Experimental gingivitis in relation to susceptibility to periodontal disease. II. Phase-contrast microbiological features and some host-response observations

Clinical, immunological and microbiological evaluation of experimental peri-implant mucositis and gingivitis in subjects with Grade C, stage III/IV periodontitis background

AIM

To compare individuals with a periodontitis background (Grade C, stage III/IV-formerly generalized aggressive periodontitis) (H-GAP) with periodontally healthy subjects (H-Health) in terms of molecular changes (immunological/microbiological) accompanying experimental peri-implant mucositis and gingivitis.

MATERIALS AND METHODS

H-GAP and control (H-Health) subjects were recruited, and experimental mucositis/gingivitis was induced around a single screw-retained implant and one contralateral tooth. Participants refrained from oral hygiene for 21 days in the selected areas, followed by professional prophylaxis and hygiene instructions for 21 days. Clinical parameters, immunological markers (multiplex analysis) and microbial data (16S rRNA gene sequencing) were collected at baseline, during induction (7, 14 and 21 days) and following remission (42 days).

RESULTS

Clinically, no significant differences were observed between the groups (n = 10/each group) (H-GAP vs. H-Health) (p > .05, Mann-Whitney test) and the type of site (tooth vs. implant) (p > .05, Wilcoxon test) at the time of onset and resolution, or severity of gingival/mucosal inflammation. H-GAP displayed lower concentrations of the cytokines interleukin (IL)-1B, IL-4, IL-17, tumor necrosis factor-α and interferon-γ around implants than H-Health at baseline and during induction of mucositis (p < .05, Mann-Whitney test). In both groups, implants showed significantly higher inflammatory background at baseline and all subsequent visits when compared with teeth (p < .05, Wilcoxon test). Alpha and β-diversity metrics showed a significant shift in the microbiome composition and abundances of core species during induction and resolution of peri-implant mucositis and gingivitis (p < .05, restricted maximum likelihood method of Shannon and Bray-Curtis indices, respectively). Differences were not significant for these parameters between the H-Health and H-GAP groups when the periodontal and peri-implant microbiomes were compared separately; however, at each time point, the peri-implant microbiome differed significantly from the periodontal microbiome.

CONCLUSIONS

Within the limitations of this pilot study (e.g. low power), it can be concluded that different microbial shifts contribute to the onset and progression of inflammatory responses around teeth and implants and that history of periodontal disease experience plays an additional role in modulating the immune response of peri-implant and periodontal tissues to biofilm accumulation.

Evaluating clinical utility of subgingival and salivary endotoxin activity levels as periodontal biomarkers

Objectives

The use of periodontal biomarkers for identification and monitoring of unique patient populations could foster better stratification of at-risk groups, increase access to treatment for those most in need, facilitate preventive measures and improve personalised care plans. The aim of this study was to examine the diagnostic and prognostic utility of oral lipopolysaccharides as bacterially-derived periodontal biomarkers.

Methods

Periodontal parameters were recorded, and saliva and subgingival plaque samples were collected at the beginning of the study from periodontally healthy volunteers and periodontitis patients, and three months after completion of conventional periodontal treatment in the periodontitis group. Endotoxin activity in the samples was measured using the recombinant factor C assay. Associations between clinical periodontal parameters and subgingival and salivary endotoxin activities were analysed using a multivariate regression model, while the ROC curve was applied to estimate the sensitivity, specificity and c-statistics for salivary and subgingival endotoxin activities as diagnostic biomarkers for periodontitis.

Results

Significant correlations were found between subgingival endotoxin activities, probing pocket depth and periodontal diagnosis, which were independent from patients' age, gender and smoking status. In addition, subgingival endotoxin levels had high specificity and sensitivity in detecting periodontal health and disease (0.91 and 0.85 respectively). Salivary endotoxin activity was positively associated with periodontal diagnosis, mean probing pocket depth, percentages of sites over 4 mm and full mouth bleeding score. However, it was inferior in discriminating patients with stable periodontium from those with periodontitis (sensitivity = 0.69, specificity = 0.61) compared to subgingival endotoxin activity.

Conclusions

Subgingival endotoxin activity has good diagnostic and prognostic values as a site-specific periodontal biomarker and is not influenced by the patient's age, gender or smoking status. In contrast, salivary endotoxin activity, as a patient-level biomarker, is dependent on patient's age, has poorer diagnostic and prognostic capability, but shows good correlations with disease susceptibility and both its extent and severity.

Dental plaque-induced gingival conditions

OBJECTIVE

This review proposes revisions to the current classification system for gingival diseases and provides a rationale for how it differs from the 1999 classification system.

IMPORTANCE

Gingival inflammation in response to bacterial plaque accumulation (microbial biofilms) is considered the key risk factor for the onset of periodontitis. Thus, control of gingival inflammation is essential for the primary prevention of periodontitis.

FINDINGS

The clinical characteristics common to dental plaque-induced inflammatory gingival conditions include: a) clinical signs and symptoms of inflammation that are confined to the gingiva: b) reversibility of the inflammation by removing or disrupting the biofilm; c) the presence of a high bacterial plaque burden to initiate the inflammation; d) systemic modifying factors (e.g., hormones, systemic disorders, drugs) which can alter the severity of the plaque-induced inflammation and; e) stable (i.e., non-changing) attachment levels on a periodontium which may or may not have experienced a loss of attachment or alveolar bone. The simplified taxonomy of gingival conditions includes: 1) introduction of the term "incipient gingivitis;" 2) a description of the extent and severity of gingival inflammation; 3) a description of the extent and severity of gingival enlargement and; 4) a reduction of categories in the dental plaque-induced gingival disease taxonomy.

CONCLUSIONS

Dental plaque-induced gingival inflammation is modified by various systemic and oral factors. The appropriate intervention is crucial for the prevention of periodontitis.

The subgingival periodontal microbiota of the aging mouth

Different mechanisms have been hypothesized to explain the increase in prevalence and severity of periodontitis in older adults, including shifts in the periodontal microbiota. However, the actual impact of aging on the composition of subgingival biofilms remains unclear. In the present article, we provide an overview of the composition of the subgingival biofilm in older adults and the potential effects of age on the oral microbiome. In particular, this review covers the following topics: (i) the oral microbiota of an aging mouth; (ii) the effects of age and time on the human oral microbiome; (iii) the potential impact of inflammaging and immunosenescence in the host-oral microbiota interactions; and (iv) the relationship of the aging oral microbiota and Alzheimer's disease. Finally, we present analyses of data compiled from large clinical studies that evaluated the subgingival microbiota of periodontally healthy subjects and patients with periodontitis from a wide age spectrum (20-83 years of age).

Learned and unlearned concepts in periodontal diagnostics: a 50-year perspective

In the past 50 years, conceptual changes in the field of periodontal diagnostics have paralleled those associated with a better scientific understanding of the full spectrum of processes that affect periodontal health and disease. Fifty years ago, concepts regarding the diagnosis of periodontal diseases followed the classical pathology paradigm. It was believed that the two basic forms of destructive periodontal disease were chronic inflammatory periodontitis and 'periodontosis'- a degenerative condition. In the subsequent 25 years it was shown that periodontosis was an infection. By 1987, major new concepts regarding the diagnosis and pathogenesis of periodontitis included: (i) all cases of untreated gingivitis do not inevitably progress to periodontitis; (ii) progression of untreated periodontitis is often episodic; (iii) some sites with untreated periodontitis do not progress; (iv) a rather small population of specific bacteria ('periodontal pathogens') appear to be the main etiologic agents of chronic inflammatory periodontitis; and (v) tissue damage in periodontitis is primarily caused by inflammatory and immunologic host responses to infecting agents. The concepts that were in place by 1987 are still largely intact in 2012. However, in the decades to come, it is likely that new information on the human microbiome will change our current concepts concerning the prevention, diagnosis and treatment of periodontal diseases.

Gingival tissue transcriptomes in experimental gingivitis

AIMS

We investigated the sequential gene expression in the gingiva during the induction and resolution of experimental gingivitis.

MATERIAL AND METHODS

Twenty periodontally and systemically healthy non-smoking volunteers participated in a 3-week experimental gingivitis protocol, followed by debridement and 2-week regular plaque control. We recorded clinical indices and harvested gingival tissue samples from four interproximal palatal sites in half of the participants at baseline, Day 7, Day 14 and Day 21 (the "induction phase"), and at Day 21, Day 25, Day 30 and Day 35 in the other half (the "resolution phase"). RNA was extracted, amplified, reversed transcribed, amplified, labelled and hybridized using Affymetrix Human Genome U133Plus2.0 microarrays. Paired t-tests compared gene expression changes between consecutive time points. Gene ontology analyses summarized the expression patterns into biologically relevant categories.

RESULTS

The median gingival index was 0 at baseline, 2 at Day 21 and 1 at Day 35. Differential gene regulation peaked during the third week of induction and the first 4 days of resolution. Leucocyte transmigration, cell adhesion and antigen processing/presentation were the top differentially regulated pathways.

CONCLUSIONS

Transcriptomic studies enhance our understanding of the pathobiology of the reversible inflammatory gingival lesion and provide a detailed account of the dynamic tissue responses during the induction and resolution of experimental gingivitis.

Effect of Age on Gingival Crevicular Fluid Concentrations of MIF and PGE2

We used an experimental gingivitis study design to compare crevicular fluid concentrations of Migration Inhibitory Factor (MIF) and Prostaglandin E2 (PGE2) in younger (18 to 30 yrs) and older (46 to 77 yrs) healthy adults. PGE2 increased after 1 wk in younger participants, whereas it decreased in older individuals after 1 wk of plaque accumulation. A significant interaction between age and time was observed for PGE2 (p = 0.04). High concentrations of MIF were identified in both age groups at baseline. MIF increased in the younger participants, whereas in the older individuals a decrease over time was observed. MIF concentration was positively correlated with plaque index and gingival index in the older age group. Total counts of bacteria, Parvimonas micra and Prevotella intermedia, were significantly correlated with MIF concentration in older participants. In conclusion, MIF and PGE2 production in response to bacterial accumulation seems to be modified by age.

Gingivitis susceptibility and its relation to periodontitis in men

The objective of this cross-sectional study was to evaluate whether gingivitis susceptibility is associated with periodontitis. We analyzed data of 462 men in the VA Dental Longitudinal Study aged 47 to 92 years who had never smoked or had quit smoking 5+ years previously. Multiple logistic regression models, with tooth-level bleeding on probing at sites with attachment loss<or=2 mm as the dependent variable, were derived with adjustment for plaque, calculus, crown coverage, age, income, education, marital status, body mass index, diabetes, and vitamin C intake, and stratification by age (<65, 65+ years). Periodontitis and mean attachment loss were positively associated with bleeding on probing, with stronger associations among men<65 years old (for periodontitis, OR 2.1; 95% CI 1.5, 3.1) than men 65+ years of age (OR 1.2; 95% CI 0.9, 1.6). Our results suggest that among never and former smokers, gingivitis susceptibility is higher among men with periodontitis compared with that in men without periodontitis.

Modulation of clinical expression of plaque-induced gingivitis: response in aggressive periodontitis subjects

AIM

The aim of this study was to characterize the gingival inflammatory response to de novo plaque accumulation in subjects treated for aggressive periodontitis (AP). The gingival inflammatory response of the AP subjects was retrospectively compared with that of periodontally healthy individuals (PH) matched for exposure to plaque and of periodontally healthy subjects previously identified as "high responders" (HR) and "low responders" (LR).

MATERIALS AND METHODS

13 AP subjects and 26 matched PH subjects participated in a 21-day experimental gingivitis trial. Plaque index (PlI), Gingival index (GI), gingival crevicular fluid volume (GCF) and angulated bleeding score (AngBS) were recorded at days 0, 7, 14 and 21. Cumulative plaque exposure (CPE), i.e. PlI over time, was also calculated.

RESULTS

GCF was significantly higher in AP compared with PH group at each observation interval (p< or =0.001). In addition, GCF was significantly higher in AP group compared with either LR or HR groups at each observation interval (p<0.001).

CONCLUSIONS

These results suggest that susceptibility to gingival inflammation in response to de novo plaque accumulation may be related to susceptibility to periodontitis.

Host response to microbial challenge following resective/non-resective periodontal therapy

BACKGROUND

The host response to microbial challenge depends on the recruitment of homing leucocytes and may be related to the experience to infectious insults over years.

PURPOSE

The aim of this study was to investigate the soft tissue reactions to de novo plaque formation at sites treated with either open flap debridement or with the use of resective means during periodontal therapy.

MATERIAL AND METHODS

Fifteen patients, who had been treated for periodontal disease (severe generalized chronic periodontitis), participated in the study. Surgical therapy was performed using either gingivectomy (GV) or open flap debridement (OFD) procedures in a split mouth design. After 6 months of healing (day 0), two gingival biopsies were obtained, one from the GV- and one from the OFD-treated sites. The experimental gingivitis model was applied and plaque accumulation was allowed for 3 weeks. New biopsies were obtained from the remaining quadrants on day 21 of plaque formation. The biopsies were snap frozen and prepared for immunohistochemical analysis.

RESULTS

Following 3 weeks of plaque accumulation, the size of the lesion in OFD sites was more than twice as large than that in GV sites (0.42 versus 0.19 mm2). In the GV units, the lesion was characterized by almost similar proportions of T cells (CD3+, 6.0%) and B cells (CD19+, 6.6%), while the ICT in OFD sites was dominated by B cells (13.8%). During the 3-week period of plaque formation the increase in cell densities of T and B cells was three times larger in OFD than in GV sites. The proportion of ELAM-1 (CD62+ cells) decreased in GV (-0.4%) and increased in OFD (0.9%) sites.

CONCLUSIONS

The host response that occurred in the gingival sites treated with OFD was more pronounced than the reaction that under similar experimental conditions took place in the regenerated gingiva at sites treated by resective means.

Modulation of clinical expression of plaque-induced gingivitis. I. Background review and rationale

OBJECTIVES

The purpose of this article is to provide the necessary background and rationale for the accompanying studies, which are ultimately aimed at identifying genetic and environmental factors determining gingivitis susceptibility.

MATERIALS AND METHODS

The literature on factors reported to modify the clinical expression of gingivitis, i.e., factors that determine individual variability in gingival inflammatory response to plaque, is presented.

RESULTS

Clinical evidence suggests that the gingival inflammatory response to plaque accumulation may differ substantially among individuals. However, most of the available studies are of small scale and not purposely designed to address the issue. Systemic factors implicated in modulation of the clinical expression of gingivitis include metabolic, genetic, environmental and other factors. The significance of such factors in designing and conducting a large-scale experimental gingivitis trial and means to account for them are discussed.

CONCLUSION

Although several factors have been implicated, genetic or environmental factors underlying differences in gingivitis expression are not fully elucidated. The accompanying studies aim to identify and characterize, among participants in a specifically designed large-scale experimental gingivitis trial, subjects that differ significantly in their gingival inflammatory response to plaque. This is the first step in an effort to determine genetic or environmental factors underlying such differences.

Periodontal diseases: current and future indications for local antimicrobial therapy

The microbial etiology of gingivitis and periodontitis provides the rationale for use of adjunctive antimicrobial agents in the prevention and treatment of periodontal diseases. Although mechanical removal of supra- and subgingival calcified and non-calcified plaque deposits has been proved effective to control the gingival inflammatory lesions as well as to halt the progression of periodontal attachment loss, some patients may experience additional benefits from the use of systemic or topical antimicrobial agents. Such agents are able to significantly affect supra- and subgingival plaque accumulation and/or suppress or eradicate periodontal pathogenic microflora. Currently, properly selected local antiseptic and systemic antibiotic therapies can provide periodontal treatment that is generally effective, low-risk and affordable. This paper will briefly review the host-related conditions in which the periodontal preventive and therapeutic approaches may be effectively assisted by a local antimicrobial regimen. Potential future indications for adjunctive local antimicrobial therapy will also be discussed.

Longitudinal association between plaque and gingival bleeding in smokers and non-smokers

BACKGROUND/AIMS

Whereas accumulation of dentogingival plaque inevitably leads to inflammatory reactions in the adjacent gingival tissue, there is limited information with regard to factors influencing naturally occurring fluctuation between gingival health and disease. The major aims of the present study were to investigate site-specific associations between plaque and gingivitis as well as transition dynamics of naturally occurring gingivitis in smoking and non-smoking young adults.

METHODS

65 systemically healthy young adults, 19 to 30 years old, participated. 33 volunteers smoked at least 20 cigarettes per day, whereas 32 subjects were non-smokers. Clinical periodontal conditions were assessed four times within a time period of 6 months. An ecological approach in data analysis as well as site-specific analyses considering the correlated structure of data were performed.

RESULTS

At the outset and after 6 months, smokers had significantly more supragingival plaque than non-smokers. At the final examination, bleeding upon probing as well as calculus were more prevalent in smokers. A site-by-site analysis revealed that smokers tended to have a weaker association between supragingival plaque and bleeding on probing than non-smokers (median Mantel-Haenszel's common odds ratio 1.91 vs. 2.89, p=0.07). Multiple logistic regression analyses adjusted for periodontal probing depth, plaque and calculus identified smoking status to significantly increase the risk for the first transition of non-bleeding to bleeding upon probing by 86% (p<0.01). In contrast, recovery of bleeding sites was positively influenced by female gender, but not smoking.

CONCLUSIONS

In multivariate analyses adjusted for probing depth, plaque and calculus, smokers appeared to be at higher risk for the transition from non-bleeding to bleeding on probing. Weaker associations between plaque and naturally occurring gingivitis in smokers may have important consequences for preventive strategies for gingivitis.

Experimental gingivitis in periodontitis-susceptible subjects

The purpose of this study was to evaluate clinical, microbiological, and gingival crevicular fluid (GCF) profiles in periodontitis-resistant and periodontitis-susceptible subjects during 4 weeks of experimental gingivitis. Experimental groups of similar ages were defined as gingivitis controls (GC; n = 10) and history of rapidly progressive periodontitis (RPP; n = 10), respectively. Prior to baseline, all subjects achieved good plaque control (plaque index (P1I) approximately 0) and gingival health (gingival index (GI) = 0), and had probing depths < or = 4 mm on experimental teeth. For 4 weeks after baseline, oral hygiene around maxillary 2nd premolar and 1st molar teeth was inhibited by a plaque guard. The plaque guard was removed weekly for GCF sampling to determine interleukin (IL)-1 beta and prostaglandin (PG)E2 amounts by ELISAs. In addition, P1I, GI, probing depth, and gingival recession measurements were made. Subgingival plaque darkfield microscopy and DNA probe analysis also were performed. Results indicated that clinical signs of inflammation, microbiological patterns and GCF profiles progressed similarly in both groups. However, plaque accumulated more rapidly in the susceptible subjects. P1I in RPP at 4 weeks was 2.1 +/- 0.1 compared to 1.5 +/- 0.2 in GC, with an incidence of P1I > of 100% versus 50%, respectively (logistic regression; p < 0.0001). Hence, the clinical, microbiological and host factors selected for this study were unrelated to previous susceptibility to periodontitis when evaluated in the experimental gingivitis model. However, the increased rate of plaque accumulation, following thorough plaque removal, in RPP patients suggests a potential factor in disease recurrence in these susceptible subjects.

Gingivitis in young and old dogs

The aim of the investigation was to study the development of gingivitis in young and old dogs. 10 beagle dogs were used. 5 of the dogs were 1 year old and 5 dogs were between 8 and 9 years of age. On day 0, all the teeth of all 10 dogs were scaled and polished. A 6-week period of plaque control was initiated. On day 42, a clinical examination was performed, microbial samples from the gingival sulcus were harvested and biopsies obtained from tooth regions 3P and 4P. The tooth-cleaning measures were abandoned following biopsy and the animals were during the subsequent 3 weeks allowed to form plaque. On day 63, i.e., day 21 of plaque formation, the clinical examination, sampling of the subgingival plaque and harvesting of biopsies were repeated in the contralateral premolar regions (P3 and P4). The histological analysis revealed that the cellular infiltrate (the lesion) of inflamed gingiva was larger and extended more apically in the old than in the young dogs. The lesion in the old dogs contained significantly more plasma cells but less macrophages, lymphocytes and PMN cells than the infiltrate in the young dogs.

Detection of high-risk groups and individuals for periodontal diseases. Evidence for the existence of high-risk groups and individuals and approaches to their detection

It is argued that the periodontal diseases can no longer be regarded as universally prevalent conditions to which all members of the world's population are at equal risk if they fail to practise good oral hygiene. Rather, they should be regarded as a range of different diseases for each of which certain individuals, which together comprise certain minority groups, are at relatively high risk. The epidemiological evidence for the existence of high-risk groups is reviewed, from which it is concluded that world-wide the prevalence of severe destructive periodontitis is of the order of only 7-15% of the adult dentate population. A working classification of the different types of gingivitis and periodontitis is offered, as is a summary of the theoretically possible approaches to the detection of high-risk groups and individuals which are explored in detail in subsequent papers. Successful identification of such individuals will permit scientifically valid, rational and targetted prevention and treatment.

The relationship of initial clinical parameters to the long-term response in 112 cases of periodontal disease

The purpose of the present study was to determine whether any of the clinical parameters recorded during an initial periodontal examination would relate to the course of periodontal cases maintained for long periods of time. Based on available documentation, cases which had a downhill course were assembled from a population previously studied. In addition, long-term cases currently under maintenance care were drawn from our private practice. On average, the patients had been under care for 23 years. The study population was heavily weighted toward downhill cases to better compare these cases with those usually found in periodontal practice. Positive statistical correlations were found between the amount of subgingival calculus and the degree of gingival inflammation at initial examination. Disease severity initially was positively correlated to long-term course of disease. The amount of subgingival calculus did not relate to the long-term result. There was a strong correlation between inflammatory gingival hyperplasia initially and good long-term maintenance. The results suggest that, in combination, initial characteristics of periodontal cases coupled with long-term results of treatment may aid in further subclassifying the periodontal diseases.

Experimental gingivitis in relation to age in individuals not susceptible to periodontal destruction

The purpose of the present investigation was to study the effect of age on the rate of development of gingival inflammation in individuals not susceptible to periodontal destruction. 7 younger (mean age 37 years) and 7 older (mean age 58 years) individuals were selected on the basis of the presence of at least 18 teeth, no evidence of extraction due to periodontal destruction, no loss of attachment, shallow pockets, gross amounts of plaque and a history of no interdental cleaning. All individuals were subjected to a carefully controlled oral hygiene program and experimental gingivitis was induced in 1 quadrant of the mouth during a period of 33 days. The amount of plaque, redness and swelling of the gingiva, and bleeding on probing were assessed before, during and after the experiment. At day 33, supra-gingival plaque samples were taken for bacteriological examination and gingival biopsies were taken for histopathological and immunohistochemical investigation. Results showed no differences between the 2 age groups with regard to the amount of plaque accumulation and the rate of development of gingival inflammation. Furthermore phase-contrast microscopy of plaque samples showed no differences between the 2 age groups. Neither histological nor immunohistochemical investigation showed any differences between the 2 age groups. All biopsies diffusely showed presence of IgG, whereas in most biopsies, IgA plasma cells and in one biopsy IgM plasma cells were found. Neither IgD, IgE nor complement deposits were found. It was concluded that age is of minor importance in the development of experimentally-induced gingivitis in individuals not susceptible to periodontal destruction.