulation, marked periodontal tissue destruction and less gingival inflammation in JP. Bone destruction and attachment loss were more marked in JP than in AP. AP had a higher plaque index and more evident gingival inflammation. SEM observations of JP as compared to AP showed gross distortions in pocket walls, an increased beaded appearance of microridges, and separation between pocket epithelial cells. TEM showed partially desquamated and separated superficial epithelial cells, but only in JP were fine granular precipitates observed in the intercellular spaces. The observations demonstrated structural features indicative of more prominent degenerative changes in JP than in AP. Also, these features were coincidental with a higher plaque index in AP than in JP, where clinical features (including a low plaque index) were not proportional to the epithelial destructive changes present.

Biology of asaccharolytic black-pigmented Bacteroides species

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Ultrastructure of the periodontal lesion in a case of Papillon-Lefèvre syndrome (PLS)

In this study, 11 permanent teeth and their associated soft tissues from an 11-year-old boy with PLS were examined. Plaque, cementum and periodontal tissues were examined by scanning (SEM) and transmission electron microscopy (TEM). Except for depressed lymphocyte transformation, there were no abnormal haematological data. Local findings included abnormally thin cementum, extensive destruction of the periodontal ligament were still attached to the root, and severe inflammation of the soft tissues. Few bacteria were found in any of the soft tissue layers. The apical border plaque was restricted to gram- cocci and rods. The features observed in this case of PLS may indicate primary defects of cementum or ligament attachment, or disruption of fibroblast and cementoblast function due to the rapid advance of the disease process. Lack of bacterial invasion in the pocket soft tissue casts doubt on its involvement in the present case of severe periodontitis. The restricted range of morphotypes observed suggests a limited range of associated organisms. Further research is required to clarify the rôle of the host response and to identify the organisms involved.