Emigration of blood neutrophils and monocytes into the gingival crevices

Histological study of diurnal changes in bacterial settlement in the rat alimentary tract

The composition of fecal bacteria is reported to change throughout the day, whereas the circadian rhythmicity of indigenous bacteria that settle on the epithelium is mostly unknown. The present study aimed to clarify the diurnal changes in the settlement of indigenous bacteria in the rat alimentary tract using histological analysis. The settlement of indigenous bacteria on the mucosal epithelium throughout the day and the diurnal changes in settlement levels were observed in the esophagus, the nonglandular area of the stomach, and the ileum. The peak of zeitgeber time (ZT) in the settlement level differed by segment: ZT 12 in the esophagus, ZT 6 in the nonglandular area of the stomach, and ZT 0 in the ileum. Moreover, 16S rRNA amplicon sequencing using tissue sections revealed that the compositions of the indigenous bacteria in the ileum differed among ZT. In the intervillous spaces of the ileum, the formation level of the mucus layer, one of the most fundamental host defenses against bacteria, was lowest at ZT 0. Bacteria were preferentially adjacent to the villous epithelium in the area without coverage by the mucus layer at ZT 0. These findings collectively suggest that the settlement level and possibly the composition of the indigenous bacteria changed diurnally in various segments of the alimentary tract, and the formation of the mucus layer might be the most likely to lead to such diurnal changes in indigenous bacteria, at least in the ileum.

Maintaining homeostatic control of periodontal bone tissue

Alveolar bone is a unique osseous tissue due to the proximity of dental plaque biofilms. Periodontal health and homeostasis are mediated by a balanced host immune response to these polymicrobial biofilms. Dysbiotic shifts within dental plaque biofilms can drive a proinflammatory immune response state in the periodontal epithelial and gingival connective tissues, which leads to paracrine signaling to subjacent bone cells. Sustained chronic periodontal inflammation disrupts "coupled" osteoclast-osteoblast actions, which ultimately result in alveolar bone destruction. This chapter will provide an overview of alveolar bone physiology and will highlight why the oral microbiota is a critical regulator of alveolar bone remodeling. The ecology of dental plaque biofilms will be discussed in the context that periodontitis is a polymicrobial disruption of host homeostasis. The pathogenesis of periodontal bone loss will be explained from both a historical and current perspective, providing the opportunity to revisit the role of fibrosis in alveolar bone destruction. Periodontal immune cell interactions with bone cells will be reviewed based on our current understanding of osteoimmunological mechanisms influencing alveolar bone remodeling. Lastly, probiotic and prebiotic interventions in the oral microbiota will be evaluated as potential noninvasive therapies to support alveolar bone homeostasis and prevent periodontal bone loss.

Natural Development of Periodontal Disease in the Dog: A Review of Clinical, Anatomical and Histological Features

Periodontal disease occurs naturally in a wide range of species from rodents to humans. Clinical studies document the development of periodontal disease. Histopathology reveals the inflammatory response to plaque accumulation. This article presents a review of the clinical and histopathological features of periodontal disease in the dog.

The Equine Gingiva: A Histological Evaluation

Equine periodontal disease in horses has long been recognized as a painful disease, leading to a poor condition. The disease is widespread and attracts growing attention in equine dental medicine. The understanding of the underlying etiological and pathological mechanisms of equine periodontal disease is necessary to develop effective prophylactic and treatment options. As a first step, a thorough description of the histological features of the healthy equine gingiva is required. Specimens were taken from six horses (3 mares, 3 geldings, age: 0.5–26 years). The animals were euthanized for reasons not related to this study. Heads were dissected and gingival specimens, including parts of the adjacent teeth, alveolar bone and the periodontal ligament, were obtained from several positions of the dentition. Histological sections were evaluated via light microscopy, with special attention to the structural components of the gingiva, i.e., the gingival sulcus, the epithelium, and the components of the lamina propria (LP). Although the equine gingiva showed the same structural components as described in humans and dogs, the equine junctional epithelium was adapted to the equine dental anatomy and attached to the equine-unique peripheral cementum. Leucocytic infiltrations (LI) of the LP, sulcular epithelium (SE) and junctional epithelium (JE) were frequently seen. The amount of LI was not associated with a macroscopically visual pathology (e.g., diastema or food entrapment) in the respective position. The gingival sulcus depth had an average depth of <1 mm.

Aggregatibacter actinomycetemcomitans induces detachment and death of human gingival epithelial cells and fibroblasts via elastase release following leukotoxin-dependent neutrophil lysis

Aggregatibacter actinomycetemcomitans is considered to be associated with periodontitis. Leukotoxin (LtxA), which destroys leukocytes in humans, is one of this bacterium's major virulence factors. Amounts of neutrophil elastase (NE), which is normally localized in the cytoplasm of neutrophils, are reportedly increased in the saliva of patients with periodontitis. However, the mechanism by which NE is released from human neutrophils and the role of NE in periodontitis is unclear. In the present study, it was hypothesized that LtxA induces NE release from human neutrophils, which subsequently causes the breakdown of periodontal tissues. LtxA-treatment did not induce significant cytotoxicity against human gingival epithelial cells (HGECs) or human gingival fibroblasts (HGFs). However, it did induce significant cytotoxicity against human neutrophils, leading to NE release. Furthermore, NE and the supernatant from LtxA-treated human neutrophils induced detachment and death of HGECs and HGFs, these effects being inhibited by administration of an NE inhibitor, sivelestat. The present results suggest that LtxA mediates human neutrophil lysis and induces the subsequent release of NE, which eventually results in detachment and death of HGECs and HGFs. Thus, LtxA-induced release of NE could cause breakdown of periodontal tissue and thereby exacerbate periodontitis.

Aggregatibacter (Actinobacillus) actimycetemcomitans leukotoxin and human periodontitis - A historic review with emphasis on JP2

Aggregatibacter (Actinobacillus) actimycetemcomitans (Aa) is a gram-negative bacterium that colonizes the human oral cavity and is causative agent for localized aggressive (juvenile) periodontitis (AgP). In the middle of 1990s, a specific JP2 clone of belonging to the cluster of serotype b strains of Aa with highly leukotoxicity (leukotoxin, LtxA) able to kill human immune cells was isolated. JP2 clone of Aa was strongly associated with in particularly in rapidly progressing forms of aggressive periodontitis. The JP2 clone of Aa is transmitted through close contacts. Therefore, AgP patients need intense monitoring of their periodontal status as the risk for developing severely progressing periodontitis lesions are relatively high. Furthermore, timely periodontal treatment, including periodontal surgery supplemented by the use of antibiotics, is warranted. More importantly, periodontal attachment loss should be prevented by early detection of the JP2 clone of Aa by microbial diagnosis testing and/or preventive means.

The periodontal pocket: pathogenesis, histopathology and consequences

The conversion of junctional epithelium to pocket epithelium is regarded as a hallmark in the development of periodontitis. Knowledge of factors contributing to the initiation and progression of pocket formation is important and may result in the development of better preventive measures and improve healing outcomes after therapeutic interventions. The periodontal pocket is a pathologically deepened gingival sulcus. In healthy periodontal conditions, the defense mechanisms are generally sufficient to control the constant microbiological challenge through a normally functioning junctional epithelium and the concentrated powerful mass of inflammatory and immune cells and macromolecules transmigrating through this epithelium. In contrast, destruction of the structural integrity of the junctional epithelium, which includes disruption of cell-to-cell contacts and detachment from the tooth surface, consequently leading to pocket formation, disequilibrates this delicate defense system. Deepening of the pocket apically, and also horizontal expansion of the biofilm on the tooth root, puts this system to a grueling test. There is no more this powerful concentration of defense cells and macromolecules that are discharged at the sulcus bottom and that face a relatively small biofilm surface in the gingival sulcus. In a pocket situation, the defense cells and the macromolecules are directly discharged into the periodontal pocket and the majority of epithelial cells directly face the biofilm. The thinning of the epithelium and its ulceration increase the chance for invasion of microorganisms and their products into the soft connective tissue and this aggravates the situation. Depending on the severity and duration of disease, a vicious circle may develop in the pocket environment, which is difficult or impossible to break without therapeutic intervention.

Janus-Faced Neutrophil Extracellular Traps in Periodontitis

Periodontitis is characterized by PMN infiltration and formation of neutrophil extracellular traps (NETs). However, their functional role for periodontal health remains complex and partially understood. The main function of NETs appears to be evacuation of dental plaque pathogen-associated molecular patterns. The inability to produce NETs is concomitant with aggressive periodontitis. But in cases with exaggerated NET production, NETs are unable to maintain periodontal health and bystander damages occur. This pathology can be also demonstrated in animal models using lipopolysaccharide as PMN activator. The progress of periodontitis appears to be a consequence of the formation of gingival pockets obstructing the evacuation of both pathogen-associated and damage-associated molecular patterns, which are responsible for the self-perpetuation of inflammation. Thus, besides the pathogenic effects of the periodontal bacteria, the dysregulation of PMN activation appears to play a main role in the periodontal pathology. Consequently, modulation of PMN activation might be a useful approach to periodontal therapy.

Impaired polymorphonuclear neutrophils in the oral cavity of edentulous individuals

Oral health is characterized by functional oral polymorphonuclear neutrophils (oPMNs). Edentulism might be associated with a loss of oPMNs because these cells enter the oral cavity primarily through the gingival crevices. The main aim of this study was to investigate the numbers of oPMNs in rinse samples obtained from edentulous (n = 21) and dentate (n = 20) subjects. A second study aim was to investigate possible differences between oPMNs and peripheral blood polymorphonuclear neutrophils (cPMNs). Apoptosis/necrosis and cell-activation markers (CD11b, CD63 and CD66b) were analyzed using flow cytometry. Reactive oxygen species (ROS) production was determined either without stimulation (constitutive) or in response to 10 μM phorbol myristate acetate or Fusobacterium nucleatum. The edentulous subjects presented with lower oPMN counts and higher percentages of apoptotic/necrotic oPMNs compared with dentate subjects. Furthermore, oPMNs from edentulous donors expressed low levels of all three activation markers and low constitutive ROS. In contrast, oPMNs from dentate subjects expressed high levels of all three activation markers and a higher level of constitutive ROS than cPMNs. When challenged, oPMNs from edentulous subjects showed no upregulation in ROS production, whereas oPMNs from dentate subjects retained their ability to respond to stimulation. The functional characteristics of cPMNs were comparable between edentulous and dentate subjects. This study demonstrates that despite having functional cPMNs, edentulous subjects have low oPMN numbers that are functionally impaired.

Levels of multiple proteins in gingival crevicular fluid and intra-amniotic complications in women with preterm prelabor rupture of membranes

OBJECTIVE

The primary aim of this study was to identify the association between the local inflammatory response in gingival crevicular fluid measured by the levels of multiple proteins and maternal and intra-amniotic inflammatory responses measured by maternal serum C-reactive protein (CRP) and amniotic fluid interleukin (IL)-6 concentrations, respectively, in women with preterm prelabor rupture of membranes (PPROM).

METHODS

A prospective study was performed in which 78 women with singleton pregnancies complicated by PPROM between 24 + 0 and 36 + 6 weeks of gestation were included. Transabdominal amniocenteses were performed at the time of admission. A bedside assessment of amniotic fluid IL-6 was performed. Maternal serum CRP concentration was also measured at the time of admission. Gingival crevicular fluid was collected from the pocket of the selected tooth (the tooth with the deepest pocket) using standard sterile paper strips within 72 h after admission. Twenty-six proteins in the gingival crevicular fluid were assessed by multiplex the Meso-Scale technology.

RESULTS

No correlations between the levels of proteins in the gingival crevicular fluid and maternal serum CRP and amniotic fluid IL-6 concentrations were found, except for a weak positive correlation between granulocyte macrophage colony-stimulating factor and CRP.

CONCLUSIONS

The local inflammatory response in the gingival crevicular fluid is not related to the maternal and intra-amniotic inflammatory responses in women with PPROM.

Edema in Oral Mucosa after LPS or Cytokine Exposure

Lowering of interstitial fluid pressure (Pif) is an important factor that explains the rapid edema formation in acute inflammation in loose connective tissues. Lipopolysaccharide (LPS) and the pro-inflammatory cytokines interleukin-1beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) are pathogenetic in gingivitis. To test if these substances induce lowering of Pif in rat oral mucosa, we measured Pif with a micropuncture technique. IL-1β and TNF-α caused lowering of Pif, whereas LPS induced an immediate increase in Pif, followed by lowering after 40 min. Measurements of fluid volume distribution showed a significant change in interstitial fluid volume (Vi) 1.5 hr after LPS exposure as Vi changed from 0.41 ± 0.02 to 0.51 ± 0.03 mL/g wet weight ( p < 0.05), confirming edema. These findings show that LPS, IL-1β, and TNF-α induce lowering of Pif in the rat oral mucosa and contribute to edema formation in LPS-induced gingivitis.

Gingival crevicular fluid in the diagnosis of periodontal and systemic diseases

Gingival crevicular fluid (GCF) can be found in the physiologic space (gingival sulcus), as well as in the pathological space (gingival pocket or periodontal pocket) between the gums and teeth. In the first case it is a transudate, in the second an exudate. The constituents of GCF originate from serum, gingival tissues, and from both bacterial and host response cells present in the aforementioned spaces and the surrounding tissues. The collection and analysis of GCF are the noninvasive methods for the evaluation of host response in periodontal disease. These analyses mainly focus on inflammatory markers, such as prostaglandin E2, neutrophil elastase and ?-glucuronidase, and on the marker of cellular necrosis - aspartat aminotransferase. Further, the analysis of inflammatory markers in the GCF may assist in defining how certain systemic diseases (e.g., diabetes mellitus) can modify periodontal disease, and how peridontal disease can influence certain systemic disorders (atherosclerosis, preterm delivery, diabetes mellitus and some chronic respiratory diseases). Major factors which influence the results obtained from the analyses of GCF are not only the methods of these analyses, but the method of GCF collection as well. As saliva collection is less technique-sensitive than GCF collection, some constituents of saliva which originate from the GCF can be analyzed as more amenable to chairside utilization.

Analysis of gingival crevicular fluid as applied to the diagnosis of oral and systemic diseases

Gingival crevicular fluid (GCF), a serum transudate or inflammatory exudate, can be collected from the gingival crevice surrounding the teeth. As such, the fluid reflects the constituents of serum, the cellular response in the periodontium, and contributions from the gingival crevice. The study of GCF has focused on defining the pathophysiology of periodontal disease, and identification of a potential diagnostic test for active periodontitis. The majority of markers that have been identified as potential candidates for such a test are measures of inflammation (i.e., prostaglandin E2 (PGE2), neutrophil elastase, and the lysosomal enzyme beta-glucuronidase). Further, analysis of inflammatory markers in GCF may assist in defining how certain systemic disorders (e.g., diabetes mellitus) can modify periodontal disease, and how periodontal disease/periodontal inflammation can influence certain systemic disorders (i.e., cardiovascular/cerebrovascular diseases). Methodological concerns related to the collection and analysis of GCF are important factors that need to be considered when studying GCF. Practical concerns argue against the widespread clinical application of GCF as an adjunct to periodontal diagnosis. Rather, analysis of GCF-derived mediators in saliva may serve as a means of rapid screening for periodontal disease.

Resistance of fluorescent-labelled Actinobacillus actinomycetemcomitans strains to phagocytosis and killing by human neutrophils

Neutrophils are initially the predominant cells involved in the host defence of bacterial infections, including periodontal disease. Aggressive periodontitis is associated with Actinobacillus actinomycetemcomitans, a Gram-negative capnophilic microorganism. Infections caused by A. actinomycetemcomitans are not resolved by the host immune response despite the accumulation of neutrophils at the site of inflammation. To better understand the role of natural host defence mechanisms in A. actinomycetemcomitans infections, the interaction of phenotypically diverse strains of this pathogen with human neutrophils was assessed directly using techniques such as genetic labelling with the gene for green fluorescent protein, fluorescence-activated cell sorting and fluorescence imaging. The study included clinical isolates of A. actinomycetemcomitans represented by self-aggregating, biofilm-associated and isogenic planktonic variants. Data obtained showed that complement-mediated phagocytosis of A. actinomycetemcomitans was generally inefficient regardless of strain-specific serotype or leukotoxin production. Furthermore, the majority of ingested bacteria remained viable after exposure to neutrophils for 1 h. Interestingly, uptake of antibody-opsonized bacteria resulted in the rapid cell death of neutrophils. This was in contrast to ingestion of complement-opsonized bacteria, which did not affect neutrophil viability. The methods used in this study provided reliable and reproducible results with respect to adherence, phagocytosis and killing of A. actinomycetemcomitans when encountering human neutrophils.

Surface morphology of pocket epithelium

The pocket epithelium in periodontitis differs from the clinically healthy epithelium in its increase in sulcular depth. However, closer surface morphological distinctions have not been described. To study the surface characteristics of pocket gingiva, the authors analyzed pocket and sulcular epithelium biopsies by scanning and transmission electron microscopy using cytochemical staining for visualization of bacterial adhesion. The clinically healthy and the marginal pocket epithelium were characterized by squamous epithelial cells joined by tight junctions and an inconspicuous surface lacking a distinctive papillary formation. The large quantity of bacteria that adhered to the clinically healthy and marginal pocket epithelium did not appear to elicit any significant defense response. The deeper part of the pocket epithelium revealed a wrinkled papillary relief, increased exfoliation of epithelial cells, leukocyte transmigration, and bacterial internalization, as well as internalization-induced epithelial apoptosis. The alteration of the deep pocket epithelium surface might be either genuine or due to environmental changes of the crevice, or both. Therefore, the periodontitis recovery after removing the deep pocket epithelium might now be related to the pathological alterations of the deep pocket epithelium.

Pathologic Tooth Migration

Pathologic tooth migration (PTM) is a common complication of moderate to severe periodontitis and is often the motivation for patients to seek periodontal therapy. In this review of the literature, available information concerning prevalence, etiology, treatment, and prevention of pathologic tooth migration is summarized. Prevalence of PTM among periodontal patients has been reported to range from 30.03% to 55.8%. A survey of the literature regarding chief complaints of periodontal patients support these high prevalence findings. The etiology of PTM appears to be multifactorial. Periodontal bone loss appears to be a major factor in the etiology of PTM. Many aspects of occlusion can contribute to abnormal migration of teeth, and more than one of those factors may be present in an individual patient. Soft tissue forces of the tongue, cheeks, and lips are known to cause tooth movement and in some situations can cause PTM. Also considered important in the etiology of PTM is pressure produced from inflammatory tissues within periodontal pockets. Because extrusion is a common form of PTM, clinical observations support the theory that eruption forces sometimes play a role in the etiology of PTM. Many oral habits have been associated with PTM which are often difficult for the therapist to detect. Most cases of severe PTM require a team approach to achieve success. Periodontal, orthodontic, and prosthodontic treatment are often required. Many patient variables enter into the selection of treatment for PTM. In early stages of PTM, spontaneous correction of migrated teeth sometimes occurs after periodontal therapy. Light intrusive forces are used successfully to treat extrusion and flaring forms of PTM. Based on the literature reviewed, it appears that many cases of PTM could be prevented through the early diagnosis and treatment of periodontal disease, occlusal contributing factors, gingival enlargement, and oral habits.

The junctional epithelium: from health to disease

The junctional epithelium is located at a strategically important interface between the gingival sulcus, populated with bacteria, and the periodontal soft and mineralized connective tissues that need protection from becoming exposed to bacteria and their products. Its unique structural and functional adaptation enables the junctional epithelium to control the constant microbiological challenge. The antimicrobial defense mechanisms of the junctional epithelium, however, do not preclude the development of gingival and periodontal lesions. The conversion of the junctional to pocket epithelium, which is regarded as a hallmark in disease initiation, has been the focus of intense research in recent years. Research has shown that the junctional epithelial cells may play a much more active role in the innate defense mechanisms than previously assumed. They synthesize a variety of molecules directly involved in the combat against bacteria and their products. In addition, they express molecules that mediate the migration of polymorphonuclear leukocytes toward the bottom of the gingival sulcus. Periodontopathogens-such as Actinobacillus actinomycetemcomitans or, in particular, Porphyromonas gingivalis-have developed sophisticated methods to perturb the structural and functional integrity of the junctional epithelium. Research has focused on the direct effects of gingipains, cysteine proteinases produced by Porphyromonas gingivalis, on junctional epithelial cells. These virulence factors may specifically degrade components of the cell-to-cell contacts. This review will focus on the unique structural organization of the junctional epithelium, on the nature and functions of the various molecules expressed by its cells, and on how gingipains may attenuate the junctional epithelium's structural and functional integrity.

Amine fluoride gel affects the viability and the generation of superoxide anions in human polymorphonuclear leukocytes: an in vitro study

Amine hydrofluorides are widely used to prevent caries. As an acidulated gel, they were also studied for their applicability to reduce pathogenic bacteria in periodontal pockets. We assessed the toxicity of this pharmaceutical amine hydrofluoride preparation on human polymorphonuclear leukocytes in vitro by measuring Trypan blue exclusion and the generation of superoxide anions (O2) by the chemotactic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) after a 3-min contact with gel. Depending on the experimental conditions, gel dilutions up to 1.3 x 10(4) resulted in an increase in Trypan blue-colored cells and liberation of beta-glucuronidase. Dilutions between 3 x 10(4) and 1 x 10(5) augmented the fMLP-mediated O2- generation, which could be prevented by Ca2+ chelation with BAPTA-AM (1,2'-bis (o-aminophenoxyethane-N.N.N'.N'-tetraacetic acid tetra (acetoxymethyl) ester) and ethyleneglycoltetraacetic acid (EGTA) or inhibition of protein kinase C (PKC) with staurosporine and bisindolylmaleimide I. respectively. Compared with data published on the minimal inhibitory concentration for periodontal pathogenic bacteria, the cytotoxicity of amine hydrofluorides on eukaryotic cells is much greater and thus of consequence for their clinical use.

Effects of smoking and treatment status on periodontal bacteria: evidence that smoking influences control of periodontal bacteria at the mucosal surface of the gingival crevice

BACKGROUND

We examined whether smoking status could influence growth of potentially pathogenic bacteria in the periodontal environment of treated and untreated periodontal patients.

METHODS

We have previously reported effects of treatment status on marker bacteria in our patients. We established a history of any smoking during 6 months prior to microbiological sampling (F-ME, 16 smokers out of 64; MHM, 70 smokers out of 185). We used a commercial immunoassay to quantitate Porphyromonas gingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans in paper point samples from periodontal sites.

RESULTS

Logistic regression showed that in smokers, neither P. gingivalis nor A. actinomycetemcomitans was quantitatively increased, while P intermedia was somewhat increased. Multiple regression demonstrated that smoking disrupts the positive relationship between increasing probing depth and increasing bacterial growth that is found in non-smokers. In smokers, growth of marker bacteria at shallow sites (< or =5 mm) was significantly increased to the levels found at deeper sites (>5 mm) in both smokers and non-smokers. Supragingival plaque biofilm was identified as a reservoir for marker bacteria; smokers and nonsmokers had equal ranges of oral cleanliness.

CONCLUSIONS

Smoking-associated periodontitis is not simply a reflection of oral cleanliness. Smoking extends a favorable habitat for bacteria such as P. gingivalis, P. intermedia, and A. actinomycetemcomitans to shallow sites (< or =5 mm). Molecular byproducts of smoking interfere with mechanisms that normally contain growth of damaging bacteria at the surface of the oral mucosa in gingival crevices. In this way, smoking can promote early development of periodontal lesions.

Detection of hepatitis C virus RNA from gingival crevicular fluid and its relation to virus presence in saliva

BACKGROUND

To search for a possible source of hepatitis C virus (HCV) in saliva, the presence and shedding patterns of HCV in gingival crevicular fluid (GCF) and saliva of HCV viremic patients were assessed based on clinical, biochemical, histological, virological, and oral health parameters.

METHODS

Saliva and GCF samples of 50 HCV viremic patients were collected to detect HCV RNA by a modified commercial polymerase chain reaction (PCR) assay. Clinical oral examination was performed and periodontal status at the collection sites was monitored. The results were correlated to specified parameters.

RESULTS

HCV RNA was detected in 59% (29/49) of the GCF specimens and in 35% (17/48) of the saliva specimens. In saliva specimens, HCV RNA was detected only in cases which also had detectable HCV RNA in the GCF samples (P=0.00002) and was significantly related to the presence of blood in saliva (P=0.03). Higher, but not significant, values of oral clinical parameters at the sites of fluid collection were found in GCF specimens harboring HCV RNA. In GCF specimens with no blood detected, HCV RNA was more often present in cases with higher plasma viral load (P=0.05).

CONCLUSIONS

The results suggest that besides blood, the other most probable source of HCV in saliva is GCF. Unknown endogenous HCV inhibitory mechanisms in the oral cavity may explain the discrepancies in HCV appearance between saliva and GCF. The results provide a biologic basis for further investigation of the role of HCV in the pathogenesis of periodontal disease.

Fluid dynamics of gingival tissues in transition from physiological condition to inflammation

BACKGROUND

An increase in gingival sulcular fluid filtration is a common clinical sign of early gingivitis. The aim of this study was to describe the fluid dynamics of the gingival interstitial tissues at the level of the sulcus in the transition towards inflammation.

METHODS

In 13 anesthetized rabbits, a silk ligature was placed around incisors close to the gingival margin, in order to prevent mechanical cleaning of plaque deposition. After 2 to 7 days, animals were anesthetized and interstitial fluid pressure measured using glass micropipettes connected to a servonull pressure system at the level of the free and attached gingiva.

RESULTS

Interstitial pressure was 3.8 +/- 2.9 cmH2O, significantly higher than the normal physiological value (about -1 cmH2O). Colloid osmotic pressure of interstitial fluid samples collected using the wick technique was measured using an osmometer whose membrane had a molecular cut-off of 30 kD and averaged 12.8 +/- 2.8 cmH2O (unchanged relative to control). Mean gingival sulcular fluid flow, measured by placing a PE tube (0.5 mm OD, 0.28 mm ID) in the sulcus, was 0.16 +/- 0.12 microl/h; the mean colloid osmotic pressure was 13.6 +/- 6.6 cmH2O, corresponding to a protein concentration of approximately 2.8 g/dl. Proteins of gingival fluid may leak from inflamed gingival interstitium or derive from bacteria of dental plaque. Histological analysis of gingival biopsies showed neutrophilic polymorphonuclear leukocyte infiltrates in both the dermis and epidermis layer.

CONCLUSIONS

Based on hydraulic and colloid osmotic data, the Starling pressure gradient favored filtration from gingival interstitium to the sulcular space, a condition opposite to that observed in healthy gingiva where fluid filtration is absent.

Proviral HIV-1 DNA in gingival crevicular fluid of HIV-1-infected patients in various stages of HIV disease

The oral cavity is rarely reported to be a site of human immunodeficiency virus (HIV) transmission, despite detectable virus in saliva and relatively frequent prevalence of periodontal disease in HIV-infected persons yielding increased excretion of mononuclear-cell-enriched gingival fluid. To search for possible sources of HIV in saliva, and using the polymerase chain-reaction technique, we sought the presence and shedding patterns of proviral HIV-1 DNA in gingival crevicular fluid in a group of patients previously determined as HIV-1-seropositive. Periodontal status at the collection sites was monitored by several clinical parameters, including Plaque Index, Gingival Index, probing depth, and clinical attachment loss. Gingival crevicular fluid samples were collected by means of paper points. Proviral HIV-1 DNA was detected in the gingival fluid of 17 out of 35 HIV-1-infected patients. Its detection correlated significantly with higher plasma HIV-1 RNA viral load (p = 0.03) and not with peripheral blood CD4+ cell count, the presence of blood in gingival fluid, or oral lesions. There was a significant correlation between clinical attachment loss at the sites of fluid collection and plasma HIV-1 RNA viral load (p = 0.002), and borderline correlation between the latter and probing depth (p = 0.54) in the group of patients harboring proviral HIV-1 DNA in gingival crevicular fluid. The results of our study suggest that mononuclear cells present in gingival crevicular fluid and harboring proviral HIV-1 DNA could represent a potential source of HIV-1 in the presence or absence of local bleeding, especially in persons with advanced HIV infection and increased loss of clinical attachment.

Role of serotype-specific polysaccharide in the resistance of Streptococcus mutans to phagocytosis by human polymorphonuclear leukocytes

To clarify the role of cell surface components of Streptococcus mutans in resistance to phagocytosis by human polymorphonuclear leukocytes (PMNs), several isogenic mutants of S. mutans defective in cell surface components were studied with a luminol-enhanced chemiluminescence (CL) assay, a killing assay, and a transmission electron microscope. The CL responses of human PMNs to mutant Xc11 defective in a major cell surface antigen, PAc, and mutant Xc16 defective in two surface glucosyltransferases (GTF-I and GTF-SI) were the same as the response to the wild-type strain, Xc. In contrast, mutant Xc24R, which was defective in serotype c-specific polysaccharide, induced a markedly higher CL response than the other strains. The killing assay showed that human PMNs killed more Xc24R than the parent strain and the other mutants. The transmission electron microscopic observation indicated that Xc24R cells were more internalized by human PMNs than the parental strain Xc. These results may be reflected by the fact that strain Xc24R was more phagocytosed than strain Xc. The CL response of human PMNs to a mutant defective in polysaccharide serotype e or f was similar to the response to Xc24R. Furthermore, mutants defective in serotype-specific polysaccharide were markedly more hydrophobic than the wild-type strains and the other mutants, suggesting that the hydrophilic nature of polysaccharides may protect the bacterium from phagocytosis. We conclude that the serotype-specific polysaccharide, but not the cell surface proteins on the cell surface of S. mutans, may play an important role in the resistance to phagocytosis.

The pathogenesis of periodontal diseases

This informational paper was prepared by the Research, Science, and Therapy Committee of The American Academy of Periodontology, and is intended for the information of the dental profession. The purpose of the paper is to provide an overview of current knowledge relating to the pathogenesis of periodontal diseases. The paper will review biological processes thought to provide protection against periodontal infections. It will further discuss the mechanisms thought to be responsible for both overcoming and subverting such protective mechanisms and those that lead to destruction of periodontal tissues. Since an understanding of pathogenic mechanisms of disease is one foundation upon which new diagnostic and therapeutic modalities are based, the practitioner can use this information to help make decisions regarding the appropriate application of such new modalities in patient care settings.

The correlation between the numbers of some bacteria in human oral cavity and blood neutrophil count

The correlation between the number of blood polymorphonuclear granulocytes (PMNs) and the counts of oral bacteria in 92 children (33 girls and 59 boys), aged 4-15 was investigated. The groups of children comprised 44 healthy individuals and 48 children suffering from acute lymphoblastic leukaemia who were given intensive antileukaemic chemotherapy. It was found that while the number of PMNs in blood decreased, the counts of Streptococcus spp., Staphylococcus spp., mutans streptococci, Lactobacillus spp., and Actinomyces spp. in the saliva tended to increase. The similar reciprocal correlation between the number of blood PMNs and the counts of these bacteria in the saliva was found in the group of healthy children. We concluded that the blood PMNs, by influencing the number of oral PMNs which control bacteria in this habitat, influence also the number of some groups of bacteria there.

Porphyromonas gingivalis infection of oral epithelium inhibits neutrophil transepithelial migration

Periodontal diseases are inflammatory disorders caused by microorganisms of dental plaque that colonize the gingival sulcus and, subsequently, the periodontal pocket. As in other mucosal infections, the host response to plaque bacteria is characterized by an influx of polymorphonuclear leukocytes (PMNs) to the gingival crevice. Neutrophil migration through the epithelial lining of the gingival pocket is thought to be the first line of defense against plaque bacteria. In order to model this phenomenon in vitro, we used the oral epithelial cell line KB and human PMNs in the Transwell system and examined the impact of Porphyromonas gingivalis-epithelial cell interactions on subsequent PMN transepithelial migration. We demonstrate here that P. gingivalis infection of oral epithelial cells failed to trigger transmigration of PMNs. Furthermore, it significantly inhibited neutrophil transmigration actively induced by stimuli such as N-formylmethionyl leucyl phenylalanine, interleukin-8 (IL-8), and the intestinal pathogen enterotoxigenic Escherichia coli. The ability of P. gingivalis to block PMN transmigration was strongly positively correlated with the ability to adhere to and invade epithelial cells. In addition, P. gingivalis attenuated the production of IL-8 and the expression of intercellular adhesion molecule 1 by epithelial cells. The ability of P. gingivalis to block neutrophil migration across an intact epithelial barrier may critically impair the potential of the host to confront the bacterial challenge and thus may play an important role in the pathogenesis of periodontal disease.

Immunohistological study of lesions induced by Porphyromonas gingivalis in a murine model

A previous study used a mouse model to demonstrate protection after challenge with Porphyromonas gingivalis ATCC 33277. In the present study, this same model was used to determine the phenotype of cells recruited into the lesions during the course of the protective immune response after immunization with this periodontal pathogen. BALB/c mice were immunized with 100 micrograms of P. gingivalis outer membrane antigens per mouse weekly for 3 weeks followed by challenge with live organisms 3 weeks after the final immunization. Hematoxylin and eosin-stained sections showed inflammatory infiltrates in all lesions from control (immunized with adjuvant only) and immunized mice. The lesions developed central necrotic cores surrounded by neutrophils, phagocytic macrophages and lymphocytes. Neutrophils were the predominant cells in the lesions 1 day after challenge with significantly more in immunized than control mice. Acid phosphatase and nonspecific esterase-positive macrophages were detected at day 4 and became the predominant cells in the healing lesions. CD4- and CD8-positive T-cells were present from day 1, and while numbers increased over time, there were no significant differences in control or immunized mice. When mice were depleted of CD4 or CD8 cells prior to immunization with P. gingivalis, fewer neutrophils were found in the lesions 1 day after challenge compared with undepleted immunized mice. Acid phosphatase and nonspecific esterase-positive macrophages were not affected by T-cell depletion. The results suggest that the P. gingivalis-induced lesion in immunized BALB/c mice is consistent with a strong innate immune response involving the recruitment of neutrophils in the first instance which may be under the control of T cells. This is followed by the infiltration of phagocytic macrophages which are involved in the healing process and do not appear to be regulated by T cells.

Investigations into the cellular contribution to host tissue proteases and inhibitors in gingival crevicular fluid

Gingival crevicular fluid (GCF) was collected from chronic periodontitis patients using plastic micropipettes and coverslip smears stained with antibodies for leukocyte markers and Toluidine Blue for mast cells. The smears consisted of 70-80% granulocytes, 10-20% monocytes/macrophages, 5% mast cells and 5% T lymphocytes; no B lymphocytes were found. Proteases and inhibitors in GCF cells were investigated by enzyme cytochemistry using 2-methoxy-4-naphthylamine-linked peptide substrates and simultaneous coupling to Fast Blue B and immunocytochemistry using biotinylated secondary antibodies and an alkaline phosphatase/new fuchsin detecting system. Elastase was detected in granulocytes, cathepsin B in macrophages, dipeptidyl peptidases II and IV in a small proportion of macrophages, dipeptidyl peptidase IV in a few T lymphocytes, tryptase in mast cells and alpha-1-proteinase inhibitor and alpha-2-macroglobulin in some macrophages. GCF was also collected on filter paper strips and eluted into buffer for biochemical enzyme assays. Lysis of cells by addition of detergent to the elution buffer increased activities to 140-240% of control values. Removal of cells by centrifugation reduced measured activities to 1-30% of original figures; this effect was less if samples were pre-treated with detergent. Proteases from inflammatory cells therefore appear to make up most of the measured enzyme activity in GCF, and this association may explain recent correlations with periodontal disease progression.

Changes in TGF-beta 1 levels in gingiva, crevicular fluid and serum associated with periodontal inflammation in humans and dogs

Transforming growth factor-beta (TGF-beta) represents a family of polypeptide growth factors, involved in embryogenesis, inflammation, regulation of immune responses and wound healing. To determine whether TGF-beta contributes to the evolution of periodontal disease, we assayed TGF-beta levels in gingiva and crevicular fluid of patients with gingivitis and periodontitis. In parallel, TGF-beta was quantified in gingival fluid and serum of beagles with experimentally-induced periodontitis. Disease was monitored by several clinical parameters including Plaque Index, Gingival Index, probing depth, and epithelial attachment loss. Gingival tissues were obtained from 9 patients at the time of periodontal surgery, and gingival fluid samples were collected from an additional population of 10 periodontal patients. In 14 beagles, experimental periodontitis was induced and gingival fluids collected 6 months later. Fluid was collected by paper strips and volume measured by Periotron. Additionally, sera was collected before and 9 months after the ligature-induced periodontitis in 7 beagles. The levels of TGF-beta 1 were measured by ELISA. In the patients, a significantly higher concentration of TGF-beta 1 was observed both in the gingival tissues and fluid samples obtained from the sites with deeper periodontal pockets than in the less involved sites. In beagles, TGF-beta 1 levels measured in gingival fluid were elevated in moderate disease, declining in fluid samples obtained from the pockets during more advanced experimental periodontitis. Furthermore, with the progression of experimental periodontitis, a decrease in TGF-beta 1 occurred in the sera of the beagle dogs. These data suggest that TGF-beta 1 may play a rôle in the pathogenesis and diagnosis of periodontal disease, and that its actions can be further explored in an animal model.

Taxonomy, biology, and periodontal aspects of Fusobacterium nucleatum

The pathogenic potential of Fusobacterium nucleatum and its significance in the development of periodontal diseases, as well as in infections in other organs, have gained new interest for several reasons. First, this bacterium has the potential to be pathogenic because of its number and frequency in periodontal lesions, its production of tissue irritants, its synergism with other bacteria in mixed infections, and its ability to form aggregates with other suspected pathogens in periodontal disease and thus act as a bridge between early and late colonizers on the tooth surface. Second, of the microbial species that are statistically associated with periodontal disease, F. nucleatum is the most common in clinical infections of other body sites. Third, during the past few years, new techniques have made it possible to obtain more information about F. nucleatum on the genetic level, thereby also gaining better knowledge of the structure and functions of the outer membrane proteins (OMPs). OMPs are of great interest with respect to coaggregation, cell nutrition, and antibiotic susceptibility. This review covers what is known to date about F. nucleatum in general, such as taxonomy and biology, with special emphasis on its pathogenic potential. Its possible relationship to other periodontal bacteria in the development of periodontal diseases and the possible roles played by OMPs are considered.

Taxonomy, biology, and periodontal aspects of Fusobacterium nucleatum

The pathogenic potential of Fusobacterium nucleatum and its significance in the development of periodontal diseases, as well as in infections in other organs, have gained new interest for several reasons. First, this bacterium has the potential to be pathogenic because of its number and frequency in periodontal lesions, its production of tissue irritants, its synergism with other bacteria in mixed infections, and its ability to form aggregates with other suspected pathogens in periodontal disease and thus act as a bridge between early and late colonizers on the tooth surface. Second, of the microbial species that are statistically associated with periodontal disease, F. nucleatum is the most common in clinical infections of other body sites. Third, during the past few years, new techniques have made it possible to obtain more information about F. nucleatum on the genetic level, thereby also gaining better knowledge of the structure and functions of the outer membrane proteins (OMPs). OMPs are of great interest with respect to coaggregation, cell nutrition, and antibiotic susceptibility. This review covers what is known to date about F. nucleatum in general, such as taxonomy and biology, with special emphasis on its pathogenic potential. Its possible relationship to other periodontal bacteria in the development of periodontal diseases and the possible roles played by OMPs are considered.

Variations in crevicular fluid elastase levels in periodontitis patients on long-term maintenance

Granulocyte elastase was determined in the gingival crevicular fluid (GCF) of 18 periodontitis patients. They initially had similar severity of disease but had responded differently to 5-yr maintenance, 13 responders and 5 non-responders. A total of 102 sites were investigated and categorized as: i) consistently healthy, ii) healthy after treatment, iii) gingivitis, and iv) periodontitis, according to clinical criteria. GCF elastase activity was determined with a granulocyte-specific substrate. The sites from non-responders had consistently higher elastase levels than the corresponding category of sites from responders, despite similar gingival inflammation and periodontal destruction, with the exception of consistently healthy sites. Within the non-responders, the periodontitis sites had higher elastase levels than the gingivitis sites commensurate with probing depth, while no difference existed between gingivitis sites and sites healthy after treatment, despite a difference in probing depth. In contrast, in the responders similar elastase levels were found at the periodontitis sites and gingivitis sites despite difference in probing depth, while both diseased sites had higher elastase levels than the sites healthy after treatment, commensurate with probing depth. This study suggests that increased granulocyte-specific elastase levels in GCF may serve as a diagnostic marker for refractory periodontitis patients.

Short-term effects of phase I therapy on crevicular cell populations

The purpose of the present study was to use a novel intracrevicular lavage technique to evaluate short-term effects of phase I therapy on crevicular cell populations. Nineteen patients with untreated advanced adult periodontitis were selected for phase I therapy. One side of the dentition was treated with ultrasonic curets (U), the other side with manual curets (M). Nine months before (-9), immediately prior to (0), and 1 month after treatment (+1) gingival index (GI), plaque index (PI), bleeding index (BI), bleeding on probing (BOP), probing depth (PD), and probing attachment levels (PAL) were measured at all sites in the dentition. Crevicular lavages were obtained from 3 to 4 selected sites per patient at the same time points. Crevicular leukocytes were vital stained with ethydium bromide-fluorescein-diacetate (EB-FDA). The total number of cells and the percentage of vital cells (%) were calculated for each sample. Clinical and lavage parameters obtained from the selected sites were compared between U and M sites, and between pre- and post-treatment values. The results showed that without treatment PAL remained at the same level at both pretreatment time points -9 and -0 (control). At 1 month after treatment there were statistically significant reductions in GI, PI, BOP, and PD (P < 0.001 for each comparison), and a statistically significant gain in PAL from 4.9 to 4.1 mm (P = 0.014). The total number of leukocytes per sample was similar at both pretreatment time points, but numerically reduced at 1 month after treatment. The percent of vital leukocytes was above 74% at both pretreatment time points (control). After treatment these values were below 70%. This reduction was statistically significant (P < 0.002). These results suggest that periodontal phase I therapy leads to shifts in crevicular cell populations.

Comparison of canine and non-human primate animal models for periodontal regenerative therapy: results following a single administration of PDGF/IGF-I

Two commonly used animal models for evaluating putative periodontal regenerative therapies are the beagle dog model with natural periodontal disease and the non-human primate with ligature-induced attachment loss. The host response, microbiology, and skeletal rates of remodeling of these two models are summarized. In addition, the results of experiments comparing the healing response to periodontal surgery with and without concurrent use of the combination of platelet-derived growth factor (PDGF) and insulin-like growth factor-I (IGF-I) in these models are presented. At 1 month, PDGF/IGF-I administration resulted in a 64.1% and 51.4% increase in new attachment formation in the non-human primate and canine, respectively, while controls (surgery plus placebo) demonstrated 34.1% and 8.6% increases in new attachment formation in the non-human primate and canine models, respectively. Further, application of PDGF/IGF-I stimulated 21.6% and 65% osseous defect fill in the non-human primate and canine, respectively, while controls demonstrated 8.5% and 14.5% osseous defect fill in the non-human primate and canine, respectively. The osseous response in the canine appears greater than that of the non-human primate, and the new attachment formation was more substantial in the non-human primate than the canine. However, in general these data demonstrate a high degree of consistency in the effects of PDGF/IGF-I in promoting periodontal regeneration. Positive results in these two models--the dog with natural periodontal disease and the non-human primate with ligature-induced attachment loss--justify human clinical trial testing of a putative regenerative therapy.

Cytokines and T cell switching

In recent years, the phenotypic characterization of T cell subsets has given way to a functional dichotomy based essentially on their cytokine profiles. In this context, the CD4+ helper T cell subset has been shown to consist of two types, termed Th1 and Th2. In general, Th1 cells produce interleukin (IL)-2 and interferon (IFN)-gamma, while Th2 cells characteristically produce IL-4, IL-5, and IL-6. The major function of the Th1 subset is to mediate delayed-type hypersensitivity reactions and their secondary function is suppression of B cell activity. In contrast, the major function of the Th2 subset is to provide B cell help, while their secondary function is cell-mediated immune suppression. A similar dichotomy has also been described for CD8+ T cells. The role that these functional T cell subsets and their cytokines play in terms of their protective and nonprotective outcomes in a variety of infectious and oral diseases is reviewed.