Interleukin-1 haplotype and periodontal disease progression following therapy

The Role of Polymorphisms at the Interleukin-1, Interleukin-4, GATA-3 and Cyclooxygenase-2 Genes in Non-Surgical Periodontal Therapy

Periodontitis is a multifactorial disease. The aim of this explorative study was to investigate the role of Interleukin-(IL)-1, IL-4, GATA-3 and Cyclooxygenase-(COX)-2 polymorphisms after non-surgical periodontal therapy with adjunctive systemic antibiotics (amoxicillin/metronidazole) and subsequent maintenance in a Caucasian population. Analyses were performed using blood samples from periodontitis patients of a multi-center trial (ClinicalTrials.gov NCT00707369=ABPARO-study). Polymorphisms were analyzed using quantitative real-time PCR. Clinical attachment levels (CAL), percentage of sites showing further attachment loss (PSAL) ≥1.3 mm, bleeding on probing (BOP) and plaque score were assessed. Exploratory statistical analysis was performed. A total of 209 samples were genotyped. Patients carrying heterozygous genotypes and single-nucleotide-polymorphisms (SNP) on the GATA-3-IVS4 +1468 gene locus showed less CAL loss than patients carrying wild type. Heterozygous genotypes and SNPs on the IL-1A-889, IL-1B +3954, IL-4-34, IL-4-590, GATA-3-IVS4 +1468 and COX-2-1195 gene loci did not influence CAL. In multivariate analysis, CAL was lower in patients carrying GATA-3 heterozygous genotypes and SNPs than those carrying wild-types. For the first time, effects of different genotypes were analyzed in periodontitis progression after periodontal therapy and during supportive treatment using systemic antibiotics demonstrating a slight association of GATA-3 gene locus with CAL. This result suggests that GATA-3 genotypes are a contributory but non-essential risk factor for periodontal disease progression.

Association of susceptible genotypes to periodontal disease with the clinical outcome and tooth survival after non-surgical periodontal therapy: A systematic review and meta-analysis

Background

The real clinical utility of genetic testing is the prognostic value of genetic factors in the clinical outcome of periodontal treatment and the tooth survival. A meta-analysis was undertaken to estimate the effect of a susceptible genotype to periodontitis on the clinical outcomes of non-surgical periodontal therapy and the tooth survival.

Material and Methods

A systematic search of MEDLINE-Pubmed, Cochrane Library and Scopus was performed. Additionally, a hand search was done in three journals. No specific language restriction was applied. Two reviewers screened independently titles and abstracts or full text copies. Quality assessment of all the included studies was held.

Results

Initial screening of electronic databases resulted in 283 articles. Ten studies met the inclusion criteria, nine of them examined the clinical outcome, while the other one investigated the tooth survival in susceptible individuals after non-surgical periodontal therapy. Eight of included studies were selected for the meta-analysis. IL-1 positive genotypes increase the risk of tooth loss, while no association found between the bleeding on probing (BOP), clinical attachment loss (CAL) and plaque index (PI) with the genotype status. Probing pocket depth (PPD) reduction in the first three months and in long-term results found to have a significant association with the genotype.

Conclusions

There is no difference in the clinical measurements after non-surgical periodontal treatment, apart from PPD. More publications are needed to identify a cause-effect relationship.

Key words:Periodontal disease, periodontitis, periodontal therapy, clinical outcome, tooth loss, susceptibility, polymorphism, genotype, meta-analysis, systematic review.

Interleukin-1 gene polymorphisms and chronic periodontitis in adult whites: a systematic review and meta-analysis

BACKGROUND

Interleukin-1 (IL-1) gene polymorphisms have been associated with increased levels of inflammatory mediators and several inflammatory diseases. Periodontitis is a bacterially induced chronic inflammatory disease that destroys the connective tissues and bone that support the teeth, affects substantial numbers of adults, and has been implicated as a contributing factor in systemic diseases. IL-1 gene polymorphisms, most prominently IL1A (-889), IL1A (+4845), and IL1B (+3954), have been associated with chronic periodontitis (CP) in whites. Since the first report, ≥125 studies have examined IL-1 gene variation in relation to periodontal disease. These studies have produced mixed findings in diverse periodontal phenotypes and in different ethnic groups. One previous meta-analysis has been published on this topic and supported an association between IL-1 genes and periodontitis, but considerable doubt remains about the patient populations in which the association may be of clinical relevance.

METHODS

A systematic review and meta-analysis was conducted in an attempt to clarify whether IL-1 gene variants were associated with well-defined clinical phenotypes of CP in white patients. Study inclusion criteria focused on the analytic framework originally proposed for the IL-1 genetic effect in which overexpression of inflammatory mediators is hypothesized to result in more severe periodontitis in response to a bacterial challenge.

RESULTS

Twenty-seven studies were included in the qualitative analysis. Nineteen studies yielded significant associations between carriage of the minor IL-1 alleles and periodontitis. The meta-analysis, based on 13 qualifying studies, found significant effects for the two individual gene variations (IL1A odds ratio [OR] = 1.48; IL1B OR = 1.54) and for a composite genotype that combines minor alleles at each locus (OR = 1.51). Statistically significant heterogeneity was found that could not be explained, but there was no indication of publication bias.

CONCLUSION

This review and meta-analysis show that IL1A and IL1B genetic variations are significant contributors to CP in whites.

IL-1-polymorphism and severity of periodontal disease

OBJECTIVE

To determine the association between the interleukin (IL)-1-polymorphism and the severity of periodontal disease prior to active periodontal therapy.

MATERIALS AND METHODS

Two hundred and six patients with obtained baseline x-rays were tested for IL-1-polymorphism. Relative bone loss before active periodontal treatment was measured with a Schei ruler and classified in five groups. Descriptive statistics and backward stepwise linear regression analyses were performed.

RESULTS

Forty-nine patients with moderate (mChP), 79 with severe chronic (sChP) and 78 with aggressive periodontitis (AgP) were included. Age correlated significantly with bone loss and number of teeth at baseline. Gender, smoking and IL-1-polymorphism were neither associated with bone loss nor with number of teeth prior to treatment. After adjusting for age as well as gender, AgP was significantly associated with more severe bone loss in untreated periodontal disease (p = 0.036). In non-smokers, mean number of teeth prior to active periodontal therapy correlated significantly with presence of IL-1 polymorphism.

CONCLUSION

The IL-1-polymorphism is associated with lower number of teeth in non-smokers with untreated periodontal disease. Untreated AgP is associated with more severe bone loss than untreated ChP.

The Effect of Interleukin-1 Allele 2 Genotype (IL-1a−889 and IL-1b+3954) on the Individual's Susceptibility to Peri-Implantitis: Case-Control Study

Individuals bearing the combination of interleukin (IL)-1 allele 2 at IL-1A−889 and IL-1B+3954 are referred to as being genotype positive and are susceptible to increased periodontal tissue destruction. The aim of this study was to assess the possible association of IL-1 allele 2 (IL-1A−889 and IL-B+3954) genotypes with the severity of peri-implantitis progression and the effect of this combination on treatment outcomes. Fifty patients with International Team for Implantology implants were studied; patients ranged in age from 35–55 years, and each patient had 1 implant. According to peri-implant tissue status, patients were divided into 2 groups: group I consisted of 25 patients with peri-implantitis, and group II comprised 25 patients with healthy peri-implant tissue. Clinical parameters were assessed at baseline and after 3 and 6 months. Epithelial cells were collected from the oral mucosa by plastic spatula and were used for IL-1 genotyping by the polymerase chain reaction technique. Group I patients were subjected to a peri-implantitis treatment and maintenance program. In all, 17 patients from group I and 5 patients from group II were genotype positive, with a statistically significant difference noted between the 2 groups. Group I genotype-positive patients presented with higher scores and measurements of clinical parameters with increased suppuration from peri-implant tissues compared with group II; differences were statistically significant (P < .05). In terms of response to treatment, genotype-negative patients demonstrated better response than genotype-positive patients. The combination of IL-1 allele 2 (IL-1A−889 and IL-1B+3954) in patients with inflamed periodontal or peri-implant tissues acts as a risk factor that leads to greater tissue destruction. IL-1 gene polymorphism at IL-1A−889 and IL-1B+3954 may affect outcomes of treatment for peri-implantitis in genotype-positive individuals.

Polymorphisms in the interleukin-1 (IL1) gene cluster are not associated with aggressive periodontitis in a large Caucasian population

Polymorphisms in the interleukin-1 (IL1) gene have been suggested to influence transcription of IL1A (interleukin-1alpha) and IL1B (interleukin-1beta) and thereby the pathophysiology of periodontitis. This case-control association study on 415 northern European Caucasian patients with aggressive periodontitis (AgP) and 874 healthy controls was conducted to examine 10 single-nucleotide polymorphisms (SNPs) in the genes of the IL1 cluster for association with IL1A, IL1B, CKAP2L (cytoskeleton-associated protein 2-like), and IL1RN (IL-1 receptor antagonist). The results do not support an association between variants in the IL1 gene cluster and AgP. This case-control study had at least 95% power to detect genuine associations with variants carrying relative risks of at least 1.5 for heterozygous carriers and 2.25 for homozygous carriers. Previous reports of an association between IL1 promoter SNPs and periodontitis might reflect subpopulation effects and have to be interpreted with care.

Salivary enzyme levels after scaling and interleukin-1 genotypes in Japanese patients with chronic periodontitis

BACKGROUND

Saliva has been used as a diagnostic fluid in medicine and dentistry. It is easy to collect using non-invasive methods. The intracellular enzymes present in saliva have been studied as markers of periodontal disease. The purpose of this study was to determine the salivary enzyme levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) after scaling and to clarify the influence of interleukin (IL)-1 genotypes on these enzyme levels.

METHODS

Forty-nine Japanese patients with chronic periodontitis (24 men and 25 women; mean age: 55.1 years) were enrolled in this study. Measurements of clinical parameters including probing depth (PD), clinical attachment level (CAL), and bleeding on probing (BOP) and collections of stimulated whole mixed saliva were performed at baseline and 4 weeks after scaling. After evaluation of salivary AST, ALT, and LDH levels, DNA was extracted from various cells in whole saliva. IL-1A+4845 G/T genotype was determined by polymerase chain reaction amplification, followed by enzyme digestion and electrophoresis. Statistical analysis was performed by the Wilcoxon signed-rank and Mann-Whitney U tests. A significant difference was set at P <0.05.

RESULTS

Mean PD, CAL, and BOP values significantly decreased after scaling (mean +/- SE: 3.2 +/- 0.1 mm to 2.6 +/- 0.1 mm in PD; 3.9 +/- 0.2 mm to 3.3 +/- 0.2 mm in CAL; and 41% +/- 4% to 18% +/- 3% in BOP) (P <0.001). The values of AST, ALT, and LDH were 77.0 +/- 7.5, 43.9 +/- 5.5, and 753.4 +/- 96.5 (units per liter [U/l]) at baseline, and significantly decreased to 55.5 +/- 6.5, 30.0 +/- 5.5, and 394.7 +/- 34.0 (U/l) after scaling, respectively (P = 0.01, P = 0.006, and P <0.001). The carriage rate of the IL-1A+4845 allele 2 was 24.5%. No difference was noted in the decrease in PD, CAL, and BOP after scaling between the carriers (N = 12) and non-carriers (N = 37) of IL-1A+4845 allele 2. However, the IL-1A allele 2 non-carriers displayed a significant decrease in salivary AST and ALT levels (P <0.001), in contrast to the carriers who did not show any changes in the salivary levels of the enzymes after scaling.

CONCLUSIONS

These results documented that salivary AST, ALT, and LDH levels reflect inflammation and destruction of periodontal tissue, suggesting clinically useful markers following periodontal therapy. In addition, although IL-1A+4845 alleles may not influence clinical parameters, they may influence post-scaling values of salivary AST and ALT.

The association of the composite IL-1 genotype with periodontitis progression and/or treatment outcomes: a systematic review

BACKGROUND

Genetically transmitted traits such as cytokine gene polymorphisms may accentuate the host inflammatory response to the bacterial challenge and influence susceptibility to periodontitis.

OBJECTIVE

To systematically review the evidence of an association between the interleukin-1 (IL-1) composite genotype, i.e. presence of the allele 2 in the gene clusters IL-1A-889 and in IL-1B +3953, and periodontitis progression and/or treatment outcomes.

MATERIAL AND METHODS

Based on the focused question, a search was conducted for longitudinal clinical trials comparing progression of periodontitis and/or treatment outcomes in IL-1 genotype-positive (carrying allele 2) and IL-1 genotype-negative (not carrying allele 2) subjects. A search in the National Library of Medicine computerized bibliographic database MEDLINE and a manual search were performed. Selection of publications, extraction of data and validity assessment were made independently by two reviewers.

RESULTS

The search provided 122 titles of which 11 longitudinal publications were included. The heterogeneity of the data prevented the performance of a meta-analysis. While findings from some publications rejected a possible role of IL-1 composite genotype on progression of periodontitis after various therapies, other reported a prognostic value for disease progression of the positive IL-1 genotype status. When assessed on a multivariate risk assessment model, several publications concluded that the assessment of the IL-1 composite genotype in conjunction with other covariates (e.g. smoking and presence of specific bacteria) may provide additional information on disease progression. The small sample size of the available publications, however, requires caution in the interpretation of the results.

CONCLUSION

Based on these findings, (i) there is insufficient evidence to establish if a positive IL-1 genotype status contributes to progression of periodontitis and/or treatment outcomes. Therefore, (ii) results obtained with commercially available tests should be interpreted with caution.

No correlation of five gene polymorphisms with periodontal conditions in a Greek population

BACKGROUND

Various studies have examined possible correlations between a number of cytokine gene polymorphisms and periodontal disease in populations of different origins. The present study sought the correlation between four single-nucleotide polymorphisms (IL1A+3954, IL1B+4845, TNFA-308, COL1A1 Sp1), a variable number of tandem repeats polymorphism (IL1RN intron 2) and periodontal conditions in subjects of Greek origin.

METHODS

One hundred and ninety-two healthy subjects, stratified as non-periodontitis and periodontitis (chronic and aggressive) cases, participated in the present study. Genotyping was performed by polymerase chain reaction-based techniques using the primers and conditions described in the literature. The frequencies of genotypes between study groups were compared using Genepop v3.3 genetic software and Instat statistical package.

RESULTS

No differences were observed among the groups concerning the distributions of genotypes under investigation.

CONCLUSIONS

Carriage rates of the polymorphisms under investigation in systemically healthy subjects of Greek origin are well within the range reported for Caucasians but these polymorphisms cannot discriminate between non-periodontitis and periodontitis (chronic or aggressive) cases.

Assessment of single nucleotide polymorphism at IL-1A+4845 and IL-1B+3954 as genetic susceptibility test for chronic periodontitis in Maharashtrian ethnicity

BACKGROUND

The inflammatory response that is directed in large part by proinflammatory cytokine interleukin (IL)-1 is genetically determined, with some people having a more vigorous response than others to the same stimulus. The reason for this is speculated that the dysregulated production of IL-1 in some individuals overrides the feedback mechanisms that normally master the dose of inflammation to a level sufficient to fight microbial invasion without long-lasting damage to the tissues involved. The aims of the present study were to determine the distribution of IL-1 gene polymorphism (IL-1A+4845 and IL-1B+3954) and their association with periodontal disease severity and to determine the significance of detecting the composite genotype (IL-1A allele2+IL-1B allele2) versus detecting either of them alone.

METHODS

A total of 120 subjects were included and divided into four groups of 30 subjects each, namely, healthy, mild, moderate, and severe periodontitis groups. After a complete clinical examination, DNA was isolated from 0.5 ml blood. Specific primers were used to detect the presence of IL-1 gene polymorphism with the help of polymerase chain reaction (PCR) and subsequent allele detection with restriction fragment length polymorphism (RFLP) and separation by gel electrophoresis.

RESULTS

The distribution of the allele1 homozygous genotype was 3% in the severe periodontitis group, and the distribution for the allele2 genotype was 30%. A higly significant difference (Wilcoxon signed-rank test; P<0.001) was seen between subjects positive and negative for the composite genotype.

CONCLUSIONS

Results of the present study reinforced the association of the IL-1 genotype as a risk factor for severe chronic periodontitis. Positivity for the composite genotype was found to be significantly associated with severe chronic periodontitis (odds ratio [OR]=12.42).

Interleukin 1 genetics, inflammatory mechanisms, and nutrigenetic opportunities to modulate diseases of aging

Inflammation plays a central role in many diseases of aging, and genetic differences in the inflammatory response appear to influence different disease courses among individuals. Variations in the genes for the family of interleukin 1 (IL-1) proteins are inherited together in a small set of patterns and provide an example of the role of inflammatory genetics as a modifier of diseases of aging. The IL-1 genetic variations are associated with variation in both the inflammatory response and the clinical presentation of a range of diseases, including coronary artery disease, Alzheimer disease, gastric cancer, and periodontitis. This growing understanding of the role of genetic variation in inflammation and chronic disease presents opportunities to identify healthy persons who are at increased risk of disease and to potentially modify the trajectory of disease to prolong healthy aging. Nutrition represents one of the promising approaches to modulation of the risk of diseases of aging because of the effects of certain nutrients on gene expression. One of the most practical applications of nutritional modulation of chronic disease may be nutrients that regulate the expression of key inflammatory genes.

Disease progression: identification of high-risk groups and individuals for periodontitis

AIMS

While the role of bacteria in the initiation of periodontitis is primary, a range of host-related factors influence the onset, clinical presentation and rate of progression of disease. The objectives of this review are (1) to present evidence for individual predictive factors associated with a patient's susceptibility to progression of periodontitis and (2) to describe the use of prognostic models aimed at identifying high-risk groups and individuals in a clinical setting.

METHODS

Relevant publications in the English language were identified after Medline and PubMed database searches. Because of a paucity of longitudinal studies investigating factors including clinical, demographic, environmental, behavioural, psychosocial, genetic, systemic and microbiologic parameters to identify individuals at risk for disease progression, some association studies were also included in this review.

FINDINGS AND CONCLUSIONS

Cigarette smoking is a strong predictor of progressive periodontitis, the effect of which is dose related. High levels of specific bacteria have been predictive of progressive periodontitis in some studies but not all. Diabetics with poor glycaemic control have an increased risk for progression of periodontitis. The evidence for the effect of a number of putative factors including interleukin-1 genotype, osteoporosis and psychosocial factors is inconclusive and requires further investigation in prospective longitudinal studies. Specific and sensitive diagnostic tests for the identification of individuals susceptible to disease progression are not yet a reality. While factors assessed independently may not be valuable in predicting risk of future attachment loss, the combination of factors in a multifactorial model may be useful in identifying individuals at risk for disease progression. A number of multifactorial models for risk assessment, at a subject level have been developed but require validation in prospective longitudinal studies.

Effect of genetic variability on the inflammatory response to periodontal infection

AIM

To review the association between genetic variability and the inflammatory response induced by periodontal infection.

MATERIAL AND METHODS

A search of MEDLINE-PubMed was performed from January 2000 up to and including March 2005. The search included all types of publications, published in English without other limitations. The following search terms were used: "cytokine polymorphism", "gene polymorphism", "periodontitis", "gingivitis", "inflammation" and "host-response". The papers resulting from the above search were used as an additional source for relevant articles.

RESULTS

Genetic variability was examined for the correlation to clinical indicators of inflammation such as bleeding on probing (BOP), gingival inflammation, cytokine in gingival crevicular fluid (GCF) and cytokine production by inflammatory cells. According to the current literature, most of the studies found no association between genetic variability and BOP, gingival inflammation or cytokine concentrations in the GCF. These studies were hampered by inappropriate study designs and the use of inflammatory parameters as secondary rather than primary outcome variables. The data suggest that the production of inflammatory mediators by inflammatory cells may be affected by different genetic traits but further studies are needed in order to establish this association.

CONCLUSIONS

To date, there is no clear correlation between any of the gene polymorphisms and clinical indicators of inflammation. The powering of studies to reveal associations between single or multiple nucleotide polymorphisms and inflammatory parameters will need to involve a much larger number of subjects than were used in the past. The available data (including the interleukin-1 composite genotype) do not currently support the utility of such tests in the diagnosis and prognostic assessments of periodontal diseases.

Identification of genetic risk factors for periodontitis and possible mechanisms of action

AIM

To review the literature for genetic risk factors associated with periodontitis.

METHODS

Computerized search of the literature in English using key words: Periodontitis; Genes; Mutation; Polymorphism; Risk.

RESULTS AND CONCLUSIONS

Mutations in the cathepsin C gene (CTSC) have been identified as causal for the Papillon-Lefèvre syndrome (PLS), which includes prepubertal periodontitis (PP). Some CTSC mutations are causal for PP without PLS. No relationship has been demonstrated between CTSC mutations and other forms of periodontitis. Genetic polymorphisms in a candidate gene approach have been explored as risk factors for periodontitis. There is limited evidence that some polymorphisms in the genes encoding interleukins (IL)-1, Fc gamma receptors (Fc gammaR), IL-10 and the vitamin D receptor, may be associated with periodontitis in certain ethnic groups. However relatively large variations in carriage rates of the Rare (R)-alleles among studies on any polymorphism were observed. The available studies appear under-powered and do not adequately take into account other pertinent risk factors for periodontitis. Future studies should include larger cohorts, should clearly define phenotypes and should adequately control for other risk factors. In addition to the candidate gene approach, alternative strategies need to be considered to elucidate the gene variations, which confer risk for periodontitis.

Analytical epidemiology of periodontitis

AIMS

To review the literature related to the analytical epidemiology of periodontitis generated over the past decade. This review does not deal with descriptive epidemiologic studies of the prevalence, extent and severity of periodontitis with respect to global geography, but focuses exclusively on analytical epidemiology issues, including the challenges posed by the use of different case definitions across studies, current theories and models of disease progression, and risk factors associated with the onset and progression of periodontitis.

METHODS

Relevant publications in the English language were identified after Medline and PubMed database searches.

FINDINGS AND CONCLUSIONS

There is a conspicuous lack of uniformity in the definition of periodontitis used in epidemiologic studies, and findings from different research groups are not readily interpretable. There is a lack of studies that specifically address the distinction between factors responsible for the onset of periodontitis versus those affecting its progression. Colonization by specific bacteria at high levels, smoking, and poorly controlled diabetes have been established as risk factors for periodontitis, while a number of putative factors, including specific gene polymorphisms, have been identified in association studies. There is a clear need for longitudinal prospective studies that address hypotheses emerging from the cross-sectional data and include established risk factors as covariates along with new exposures of interest. Intervention studies, fulfilling the "targeting" step of the risk assessment process, are particularly warranted. Obvious candidates in this context are studies of the efficacy of elimination of specific bacterial species and of smoking cessation interventions as an alternative to the traditional broad anti-plaque approach in the prevention and control of periodontitis. Ideally, such studies should have a randomized-controlled trial design.

Modulation of Clinical Expression of Plaque-Induced Gingivitis: Interleukin-1 Gene Cluster Polymorphisms

BACKGROUND

The purpose of the present study was to determine the association of interleukin-1 (IL-1) gene polymorphisms with clinical parameters of gingivitis in a large experimental gingivitis trial and with each of two subgroups, high responders (HR) and low responders (LR), with distinct susceptibility to gingivitis.

METHODS

Ninety-six systemically and periodontally healthy non-smokers, 46 males (mean age: 23.9+/-1.7) and 50 females (mean age: 23.3+/-1.6) were included in a randomized, split-mouth, localized 21-day experimental gingivitis trial. Plaque index (PI), gingival index (GI), gingival crevicular fluid volume (GCF), and angulated bleeding score (AngBS) were recorded. Two subgroups were defined from the total study population (HR, LR) characterized by substantially different severity of gingival inflammation despite similar plaque accumulation rate. The study population was typed for interleukin-1 alpha (IL-1A+4845), interleukin-1 beta (IL-1B+3953, IL-1B-511), and IL-1 receptor antagonist (IL-1RN, intron 2 variable number tandem repeats) gene polymorphisms. Gene variants were analyzed by amplifying the polymorphic region using polymerase chain reaction, followed by restriction-enzyme digestion and agarose gel electrophoresis.

RESULTS

Neither IL-1A+4845, IL-1B+3953, or the combined (IL-1A+4845 x 2 - IL-1B+3953 x 2) genotype was associated with clinical parameters in the overall population. IL-1RN was significantly associated with test quadrant PI (P= 0.046), GCF (P= 0.05), and GI (P= 0.018). The genotype distribution in HR and LR subjects was significantly different for IL-1RN (P= 0.045) and for IL-1B-511 (P= 0.023).

CONCLUSION

The results of the present study suggest an association between IL-1RN polymorphism and subject-based clinical behavior of the gingiva in response to de novo plaque accumulation, as well as a possible association between IL-1B-511 polymorphism and gingivitis susceptibility.

Effect of the Interleukin-1 Genotype on Outcomes of Regenerative Periodontal Therapy With Bone Replacement Grafts

BACKGROUND

Previous studies have shown an association between a specific genotype for the inflammatory cytokine interleukin (IL)-1 and the severity of periodontal disease. The purpose of this study was to evaluate the effect of the IL-1 genotype on the outcomes of periodontal surgical regenerative treatment with bone replacement grafts.

METHODS

Forty-four patients with interproximal intrabony defects were treated with bone replacement grafts. Probing depths (PD) and clinical attachment levels (CAL) were measured before treatment and at least 9 months post-treatment. Whole-mouth plaque index (WMPI) and bleeding index (WMBI) were recorded as well. All patients were tested for the IL-1 genotype.

RESULTS

Thirteen (29.55%) of the patients were IL-1 genotype positive. There was no statistically significant difference between the genotype-positive and genotype-negative groups regarding age, smoking status, gender, WMPI, and WMBI. There was no significant difference in PD or CAL between the genotype-positive and genotype-negative groups at baseline. Genotype-positive patients had a smaller reduction in probing depth (1.86 mm versus 2.13 mm) and a greater gain of clinical attachment (1.20 mm versus 0.65 mm). These differences were not statistically significant (P = 0.70, P = 0.40). Multivariate regression analysis showed that presurgical PD significantly influenced post-surgical PD and CAL, and only WMPI significantly influenced CAL.

CONCLUSION

In this study, there was no evidence that the IL-1 genotype influences the clinical treatment outcomes of regenerative periodontal therapy with bone replacement grafts.

Environmental factors and not genotype influence the plasma level of interleukin-1 receptor antagonist in normal individuals

Cytokine production may be regulated by both genotypic (single nucleotide or tandem repeat polymorphisms) and non-genotypic factors relating to the environment and inherent biology (i.e. gender). Interleukin (IL)-1 is one of the body's most highly proinflammatory cytokines and is implicated in the pathophysiology of numerous diseases, but also in the maintenance of homeostasis in a number of tissues. The cytokine IL-1 receptor antagonist (IL-1Ra) is the competitive inhibitor of the IL-1 agonists IL-1alpha and IL-1beta. In vivo IL-1Ra was measured in a cohort of 200 + blood donors and the effect of the IL-1 gene polymorphisms, environmental and biological factors assessed. In this study, we observed that possession of particular alleles of 5 IL-1 gene polymorphisms (IL1A-889, IL1Alpha VNTR, IL1B -511, IL1B +3953 and the IL1RN VNTR) did not correlate with higher plasma IL-1Ra levels. Environmental factors such as smoking and non-steroidal anti-inflammatory drug ingestion were associated with higher in vivo IL-1Ra levels (P = 0.015 and 0.022, respectively), but biological factors such as gender, age and menstruation status did not have any impact upon in vivo IL-1Ra levels. Genotypic associations of IL-1 gene family polymorphisms with disease features may reflect characteristics of stressed rather than normal control circuits for cytokine production.

Genes and gene polymorphisms associated with periodontal disease

The scientific literature during the last ten years has seen an exponential increase in the number of reports claiming links for genetic polymorphisms with a variety of medical diseases, particularly chronic immune and inflammatory conditions. Recently, periodontal research has contributed to this growth area. This new research has coincided with an increased understanding of the genome which, in turn, has permitted the functional interrelationships of gene products with each other and with environmental agents to be understood. As a result of this knowledge explosion, it is evident that there is a genetic basis for most diseases, including periodontitis. This realization has fostered the idea that if we can understand the genetic basis of diseases, genetic tests to assess disease risk and to develop etiology-based treatments will soon be reality. Consequently, there has been great interest in identifying allelic variants of genes that can be used to assess disease risk for periodontal diseases. Reports of genetic polymorphisms associated with periodontal disease are increasing, but the limitations of such studies are not widely appreciated. While there have been dramatic successes in the identification of mutations responsible for rare genetic conditions, few genetic polymorphisms reported for complex genetic diseases have been demonstrated to be clinically valid, and fewer have been shown to have clinical utility. Although geneticists warn clinicians on the over-enthusiastic use and interpretation of their studies, there continues to be a disparity between the geneticists and the clinicians in the emphasis placed on genes and genetic polymorphism associations. This review critically reviews genetic associations claimed for periodontal disease. It reveals that, despite major advances in the awareness of genetic risk factors for periodontal disease (with the exception of periodontitis associated with certain monogenetic conditions), we are still some way from determining the genetic basis of both aggressive and chronic periodontitis. We have, however, gained considerable insight into the hereditary pattern for aggressive periodontitis. Related to our understanding that it is autosomal-dominant with reduced penetrance comes a major clinically relevant insight into the risk assessment and screening for this disease, in that we appreciate that parents, offspring, and siblings of patients affected with aggressive periodontitis have a 50% risk of this disease also. Nevertheless, we must exercise caution and proper scientific method in the pursuit of clinically valid and useful genetic diagnostic tests for chronic and aggressive periodontitis. We must plan our research using plausible biological arguments and carefully avoid the numerous bias and misinterpretation pitfalls inherent in researching genetic associations with disease.

Comparison of interleukin-1 genotypes in two populations with aggressive periodontitis

The genetic association of interleukin-1 (IL-1) with periodontitis has been investigated in different populations. Failure to detect an association with IL-1 genotypes in European Caucasians with aggressive periodontitis (AGP) has recently been reported. No data from Central American Hispanics are available. The purpose of this explorative study was to study the association between IL-1 genotypes and AGP in two populations. Ninety-one subjects, 28 North European patients and 33 controls together with 16 Central American patients and 14 controls were included in the study according to validated radiographic and clinical criteria. Two polymorphisms, IL-1alpha G(+4845)-T and IL-1beta C(+3954)-T were analysed by means of polymerase chain reaction-restriction fragment length polymorphism. The association between presence of specific genotypes and disease status was estimated by the odds ratio. A logistic regression was also used in order to investigate whether the occurrence of the disease depends upon the combination of the IL-1A and IL-1B alleles in the population. A similar distribution of genotypes between patients and controls in both populations was detected. The frequency of allele 1 of the IL-1A gene was higher in patients of both populations compared with controls, however, no statistical significant differences were found between patients and controls.

Position Paper: Diagnosis of Periodontal Diseases

At the present time, the diagnosis and classification of periodontal diseases are almost entirely based on traditional clinical assessments. Supplemental quantitative and qualitative assessments of the gingival crevicular fluid and subgingival microflora can potentially provide useful information about the patient's periodontal disease. In certain situations, these supplemental risk-assessment tests may be particularly valuable in establishing the endpoint of therapy prior to placing patients on a periodontal maintenance program. Although the clinical utility of none of these tests has been validated, their further development is warranted. A genetic test for susceptibility to periodontitis has become commercially available. How best to use this and future host-based tests in clinical practice remains to be determined. Probing depth and clinical attachment loss measurements obtained with periodontal probes are practical and valid methods for assessing periodontal status. Computer-linked, controlled-force electronic periodontal probes are commercially available and are currently in use by some practitioners. Many of the logistical problems associated with subtraction radiography are being overcome and this powerful diagnostic tool may soon come into widespread use. Future developments in this and other imaging techniques are likely to have a profound effect on our approach to the diagnosis of periodontal diseases.

A systematic review on the effect of systemic antimicrobials as an adjunct to scaling and root planing in periodontitis patients

BACKGROUND

Scaling and root planing (SRP) are the bases of non-surgical therapy in the treatment of periodontitis. However, results from this therapy are often unpredictable and dependable from many different factors.

OBJECTIVES

The aim of this systematic review was to evaluate the effectiveness of the adjunctive use of systemic antimicrobials with scaling and root planing (SRP) vs. SRP alone in the treatment of chronic (CP) or aggressive periodontitis (AgP).

SEARCH STRATEGY

Use of computerized databases, namely MEDLINE, the Cochrane Oral Health Group Specialty Trials Register and EMBASE; reference lists from relevant articles were hand-searched; and a hand-search of selected journals until April 2001.

SELECTION CRITERIA

Studies were selected if they were designed as controlled clinical trials in which systemically healthy patients with either AgP or CP were treated with SRP plus systemic antimicrobials in comparison with SRP alone or with placebo, for a minimum of 6 months. Main outcome measures were clinical attachment level (CAL) change and probing pocket depth (PPD) change.

DATA COLLECTION AND ANALYSIS

Two reviewers extracted independently information regarding quality and study characteristics, in duplicate. Kappa scores determined their agreement. Main results were collected and grouped by drug, disease and PPD category. For the quantitative data synthesis, the data was pooled (when mean differences and standard errors were available), and either a Fixed Effects or Random Effects meta-analysis was used for the analysis.

RESULTS

After an initial selection, 158 papers were identified by the manual and electronic searches; 25 papers were eligible for inclusion. Their quality assessment showed that randomization and allocation concealment methods were seldom reported and blindness was usually not defined clearly. In general, selected studies showed high variability and lack of relevant information for an adequate assessment. Overall, SRP plus systemic antimicrobial groups demonstrated better results in CAL and PPD change than SRP alone or with placebo groups. Only limited meta-analyses could be performed, due to the difficulties in pooling the studies and the lack of appropriate data. This analysis showed a statistically significant additional benefit for spiramycin (PPD change) and amoxicillin/metronidazole (CAL change) in deep pockets.

CONCLUSION

Systemic antimicrobials in conjunction with SRP, can offer an additional benefit over SRP alone in the treatment of periodontitis, in terms of CAL and PPD change, and reduced risk of additional CAL loss. However, differences in study methodology and lack of data precluded an adequate and complete pooling of data for a more comprehensive analyses. It was difficult to establish definitive conclusions, although patients with deep pockets, progressive or 'active' disease, or specific microbiological profile, can benefit more from this adjunctive therapy.

The interleukin-1 polymorphism, smoking, and the risk of periodontal disease in the population-based SHIP study

Several studies have shown a role for interleukin-1 gene cluster polymorphisms in the risk assessment for periodontal diseases. In the Study of Health in Pomerania (SHIP), 3148 subjects were randomly selected from the population and assessed for a broad range of diseases and environmental/behavioral risk factors. From the complete study group in the age 40 to 60 years, N = 1085 subjects were genotyped for the interleukin-1 genotype composite polymorphism in relation to periodontal parameters. The study objective was to elucidate the gene-environment interaction between the risk factors smoking and IL-1 polymorphism. An increased risk of periodontal disease was found for IL-1 genotype-positive smokers: odds ratio adjusted for age, sex, education, and plaque OR = 2.50 (95% C.I. 1.21 to 5.13; p = 0.013). This was not the case with subjects who never smoked: OR = 1.09 (0.73-1.62; p = 0.676). These results support the hypothesis of gene-environmental interaction in periodontitis.

Association of the -1087 IL 10 gene polymorphism with severe chronic periodontitis in Swedish Caucasians

BACKGROUND

Severe forms of periodontitis are suggested to have a genetic basis.

OBJECTIVE

The aim of the present investigation was to study association of an IL10 gene polymorphism (G to A transition at the -1087 position) with severe chronic periodontitis.

MATERIALS AND METHODS

Two groups of Swedish Caucasian subjects were included. One group consisted of 60 patients (aged 36-74 years; mean 54.5+/-8.5) with severe and generalized chronic periodontitis. The patients exhibited bone loss >50% at all teeth. Thirty-nine periodontally healthy subjects between 35-78 years of age (mean 51.0+/-10.9) were also recruited. DNA was isolated from peripheral blood cells and genotyping was performed by combination of PCR with restriction endonuclease mapping.

RESULTS

The proportion of subjects that exhibited the GG genotype was significantly larger in the group with severe periodontitis than in the periodontally healthy group. The difference regarding the occurrence of the GG genotype between the two groups was more conspicuous in non-smokers and yielded an odds ratio of 6.1. The G allele carriage in non-smokers was >90 % in the periodontitis group and was significantly higher than in the healthy controls.

CONCLUSION

It is suggested that the -1087 IL10 polymorphism in Caucasian subjects of a north European origin is associated with severe chronic periodontitis.

Interleukin-1 gene polymorphisms and experimental gingivitis

BACKGROUND

Recently, an association between the severity of periodontitis and specific variations in the interleukin-1 (IL1) alpha and beta genes has been demonstrated.

AIM

: The purpose of this study was to evaluate the relationship of the IL1 genotype to the development of experimental gingivitis.

MATERIALS AND METHODS

Twenty young adult subjects presenting with healthy gingival conditions participated after giving their informed consent. The group included 10 risk genotype positive (P+) and 10 risk genotype negative (P-) individuals. The IL1 genotypes were determined on DNA samples from peripheral blood using PCR-RFLP analyses for the IL1alpha and IL1beta polymorphisms. Experimental gingivitis was allowed to develop in two posterior sextants per subject. Bleeding on probing (BOP%) and gingival crevicular fluid volume (GCF) were assessed at baseline and days 2, 7, 9, 14, 16 and 21. The day 21 results for BOP and GCF as well as the rate of increase of these parameters - mean area under the curve (AUC) and mean increase per day (slope) - were evaluated using risk analyses for IL1 genotype, smoking status and gender.

RESULTS

Experimental gingivitis developed with a gradual increase in BOP scores and GCF values (expressed as Periotron units=PU) from baseline to day 21 (BOP, P+: 0.5 to 26.0%; P-: 1.0 to 28.1%; GCF, P+: 36.8 to 138.5 PU, P-: 43.1 to 143.4 PU). No significant risk was associated with P+ and P- for day 21 results, AUC or slope.

CONCLUSION

The results of this study failed to provide evidence that the IL1 risk genotype was associated with higher GCF volume and percentage BOP during the development of experimental gingivitis.

Periodontal risk assessment, diagnosis and treatment planning

The prevention and treatment of the periodontal diseases is based on accurate diagnosis, reduction or elimination of causative agents, risk management and correction of the harmful effects of disease. Prominent and confirmed risk factors or risk predictors for periodontitis in adults include smoking, diabetes, race, P. gingivalis, P. intermedia, low education, infrequent dental attendance and genetic influences. Several other specific periodontal bacteria, herpesviruses, increased age, male, sex, depression, race, traumatic occlusion and female osteoporosis in the presence of heavy dental calculus have been shown to be associated with loss of periodontal support and can be considered to be risk indicators of periodontitis. The presence of furcation involvement, tooth mobility, and a parafunctional habit without the use of a biteguard are associated with a poorer periodontal prognosis following periodontal therapy. An accurate diagnosis can only be made by a thorough evaluation of data that have been systematically collected by: 1) patient interview, 2) medical consultation as indicated, 3) clinical periodontal examination, 4) radiographic examination, and 5) laboratory tests as needed. Clinical signs of periodontal disease such as pocket depth, loss of clinical attachment and bone loss are cumulative measures of past disease. They do not provide the dentist with a current assessment of disease activity. In an attempt to improve the ability to predict future disease progression, several types of diagnostic tests have been studied, including host inflammatory products and mediators, enzymes, tissue breakdown products and subgingival temperature. In general, the usefulness of these tests for predicting future disease activity remains to be established in terms of sensitivity, specificity and predictive value. Although microbiological analysis of subgingival plaque is not necessary to diagnose and treat most patients with periodontitis, it is helpful when treating patients with unusual forms of periodontal disease such as early-onset, refractory and rapidly progressive disease. There appears to be a strong genetic component in some types of periodontal disease and genetic testing for disease susceptibility has potential for future use, but more research is needed to determine its utility for use in clinical practice. Treatment of the periodontal diseases may be divided into four phases: systemic, hygienic, corrective and maintenance or supportive periodontal therapy. Regardless of the type of treatment provided, periodontal therapy will fail or will be less effective in the absence of adequate supportive periodontal therapy.

Clinical utility of a genetic susceptibility test for severe chronic periodontitis: a critical evaluation

BACKGROUND

A genetic susceptibility test for severe chronic periodontitis is now commercially available. It detects the simultaneous presence of a specific form of two interleukin genes--allele 2 at the IL1A+4845 and IL1B+3954 loci. Patients are referred to as being "genotype-positive" if both of these alleles are present. A fundamental premise of the test is that a combination of these alleles is responsible for increased secretion of IL-beta, which results in a hyperinflammatory response to a bacterial challenge, thereby predisposing a person to develop severe chronic periodontitis.

TYPES OF STUDIES REVIEWED

The authors reviewed controlled clinical trials that assessed the association between specific genotypes and the patient's susceptibility to increased bleeding on probing, periodontitis and loss of teeth or dental implants.

RESULTS

The relationship between specific IL-1 genotypes and the level of IL-1beta in the gingival crevicular fluid is unclear. Similarly, the ability of the genetic susceptibility test to forecast which patients will develop increased bleeding on probing, periodontitis, or loss of teeth or dental implants is ambiguous.

CLINICAL IMPLICATIONS

Additional prospective clinical trials are needed to determine the risk of developing periodontitis or peri-implantitis when allele 2 at the IL1A+4845 and IL1B+3954 loci is present. Therefore, it is unclear how results of the genetic susceptibility test can be used to alter patients' periodontal maintenance schedules or to change treatment regimens in periodontally symptomatic or asymptomatic patients.

Effect of interleukin-1 gene polymorphism in a periodontally healthy Hispanic population treated with mucogingival surgery

OBJECTIVES

A genetic test for susceptibility of periodontal disease has been introduced. A positive test indicates a risk factor for more severe periodontal destruction. The prevalence of genotype positive subjects has been reported around 30%. In a Mexican population, we have found a 26% prevalence of genotype positive individuals. Few studies have reported the response to therapy in these individuals. The purpose of this study was to assess the response to mucogingival surgery in an otherwise periodontally healthy Hispanic population.

MATERIALS AND METHODS

22 subjects (7 male and 15 female) with a mean age of 45 years participated. They were treated 3 years prior for the treatment of Types I and II recession defects using connective tissue grafts. No other active periodontal treatment was required, except for preventive maintenance. A full-mouth clinical evaluation was performed which included assessment of gingival inflammation and measurements of probing pocket depth and clinical attachment levels. Mean values per patient were determined. A finger stick blood sample was collected using specially provided DNA filter paper, let dried, and mailed for processing.

RESULTS

Results indicated that 5 out of the 22 subjects were genotype positive. The genotype positive subjects presented the following values: GI 1.13+/-0.17, PPD 2.48+/-0.46, and CAL 3.38+/-0.66. The values for the genotype negative subjects were GI 1.06+/-0.14, PPD 2.38+/-0.31 and CAL 3.11+/-0.53. No statistical significant differences were found when both groups were compared (p>0.05). Furthermore, the treatment of the localized recessions was effective and provided similar amount of coverage in genotype positive and negative subjects. However, more genotype negative subjects showed complete coverage of the recession than genotype positive individuals.

CONCLUSIONS

Within the limits of this study it is concluded that (1) periodontal health can be maintained with proper preventive maintenance irrespective of the genotype present, (2) the mean response to mucogingival surgery to cover localized gingival recessions is similar irrespective of the IL-1 periodontal genotype, however, full coverage is achieved more frequently in genotype negative subjects.

A critical assessment of interleukin-1 (IL-1) genotyping when used in a genetic susceptibility test for severe chronic periodontitis

BACKGROUND

This review addresses the ability of a commercially available genetic susceptibility test to determine the risk of developing severe chronic periodontitis. The test is used to detect the simultaneous occurrence of allele 2 at the IL-1A+4845 and IL-1B+3954 loci. If both of these polymorphisms are present, patients are referred to as being genotype-positive and considered predisposed to becoming afflicted with severe chronic periodontitis. A basic premise of this test is the assumption that individuals who are genotype-positive produce increased amounts of IL-beta in response to microbial lipopolysaccharides, which allegedly predisposes them to an exaggerated inflammatory response and an increased incidence of chronic periodontitis.

METHODS

Controlled clinical trials were selected that evaluated the ability of the genetic test to predict which patients were susceptible to bleeding upon probing, periodontitis, peri-implantitis, and tooth loss.

RESULTS

Comparison of results from test (genotype-positive) and control groups (genotype-negative) revealed that there is ambiguity with regard to predicting which patients will manifest elevated sub-gingival levels of IL-beta. Similarly, it is questionable if the test is able to forecast which individuals will demonstrate an increased occurrence of bleeding upon probing, diminished clinical attachment, decreased osseous support, or loss of teeth.

CONCLUSIONS

There are many unanswered questions concerning the utility of detecting allele 2 at the IL-1A+4845 and IL-IB+3954 loci to foretell which patients will develop severe chronic periodontitis. Therefore, clinicians must cautiously interpret results obtained with the commercially available genetic susceptibility test before they alter maintenance schedules or treatment regimens of symptomatic or asymptomatic patients.

Failure to detect an association with IL1 genotypes in European Caucasians with generalised early onset periodontitis

OBJECTIVES

In order to elucidate the genetic background to EOP it is useful to investigate associations with genetic polymorphisms of immune response genes, whose products play a r le in the inflammatory process. The aim of this study was to examine IL1A and IL1B genetic polymorphisms in unrelated European white Caucasian patients with generalised early-onset periodontitis (GEOP).

MATERIAL AND METHODS

Polymerase chain reaction (PCR) amplification of the ILIA (-889) gene and IL1B (+3953) gene (56 patients, 56 controls) was carried out and PCR products subjected to restriction fragment length polymorphism (RFLP) analysis.

RESULTS

There were no significant differences between patients and controls for any of the genotype or allele frequencies investigated (p = 1.0). Smoking status was also included as a covariate but this did not alter the results. Furthermore, expression of the composite genotype described by Kornman and coworkers was also investigated in these subjects. No significant differences were found between patients and controls whether smoking was included as a covariate or not.

CONCLUSION

The lack of any association between the IL1 polymorphisms and GEOP, in the population presented here, brings into doubt the usefulness of these candidate genes as markers of susceptibility to this form of periodontitis.

Interleukin-1 gene polymorphism and periodontal status

OBJECTIVES

This case-control study examined polymorphisms at the interleukin-1 gene in relation to periodontal status, subgingival bacteria and systemic antibodies to periodontal microbiota.

METHODS

132 periodontitis patients were age- and gender-matched with 73 periodontally intact controls. Full-mouth clinical assessments of the periodontal tissues were performed. Subgingival plaque samples (2440 in total) were analyzed by genomic DNA probes, and serum IgG antibodies to periodontal microbiota were assessed by an immunoassay. Polymorphisms in the IL-1A gene at position +4845 and the IL-1B gene at position +3953 were studied by PCR. A composite positive genotype was defined as at least one rare (#2) allele present at each locus.

RESULTS

No skewed distribution of the composite genotype was observed between cases and controls (45.2% vs 41.7%). In cases, both the composite genotype and the number of #2 alleles were positively correlated with the severity of attachment loss. No relationship between genotype and subgingival microbial profiles was observed. Genotype positive patients revealed both overall lower serum antibody levels and specific titers against selected bacteria.

CONCLUSIONS

The composite genotype failed to distinguish between periodontitis patients and controls but correlated in patients with the severity of the disease and the antibody responses to periodontal microbiota.

Smoking and polymorphisms of the interleukin-1 gene cluster (IL-1alpha, IL-1beta, and IL-1RN) in patients with periodontal disease

BACKGROUND

Polymorphisms within the interleukin-1 cluster are known to be associated with adult periodontal disease. However, interactions of genetic with other risk factors, especially smoking, remain questionable. The aim of this cross-sectional study was to evaluate the genetic influence on periodontal variables in relation to environmental factors.

METHODS

One-hundred fifty-four (154) Caucasian subjects were clinically and radiographically assessed for their periodontal status, their smoking history recorded, and their allelic pattern of IL-1alpha, IL-1beta, and IL-1RN polymorphisms determined by genotyping.

RESULTS

In assessing periodontitis with mean probing depth, mean attachment loss, or mean bone loss, no differences were found in allele frequencies or combined allotypes between subjects with mild or moderate versus those with severe signs of periodontitis. However, the extent of attachment loss defined as percentage of sites >4 mm was significantly associated with the composite genotype of IL-1alpha/1beta in smokers (odds ratio [OR] = 4.00; 95% confidence interval [CI] 1.03 to 16.70; P= 0.02). No differences were found in genotype negative subjects irrespective of their smoking status. They had nearly identical attachment loss as genotype positive non-smokers. Similar non-significant results were found with respect to extent of bone loss. An increased risk of more extended attachment loss was observed also in individuals carrying mutations of the combined genotype IL-1alpha/IL-1RN, again showing enhanced risk only in genotype-positive and smoking subjects.

CONCLUSIONS

The results provide evidence that the composite genotypes studied show interaction with smoking, the main exposition-related risk factor of periodontal disease. Non-smoking subjects are not at increased risk, even if they are genotype-positive.

Tumor necrosis factor-alpha gene polymorphisms in relation to periodontitis

BACKGROUND

Genetic polymorphisms for cytokines have been proposed as potential genetic markers for destructive periodontal disease. The present aim was to investigate 4 bi-allelic polymorphisms in the TNF-alpha gene in relation to susceptibility for and severity of periodontitis. The polymorphisms were all transitions from G to A, 3 in the promoter positions: -376, -308, -238; and one in the first intron at position +489.

METHODS

90 periodontitis patients and 264 reference control subjects were genotyped and frequencies of genotypes and alleles were analyzed. Also genotype frequencies among severe and moderate periodontitis patients were explored, and the % of teeth with 50% bone loss and the % of teeth without any bone loss for patients with the A allele (A+ genotype) and patients without (A- genotype) were compared.

RESULTS

The distributions of genotypes and frequencies of A allele carriage rates for the 4 TNF-alpha polymorphisms were not different between patients and reference controls; Hardy-Weinberg equilibrium criteria were fulfilled. Also the distribution of A+ and A- genotypes, alone or in combinations, were not different for severe periodontitis compared to moderate periodontitis patients. None of the A+ genotypes showed a significant different bone loss pattern compared to A- genotype patients. Smoking status of the patients did not influence the results.

CONCLUSIONS

Genetic polymorphisms in the TNF-alpha gene at positions -376, -308, -238 and +489 could not be identified as susceptibility or severity factors in periodontitis, irrespective of the smoking status of the patients.

A longitudinal study of interleukin-1 gene polymorphisms and periodontal disease in a general adult population

BACKGROUND

Cross-sectional studies have demonstrated that a specific polymorphism (allele 2 of both IL-1A +4845 and IL-1B +3954) in the IL-1 gene cluster has been associated with an increased susceptibility to severe periodontal disease and to an increased bleeding tendency during periodontal maintenance. The aim of the present study was to investigate the relationship between IL-1 genotype and periodontitis in a prospective longitudinal study in an adult population of essentially European heritage.

METHODS

From an ongoing study of the Oral Care Research Programme of The University of Queensland, 295 subjects consented to genotyping for IL-1 allele 2 polymorphisms. Probing depths and relative attachment levels were recorded at baseline, 6, 12, 24, 36, 48 and 60 months using the Florida probe. Periodontitis progression at a given site was defined as attachment loss > or =2 mm at any observation period during the 5 years of the study and the extent of disease progression determined by the number of sites showing attachment loss. Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans and Prevotella intermedia were detected using ELISA.

RESULTS

38.9% of the subjects were positive for the composite IL-1 genotype. A relationship between the IL-1 positive genotype and increased mean probing pocket depth in non-smokers greater than 50 years of age was found. Further, IL-1 genotype positive smokers and genotype positive subjects with P. gingivalis in their plaque had an increase in the number of probing depths > or =3.5 mm. There was a consistent trend for IL-1 genotype positive subjects to experience attachment loss when compared with IL-1 genotype negative subjects.

CONCLUSION

The results of this study have shown an interaction of the IL-1 positive genotype with age, smoking and P. gingivalis which suggests that IL-1 genotype is a contributory but non-essential risk factor for periodontal disease progression in this population.

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.