The interleukin-1 genotype as a severity factor in adult periodontal disease

Periodontal diseases and dental implants in older adults

Older adults present special problems for the dentist trying to establish or reestablish esthetics. Periodontal diseases are of concern for this population since tooth loss from these widespread problems increases with age. In general, this loss occurs because of increased exposure time to pathogenic bacteria, not some change inherent in the body brought on by the aging process. The profession has begun to place more emphasis on systemic risk factors and their role in modifying periodontal inflammation. The current thinking is that bacteria are necessary to initiate and sustain periodontal diseases, but the clinical manifestation is dictated to a significant extent by systemic factors. Smoking, diabetes, and being positive for the interleukin-1 genotype predispose the patient to developing more severe disease. For those older adults who lose teeth, dental implants have emerged as reliable replacements, and concerns about placing these devices in patients who have lost teeth as a result of periodontitis appear to be largely unfounded.

Polymorphisms of the IL-1 gene complex in coal miners with silicosis

BACKGROUND

Silicosis is characterized by fibrosing nodular lesions that eventually develop into progressive pulmonary fibrosis. Pro-inflammatory cytokines, such as interleukin-1 (IL-1), play a key role in the development of silicosis by regulating mediators which are responsible for lung injury, inflammation, and potentially fibrosis. To study whether functional single nucleotide polymorphisms (SNPs) located in the regulatory elements of genes coding for the IL-1alpha, IL-1beta, and IL-1 receptor antagonist (RA) cytokines are associated with silicosis, we examined 318 Caucasian cases confirmed histopathologically with pulmonary silicosis and 163 controls without any apparent inflammation or other pulmonary disease.

METHODS

Genotyping was carried out by polymerase chain reaction-restriction fragment length polymorphism technique.

RESULTS

The proportion of the IL-1RA (+ 2018) allele 2 genotype was increased in miners with silicosis (0.27) compared to controls (0.16). The odds of being a case were 2.15 (CI = 1.4-3.3) times higher for subjects with at least one copy of allele 2. No statistically significant differences in the allelic frequencies or genotype distributions for IL-1alpha (+ 4845) or IL-1beta (+ 3953) were found between the control and disease groups.

CONCLUSIONS

This is the first report showing an association between the IL-1RA (+ 2018) polymorphism and silicosis, and suggests that this polymorphism may confer increased risk for the development of the disease.

Increased frequency of FcgammaRIIIb-NA1 allele in periodontitis-resistant subjects in an elderly Japanese population

Many elderly people show minimum periodontal tissue destruction, which might be partly due to genetic advantages in host immune response against periodontopathic bacteria. The human IgG Fc receptor IIIb on neutrophils bears a NA1-NA2 polymorphism. The FcgammaRIIIb-NA1 displays a more efficient interaction with IgG1- and IgG3-opsonized bacteria, compared with the FcgammaRIIIb-NA2. We investigated a 70-year-old Japanese population (n = 599) to determine whether the FcgammaRIIIb polymorphism was associated with resistance to periodontitis. Among subjects with > or = 20 teeth present, periodontitis-resistant (n = 46) and periodontitis-susceptible groups (n = 73) were selected based on the percentage of sites with > or = 4 mm probing attachment loss in the entire dentition. The FcgammaRIIIb-NA1 allotype was overrepresented in the periodontitis-resistant group, compared with the periodontitis-susceptible group (chi2 = 4.89, p = 0.03, odds ratio = 1.87, 95% CI, 1.07 to 3.28). This suggests that FcgammaRIIIb-NA1 may be associated with resistance to periodontitis.

Familial and genetic determinants of systemic markers of inflammation: the NHLBI family heart study

Inflammation is thought to play a central role in the etiology and outcome of atherosclerosis. Animal studies as well as in vitro and in vivo human studies suggest that host factors modulate the magnitude and extent of inflammatory responses. We investigated familial aggregation of three systemic markers of inflammation (C-reactive protein (CRP), white blood cell count (WBC), and albumin) in a large, cross-sectional study conducted in four US communities. We found evidence of substantial heritability (35-40%) for CRP levels as well as for WBC and albumin levels. Negligible spouse correlations suggested little influence of shared household environment on these traits. The combination of sociodemographic factors (age, center, education), behavioral and lifestyle factors (cigarette smoking, alcohol intake, hormone replacement therapy), obesity and fat patterning, and prevalent diabetes explained 13-30% the interindividual variability of these traits. There was no evidence that these inflammation phenotypes were linked to a microsatellite marker in the interleukin-1 gene cluster on chromosome 2q, a region that includes several candidate genes for chronic inflammatory diseases. Our findings suggest that CRP levels, albumin levels, and WBC are determined at least partially by genetic factors. Further efforts to identify gene loci affecting these traits are warranted.

Interleukin 1 signal transduction--current concepts and relevance to periodontitis

This review examines a well-characterized factor, interleukin 1 (IL-1), that has recently received considerable attention. A level of understanding is emerging that goes beyond simple recognition that IL-1 plays a role in disease, and begins to explain the molecular mechanisms of function. This review summarizes some current information on the importance of IL-1 in periodontitis as well as the signal transduction of IL-1, from binding to its cell-surface receptors, to the activation of cytoplasmic mediators and transcription factors responsible for the induction of target genes. The effect of IL-1 signal transduction is ultimately the activation and repression of specific transcription factors that regulate genes responsible for cellular activities. As additional steps of signal transduction become better-characterized, these insights may facilitate the development of improved therapeutic approaches for controlling inflammation and connective tissue destruction in a variety of diseases.

Radiographic patterns of periodontitis in cats: 147 cases (1998-1999)

OBJECTIVE

To determine patterns of alveolar bone loss (periodontitis) and other lesions evident on full-mouth survey radiographs of cats.

DESIGN

Retrospective study.

ANIMALS

147 cats.

PROCEDURE

Full-mouth radiographs were evaluated for evidence and severity of alveolar bone loss, odontoclastic resorption lesions (ORL), retained roots, missing teeth, signs of endodontic disease secondary to periodontitis, and apical resorption.

RESULTS

106 (72%) cats had some degree of periodontitis, 100 (68%) were missing teeth, 98 (67%) had ORL, 78 (53%) had expansion of the buccal alveolar bone at 1 or more canine teeth, 75 (51%) had retained roots, 48 (33%) had apical resorption, and 12 (8%) had signs of endodontic disease secondary to periodontitis. Cats < 4 years old were not significantly more likely than the general population to have normal alveolar bone height. Prevalence of ORL increased with age, but cats > or =13 years old were less likely than the general population to have moderate or severe generalized periodontitis. Purebred cats were not significantly more likely to have periodontitis or ORL than mixed-breed cats.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that periodontitis is common in cats and that horizontal bone loss is the most common radiographic pattern of alveolar bone loss. Purebred cats were not more likely than mixed-breed cats to have ORL or periodontitis, but when they did have periodontitis, it was more likely to be moderate to severe. Cats with ORL were less likely than cats without ORL to have normal alveolar bone height and more likely to have severe focal vertical bone loss.

Focus on primary care: periodontal disease: implications for women's health

A definite relationship is emerging between periodontal infections and systemic conditions. The objective of this review is to address this relationship as it pertains to cardiovascular disease and diabetes mellitus. Furthermore, because recent reports link the presence of periodontal disease to preterm delivery, the possible relationship between the development and progression of periodontal disease and certain hormonal states in women such as puberty, oral contraceptive use, menopause, and pregnancy will also be discussed. Although the current literature suggests a strong association between periodontal disease and a number of the discussed systemic conditions, causality can only be established with prospective studies. Intervention studies are needed to address how treatment effects the incidence and/or severity of periodontal disease-related systemic illness.

Polymorphism in regulatory gene sequences

The extensive polymorphism revealed in non-coding gene-regulatory sequences, particularly in the immune system, suggests that this type of genetic variation is functionally and evolutionarily far more important than has been suspected, and provides a lead to new therapeutic strategies.

Nonsurgical periodontal therapy in 2000: a literature review

BACKGROUND

This article addresses the advantages and limitations of nonsurgical periodontal therapies to treat patients with mild-to-moderate chronic periodontitis.

TYPES OF STUDIES REVIEWED

Controlled clinical trials were selected that assessed the efficacy of the following treatment methods: mechanical instrumentation, ultrasonic débridement, supragingival irrigation, subgingival irrigation, local drug delivery, administration of systemic antibiotics and host-response modulation. Evidently, data with regard to alterations of probing depth, clinical attachment levels and inflammatory status were evaluated.

RESULTS

Comparison of the data from test and control groups revealed the following results. Manual and ultrasonic débridement can be used to treat most patients with mild-to-moderate chronic periodontitis. Patients who do not practice optimal plaque control can enhance their personal hygiene procedures by using supragingival irrigation. Subgingival irrigation usually does not provide any benefit beyond that achieved with root planing. Systemic and locally delivered antimicrobial agents appear to be most beneficial among patients who do not respond to conventional treatment. Host modulation may enhance root planing modestly.

CLINICAL IMPLICATIONS

The data indicate that most patients with mild-to-moderate periodontitis can be treated with nonsurgical therapies. However, clinicians need to be aware of the limitations of each technique with regard to the magnitude of improvement that it can induce at specific sites.

Polymorphisms in the IL-1A gene are correlated with levels of interleukin-1alpha protein in gingival crevicular fluid of teeth with severe periodontal disease

Interleukin-1 (IL-1) is a potent stimulator of bone resorption and is strongly implicated in the destruction due to bystander damage seen in periodontal disease. Recent studies suggest that polymorphisms of the (IL-1) gene complex may be significant risk factors for a number of chronic inflammatory diseases. The severity of periodontal disease has been positively associated with carriage of allele 2 at position -889 of the IL-1A gene in conjunction with allele 2 of the IL-1B gene at position +3953. In this study, we tested the hypothesis that allele 2 of the IL-1A gene at position -889 might act to elevate levels of IL-1alpha protein in patients with periodontal disease. Since levels of IL-1alpha protein are low in healthy individuals, we used a group of patients with severe periodontal disease to investigate if levels of IL-1alpha protein in gingival crevicular fluid can be correlated to patient genotype. IL-1alpha levels were measured by enzyme immunoassay in 46 patients with severe periodontal disease. These patients were genotyped by PCR and allele-specific restriction digests. The carriage rate for allele 2 in the diseased population was 68%. Overall, the carriage of allele 2 was associated with almost a four-fold increase in IL-1alpha protein levels. Differences were most pronounced in non-smokers, while heavy smokers showed reduced levels of IL-1alpha protein regardless of genotype. These results suggest a mechanism whereby this genetic polymorphism acts to modulate IL-1alpha protein production and may influence the pathogenesis of periodontal disease by affecting the extent of IL-1-associated bystander damage.

Evidence of a substantial genetic basis for risk of adult periodontitis

BACKGROUND

A few previous studies have suggested that risk for adult periodontitis (AP) has a genetic (heritable) component. We estimated genetic and environmental variances and heritability for gingivitis and adult periodontitis using data from twins reared together.

METHODS

One hundred seventeen (117) pairs of adult twins (64 monozygotic [MZ] and 53 dizygotic [DZ] pairs) were recruited. Probing depth (PD), attachment loss (AL), plaque, and gingivitis (GI) were assessed on all teeth by two examiners. Measurements were averaged over all sites, teeth, and examiners. Extent of disease in subjects was defined at four thresholds: the percentage of teeth with AL > or = 2, AL > or = 3, PD > or = 4, or PD > or = 5 mm. Genetic and environmental variances and heritability were estimated using path models with maximum likelihood estimation techniques.

RESULTS

MZ twins were more similar than DZ twins for all clinical measures. Statistically significant genetic variance was found for both the severity and extent of disease. AP was estimated to have approximately 50% heritability, which was unaltered following adjustments for behavioral variables including smoking. In contrast, while MZ twins were also more similar than DZ twins for gingivitis scores, there was no evidence of heritability for gingivitis after behavioral covariates such as utilization of dental care and smoking were incorporated into the analyses.

CONCLUSIONS

These results confirm previous studies and indicate that approximately half of the variance in disease in the population is attributed to genetic variance. The basis for the heritability of periodontitis appears to be biological and not behavioral in nature.

Advances in periodontology

Advances in periodontal science and practice over the last decade have radically changed the understanding of periodontal diseases and have opened new, exciting prospects for both medical and surgical therapy of periodontal diseases. Establishment of the aetiology and pathogenesis of periodontitis, understanding of the unique genetic and environmental susceptibility profile of affected subjects, and recognition of the systemic implications of periodontal infections are the key research findings. The use of randomised, controlled, clinical trials has allowed the development of evidence-based periodontology. Adjunctive antimicrobial therapy, regenerative periodontal surgery, periodontal plastic surgery, bone regeneration surgery in the light of implant treatment, and advanced soft tissue management at implant sites have radically changed practice.

An IL6 promoter polymorphism is associated with a lifetime risk of development of Kaposi sarcoma in men infected with human immunodeficiency virus

Kaposi sarcoma (KS) is an angioproliferative inflammatory condition that occurs commonly in patients infected with human immunodeficiency virus (HIV). Inflammatory cytokines and growth factors promote the development of KS. Because physiologically important cytokine polymorphisms modulate host inflammatory responses, we investigated the association between KS and common regulatory polymorphisms in 5 proinflammatory cytokine genes encoding interleukin (IL) IL-1α, IL-1β, tumor necrosis factor (TNF) α, TNF-β, and IL-6 and in the IL-1 receptor antagonist (IL1RN). We also examined the contribution of stromal-derived factor 1 and chemokine receptor 5 (Δ32) polymorphisms to KS development. The population consisted of 115 HIV-infected men with KS and 126 deceased HIV-infected men without KS. The only strong association was observed between an IL6promoter polymorphism (G-174C) and susceptibility to KS in HIV-infected men (P = .0035). Homozygotes for IL6 allele G, associated with increased IL6 production, were overrepresented among patients with KS (P = .0046), whereas allele C homozygotes were underrepresented (P = .0062). Substantial in vitro evidence indicates that IL-6 contributes to the pathogenesis of KS. Our results show thatIL6 promoter genotypes associated with altered gene expression are risk factors for development of KS. Identification of a genetic risk factor for development of KS has important clinical implications for prevention and therapy.

An IL6 promoter polymorphism is associated with a lifetime risk of development of Kaposi sarcoma in men infected with human immunodeficiency virus

Kaposi sarcoma (KS) is an angioproliferative inflammatory condition that occurs commonly in patients infected with human immunodeficiency virus (HIV). Inflammatory cytokines and growth factors promote the development of KS. Because physiologically important cytokine polymorphisms modulate host inflammatory responses, we investigated the association between KS and common regulatory polymorphisms in 5 proinflammatory cytokine genes encoding interleukin (IL) IL-1α, IL-1β, tumor necrosis factor (TNF) α, TNF-β, and IL-6 and in the IL-1 receptor antagonist (IL1RN). We also examined the contribution of stromal-derived factor 1 and chemokine receptor 5 (Δ32) polymorphisms to KS development. The population consisted of 115 HIV-infected men with KS and 126 deceased HIV-infected men without KS. The only strong association was observed between an IL6promoter polymorphism (G-174C) and susceptibility to KS in HIV-infected men (P = .0035). Homozygotes for IL6 allele G, associated with increased IL6 production, were overrepresented among patients with KS (P = .0046), whereas allele C homozygotes were underrepresented (P = .0062). Substantial in vitro evidence indicates that IL-6 contributes to the pathogenesis of KS. Our results show thatIL6 promoter genotypes associated with altered gene expression are risk factors for development of KS. Identification of a genetic risk factor for development of KS has important clinical implications for prevention and therapy.

Genetic control of susceptibility to Porphyromonas gingivalis-induced alveolar bone loss in mice

Periodontal disease affects a large percentage of the human population. Resorption of the alveolar bone of the jaw is a pivotal sequela of periodontal disease, because this bone is the attachment site for the periodontal ligaments that anchor the teeth. Using a murine model in which alveolar bone loss is induced by oral infection with Porphyromonas gingivalis, a gram-negative bacterium associated with human adult periodontal disease, we provide evidence suggesting that susceptibility to such bone loss is a genetically determined trait. AKR/J, DBA/2J, and BALB/cByJ or BALB/cJ mice were highly susceptible, while A/J, A/HeJ, 129/J, SJL/J, and C57BL/6J mice were much more resistant. When susceptible BALB/cJ and BALB/cByJ mice were crossed to resistant strains, two patterns were observed. (BALBc/ByJ x C57BL/6J)F(1) offspring were susceptible, suggesting C57BL/6J has recessive resistance alleles, while (BALB/cJ x A/J)F(1) mice were all resistant, suggesting that A/J mice have dominant resistance alleles. These results suggest a tractable genetic basis for P. gingivalis-induced alveolar bone loss and open the possibility of exploiting the mouse model to identify loci important for host susceptibility and resistance to periodontal disease.

The Fcgamma receptor genotype as a risk factor for generalized early-onset periodontitis in Japanese patients

BACKGROUND

Genetic polymorphisms of immunoglobulin G (IgG) Fc receptors (FcgammaR) were recently shown to be associated with recurrence rates of adult periodontitis (AP). The purpose of this study was to evaluate whether FcgammaR polymorphisms are also associated with generalized early-onset periodontitis (G-EOP) in Japanese patients.

METHODS

Thirty-eight Japanese patients with G-EOP and 83 Japanese patients with AP were identified according to established clinical criteria, including measurements of probing depth, clinical attachment level, and alveolar bone level. FcgammaR genotypes for 3 bi-allelic polymorphisms were determined in these G-EOP and AP patients and 104 race-matched healthy controls by means of allele-specific polymerase chain reactions.

RESULTS

There was a significant difference in the distribution of FcgammaRIIIb genotypes between G-EOP patients and healthy controls (P = 0.02). Additionally, a significant over-representation of FcgammaRIIIb-NA2 allele was observed in G-EOP patients as compared to AP patients and controls (P= 0.02, P= 0.009, respectively). Moreover, we found a strong association between G-EOP and the composite genotype comprising FcgammaRIIIb-NA2 and FcgammaRIIIa-158F (G-EOP versus controls: odds ratio 2.4, 95% CI 1.0-6.0, chi2 = 4.13, P= 0.04).

CONCLUSIONS

This study indicates that the FcgammaRIIIb-NA2 allele and possibly FcgammaRIIIa-158F could be associated with susceptibility to G-EOP in Japanese patients.

Neither IL-1beta, IL-1 receptor antagonist, nor TNF-alpha polymorphisms are associated with susceptibility to COPD

The cytokines that contribute to airway inflammation, including interleukin-1beta (IL-1beta) and tumour necrosis factor alpha (TNFalpha), might have key roles in the development of chronic obstructive pulmonary disease (COPD). Interleukin-1 receptor antagonist (IL-1RN), the physiological antagonist of IL-1beta, is also known to play a crucial role in several chronic inflammatory diseases. In this study, we investigated the association of the polymorphisms of IL-1beta, IL-1RN and TNFalpha with susceptibility to COPD. To elucidate the genotype of the IL-1beta polymorphisms at position -511 base and at the amino acid residue 105, the IL-1RN polymorphism in intron 2, and TNFalpha polymorphism at position -308, polymerase chain reaction (PCR) and restriction enzyme fragment length polymorphism (RFLP) were performed on blood samples from both patients with COPD (n = 53) and control subjects (n = 65). There were no differences on the allele and genotype frequency of IL-1beta, IL-1RN, and TNFalpha between the two groups. We could not find a significant link between the polymorphism of TNFalpha, which was previously reported to be associated with chronic bronchitis, and COPD. Furthermore, no association between genetic polymorphisms of IL-1beta and IL-1RN and individual susceptibility to COPD was found.

Cytokine responses to treponema pectinovorum and treponema denticola in human gingival fibroblasts

Human gingival fibroblasts were challenged with Treponema pectinovorum and Treponema denticola to test three specific hypotheses: (i) these treponemes induce different cytokine profiles from the fibroblasts, (ii) differences in cytokine profiles are observed after challenge with live versus killed treponemes, and (iii) differences in cytokine profiles are noted from different gingival fibroblast cell lines when challenged with these treponemes. Three normal gingival fibroblast cell cultures were challenged with T. pectinovorum and T. denticola strains, and the supernatants were analyzed for cytokine production (i.e., interleukin-1alpha [IL-1alpha], IL-1beta, IL-6, IL-8, IL-10, gamma interferon, macrophage chemotactic protein 1 [MCP-1], platelet-derived growth factor, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor). Unstimulated fibroblast cell lines produced IL-6, IL-8, and MCP-1. T. pectinovorum routinely elicited the greatest production of these cytokines from the fibroblast cell lines, increasing 10- to 50-fold over basal production. While T. denticola also induced IL-6 and IL-8 production, these levels were generally lower than those elicited by challenge with T. pectinovorum. MCP-1 levels were significantly lower after T. denticola challenge, and the kinetics suggested that this microorganism actually inhibited basal production by the fibroblasts. No basal or stimulated production of the other cytokines was observed. Significant differences were noted in the responsiveness of the various cell lines with respect to the two species of treponemes and the individual cytokines produced. Finally, dead T. pectinovorum generally induced a twofold-greater level of IL-6 and IL-8 than the live bacteria. These results supported the idea that different species of oral treponemes can elicit proinflammatory cytokine production by gingival cells and that this stimulation did not require live microorganisms. Importantly, a unique difference was noted in the ability of T. pectinovorum to induce a robust MCP-1 production, while T. denticola appeared to inhibit this activity of the fibroblasts. While the general cytokine profiles of the fibroblast cell cultures were similar, significant differences were noted in the quantity of individual cytokines produced, which could relate to individual patient variation in local inflammatory responses in the periodontium.

The role of immune responses in bone loss during periodontal disease

A network of cytokines and other soluble mediators unites the immune system and bone; bacterial infections induce immune responses which may perturb this network. Periodontal diseases are Gram-negative infections resulting in bone loss in the jaw. Evidence is presented that immune responses to these infections produces net resorption of bone.

The mouthwash: a non-invasive sampling method to study cytokine gene polymorphisms

BACKGROUND

We describe a simple, non-invasive mouthwash sampling method for rapid DNA isolation to detect cytokine gene polymorphisms. In the present paper, interleukin- 1beta(IL-1B) and interleukin-1 receptor antagonist (IL-1RN) gene polymorphisms were studied.

METHODS

Two mouthwash samples and blood samples were collected from 11 healthy individuals. The second mouthwash sample was stored for 7 days at room temperature. Polymerase chain reaction amplification was used to identify a bi-allelic polymorphism at position +3953 in the IL-1B gene and a variable number of tandem repeats (VNTR) polymorphism in the IL-1RN gene.

RESULTS

Our results show that the typing of these cytokine gene polymorphisms using DNA isolated from mouthwash samples did not differ from those obtained by a phenol/chloroform isolation method from EDTA anti-coagulated blood. Moreover, reliable results from mouthwash samples were obtained after storage for at least 7 days at room temperature.

CONCLUSIONS

Mouthwash can be the method of choice to study gene polymorphisms in periodontitis and other chronic inflammatory diseases.

Periodontal disease and atherosclerotic cardiovascular disease: confounding effects or epiphenomenon?

Recent evidence suggests that periodontal disease may predispose to atherosclerotic cardiovascular disease. Data support mechanisms of host-derived local and systemic proinflammatory responses similar to atherosclerosis, consisting of monocytic-derived cytokines and other inflammatory mediators, which are induced by periodontal pathogens and its endotoxin, lipopolysaccharide. These mechanisms may contribute to the start of vascular endothelial dysfunction and further sequelae leading to atherosclerosis. Experimental evidence and biologic plausibility appear to support this proposal. However, clinical evidence from a MEDLINE search from January 1966-December 1999 proposed a weak or no correlation primarily due to confounding factors. The aim of care is to reduce vulnerable pathogens from the infected periodontium by standard treatment; however, new approaches appear promising. Increased awareness of a potential link among infective agents, immunoinflammatory processes, and atherosclerosis may clarify clinical implications.

Neutrophils die in the gingival crevice, periodontal pocket, and oral cavity by necrosis and not apoptosis

BACKGROUND

Neutrophils play important roles in the homeostasis of periodontal tissues. However, remarkably little is known about how these cells live and die in the gingival crevice and periodontal pocket. We have examined whether subgingival neutrophils die by necrosis or apoptosis and have begun to study the mechanisms controlling the functional lifespan of these cells.

METHODS

Neutrophils collected from clinically healthy gingival crevices, periodontal pockets, and the oral cavity (saliva) were examined with Hoechst dye 33342, propidium iodide/eithidium bromide, and FITC-annexin V to identify live, dead, and apoptotic cells. Blood neutrophils were cultured for 17 to 20 hours in the presence or absence of gingival crevice washings (GC-w) to study the effect of GC-w on neutrophil apoptosis. In addition, endotoxin was removed from GC-w by affinity resin to investigate the contribution of LPS to the inhibitory effect of GC-w on blood neutrophils.

RESULTS

The percentage of dead neutrophils in all subgingival sites and in all oral samples far exceeded the percentage of apoptotic neutrophils. In all 3 locations, approximately 30% of neutrophils were dead, whereas less than 1% of neutrophils were apoptotic. We conclude that the majority of neutrophils which lose their viability within gingival crevices, periodontal pockets and the oral cavity die by necrosis and not by apoptosis. Washings obtained from clinically healthy gingival crevices (GC-w) variably, but significantly, delayed apoptosis of peripheral blood neutrophils (mean suppression 45.7% +/- SD 22.3). Removal of endotoxin from GC-w significantly reduced this inhibitory effect.

CONCLUSIONS

Our findings provide insights into the mechanisms of neutrophil death and the control of the functional lifespan of neutrophils in gingival crevices and periodontal pockets and therefore into the pathogenesis of periodontal diseases.

Adhesion molecule deficiencies increase Porphyromonas gingivalis-induced alveolar bone loss in mice

Alveolar bone resorption can be induced in specific-pathogen-free mice by oral infection with Porphyromonas gingivalis (P. J. Baker, R. T. Evans, and D. C. Roopenian, Arch. Oral Biol. 39:1035-1040, 1994). Here we used a mouse strain, C57BL/6J, which is relatively resistant to P. gingivalis-induced bone loss to examine whether partial or complete deletion of various adhesion molecules would increase susceptibility. Complete deletion of P-selectin or nearly complete lack of expression of intercellular adhesion molecule 1 (ICAM-1) led to increased susceptibility to bone resorption after oral infection, while a hypomorphic defect in beta(2)-integrins did not. Both the total amount of bone lost and the number of sites at which there was significant loss were increased in mice deficient in either ICAM-1 or P-selectin. Each of the three adhesion molecule deficiencies was sufficient to decrease P. gingivalis-specific serum immunoglobulin G responses, but lower antibody titers did not lead to increased bone loss in partially beta(2)-integrin-deficient mice. In conclusion, P-selectin and ICAM-1 deficiencies increase susceptibility to and severity of alveolar bone loss after P. gingivalis infection. This finding underscores the importance of innate immunity in protection against P. gingivalis-induced alveolar bone resorption.

Metabolic diseases and their possible link to risk indicators of periodontitis

BACKGROUND

During the last few years, risk assessment has become one of the main topics of periodontal research. Therefore, the aim of this study was to determine whether a predisposition to metabolic disorders such as diabetes mellitus (in the absence of diagnosed diabetic disease) or hyperlipidemia may be risk indicators for periodontitis.

METHODS

One hundred patients ranging in age from 40 to 70 years were examined. The patients were classified as having impaired glucose tolerance (IGT) but no manifest diabetes (56 patients), hyperlipidemia (17 patients, HL), or normal metabolic status (27 control patients). Probing depth (PD), attachment level (AL), plaque index (PI), and gingival bleeding on probing (BOP) were recorded. Serum antibody titers (SAT) to A. actinomycetemcomitans (A.a.), P. intermedia (P.i.), and P. gingivalis (P.g.) were determined by enzyme-linked immunosorbent assay (ELISA). Pooled subgingival plaque samples were analyzed using indirect immunofluorescence to detect the same organisms. In addition, respiratory burst activity of peripheral polymorphonuclear leukocytes (PMN) was evaluated by chemiluminescence (CL).

RESULTS

No significant differences were observed between the IGT group and normal controls in the following parameters: 1) percentage of sites exhibiting BOP; 2) mean PI; 3) mean PD and AL; 4) percentage of periodontal microorganisms; and 5) increased SAT. The IGT probands exhibited a significantly higher mean serum level of triglycerides, as well as higher formyl-methionyl-leucyl-phenylalanine (FMLP)-stimulated PMN chemiluminescence than the control group. Patients with hyperlipidemia (HL) showed a significantly higher number of sextants with increased PD (73.4%) than the control group (50.6%). Similar results were obtained when comparing the percentage of all sites with increased PD (HL = 16.7%, control 12.3%). The mean FMLP-stimulated CL in patients with hyperlipidemia was significantly higher than the control group. When looking at all patients, there was a small but statistically significant correlation between PD and lipid levels. In addition, a significant correlation was observed between lipid serum levels and the FMLP-stimulated chemiluminescence.

CONCLUSIONS

These findings suggest that abnormal glucose tolerance, which is a predisposing factor for diabetes mellitus, does not appear to be a risk indicator for periodontal disease. On the other hand, impaired lipid metabolism does seem to be a risk indicator for periodontitis.

Periodontal disease: bacterial virulence factors, host response and impact on systemic health

Teeth are coated with a biofilm that contains periodontal pathogens. Pathogens express virulence factors which enable them to invade and replicate within epithelial cells and to invade the underlying connective tissue. This stimulates production of prostaglandins and cytokines that induce tissue loss. In addition, these bacteria have the potential to modulate the course of systemic diseases such as atherosclerosis and to contribute to low birthweight and preterm labor.

The interleukin-1 and interleukin-10 gene polymorphisms in primary sclerosing cholangitis: no associations with disease susceptibility/resistance

BACKGROUND/AIMS

Although primary sclerosing cholangitis is believed to be an autoimmune disorder, no tissue-specific auto-antibodies have yet been identified, and the strongest support for an autoimmune aetiology comes from HLA-association studies. Three different HLA haplotypes are associated with susceptibility to the disease and one with protection from it. These HLA haplotypes, however, do not account for all of the disease risk and genes outside the HLA region may also have a role in disease pathogenesis. The aim of this study was to investigate, for the first time, polymorphic genes/sites within the interleukin-1 and interleukin-10 genes in a large well-characterised group of patients.

METHODS

Ninety-six patients and 96 control subjects were studied. A single base-exchange polymorphism at position +3953 in the first exon of the IL-1B gene, a penta-allelic repeat sequence in the IL-1 receptor antagonist gene (IL-1RN) and three single base-exchange polymorphisms at positions -592, -819 and -1082 in the IL-10 gene promoter were determined by standard PCR-based techniques.

RESULTS

Overall, there was no significant difference in the distribution of any of the IL-1B, IL-1RN or IL-10 alleles or genes sequences comparing patients and controls. In addition, there was no difference when the patients were stratified for the presence and absence of the HLA DRB1*0301 (DR3) allele or concurrent inflammatory bowel disease.

CONCLUSION

Neither the IL-1B +3953, IL-1RN microsatellites polymorphisms on chromosome 2q13 nor the IL-10 -592, -819, -1082 promoter gene polymorphisms on chromosome 1q31-32 are associated with susceptibility or resistance to primary sclerosing cholangitis.

Interleukin-1 and the immunogenetics of Alzheimer disease

Established genetic causes of familial Alzheimer disease (AD) involve genes for beta-amyloid precursor protein (betaAPP), presenilin-1, and presenilin-2. For the more common sporadic forms of AD, increased risk has been associated with a number of genes; the most important of which is the epsilon4 allele of apolipoprotein E. Two recent studies, one clinical and one using postmortem material, now show increased risk for AD associated with certain polymorphisms in the genes encoding the alpha and beta isoforms of interleukin-1 (IL-1). IL-1 levels are elevated in Alzheimer brain, and overexpression of IL-1 is associated with beta-amyloid plaque progression. IL-1 interacts with the gene products of several other known or suspected genetic risk factors for AD, including betaAPP, apolipoprotein E, alpha1-antichymotrypsin, and alpha2-macroglobulin. IL-1 overexpression is also associated with environmental risk factors for AD, including normal aging and head trauma. These observations suggest an important pathogenic role for IL-1, and for IL-1-driven cascades, in the pathogenesis of AD.

Genetic polymorphisms of the IL-1alpha and IL-1beta genes in African-American LJP patients and an African-American control population

BACKGROUND

A functional polymorphism of the interleukin-1 beta (IL-1beta) gene has been proposed to be a risk factor for periodontitis. In adult forms of periodontitis, non-smokers of northern European heritage carrying the "2" allele of the IL-1alpha-889 and the IL-1beta +3953 RFLPs in either the heterozygous or the homozygous state at both loci were observed to have a greater risk for developing severe periodontitis. Studies of early-onset periodontitis (EOP) found that allele "1" of both IL-1alpha-889 and IL-1beta +3953 was transmitted more frequently with the EOP phenotype. The purpose of the present study was to determine the prevalence of the IL-1alpha and IL-1beta genotype polymorphisms in an African-American (AA) control population and in 37 African-Americans with localized juvenile periodontitis (LJP).

METHODS

The IL-1alpha +4845 and IL-1beta +3953 loci were genotyped by PCR amplification, followed by restriction enzyme digestion and gel electrophoresis. The IL-1alpha +4845 locus, in linkage disequilibrium (>99%) with IL-1alpha-889, was genotyped because it is technically easier. Data were analyzed using r x c contingency tables.

RESULTS

The IL-1beta +3953 allele "1" was carried by >99% of the AA control population and by 100% of the AA LJP group, with most individuals being homozygous 1,1. The prevalence of the composite genotype with at least one allele "2" at each of the IL-1beta +3953 and IL-1alpha +4845 loci was 14% (AA control group) and 8% (AA LJP group).

CONCLUSIONS

Given the high frequency of the IL-1beta allele "1" in the African-American population, it would appear that knowledge of this +3953 polymorphism would provide little diagnostic or predictive information for LJP.

The prevalence of pathogenic periodontal microflora in healthy young adult smokers

BACKGROUND

Smoking is a major risk factor in periodontitis, although the mechanisms of its effects are not well understood. The overall goal of this clinical study was to determine if smoking enhances the colonization of the oral cavity by pathogenic bacteria in a periodontitis-free population. The prevalence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, Campylobacter rectus, Eikenella corrodens, Bacteroides forsythus, and Treponema denticola was investigated in 25 smokers and 25 non-smokers by using DNA probes.

METHODS

The subjects were 21 to 35 years of age with a healthy periodontium or slight gingivitis and were systemically healthy. The test group included subjects who had a minimum of a 1.5 pack-year history of smoking, while the control subjects never smoked. Subgingival plaque samples were taken by paper point following the assessment of multiple clinical parameters.

RESULTS

This investigation showed: 1) no statistically significant differences were noted in any clinical parameter measured between the groups; 2) of the 8 subjects who were infected by at least 1 tested pathogen, seven were smokers (P= 0.02); 3) infected smokers had a 15.7+/-3.5 pack-year history and smoked a mean of 27+/-5 cigarettes/day versus 4.4+/-0.8 pack years and 15+/-1 cigarettes/day for the non-infected smokers (P = 0.0001 and P = 0.004); and 4) smokers were 18 times more likely to exhibit the presence of pathogens than non-smokers.

CONCLUSIONS

These data indicate that the prevalence of colonization of the sulcus by pathogenic bacterial species in periodontitis-free individuals is related to the quantity and duration of cigarette smoking.

Interleukin-1 gene polymorphisms and long-term stability following guided tissue regeneration therapy

BACKGROUND

Specific interleukin (IL)-1 gene polymorphisms are associated with an increased susceptibility to severe periodontitis, increased inflammation, and increased likelihood of tooth loss during the maintenance phase after conventional periodontal therapy. The aim of the present study was to evaluate the impact of genotype on the maintenance of gained clinical attachment obtained after guided tissue regeneration (GTR) surgical therapy in deep intrabony defects.

METHODS

Forty deep (> or =4 mm) interproximal angular bony defects with presurgical clinical attachment loss of >8 mm were treated by GTR using a non-absorbable expanded polytetrafluoroethylene (ePTFE) membrane. Membranes were surgically removed 4 to 6 weeks after surgery. Afterwards patients were placed on monthly recall for the first year and every 3 months for the following 3 years. At the 4-year re-evaluation, a IL-1 genetic susceptibility test was performed on all patients.

RESULTS

Fourteen (35% of the 40 patients) were genotype-positive (+). At baseline no statistically significant differences were found between patients with different genotypes in full mouth plaque score (FMPS), full mouth bleeding score (FMBS), clinical attachment level (CAL), probing depth (PD), or gingival recession. At year 1 follow up visit, no statistically significant differences were noted between genotype + and genotype - patients in FMPS, FMBS, amount of CAL gain, decrease in PD, or increase in gingival recession. Sixteen patients had membrane exposure after the GTR procedures. In these patients, the amount of CAL gain (P <0.001) and PD reduction (P <0.01) 1 year after surgery was significantly lower than those observed in patients without membrane exposure. At the year 4 follow-up visit, no significant differences were found between genotype negative and positive patients in FMPS or FMBS and both groups showed a significant loss in CAL (P<0.001) and increase in PD (P<0.001) when compared to year 1 visit. No change in gingival recession was noted. Genotype + patients showed significantly more CAL loss (P<0.002) and increase in PD (P<0.001) between the years 1 and 4 when compared to genotype - patients. A significant association between genotype and stability of the regenerated attachment was also demonstrated.

CONCLUSIONS

The results of this study demonstrate that genotype expression did not effect GTR treatment response at 1 year, but had a great impact on long-term stability (year 4). In a 3-year period, patients with positive IL-1 genotype lost about 50% of the first year gained CAL and were about 10 times more likely of experiencing > or = 2 mm CAL loss when compared to oral hygiene matched genotype-negative patients.

The impact of molecular genetics on oral health paradigms

As a result of our increased understanding of the human genome, and the functional interrelationships of gene products with each other and with the environment, it is becoming increasingly evident that many human diseases are influenced by heritable alterations in the structure or function of genes. Significant advances in research methods and newly emerging partnerships between private and public sector interests are creating new possibilities for utilization of genetic information for the diagnosis and treatment of human diseases. The availability and application of genetic information to the understanding of normal and abnormal human growth and development are fundamentally changing the way we approach the study of human diseases. As a result, the issues and principles of medical genetics are coming to bear across all disciplines of health care. In this review, we discuss some of the potential applications of human molecular genetics for the diagnosis and treatment of oral diseases. This discussion is presented in the context of the ongoing technological advances and conceptual changes that are occurring in the field of medical genetics. To realize the promise of this new molecular genetics, we must be prepared to foresee the possibilities and to incorporate these newly emergent technologies into the evolving discipline of dentistry. By using examples of human conditions, we illustrate the broad application of this emerging technology to the study of simple as well as complex genetic diseases. Throughout this paper, we will use the following terminology: Penetrance--In a population, defined as the proportion of individuals possessing a disease-causing genotype who express the disease phenotype. When this proportion is less than 100%, the disease is said to have reduced or incomplete penetrance. Polymerase chain reaction (PCR)--A technique for amplifying a large number of copies of a specific DNA sequence flanked by two oligonucleotide primers. The DNA is alternately heated and cooled in the presence of DNA polymerase and free nucleotides, so that the specified DNA segment is denatured, hybridized with primers, and extended by DNA polymerase. MIM--Mendelian Inheritance in Man catalogue number from V. McKusick's Mendelian Inheritance in man (OMIM, 1998).

Clinical and genetic analysis of a large North European Caucasian family affected by early-onset periodontitis

Genetic studies of early-onset periodontitis (EOP) are hampered by several factors. These include delayed onset of the trait, an upper age limit of expression of the disease, and lack of phenotypic information for edentulous family members. Segregation analyses of families with EOP support a major locus hypothesis but fail to define clearly the criteria used for diagnosis of the relatives. Confirmation of a proposed mode of inheritance and the identification of risk genes is awaited by means of family linkage studies. It is suggested that a system can be developed for the current and retrospective diagnosis of relatives of EOP probands. In addition, it is hypothesized that the large family presented here is suitable for a linkage study. Relatives of the proband who were unavailable for a full periodontal examination, were edentulous, or were deceased, were diagnosed by means of documented clinical evidence of periodontal disease or from reported case histories. Segregation analysis was performed. Analysis of the power of the pedigree to detect linkage was carried out by means of the SIMLINK program. Three different categories were defined according to the reliability of diagnosis of EOP. Segregation analysis indicated either autosomal-dominant or X-linked-dominant inheritance in this family. The simulations showed lod scores above 3.0 for all locations of the disease gene, and for each category of diagnosis. In conclusion, a method has been developed which can be used for the diagnosis of relatives of EOP probands when ideal clinical data are unavailable. The simulations suggest that this family is suitable for a genetic linkage study with the aim of identifying the location of one or more susceptibility genes.

Interleukin-1 genetic association with periodontitis in clinical practice

BACKGROUND

Periodontitis is a bacterial disease modified by multiple risk factors. The pro-inflammatory cytokine interleukin- (IL-1) is a key regulator of the host responses to microbial infection and a major modulator of extracellular matrix catabolism and bone resorption. It has been reported that variations in the IL-1 gene cluster on chromosome 2 are associated with increased susceptibility to severe adult periodontitis.

METHODS

The present study evaluated the association between a composite IL-1 genotype, including allele 2 at each of two loci (IL-1A +4845 plus IL- B +3954), and a broad spectrum of periodontally healthy to diseased patients in a population that is typically encountered in a dental practice setting. Ninety patients, non-smokers or former smokers with less than 10 pack-year (pk/yr) history, were recruited from a private dental practice. The major outcome variable was bone loss determined by computerized linear measurements of radiographs. Genotypes were analyzed from finger-stick blood samples using previously reported methods.

RESULTS

Multivariate logistic regression models demonstrated that patient age, former smoking history, and the IL-1 genotype were significantly associated with severity of adult periodontitis. For non-smokers or former light smokers (<5 pk/yr), IL-1 genotype positives were at increased odds ratio of having moderate to severe periodontal disease of 3.75 (95% CI: 1.04-13.50) to 5.27 (95% CI: 1.23-22.70), depending on ethnicity, compared to IL-1 genotype negatives. Former moderate smokers (>5 pk/yr and <10 pk/yr) who were IL-1 genotype negative were at increased odds ratio of having moderate to severe periodontal disease of 7.43 (95% CI: 1.20-46.20) compared to non-smokers or former light smokers who were IL-1 genotype negative. In addition, past smoking history was also a significant effect modifier as demonstrated by the statistically significant interaction between past smoking history status and IL-1 genotype status.

CONCLUSIONS

This study demonstrates that the composite IL-1 genotype is significantly associated with the severity of adult periodontitis. It also confirmed that both IL-1 genotyping and smoking history provide objective risk factors for periodontal disease in a private practice environment.

Low prevalence of a periodontitis-associated interleukin-1 composite genotype in individuals of Chinese heritage

BACKGROUND

Polymorphisms in the interleukin-1 (IL-1) gene cluster have been associated with an increased risk of developing certain diseases. A specific composite genotype of IL-1A and IL-1B polymorphisms, consisting of allele 2 of both IL-1A +4845 and IL-1B +3954 (formerly +3953) has been associated with an increased risk of severe adult periodontitis. Approximately 30% of the European population carry this genotype. The prevalence of the above IL-1A and IL-1B composite genotype in populations of different ethnic origins is unknown. Therefore, the primary aim of this study was to determine the prevalence of the IL-1 composite genotype in individuals of Chinese heritage, since epidemiologic studies indicate that periodontitis is widespread among ethnic Chinese. An additional aim was to evaluate if there was an association between the composite genotype and the severity of periodontal disease.

METHODS

A convenience sample of 300 volunteers of Chinese heritage (ages 21 to 69 years) received a periodontal examination including full-mouth clinical attachment loss measurements, probing depths, plaque index scores, and bleeding on probing. Blood was collected from a fingerstick and placed on a blotting paper card. The blood samples were analyzed for IL-1A +4845 and IL-1B +3954 polymorphisms using polymerase chain reaction (PCR)-based methods.

RESULTS

Only 7 of the 300 subjects (2.3%) carried the composite IL- 1 genotype consisting of allele 2 of both IL-1A +4845 and IL-1B +3954. Allele 2 of the IL-1A +4845 polymorphism was carried by 17.0% (51/300) of the subjects; of these, only 2 were homozygous. Allele 2 of the IL-1B +3954 polymorphism was much rarer with only 3.3% (10/300) of the study population carrying this marker. All of the people who carried the IL-1B polymorphism were heterozygous. Too few of the subjects were positive for the IL-1 composite genotype to establish any relationship with the susceptibility to periodontitis.

CONCLUSIONS

It was concluded that the prevalences of both IL-1A and IL-1B polymorphisms are dramatically lower in Chinese than those reported for Europeans. Findings from this study bring into question the usefulness of the composite genotype of allele 2 of both IL-1A +4845 and IL-1B +3954 as a method for determining the susceptibility of Chinese patients to adult periodontitis.

The impact of advances in dental sciences on primary dental care

The next century will see phenomenal changes especially and, most importantly, in patient empowerment, in the improvement of health in the disadvantaged, and in the harmonisation of standards of healthcare throughout the world. Advances in the dental sciences will facilitate these improvements but the major changes surely will be largely stimulated and motivated by the information revolution and the advances in molecular and materials sciences. The identification, and protection against disease, of patients who, because of a genetic predisposition, are at particular risk of disease is likely to become possible. Simple, sensitive, effective, non-invasive and safe diagnostic procedures will become available, as will chairside diagnostic test kits that would identify specific microorganisms causal of oral disease. The advances in digital imaging will be taken further and linked to record-keeping. Specific safe agents targeted at responsible microorganisms will be devised, and systems to deliver therapeutic agents effectively and prevent tissue damage simply will be perfected. Painless, minimally-invasive techniques for the removal of diseased oral tissues will become available, as will biocompatible materials for replacement of lost oral tissues.

Lowered yields of virus-induced interferon production in leukocyte cultures and risk of recurrent respiratory infections in children

OBJECTIVE

To study the correlation between the yield of virus-induced interferon (IFN) production in leukocyte cultures and the risk of recurrent respiratory infections.

METHODS

A sample of 71 consecutive children enrolled in the Finnish Otitis Media Cohort Study were selected. Children suffering from frequently recurring respiratory infections (FRRIs) were defined as the highest quintile of the entire cohort of 329 children, as regards the number of upper respiratory infections (URIs) and/or episodes of acute otitis media (AOM) during the follow-up period from 2 to 24 months.

RESULTS

In the sample of 71 children, there were 18 children with FRRI (> or = 9 URI and/or > or = 4 AOM). Leukocyte cultures, prepared from blood drawn from these 18 children at 6 months of age, produced lower yields of IFN than those of the remaining 53 children, when stimulated with adenovirus (P <0.001), coronavirus (P<0.001) or rhinovirus (P=0.002). The difference in IFN yields was even greater (P<0.001 with all three viruses) if the comparison was made between children with FRRI and those with no or maximally one URI during the follow-up period. When the IFN production capacity induced by rhinovirus was measured at the age of 24 months, a statistically significant difference between the children with FRRI and the others was also seen (P=0.002). Influenza A virus-induced IFN production capacity did not differ between the groups at either age (P=0.209).

CONCLUSIONS

Lowered IFN responses in children suffering from recurrent URIs and/or AOM may, in a subgroup of the children, be due to a genetic property of the child. However, because of the great interindividual variations, we cannot use the IFN production capacity as such for prediction of forthcoming respiratory infections and/or otitis media.

Early-onset periodontitis

In 1993, the 1st European Workshop on Periodontology explicitly recognized that there was insufficient knowledge to differentiate truly different forms of periodontal disease from differences in the presentation/severity of the same disease. In spite of recent progress in our understanding of periodontal diseases, the issue is far from having been resolved. Classification of periodontal diseases, therefore, remains based upon the definition of specific clinical syndromes. Early-onset periodontitis (EOP) is one such syndrome and comprises a group of pathological conditions leading to loss of periodontal tissues early in life. The notion that classifies periodontitis syndromes as "early-onset" or "adult" is primarily epidemiological in nature and is based on the observation that periodontitis is rather infrequent in children and young adults. Nevertheless, considerable epidemiological evidence indicates that periodontitis does affect children and young adults to a level of severity that may lead to premature exfoliation of primary and/or permanent teeth. Clinical presentation of periodontitis early in the life of an individual is thought to indicate that the etiologic agents have been able to cause considerable tissue damage over a relatively short period of time. It also implies either infection with highly virulent bacteria and/or a highly susceptible subject. The purpose of this review is to discuss the criteria generally utilized to classify EOP, provide the rationale to designate EOP as a distinct disease entity, and to review the evidence justifying a subclassification into particular subgroups of EOP.

Interleukin-1 haplotype and periodontal disease progression following therapy

The purpose of this study was to assess the prognostic value of the IL-1 haplotype on the progression of periodontal disease following therapy. 48 adult patients with untreated periodontitis harboring Actinobacillus actinomycetemcomitans and/or Porphyromonas gingivalis were randomly assigned to receive full-mouth scaling alone (control) or in combination with systemic metronidazole plus amoxicillin and supragingival irrigation with chlorhexidine digluconate (test). All patients received supportive periodontal therapy at 3 to 6 months intervals. In 33 patients, lymphocyte DNA was analyzed for polymorphism in the IL-1A gene at position -889 and IL-1B gene at position +3953. Overall, 16 of 33 patients (7 of 17 test and 9 of 16 control) carried the IL-1 haplotype. 2 years following initial periodontal therapy, no differences in the survival rates of sites or teeth not exhibiting probing attachment loss of 2 mm or more compared to baseline, were found between patients who tested positive (85% sites, 53% teeth) and patients who tested negative (89% sites, 56% teeth) for the IL-1 haplotype. The results indicated that the IL-1 haplotype may be of limited value for the prognosis of periodontal disease progression following non-surgical periodontal therapy.

Increased interleukin-1beta concentration in gingival crevicular fluid as a characteristic of periodontitis

BACKGROUND

The levels of interleukin-1beta (IL-1beta) have been reported to be higher in sites with periodontitis than in healthy controls. This may be the result of a more severe inflammation and/or constitutional differences in IL-1beta production. Our aim was to test the hypothesis that the level of IL-1beta in gingival crevicular fluid (GCF) is a characteristic trait of periodontitis, regardless of the degree of tissue destruction. As a secondary aim, we investigated the correlation between IL-1beta and neutrophil elastase. An untreated population was used.

METHODS

GCF samples from inflamed sites in 13 patients with gingivitis (GG), and from inflamed sites with shallow (GP) and deep (PP) pockets in 18 patients with periodontitis were collected. Interleukin-1beta, elastase-alpha-1-antitrypsin complex (E-A1AT), alpha-1-antitrypsin (A1AT), and alpha-2-macroglobulin (A2MG) were measured with ELISA. Elastase activity was measured with a specific substrate.

RESULTS

The concentration of IL-1beta was significantly higher in PP than in GG, but no significant differences were detected between PP and GP. A weak positive correlation between the elastase activity and IL-1beta was also observed. The elastase activity had a tendency to be higher in PP, although no significant difference was found among the 3 groups. The concentrations of E-A1AT, A1AT, and A2MG were similar in the 3 types of sites.

CONCLUSIONS

The levels of IL-1beta in GCF were increased in samples from periodontitis patients, regardless of the severity of disease at the sampled site, suggesting that the levels of IL-1beta are typical of a given patient.

Association between periodontitis and hyperlipidemia: cause or effect?

BACKGROUND

Epidemiological studies suggest a relationship between periodontitis and coronary artery disease, but the mechanism has not been established. Recent studies in animals indicate that low dose endotoxin, as in a gram-negative infection, can induce hyperlipidemia and myeloid cell hyperactivity. The association between periodontitis, systemic exposure to Porphyromonas gingivalis, lipopolysaccharides (LPS), and hyperlipidemia has not been examined in humans.

METHODS

Sera were obtained from 26 adult periodontitis patients and 25 healthy control (C) subjects selected from patients and staff. Serum antibodies against Porphyromonas gingivalis and its LPS were analyzed by enzyme-linked immunosorbent assay (ELISA) and Western blotting, respectively. Serum triglycerides (TG) and cholesterol (CHOL) were assayed by a commercial laboratory. The associations between AP and blood levels of TG, CHOL, and anti-P. gingivalis whole cells and LPS were examined by logistic regression analysis. Peripheral blood polymorphonuclear leukocytes (PMNs) from 6 healthy fasted donors were incubated with purified TG (0.1 mg/ml) for 2 hours at 37 degrees C, stimulated with 100 ng/ml P. gingivalis LPS, and the release of IL-1beta measured by ELISA.

RESULTS

The presence of periodontitis was significantly associated with age (odds ratio = 3.5, P = 0.04), elevated TG levels (odds ratio = 8.6, P = 0.0009), elevated CHOL levels (odds ratio = 7, P = 0.004), elevated ELISA titer (odds ratio = 35, P = 0.003) and reactivity with P. gingivalis LPS (odds ratio = 41, P = 0.001). PMNs from all 6 healthy patients released modest levels of IL-1beta (10 to 60 pg/ml) when stimulated with 100 ng/ml P. gingivalis LPS. Addition of TG resulted in a significant increase (P <0.05) in IL- 1beta secreted that ranged from 7 to 150% over LPS alone. No IL-1beta was elicited by TG or vehicle alone.

CONCLUSIONS

The results of this study indicate the presence of a significant relationship between periodontitis, hyperlipidemia, and serum antibodies against P. gingivalis LPS that warrants further examination in a larger patient population. Furthermore, these studies indicate that elevated triglycerides are able to modulate IL-1beta production by PMNs stimulated with P. gingivalis LPS.

Molecular genetics and nomenclature of proteases of Porphyromonas gingivalis

The strategies used by bacterial pathogens to establish and maintain themselves in the host represent one of the fundamental aspects of microbial pathogenesis. Characterization of these strategies and the underlying molecular machinery offers new opportunities both to our understanding of how organisms cause disease in susceptible individuals and to the development of novel therapeutic measures designed to undermine or interfere with these determinants of successful survival. With respect to the microbial aetiology of the periodontal diseases, a growing body of evidence suggests that the proteolytic enzymes of Porphyromonas gingivalis represent key survival and, by extrapolation, virulence determinants of this periodontal bacterium. This in turn has led to international efforts to characterize these enzymes at the gene and protein level. Approximately 20 protease genes of P. gingivalis with different names and accession numbers have been deposited in the gene databases and a correspondingly heterogeneous nomenclature system is employed for the products of these genes in the literature. However, it is evident, through comparison of these gene sequences and through gene inactivation studies, that the genetic structure of the proteases of this organism, particularly those with specificity for arginyl and lysyl peptide bonds, is less complicated than originally thought. The major extracellular and surface associated arginine specific protease activity is encoded by 2 genes which we recommend be designated rgpA and rgpB (arg-gingipains A & B). Similarly we recommend that the gene encoding the major lysine specific protease activity is designated kgp (lys-gingipain). These three genes, which account for all the extracellular/surface arginine and lysine protease activity in P. gingivalis, belong to a family of sequence-related proteases and haemagglutinins.

Milestones in periodontal research and the remaining critical issues

A significant recent development in periodontal research has been the convergence of basic and clinical research resulting in a logarithmic increase in the rate of progress. Scientific consensus has been reached in many areas. In most populations, moderate to severe periodontitis affects a relatively small segment of adults who are at high risk. The microbial etiology is accepted and the identity of the major pathogenic bacterial species is known. The mechanisms through which resistant individuals successfully fend off the microbial challenge are known, and the immuno-inflammatory pathways activated by bacteria that underlie destruction of the alveolar bone and the connective tissues of the periodontium are reasonably well understood. The evidence shows that these pathways are held in common by all forms of periodontitis. Therapeutic modulation of these pathways is now possible, and new treatments based on such modulation are now becoming available. Although bacteria are essential for disease to occur, they are insufficient; a susceptible host is also necessary. Host susceptibility, disease progression and response to treatment are determined predominantly by heredity and environmental and acquired risk factors. Some of these can be changed while others are immutable. Concepts and procedures for treatment are generally scientifically based and appropriately applied. Preventive measures are largely successful and widely practiced in industrialized countries. Clearly, control of these ancient chronic diseases is now within our reach. In spite of the tremendous progress, many unresolved issues remain. The purpose of this paper is to summarize some of the major accomplishments of periodontal research, and identify and discuss some of the more important critical issues that still need to be addressed.

Interleukin-1 genotypes and the association between periodontitis and cardiovascular disease

An epidemiological association between periodontitis and cardiovascular disease has been reported in multiple studies. Various mechanisms have been proposed as potential explanations for this association, including a common factor that predisposes certain individuals to a hyper-responsive inflammatory response. Variations in the genes that regulate the interleukin-1 (IL-1) response have been associated with both periodontal disease and cardiovascular disease. New data indicate that one pattern of IL-1 genetic polymorphisms, characterized by the IL-1A (+4845) and IL-1B (+3954) markers, is associated with periodontitis but not certain measures of atherosclerosis. Another IL-1 genetic pattern, characterized by the IL-1B (-511) and IL-1RN (+2018) markers, is associated with atherosclerotic plaque formation, as measured by angiography and arterial wall thickness, but not periodontitis. These two patterns also have different functional implications relative to IL-1 biological activity. Studies of IL-1 gene polymorphisms, atherosclerotic plaque instability and cardiovascular clinical events are in progress. Hypothetical models are presented to explain how IL-1 genetic factors may be involved in cardiovascular disease.

Periodontal attachment loss in HIV-infected patients is associated with the major histocompatibility complex 8.1 haplotype (HLA-A1,B8,DR3)

Periodontal attachment loss is mediated by overproduction of tumour necrosis factor (TNF) and interleukin (IL)-1, and appears to have a genetic component. The 8.1 major histocompatibility complex (MHC) ancestral haplotype (HLA-A1,B8,TNFA-308(2),DR3) is associated with elevated TNF production and predisposes carriers to several autoimmune/immunopathological disorders, including rapid progression of HIV disease, but not early onset periodontal disease in healthy individuals. Rather a high proportion of subjects with severe periodontal disease carry allele 2 at IL-1A-889 and IL-1B+3953. We predicted that genetic associations may be different or clearer in HIV patients, as they often show elevated production of TNF and IL-1 and periodontal attachment loss. Hence periodontal parameters and IL-1 polymorphisms were assessed in HIV-positive subjects expressing HLA-B8 with or without other markers of the 8.1 haplotype. Of 16 HLA-B8 subjects, 13 demonstrated elevated probing pocket depth and clinical attachment loss. The difference was statistically significant and did not correlate with smoking, age, CD4 T-cell counts, HIV viral load or levels of dental plaque. As TNFA-308 (allele 2) was present in four non-B8 subjects who had minimal attachment loss, it may not mediate the effect of the 8.1 haplotype. Moreover, polymorphisms at IL-1A-889 and IL-1B+3953 did not significantly affect periodontal parameters. Thus a central MHC gene characteristic of the 8.1 haplotype was the clearest determinant of periodontal attachment loss in HIV-infected individuals.

Association of a vitamin D receptor gene polymorphism with localized early-onset periodontal diseases

BACKGROUND

Early-onset periodontal diseases (EOP) are caused by interactions between host factors, specific microbial pathogens, and environmental factors. It is, therefore, of interest to investigate the nature of host factors as they may provide useful risk markers and reveal important information regarding the disease pathogenesis. Genetic polymorphisms in the vitamin D receptor (VDR) gene are associated with parameters of bone homeostasis and with diseases in which bone loss is a cardinal sign, in particular osteoporosis. Rapidly progressive bone loss is one feature of EOP. We, therefore, sought to determine whether EOP is associated with a polymorphism in the VDR gene.

METHODS

A restriction fragment length polymorphism (RFLP) for Taq I in exon nine of the VDR gene was analyzed by PCR, followed by restriction digestion with Taq I and gel electrophoresis. We analyzed the genotypes of 69 EOP patients, including 20 patients with unequivocal evidence of localized disease (L-EOP), and 72 controls with no history of EOP.

RESULTS

The genotype distribution in the L-EOP patient group was 7 (35%), 5 (25%) and 8 (40%) and in the control group 31 (43.1%), 36 (50.0%) and 5 (6.9%) for TT, Tt and tt respectively (where t and T represent the alleles with and without the Taq I RFLP respectively). Chi2 analysis indicated that the distribution of the genotypes between these two groups was highly significantly different (P = 0.001). Allele frequencies were 47.5% and 52.5% for T and t in the L-EOP group; 68.1% and 31.9% in the control group, showing a significant association between the prevalence of the less frequent allele (t) and L-EOP (P = 0.017). There was no significant difference in the genotype distribution or the allele frequencies between the control samples and the larger EOP patient group (n = 69) which included patients with generalized and localized disease.

CONCLUSIONS

These data indicate that carriage of the less frequent allele of the Taq I RFLP (t) in the VDR gene significantly increases the risk of developing L-EOP. However, VDR genotype may not affect the incidence of all cases of EOP. These findings contribute to our understanding of the genetic basis for periodontal disease and may help define sub-groups of this disease which share common pathogenic factors.

Relevance of Fc gamma RIIIa-158V-F polymorphism to recurrence of adult periodontitis in Japanese patients

The immunoglobulin receptor Fc gamma RIIIa (CD16) is distributed on natural killer (NK) cells, macrophages, and gamma delta T cells, and is polymorphic. Fc gamma RIIIa-158V has a higher affinity for both monomeric and immune complexed IgG1, IgG3, and IgG4 than IIIa-158F. We determined Fc gamma RIIIa-158V/F genotypes of Japanese patients with adult periodontitis. A significant over-representation of Fc gamma RIIIa-158F was found in patients with recurrence, compared with patients without recurrence, making Fc gamma RIIIA a candidate gene for recurrence risk of adult periodontitis.