Gareth S. Griffiths

Gene Polymorphisms and the Prevalence of Key Periodontal Pathogens

Growing evidence suggests that individual genetic susceptibility may influence the host’s response to infections. The aim of this project was to study whether gene polymorphisms of inflammatory markers are associated with the presence of viable periodontopathogenic bacteria. We extracted genomic DNA from 45 young adults diagnosed with generalized aggressive periodontitis to study Fc receptors, formyl peptide receptor, Interleukin-6, tumor necrosis factor-α, and vitamin D receptor polymorphisms. The presence and viable numbers of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythensis were determined by culture, and their identities confirmed by PCR. Multiple logistic regressions revealed that both Fcγ receptor and IL-6 -174 polymorphisms were associated with increased odds of detecting A. actinomycetemcomitans, P. gingivalis, and T. forsythensis after adjustment for age, ethnicity, smoking, and periodontitis extent. These findings support the hypothesis that complex interactions between the microbiota and host genome may be at the basis of susceptibility to aggressive periodontitis.

Amoxicillin and metronidazole as an adjunctive treatment in generalized aggressive periodontitis at initial therapy or re‐treatment: a randomized controlled clinical trial

BACKGROUND Previously, we showed that systemic metronidazole and amoxicillin significantly improved the outcomes of non-surgical debridement in generalized aggressive periodontitis patients. This study aimed to observe whether re-treatment with adjunctive antimicrobials would give the placebo group benefits comparable with the test group. METHODS Thirty-eight of 41 subjects, from the initial 6-month trial, completed the second phase, re-treatment of sites with remaining pockets 5 mm. Subjects on placebo in phase one, received adjunctive antibiotics for 7 days. Clinical parameters were collected at 2 months posttreatment (8 months from baseline). RESULTS Patients who received antibiotics at initial therapy, showed statistically significant improvement in pocket depth reduction and in the % of sites improving above clinically relevant thresholds, compared with patients who received antibiotics at re-treatment. In deep pockets (7 mm), the mean difference was 0.9 mm (p=0.003) and in moderate pockets (4-6 mm) it was 0.4 mm (p=0.036). For pockets converting from 5 to 4 mm, this was 83% compared with 67% (p=0.041) and pockets converting from 4 to 3 mm was 63% compared with 49% (p=0.297). CONCLUSIONS At 8 months, patients who had antibiotics at initial therapy showed statistically significant benefits compared with those who had antibiotics at re-treatment.

Association between periodontitis and common variants in the promoter of the interleukin-6 gene

We recently reported an association between interleukin-6 (IL6) polymorphisms (SNPs) and haplotypes and aggressive periodontitis (AgP). The aim of this study was to investigate this association in a larger cohort of subjects, affected by either aggressive or chronic periodontitis. Five IL6 SNPs were analyzed in 765 subjects (167 generalized aggressive periodontitis, 57 localized aggressive, 310 chronic periodontitis and 231 periodontally healthy). Among Caucasians (n=454) there were moderate associations for -1363T allele (p=0.011) and for -174GG and -1363GG genotypes with diagnosis of periodontitis (respectively, p=0.044, OR=1.6, 95% CI=1.0-2.4, and p=0.017, OR=1.8, 95% CI=1.1-2.8, adjusted for age, gender and smoking). Haplotypes containing the -174G>C, -1363G>T and -1480C>G polymorphisms were associated with diagnosis of periodontitis (p=0.02). Subgroup analysis by disease phenotype showed associations for the localized AgP (LAgP) group and -1480C>G and -6106A>T SNPs (p=0.007 and 0.010, respectively). Among Caucasians the genotypes IL6 -1480 CC and -6106 TT increased the adjusted OR for LAgP (OR=3.09 and 2.27, respectively). This study supports the hypothesis that IL6 polymorphisms and haplotypes are moderately associated with periodontitis, possibly acting through influencing tissue levels of IL6. This association is stronger for LAgP than for other periodontal disease phenotypes.

Association between interleukin‐6 promoter haplotypes and aggressive periodontitis

BACKGROUND Interleukin-6 (IL-6) polymorphisms have been shown to affect IL-6 promoter activity. This study investigated the possible role of IL-6 genetic polymorphisms and haplotypes in the predisposition to aggressive periodontitis (AgP). MATERIAL AND METHODS A case-control association study on 224 AgP patients and 231 healthy controls was performed in order to detect differences in genotype distributions of five single nucleotide polymorphisms (SNPs) located in the promoter region of the IL-6 gene. RESULTS The IL-6 -1363 polymorphism was associated with a diagnosis of AgP in subjects of all ethnicities (p=0.006, adjusted logistic regression). The -1480 SNP was associated with LAgP in subjects of all ethnicities (p=0.003). The -1480 and -6106 polymorphisms were associated with Localized AgP in Caucasians (n=24) (p=0.007 and 0.010, respectively). Haplotypes determined by the -1363 and -1480 polymorphisms were also associated with LAgP (p=0.001) in Caucasians. CONCLUSIONS This study supports the hypothesis of a link between IL-6 genetic factors and AgP and highlights the importance of two IL-6 polymorphisms (-1363 and -1480) in modulating disease phenotype and susceptibility.

Is Reduction of Pocket Probing Depth Correlated with the Baseline Value or is it “Mathematical Coupling”?

Previous studies using correlation or regression analysis have showed that treatment effects measured by the change in clinical parameters are often associated with baseline values of the same parameters. These studies, however, have a methodological weakness. Correlation/regression between baseline measures and the derived change variable invalidates the statistical procedures of testing the null hypothesis: that the coefficient of correlation/regression is zero. This is due to the phenomenon of mathematical coupling. To investigate the impact that this has on the observed correlation/regression coefficient when in reality this is zero, we used random simulations of hypothetical data to model the treatment of periodontal pockets. Results showed a strong probability of obtaining statistically significant correlation/regression coefficients. To separate this artificial effect of mathematical coupling from the true underlying biological relationship, one must apply appropriate analytical strategies to re-evaluate previous evidence within the periodontal literature.

A familial analysis of aggressive periodontitis – clinical and genetic findings

BACKGROUND AND OBJECTIVE Family history is a primary diagnostic criterion for current classification of aggressive periodontitis (AgP). However, results of previous studies have shed controversy over the degree of familiarity of AgP and its possible inheritance mechanisms. The aims of this study were to estimate the percentage of affected relatives of AgP individuals, to analyse the disease phenotypes in relatives and to explore the distributions of genetic polymorphisms of interleukin-6 (IL-6) in AgP patients and in diseased and healthy relatives. MATERIAL AND METHODS Patients with AgP were clinically examined and asked to provide relatives for examination. First-degree relatives were clinically and radiographically diagnosed. Blood samples were collected, DNA was extracted and analysis of single nucleotide polymorphisms of IL-6 (at positions -174, -1363 and -1480) by polymerase chain reaction was performed in patients and relatives. RESULTS Fifty-five AgP patients provided relatives for examination. A total of 100 first-degree relatives were assessed and 10 of them (10%) were found to have AgP. All relatives diagnosed with AgP had the same disease as the corresponding proband (localized AgP/localized AgP or generalized AgP/generalized AgP). The same IL-6 genotypes (-174 GG, -1480 CC) previously associated with AgP showed a tendency for association with AgP in relatives. CONCLUSION This pilot study confirmed a relatively high risk for relatives of AgP patients to have AgP (10%). Genetic polymorphisms in the IL-6 gene may have an impact in aetiopathogenesis. This study provides a sample size calculation for a novel study design using healthy relatives as control subjects.

Permeability of the gingival tissues to IgM during an experimental gingivitis study in man.

Changes in the permeability of the underlying vasculature of the gingival crevice region may occur either as part of an inflammatory response during gingivitis or as a response to trauma during collection of gingival crevicular fluid IgM was selected as a marker of permeability and the concentration in gingival crevicular fluid was determined immunochemically by dot blotting, using rabbit antihuman IgM specific for mu chain. Gingival crevicular fluid samples were derived from experimental (non-cleaning) and control (cleaning) sites in six individuals participating in a 28-day experimental gingivitis study using a split-mouth protocol. The fluid was collected by a filter-paper method. At each site, four gingival crevicular fluid samples were collected for 5 s each over a 3-min period and a fifth sample was collected after a further 6 min. IgM was detected in 7/30 experimental strips at baseline (after intensive professional prophylaxis) and this increased to 21/30 by 24 days: control values were 13/30 and 12/30, respectively. The data indicate that IgM was detected with greater frequency as gingivitis becomes evident, suggesting increased permeability in response to plaque accumulation. IgM was detected in 17/120 of the first strip samples, collected over the 66-day study period, whereas in the fifth strip samples IgM was detected in 68/120, and the concentration of IgM in gingival crevicular fluid also increased, indicating that sequential collection induced permeability. It is concluded that the permeability of the gingiva changes in response to both an inflammatory stimulus and trauma due to collection.

A study of the periodontal state of a late Medieval United Kingdom population.

OBJECTIVE To study the severity of bone loss in a Medieval UK population, and compare this with other ancient UK populations from different time periods. DESIGN Skulls from a burial site in York (XI-XV century) were investigated. Skulls with a minimum of 17 teeth were included and were divided from childhood into five age groups. Direct measurements from the cement enamel junction (CEJ) to the alveolar crest (AC) were undertaken at six points around each tooth with a UNC 15 probe. The mean bone loss was calculated for each tooth type. RESULTS Seventy five skulls were included in the study (12-60 years of age). Bone loss was found to increase with age, but stabilized in older individuals (>45 years). The mean CEJ-AC distance varied from 2.1mm in the youngest group to a maximum of 4.1mm in 36-45 year olds. Results were compared with a Roman-British population (Whittaker et al., 1982) where comparable values for mean bone loss were 2.2mm and 5.4mm respectively, and a population of XVIII century Londoners (Whittaker et al., 1998) where bone loss of 1.1mm and 4.0mm was reported for the youngest and oldest age groups respectively. CONCLUSION Measuring the CEJ-AC distance in dried skulls from ancient populations may be used as a proxy for the levels of periodontal disease irrespective of tooth wear. The findings from the current study suggest that the severity of periodontitis as determined by measurements of alveolar bone loss on dried skulls from this ancient population, seems to have declined in the United Kingdom from the III-V century to XVIII century. This may be due to changes in environmental factors including living conditions and diet, together with individual characteristics including systemic illness and genetic make up.