Gingival thickness and gingival width in children: a cross-sectional study utilizing ultrasonography

PURPOSE

To measure the gingival phenotype-related features, gingival thickness (GT) and gingival width (GW), in healthy children and to investigate their association between them, with age, gender, tooth-type and arch.

METHODS

The gingival sites of 1029 teeth were included from 64 children (36 males and 28 females), with primary and mixed dentition, attending the paediatric dental clinic of Aristotle University, Thessaloniki. GT and GW were measured ultrasonically and with a periodontal probe, respectively. Mixed effects linear regression models were used to evaluate the association of gingival thickness and gingival width with the under-investigation parameters. Spearman's correlation coefficient was used to evaluate correlation between GT and GW.

RESULTS

Significantly thicker gingiva is found in posterior teeth compared to anterior teeth, in permanent teeth versus primary teeth and in maxillary teeth in comparison to mandibular teeth (p value < 0.001). Regarding GW, significantly wider gingiva is noted in posterior regions (p value = 0.022) and the maxilla (p value < 0.001). Gender-wise and concerning age GT and GW are not significantly affected. A weak and positive correlation between GT and GW is noted (rho 0.30, p < 0.001).

CONCLUSIONS

GT and GW present significant associations with arch and tooth-type. Findings from this study fulfil the further understanding of GT and GW of paediatric patients that are investigated sparsely throughout the literature and demonstrate an accurate, painless and simple method to map the gingiva.

Tooth Wear Epidemiology and Its Associated Periodontal Health and Sociodemographic Factors in a Cluster of Senior Citizens in Northern Greece

Tooth wear (TW) is an irreversible and cumulative phenomenon causing aesthetic and functional compromise. Increasing wear has been associated with age, and various other factors have been reported to influence its type and/or severity both in individuals and groups. Increased TW may constitute a major future problem for the elderly. The present cross-sectional study aims at determining the prevalence of TW in senior citizens from Northern Greece and evaluating the patient-level associations between TW, periodontal condition, and sociodemographic factors. A sample of 363 dentate individuals, aged between 65 and 74 years, was considered according to the WHO guidelines for national pathfinder surveys and three different dentists examined the representative population groups from different urban and rural areas in Northern Greece. The examiners were calibrated prior to the survey, with an interexaminer agreement of over 85%. The simplified TWI, community periodontal index (CPI), attachment loss (AL), plaque index (DI), calculus index (CI), and sociodemographic factors were detected and measured. TW is very prevalent among senior citizens in Northern Greece, with males having been found to experience more wear. Age and oral health status, when measured by the periodontal indices AL, DI, and CI, are significantly combined with TW in both urban and rural areas.

Use of Hyaluronic Acid in Periodontal Disease Treatment: A Systematic Review

AIM

The main purpose of the present study was to investigate the potential benefit of local use of hyaluronic acid as an adjunct to periodontal therapy, since commercial products of hyaluronic acid (HA), due to its anti-inflammatory and anti-bacterial actions and its significant role in wound repair, have been proposed as adjuncts to either nonsurgical or surgical periodontal therapy.

MATERIALS AND METHODS

A total of 19 electronic databases were searched and the appropriate studies were identified with the use of specific eligibility criteria, according to PRISMA guidelines. Two reviewers independently screened and selected the studies and made the data extraction and the assessment of risk of bias, by using the Cochrane risk of bias tool.

RESULTS

Out of 3,186 papers, 38 randomized clinical trials (8 related to gingivitis therapy, 20 related to nonsurgical periodontal therapy, and 10 related to surgical periodontal therapy) were finally included in the review. The outcomes were categorized as primary (that answered the focus question) and secondary (regarding additional quality characteristics). The adjunct use of HA combined to all treatment modalities shows improvement of patients' postoperative course, in terms of decreased inflammatory reactions, and changes in periodontal pocket depth and clinical attachment level. No side effects were reported in any of the included studies. Among the secondary outcomes were the variety of HA formulations and chemical forms, the variety in application, follow-up protocol and blinding design, the uneven geographic distribution of the studies, and the low bibliometric characteristics of most studies.

CONCLUSION

Overall and despite the positive effects reported, further research is needed to define the ideal HA compound, formulation, and regimen characteristics for periodontal disease treatment.

CLINICAL SIGNIFICANCE

The adjunct use of HA may lead in the reduction of the prescription of nonsteroid anti-inflammatory drugs and achieve improved clinical parameters, including periodontal probing depth, periodontal inflammation, and clinical attachment level.

Socio-behavioral factors, oral hygiene level and periodontitis prevalence in a 35-44-year-old Greek adult population: A cross-sectional survey

Background

Sub-optimal oral hygiene is considered as a primary risk factor for periodontitis occurrence. Various socio-behavioral determinants may contribute either independently or by influencing adversely the oral hygiene (OH) level. The aim of the present study was to examine the periodontal status of 35-44-year-old Greek adults and determine the contribution of risk indicators, including the socio-behavioral aspects and the population’s oral hygiene level, on disease prevalence.

Material and Methods

In 1218 participants, Community Periodontal Index (CPI), Loss of Attachment (LoA) and simplified Oral Hygiene Index (OHI-S) were calculated. Multivariable regression models examined the effect of socio-behavioral factors with/without the inclusion of OHI-S level on pocket depth (PD)≥4mm and LoA≥4mm presence.

Results

11.8% of the participants had healthy periodontium, whereas 37.3% and 5.6% presented with shallow and deep pocketing, respectively. 60.4%, 28.8%, and 10.8.% of the adults demonstrated LoA≤3mm, 4-5mm, and ≥6mm, accordingly. Fair and poor oral hygiene significantly increased the likelihood for PD≥4mm (OR=4.8-20.3) and LoA≥4mm (OR=3.3-6.0) presence. ‘Emergency-oriented dental visiting pattern’ significantly elevated the chance for PD≥4mm presence (OR=1.7). ‘Lower education level’ ‘urban location’, and ‘using an interdental brush’ were significantly independently linked to LoA≥4mm occurrence (OR=1.7-2.1, 1.5, and 2.0, respectively). Lower educated individuals demonstrated inferior oral hygiene status, which in turn elevated significantly the chances of PD≥4mm presence. Smoking more than 10 cigarettes/day, emergency-oriented dental attendance pattern and not flossing were linked to worse oral hygiene levels, which consequently increased significantly the likelihood of LoA≥4mm occurrence.

Conclusions

Fair and poor oral hygiene contribute strongly to periodontitis occurrence. Various socio-behavioral factors may influence adversely oral hygiene maintenance, leading to periodontitis manifestations.

Key words:Community periodontal index, periodontal attachment loss, oral hygiene, adults 35-44, cross-sectional survey, socio-behavioral indicators.

Aggravated Dental and Periodontal Status in Patients with Sickle Cell Disease and Its Association with Serum Ferritin

AIM

The present study aimed to evaluate the possible consequences of sickle cell disease (SCD) on dental and periodontal health in middle-aged patients and to examine the association of certain cardiovascular parameters and serum ferritin with the dental and periodontal status.

MATERIALS AND METHODS

Thirty-seven patients (mean age 43.2 years old) with SCD and 30 non-SCD and otherwise healthy individuals (mean age 38.9 years old) were examined for caries experience and periodontal status in addition to cardiovascular characteristics and ferritin level in serum.

RESULTS

Compared to controls, SCD patients exhibited higher plaque and gingival bleeding scores, higher prevalence of periodontal diseases, and higher caries experience. Multiple stepwise linear regression analysis showed that caries experience was predominantly determined by the presence of SCD and the age, while major determinants of periodontitis were the ferritin levels and the male gender. The results reveal an aggravation of oral health in SCD patients regarding both caries and periodontal diseases.

CONCLUSION

A potential role of the increased central inflammatory response, reflected by the elevated ferritin level in serum, is suggested for the impaired periodontal health of SCD patients.

CLINICAL SIGNIFICANCE

Compliance with precautionary dental checks and early management of dental complications is of great importance in order to improve oral health status and prevent general health complications in SCD patients.

A novel biofilm removal approach (Guided Biofilm Therapy) utilizing erythritol air-polishing and ultrasonic piezo instrumentation: A randomized controlled trial

OBJECTIVE

To evaluate the effectiveness of biofilm removal of a treatment protocol combining an air-abrasive device using erythritol powder (AIRFLOW®) and an ultrasonic piezon instrumentation (Guided Biofilm Therapy/GBT) compared with the conventional mechanical approach (Scaling and Root Planing/SRP) during supportive periodontal treatment (SPT).

MATERIALS AND METHODS

Fifty patients, scheduled for supportive periodontal treatment at the Department of Preventive Dentistry, Periodontology and Implant Biology of the Aristotle University of Thessaloniki were randomly assigned to either a GBT (group A: 24 participants) or a SRP (Group B: 26 participants) treatment protocol. Therapeutic interventions and clinical measurements were performed at baseline and repeated at 6 weeks. Oral hygiene instructions were reinforced at each visit. A questionnaire was handed to the participants for evaluation of patient perception of both utilized approaches.

RESULTS

At 6 weeks, the two groups showed statistically significant reduction in plaque score and in gingival bleeding index compared with baseline. GBT required approximately 15% less chair-time than SRP with a mean difference of 5.1 min, which was statically significant (p = 0.049). Patient perception was more favourable for GBT than SRP.

CONCLUSIONS

Biofilm removal using erythritol AIRFLOW® and ultrasonic piezo-electric instruments (GBT) can be considered equally efficient compared with the conventional SRP. Moreover, GBT seemed to require shorter treatment time and to exhibit a more favourable patient perception than the conventional approach.

Dental caries and psychosocial factors: Testing a conceptual model in adolescents

OBJECTIVES

A conceptual model was designed to examine interrelations among psychosocial factors, oral health behaviour, and dental caries in a sample of adolescents.

METHODS

This cross-sectional study design of 531 Greek families included an oral examination and a survey completed by adolescents, and a survey completed by mothers. The outcome measure was dental caries experience. Additionally, dental sealants were recorded. The participants provided information which comprised the Sense of Coherence (SoC) scale and 11 psychosocial and behavioural variables that formed 6 composite variables (life-course experiences, socio-economic status, perceived parental support, perceived parental punishment, preventive measures, sugar intake frequency). The composite variables of preventive measures and sugar intake formed the latent variable of oral health behaviour. The interrelations of the above factors were included in a conceptual model and tested using a Structural Equation Modelling analysis.

RESULTS

Data fit the proposed conceptual model (χ²  = 23.338, df = 14, P = .055, RMSEA = 0.036). Among psychosocial variables, adolescent's SoC was the best predictor of both dental caries (Standardized Regression Coefficient - Std. RC ± Standard Error (SE) = -0.178 ± 0.04) and oral health behaviour (Std. RC ± SE = -0.378 ± 0.09). All psychosocial factors were associated with SoC (Std. RCs ± SE between -0.162 ± 0.04 and 0.211 ± 0.04) and via SoC with oral health behaviour (Std. RCs ± SE between -0.080 ± 0.03 and 0.061 ± 0.02).

CONCLUSIONS

A conceptual model was tested that integrated SoC with the psychosocial factors theoretically shaping it and clarified all factors' predictive abilities on dental caries via oral health behaviour.

Low prevalence of multi-resistant bacteria in undergraduate dental students; an observational case-control multi-centre study in Europe

Objective: This study assessed the prevalence of MRSA, ESBL and VRE in students from four dental schools in Europe.

Methods: The hand, tongue and nostrils of the students who treated patients (study group) and who did not treat patients (control group) were sampled. After incubation in TSB and subculturing in the presence of 4 µg/ml oxacillin, positive cultures were identified for Staphylococcus aureus by Mannitol salt agar and agglutination tests. The presence of MRSA was confirmed by specific PCR on the species and on the SSCmec genes. ESBL and VRE were isolated using specific CHROMagar and confirmed using antibiotic sensitivity tests.

Results: Of the 879 students who participated in this study (454 students which treated patients, 425 controls) a total of 50 students (5.7%) tested positive for a multi-drug resistant bacterium (MDRB); 13 (1.5%) students tested positive for MRSA, 26 (3.0%) for ESBL and 12 (1.4%) for VRE. No statistically significant differences were found between the students who treated patients compared to the control group for any of the MDRB and study centres, excluding MRSA carriage in the Italian student population. The use of antibiotics the year before sampling, was positively associated with the presence of an MDRB (OR 2.0; 95% Confidence Interval 1.10–3.68; p = 0.02).

Conclusion: The risk for MDRB carriage and sequential transmission of MDRB for dental health care students and their patients were acceptably low.

Tooth Wear in a Sample of Community-Dwelling Elderly Greeks

PURPOSE

Increased wear of teeth may constitute a major problem in the future for the elderly. The aim of the present study was to investigate tooth wear in a sample of elderly Greeks and explore the presence and extent of severe occlusal/incisal wear in relation to the parameters of age, gender and remaining teeth.

MATERIALS AND METHODS

A convenience sample of 70 dentate elderly (60-92 years old) was examined. Tooth wear was assessed using a modification of the tooth wear index. The presence of severe occlusal/incisal wear was explored using the multiple correspondence analysis (MCA) and x2 tests and the extent (% of surfaces) with analysis of variance (ANOVA).

RESULTS

Increased prevalence of severe wear was observed in the occlusal/incisal and, to a lesser extent, in the cervical surfaces of the examined teeth. Seventy per cent (70%) of the participants had at least one severely worn tooth surface. Advanced age seemed to be associated with severe occlusal/incisal wear (>70 years: 79.4%; 60-70 years: 52.8%; x2 test, p = 0.024). The mean (± SD) percentage of severely worn teeth and surfaces was 34.2 ± 32.6% and 9.6 ± 9.6%, respectively. ANOVA showed that males and those with less than 20 remaining teeth exhibited more severely worn occlusal/incisal surfaces (p = 0.031 and p = 0.000, respectively).

CONCLUSIONS

The presence and the extent of severe wear in the sample of the examined elderly is high compared to elderly populations in other countries. Severe wear was more prevalent with advanced age and more extensive in the occlusal/incisal surfaces in males and those having less than 20 remaining teeth.

A single-centre investigator-blinded randomised parallel group clinical trial to investigate the effect of probiotic strains Streptococcus salivarius M18 and Lactobacillus acidophilus on gingival health of paediatric patients undergoing treatment with fixed orthodontic appliances: study protocol

BACKGROUND

There is limited data on the beneficial effects of probiotics on the gingival health of patients undergoing treatment with fixed orthodontic appliances. This study aims to compare the effect of probiotic tablets combined with regular oral hygiene versus regular oral hygiene alone on gingival status in these patients. The effect of probiotic intake on plaque formation and salivary microbiome composition will be also assessed.

METHODS AND ANALYSIS

This is a 3 month single-centre, single blind (clinical and laboratory examiners), parallel group randomised controlled two arm superiority trial. Fifty paediatric patients attending the Postgraduate Orthodontic Clinic at the Hamdan Bin Mohammed College of Dental Medicine (HBMCDM), Mohammed Bin Rashid University of Medicine and Health Sciences (MBRU), Dubai, United Arab Emirates, who meet the eligibility criteria will be recruited. Block randomisation with 1:1 allocation and concealment of allocation will be carried out. The treatment group will receive probiotic tablets containing Streptococcus salivarius M18 and Lactobacillus acidophilus together with regular oral hygiene versus the control group on regular oral hygiene alone. Clinical examination and collection of saliva for microbiome assay will be carried out at baseline and end of study. Self-reporting by patients will be used to document acceptability and adverse effects. Statistically significant decrease in gingival bleeding on probing in the treatment group will be classified as primary outcome of treatment success. Statistically significant reduction in Plaque Index, Gingival Index and shift in the composition of the oral microbiome in favour of beneficial bacteria are secondary outcomes indicative of efficacy of probiotic intake.

ETHICS AND DISSEMINATION

Ethical approval for the study has been granted by the HBMCDM, MBRU, Institutional Review Board (Reference #: MBRU-IRB-2018-015). Study findings will be disseminated via publication in peer-reviewed journal.

TRIAL REGISTRATION NUMBER

ISRCTN95085398.

Psychosocial factors and traumatic dental injuries among adolescents

OBJECTIVES

To examine the association of traumatic dental injuries (TDI) and psychosocial factors in adolescents and to identify psychological profiles associated with TDI.

METHODS

A cross-sectional study was conducted involving 531 students aged 13-16 years. Data were collected through oral examination and a structured interview with the adolescents, in conjunction with a questionnaire answered by their mothers. Associations between TDI and independent variables were analysed using a model-based approach, while an exploratory data analysis was applied to identify homogenous clusters of adolescents in relation to their sense of coherence (SoC), perception of parental support and their mothers' SoC. These clusters were examined further for associations with TDI and psychosocial variables.

RESULTS

The prevalence of TDI was 15.8%. Adolescents with high TDI prevalence were males, nonfirstborns, or those frequently engaging in physical activity. In addition, both their own SoC and that of their mother were low and they reported low parental support. They were also prone to complaining about the behaviour of their peer group. The hierarchical cluster analysis (HCA) demonstrated three homogenous clusters. The cluster with the highest scores for all psychological variables included adolescents with low TDI prevalence, low paternal punishment, spacious home environment, high Family Affluence Scale (FAS) score, good school grades, few complaints about schoolmates and higher maternal education.

CONCLUSIONS

Psychosocial factors appear to influence an adolescent's risk of TDI. High parental support, high own and maternal SoC and a higher socioeconomic status (SES) are typical of adolescents with low TDI experience.

Salivary concentration of the antimicrobial peptide LL-37 in patients with oral lichen planus

Background

The antimicrobial peptide LL-37 is a significant molecule of innate immunity and recent studies indicate that it plays an important role in maintaining oral health. Yet limited knowledge exists on its role in oral diseases and oral lichen planus (OLP) in particular.

Objective

The study aimed to examine: 1) the salivary concentration of LL-37 in patients with OLP and healthy subjects, 2) the relation between the type (reticular or erosive) and size of OLP lesions and LL-37 concentration, and 3) the effect of the therapeutic modalities on LL-37 levels.

Design

The salivary peptide concentration in samples from 20 patients and 30 healthy subjects at the same age range was determined by ELISA.

Results

Despite the wide variation in peptide concentration found in both groups, the healthy subjects exhibited significantly lower levels than patients. Patients with the erosive form had significantly higher peptide concentrations than patients with the reticular form. Systemic treatment with corticosteroids resulted in a significant decrease of the salivary peptide concentration, while other treatment modalities, such as administration of vitamins A and E or local application of corticosteroids had no effect. Improved clinical appearance of the lesions was followed by a decrease in the salivary LL-37 level.

Conclusions

Salivary concentration of LL-37 correlates to the manifestation of mucosa lesions in OLP patients, the highest levels being observed in the most severe cases. This increase in peptide levels may protect against lesion infection and promote a quick wound healing.

Salivary alpha-amylase activity and salivary flow rate in young adults

The secretion of salivary alpha-amylase (sAA) is more associated with psychoneuroendocrinological response to stress than with the flow rate and age. The aim of this cross sectional study is to build an explanatory model based on patterns of relationship between age 20-39 in resting and stimulated saliva under no stressful condition in healthy volunteers. Both resting and stimulated saliva were collected from 40 subjects. The sAA values were log-transformed, the normality assumption was verified with the Shapiro-Wilk test and the reliability of the measurements was estimated by the Pearsons’ r correlation coefficient. The estimated model was based on the theory of the Linear Mixed Models. Significant mean changes were observed in flow rate and sAA activity between resting and stimulated saliva. The final model consists of two components, the first revealed a positive correlation between age and sAA while the second one revealed a negative correlation between the interaction of age × flow rate in its condition (resting or stimulated saliva), with sAA. Both flow rate and age influence sAA activity.

Salivary concentration of free LL-37 in edentulism, chronic periodontitis and healthy periodontium

OBJECTIVE

The antimicrobial peptide LL-37, a component of innate immunity, has an important role in maintaining oral health. This study aimed to investigate the concentration of free LL-37 in whole saliva of periodontally healthy, edentulous and chronic periodontitis subjects.

DESIGN

Unstimulated whole saliva was sampled from 154 subjects (76 periodontally healthy, 20 edentulous, and 58 subjects with chronic periodontitis). All participants were in good general health. The salivary LL-37 was determined by ELISA.

RESULTS

The median salivary concentrations of free LL-37 were 30.5, 22.5, and 1.8ng/ml for the healthy, the chronic periodontitis and the edentulous group, respectively. The differences in concentration between the edentulous and the others were statistically significant (Mann-Whitney test, p<0.001). In the healthy subjects, women displayed significantly higher peptide concentrations compared to men (Mann-Whitney test, p<0.05). The intra-subject variation in LL-37 concentration was wider for the healthy (range 0.75-285ng/ml) and chronic periodontitis patients (range 1-207ng/ml) than for the edentulous subjects (range 0.15-4.4ng/ml).

CONCLUSIONS

The present findings show that edentulism correlates with a substantial decrease in salivary levels of free LL-37, thus indicating the considerable contribution of the gingival tissues in the secretion of the peptide in the oral environment.

Heart rate, salivary α-amylase activity, and cooperative behavior in previously naïve children receiving dental local anesthesia

PURPOSE

Psychosomatic indicators, such as heart rate (HR), salivary alpha amylase (sAA) activity, and behavior, can be used to determine stress. This study's aim was to assess the pattern of changes of salivary alpha amylase, heart rate, and cooperative behavior in previously naïve children receiving dental treatment under local anesthesia.

METHODS

Included were 30 children with no prior dental experience who needed 4 or more sessions of dental treatment involving local anesthesia. In each session, sAA, HR, and behavior were assessed before and during the application of local anesthesia and at the end of the treatment.

RESULTS

The highest sAA value was always observed at the end of each session; overall, the value was lower in the fourth session. HR always increased during the local anesthesia, and did not vary across sessions. No significant relationship was found between child cooperation and either sAA or HR.

CONCLUSION

In this sample, child cooperation may not be an accurate indicator of stress. Based on salivary alpha amylase activity changes, dental treatment involving local anesthesia in naïve children appeared to be less stressful after 3 sessions.

Carbonization of a radicular cyst using fiber-optic diode laser: a case report

A female patient, 51 years old, complaint of painful swelling on the anatomical area of the upper left lateral incisor. The diagnosis of radicular cyst was confirmed histo-pathologically. Nowadays, radicular cysts may be treated using conventional root canal methods or surgical apicectomy. The possible soft-laser reaction to radicular cysts after contact application has not been investigated. We present an in vitro case of a diagnosed radicular cyst which carbonized after contact application of diode laser. The need for future clinical trials will be essential to prove the sensitivity of this procedure in humans.

Transient oral microflora in Greeks attending day centres for the elderly and residents in homes for the elderly

OBJECTIVE

To examine the isolation frequency and the carriage of yeasts, Enterobacteriaceae, Staphylococcus and Enterococcus species in oral samples from elderly Greeks living alone or in institutions.

BACKGROUND

Ageing may promote changes in the oral ecosystem, which lead to colonisation of the mouth by microbes found less commonly or only transiently in younger subjects. Previous studies indicate a geographical variation in the isolation frequency of such bacteria in elderly populations.

MATERIALS AND METHODS

Medical and dental records were obtained from 66 attenders at elderly people's day centres (EPDC), and 82 residents of elderly people's homes (EPH), 66-95 years old. Mucosa smear samples were cultured on appropriate media for enumeration of the above species. Microbial identification was performed by conventional microbiological tests. The results were analysed using the Multiple Correspondence Analysis (MCA), ANOVA and other traditional statistical tests.

RESULTS

No statistically significant association was found between the place of residence and the wearing of dentures. The isolation frequencies of Staphylococcus aureus, Enterococcus and Enterobacteriaceae species were 21.6, 20.3 and 7.4% respectively. MCA, and further statistical analysis, revealed that the place of residence affected the isolation frequency of years (54.9% in EPH vs. 37.9% in EPDC). Moreover, ANOVA showed that living in EPH increased the carriage of yeasts.

CONCLUSIONS

Elderly Greeks exhibit a moderate to high oral carriage of transient bacteria compared with other elderly populations. Living in EPH seems to increase both the isolation frequency and carriage of yeasts.

Cytokine responses of human gingival fibroblasts to Actinobacillus actinomycetemcomitans cytolethal distending toxin

Actinobacillus actinomycetemcomitans is implicated in the pathogenesis of localized aggressive periodontitis, and has the capacity to express a cytolethal distending toxin (Cdt). Gingival fibroblasts (GF) are resident cells of the periodontium, which can express several osteolytic cytokines. The aims of this study were a) to investigate the role of Cdt in A. actinomycetemcomitans-induced expression of osteolytic cytokines and their cognate receptors in GF and b) to determine if the previously demonstrated induction of receptor activator of NFkappaB ligand (RANKL) by A. actinomycetemcomitans is mediated by these pro-inflammatory cytokines or by prostaglandin E(2) (PGE(2)). A. actinomycetemcomitans clearly induced interleukin (IL)-6, IL-1beta, and to a minimal extent, tumor necrosis factor (TNF)-alpha mRNA expression. At the protein level, IL-6 but not IL-1beta or TNF-alpha expression was stimulated. The mRNA expression of the different receptor subtypes recognizing IL-6, IL-1beta and TNF-alpha was not affected. A cdt-knockout strain of A. actinomycetemcomitans had similar effects on cytokine and cytokine receptor mRNA expression, compared to its parental wild-type strain. Purified Cdt stimulated IL-6, but not IL-1beta or TNF-alpha protein biosynthesis. Antibodies neutralizing IL-6, IL-1 or TNF-alpha, and the PGE(2) synthesis inhibitor indomethacin, did not affect A. actinomycetemcomitans-induced RANKL expression. In conclusion, a) A. actinomycetemcomitans induces IL-6 production in GF by a mechanism largely independent of its Cdt and b) A. actinomycetemcomitans-induced RANKL expression in GF occurs independently of IL-1, IL-6, TNF-alpha, or PGE(2).

The cytolethal distending toxin induces receptor activator of NF-kappaB ligand expression in human gingival fibroblasts and periodontal ligament cells

Actinobacillus actinomycetemcomitans is associated with localized aggressive periodontitis, a disease characterized by rapid loss of the alveolar bone surrounding the teeth. Receptor activator of NF-kappaB Ligand (RANKL) and osteoprotegerin (OPG) are two molecules that regulate osteoclast formation and bone resorption. RANKL induces osteoclast differentiation and activation, whereas OPG blocks this process by acting as a decoy receptor for RANKL. The purpose of this study was to investigate the effect of A. actinomycetemcomitans on the expression of RANKL and OPG in human gingival fibroblasts and periodontal ligament cells. RANKL mRNA expression was induced in both cell types challenged by A. actinomycetemcomitans extract, whereas OPG mRNA expression remained unaffected. Cell surface RANKL protein was also induced by A. actinomycetemcomitans, whereas there was no change in OPG protein secretion. A cytolethal distending toxin (Cdt) gene-knockout strain of A. actinomycetemcomitans did not induce RANKL expression, in contrast to its wild-type strain. Purified Cdt from Haemophilus ducreyi alone, or in combination with extract from the A. actinomycetemcomitans cdt mutant strain, induced RANKL expression. Pretreatment of A. actinomycetemcomitans wild-type extract with Cdt antiserum abolished RANKL expression. In conclusion, A. actinomycetemcomitans induces RANKL expression in periodontal connective tissue cells. Cdt is crucial for this induction and may therefore be involved in the pathological bone resorption during the process of localized aggressive periodontitis.

Abundant secretion of bioactive interleukin-1beta by human macrophages induced by Actinobacillus actinomycetemcomitans leukotoxin

Actinobacillus actinomycetemcomitans produces a leukotoxin that selectively kills human leukocytes. Recently, we reported that macrophages are highly sensitive to leukotoxin and that their lysis involves activation of caspase 1. In this study, we show that leukotoxin also induces the production and release of proinflammatory cytokines from human macrophages. The macrophages were challenged with leukotoxin or lipopolysaccharide (LPS) from A. actinomycetemcomitans or LPS from Escherichia coli, and the production and secretion of interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor alpha (TNF-alpha) were determined at the mRNA and protein levels by reverse transcription-PCR and enzyme-linked immunosorbent assay, respectively. Leukotoxin (1 to 30 ng/ml) induced abundant production and secretion of IL-1beta, while the effects on IL-6 and TNF-alpha production were limited. Leukotoxin (1 ng/ml) caused a 10-times-higher release of IL-1beta than did LPS (100 ng/ml). The secreted IL-1beta was mainly the bioactive 17-kDa protein. At higher concentrations (>30 ng/ml), leukotoxin caused secretion of mainly inactive cytokine, the 31-kDa pro-IL-1beta. The presence of specific antibodies to IL-1beta or of a caspase 1 inhibitor blocked the secretion and production of the cytokine. Supernatants of leukotoxin-challenged macrophages stimulated bone resorption when tested in a mouse calvarial model. The activity could be blocked by an IL-1 receptor antagonist or specific antibodies to IL-1beta. We concluded that A. actinomycetemcomitans leukotoxin can trigger abundant production and secretion of bioactive IL-1beta by human macrophages, which is mediated by activation of caspase 1.

Caspase 1 involvement in human monocyte lysis induced by Actinobacillus actinomycetemcomitans leukotoxin

Actinobacillus actinomycetemcomitans, an oral bacterium implicated in the etiology of periodontal diseases, produces a leukotoxin that selectively lyses primate neutrophils and monocytes, the major populations of defense cells in the periodontium. Though lysis requires expression of the receptor lymphocyte function-associated molecule 1 (LFA-1) on the cell surface, not all LFA-1-expressing leukocyte populations are equally susceptible to the toxin. In this study, the susceptibility of human leukocytes to leukotoxin-induced lysis is compared to their expression of LFA-1 and the activity of caspase 1. Cytolysis was determined by the activity of lactate dehydrogenase released from peripheral human leukocytes after 1-h exposure to leukotoxin. Monocytes were lysed at leukotoxin concentrations of > or = 5 ng/ml, while the corresponding values for neutrophils and lymphocytes were approximately 10 times greater. Similar LFA-1 expression was found in all susceptible cell populations irrespective of their degree of sensitivity to the toxin. Exposure of monocytes to leukotoxin increased their caspase 1 activity about fivefold within 10 to 20 min. Presence of the caspase 1 inhibitor Ac-YVAD-CMK significantly blocked the leukotoxin-induced lysis of monocytes only. At sublytic concentrations, leukotoxin induced no apoptotic activity in monocytes, as revealed by the lack of caspase 3 activation and DNA fragmentation. Monocytes are the most lysis-sensitive leukocytes for A. actinomycetemcomitans leukotoxin. Their lysis by this toxin depends on caspase 1 activation and proceeds through a process that differs from classical apoptosis.

Serum-mediated release of leukotoxin from the cell surface of the periodontal pathogen Actinobacillus actinomycetemcomitans

The leukotoxin of the periodontopathogen Actinobacillus actinomycetemcomitans is an important virulence factor that lyses human neutrophils and monocytes and thus, it may enable the bacterium to evade the local host defense. The toxin also induces degranulation of neutrophils and cytokine release in monocytes. To trigger these biological activities, leukotoxin has to be released from the bacterium and diffuse into the periodontal tissues. To date, the conditions found to cause toxin release have been artificial and have included high ion concentration and alkaline conditions. To study the release of the toxin under conditions mimicking the natural environment of the periodontium the ability of human serum to enable leukotoxin release from the bacterial surface was examined. Suspensions of leukotoxic A. actinomycetemcomitans strains were incubated with various concentrations of human serum or serum albumin. The suspensions were centrifuged and the leukotoxin in the supernatants or the cell pellets was detected by gel electrophoresis and immunoblotting. Serum was found to cause the rapid release of leukotoxin from the bacteria in a concentration-dependent manner. Pure albumin exhibited a similar effect. The leukotoxin released was active against human neutrophils. Only a minor proportion of it was associated with membranous vesicles produced by the bacteria. The results indicate that serum, a fluid closely related to the exudate in inflamed periodontal pockets, releases leukotoxin from the cell surface of A. actinomycetemcomitans. The process may enable the diffusion of the toxin from the bacterial biofilm into the surrounding tissues, where it can exert its biological effect.

Lack of lipoprotein-dependent effects on the cytotoxic interactions of Actinobacillus actinomycetemcomitans leukotoxin with human neutrophils

A high odds ratio has been reported for hyperlipidemia and periodontal diseases in humans, and the severity of periodontitis seems to correlate with the hyperlipidemic status of the patients. Early studies indicated that the lipoprotein-containing fraction of the serum enhances the leukotoxic activity of the periodontopathogen Actinobacillus actinomycetemcomitans against human polymorphonuclear leukocytes (PMNL). The protease inhibitors of normal serum account for this enhancement, while delipidated serum has no effect on the leukotoxin-dependent PMNL cytolysis. No information exists for the effect of serum lipoproteins or hyperlipidemic serum. The aim of this study was to evaluate the role of serum lipoproteins in the interaction of the leukotoxin of A. actinomycetemcomitans with human PMNL. Purified leukotoxin was mixed with human PMNL prepared from venous blood of healthy subjects and various varying amounts of hyperlipidemic or delipidated serum, or purified serum lipoproteins. The cytolytic activity of leukotoxin was determined by activity of the cytosol enzyme lactate dehydrogenase released from injured PMNL. The degranulating activity of the toxin was measured through the release of the granule components elastase and lactoferrin. Normal human serum without leukotoxin-neutralizing antibodies caused a 4-fold enhancement of the leukotoxic activity when present at concentrations of 5-10% in the reaction mixture. Serum lipoproteins had no effect when added at concentrations that occur normally in serum. At high concentrations, purified low density and very low-density lipoproteins increased the leukotoxicity of the mixture. Nevertheless, hyperlipidemic serum prepared from a normal serum by the addition of autologous lipoproteins had no influence on the leukotoxin-caused cytolysis compared to the normal serum. Pre-incubation of PMNL for 1 h in hyperlipidemic or delipidated serum had no effect on the leukotoxin-induced degranulation of PMNL. The results indicate that the cytotoxic interactions of A. actinomycetemcomitans leukotoxin against human PMNL are not influenced by the presence of serum lipoproteins.

Release and activation of matrix metalloproteinase 8 from human neutrophils triggered by the leukotoxin of Actinobacillus actinomycetemcomitans

Matrix metalloproteinase 8 (MMP 8) degrades type I collagen and may be involved in the pathogenesis of periodontitis. Latent MMP 8 is stored in neutrophil granules and can be activated when released extracellularly. The periodontitis-associated bacterium Actinobacillus actinomycetemcomitans produces an RTX-toxin, leukotoxin, that degranulates and lyses human neutrophils. This study deals with the ability of leukotoxic A. actinomycetemcomitans to trigger the release and activation of MMP 8. Whole bacteria of three A. actinomycetemcomitans strains or leukotoxin purified from the highly toxic strain HK 1519 were incubated with human neutrophils. The extracellularly released latent and active forms of MMP 8 were detected by an immunoblot technique using specific antibodies against the protease. The activity of MMP 8 was determined by a collagen degradation assay. All strains induced release and activation of MMP 8. The effect was more pronounced under aerobic than anaerobic conditions and correlated with the leukotoxicity of the strains. Pure leukotoxin also induced MMP 8 release and activation in a concentration-dependent manner. Under aerobic conditions, oxidising substances formed by the neutrophils contributed to the rapid activation of the latent enzyme. Upon anaerobic incubation, the activation was slow and mainly caused by other proteases released during neutrophil degranulation. The activation was totally abolished in the presence of serum, probably due to the serum-protease inhibitors. Compared to the calcium ionophore A 23187, a well-known stimulus of neutrophil degranulation, leukotoxin was a more powerful inducer of MMP 8 release, since it triggered the process at a 1000-fold lower concentration. The present findings reveal a specific mechanism that can be induced by A. actinomycetemcomitans leukotoxin and which may contribute to the degradation of periodontal tissues under certain conditions.

Inhibited proliferation of human periodontal ligament cells and gingival fibroblasts by Actinobacillus actinomycetemcomitans: involvement of the cytolethal distending toxin

Actinobacillus actinomycetemcomitans can inhibit fibroblast proliferation. The objective of this study was to characterize the early proliferative responses of human periodontal ligament cells (PDLC) and gingival fibroblasts (GF) to A. actinomycetemcomitans components and to investigate the possible involvement of the cytolethal distending toxin (cdt) produced by this bacterium. The PDLC and GF were challenged with surface components of A. actinomycetemcomitans. Both DNA and protein synthesis as well as cell lysis or apoptosis were assayed for a 6-h period after addition of the bacterial extract. Unlike the controls, inhibition of DNA synthesis had already occurred in the challenged cells at the end of the initial 3- to 6-h period. No lysis or apoptosis was detected, and the total protein synthesis remained unaffected. The persistence of the effect on cell growth was confirmed after a 72-h period of challenge, during which the cells remained viable but exhibited an elongated and distended cell body. No significant differences were observed between PDLC and GF. When a cdt-knockout strain of A. actinomycetemcomitans was used almost no inhibitory effect on cell proliferation was observed. It was concluded that A. actinomycetemcomitans causes a non-lethal inhibition of proliferation in PDLC and GF as a result of an early arrest of DNA synthesis. Cytolethal distending toxin is responsible for most of this effect. This bacterial property may compromise tissue homeostasis in the periodontium.

Protease inhibitors, the responsible components for the serum-dependent enhancement of Actinobacillus actinomycetemcomitans leukotoxicity

Serum enhances the leukotoxic activity of Actinobacillus actinomycetemcomitans against human polymorphonuclear leukocytes (PMNL) by a mechanism that still is unknown. Early attempts to identify the serum components responsible for this enhancement gave no conclusive results, but indicated that the lipoprotein-containing fraction of the serum was involved in the interaction. This study aimed to clarify the role of serum lipoproteins in the leukotoxin interaction, and to identify other serum components involved. The main hypothesis examined was that the leukotoxicity enhancement might depend on serum protease inhibitors that block proteolytic cleavage of leukotoxin by enzymes released from the leukocytes. PMNL were isolated from human peripheral blood and incubated with purified leukotoxin in the presence of serum or purified serum components or lipoprotein-deficient serum. Leukotoxin was also incubated with purified elastase and cathepsin G or with enzyme mixtures from degranulated PMNL. The leukotoxic activity in these mixtures was determined as the extracellular release of lactate dehydrogenase from PMNL. Cleavage of the toxin was showed by gel electrophoresis and Western blot. Morphological changes in PMNL from the above mixtures were examined by electron microscopy. Enzymes from degranulated PMNL cleaved leukotoxin to non-cytotoxic fragments. Elastase and cathepsin G were mainly responsible for the cleavage. Inhibition of leukotoxin degradation was found in the presence of whole serum or of the serum protease inhibitors alpha2-macroglobulin and alpha1-proteinase inhibitor. Under these conditions enhanced PMNL lysis was also observed. A similar enhancement of PMNL lysis was found when PMNL degranulation was blocked by EDTA. On the other hand, lipoprotein-deficient serum had no influence on the leukotoxic activity. The results indicate that the increased leukotoxicity of A. actinomycetemcomitans observed in the presence of human serum is caused by the serum protease inhibitors that counteract proteolytic degradation of leukotoxin. The degradation is caused by enzymes from degranulated PMNL triggered by leukotoxin.

Proteolytic degradation of oral biofilms in vitro and in vivo: potential of proteases originating from Euphausia superba for plaque control

This paper deals with enzymatic removal of dental plaque, in vitro as well as in vivo, using proteases from the Antarctic krill shrimp (Euphausia superba), referred to as Krillase. Krillase exhibits both endo- and exopeptidase activity but has no microbicidal effect. In model systems with pure cultures of oral microorganisms. Krillase demonstrated inhibition of microbial adhesion to saliva-coated hydroxyapatite. Furthermore, a protocol for the growth of reproducible in vitro plaque films has been developed, and effects of Krillase on the plaque film were investigated by means of scanning electron microscopy (SEM). The results showed that Krillase efficiently released microorganisms from plaque in vitro, the effect being dependent on the enzymatic activity. The surface energy of the substratum had a minor influence on the formation and removal of plaque in vitro. Ellipsometric studies on the formation and enzymatic removal of a salivary pellicle indicated that the enzymatic effect on plaque may partly depend on degradation of the salivary pellicle. Krillase was also able to remove plaque accumulated on dentures in vivo. Our results demonstrate the potential of Krillase for plaque control, and that these enzymes are worthy of further investigations including clinical studies and work to find a suitable vehicle.

A new bacterial species associated with failed endodontic treatment: identification and description of Actinomyces radicidentis

OBJECTIVE

This report describes 2 endodontic patients who had persistent signs and symptoms after conventional root canal treatment. The aim of this study was to determine what microorganisms were present in the root canals of the teeth with failed endodontic therapy.

STUDY DESIGN

After removal of the root fillings, the canals were sampled by advanced microbiological techniques and the isolates were characterized by various tests.

RESULTS

Bacteria, which grew in pure cultures, were isolated in each case. The bacteria were similar to each other and were classified as Actinomyces on the basis of phylogenic and phenotypic evidence. The bacteria were different from others within the genus, thus warranting designation as a new species, Actinomyces radicidentis.

CONCLUSIONS

The 2 cases of endodontic failure were infected with A radicidentis, a new Actinomyces species. This bacterium joins a restricted group of other microorganisms that have been associated with failure of root canal treatment.

Characterization of Actinomyces isolates from infected root canals of teeth: description of Actinomyces radicidentis sp. nov

Two strains of a previously undescribed Actinomyces-like bacterium were recovered in pure culture from infected root canals of teeth. Analysis by biochemical testing and polyacrylamide gel electrophoresis of whole-cell proteins indicated that the strains closely resembled each other phenotypically but were distinct from previously described Actinomyces and Arcanobacterium species. Comparative 16S rRNA gene-sequencing studies showed the bacterium to be a hitherto unknown subline within a group of Actinomyces species which includes Actinomyces bovis, the type species of the genus. Based on phylogenetic and phenotypic evidence, we propose that the unknown bacterium isolated from human clinical specimens be classified as Actinomyces radicidentis sp. nov. The type strain of Actinomyces radicidentis is CCUG 36733.

Inhibition of Actinobacillus actinomycetemcomitans leukotoxicity by bacteria from the subgingival flora

Actinobacillus actinomycetemcomitans produces a pore-forming leukotoxin that lyses human polymorphonuclear leukocytes and monocytes. Certain proteolytic bacteria may coexist with A. actinomycetemcomitans in periodontal pockets. We aimed therefore to examine whether oral bacteria can modify the leukotoxicity of A. actinomycetemcomitans. A total of 55 strains representing 45 bacterial species of the subgingival flora were tested. Each strain was incubated with the highly toxic strain of A. actinomycetemcomitans HK 1519 and the leukotoxic activity of the suspension against human polymorphonuclear leukocytes was determined from the activity of the lactate dehydrogenase released upon lysis of the leukocytes. Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Prevotella melaninogenica and Prevotella loeschii inhibited the leukotoxicity of A. actinomycetemcomitans cells as well as the activity of leukotoxin purified from the same strain. The bacterial strains without the ability to block leukotoxic activity also failed to destroy pure leukotoxin even after 5 h of incubation. The proteolytic degradation of leukotoxin by P. gingivalis was mainly dependent on the activity of the enzymes R- and K-gingipains. P. intermedia and P. nigrescens also degraded the leukotoxin by enzymes. The results imply a role of the periodontal microflora in modifying the virulence of A. actinomycetemcomitans by destroying its leukotoxin.

Cytocidal and apoptotic effects of the ClyA protein from Escherichia coli on primary and cultured monocytes and macrophages

Cytolysin A (ClyA) is a newly discovered cytolytic protein of Escherichia coli K-12 that mediates a hemolytic phenotype. We show here that highly purified ClyA and ClyA-expressing E. coli were cytotoxic and apoptogenic to fresh as well as cultured human and murine monocytes/macrophages.

Polymorphonuclear leukocyte degranulation induced by leukotoxin from Actinobacillus actinomycetemcomitans

The ability of leukotoxin from Actinobacillus actinomycetemcomitans to induce release of lysosomal constituents was studied with human polymorphonuclear leukocytes (PMNL). Leukotoxin purified from A. actinomycetemcomitans or bacterial cells of a leukotoxic strain were mixed with human PMNL and the suspension was incubated under anaerobic conditions. Samples were taken at certain time intervals to examine the cell morphology of PMNL by electron microscopy and the extracellular concentrations of the granule components lactoferrin and elastase by enzyme-linked immunosorbent assay (ELISA). Electron microscopy revealed that within 10 min of exposure to leukotoxin, the number of intracellular granules was markedly reduced and the remaining granules were translocated to the periphery in PMNL. At the same time, the extracellular concentrations of lactoferrin and elastase were elevated, while that of the cytosolic enzyme lactate dehydrogenase, an indicator of cell lysis, remained low. The lysosome molecules CD63 and CD66b were also exposed on the PMNL surface, indicating fusion of lysosomes with the plasma membrane. These effects were completely abolished by the addition of anti-leukotoxin serum. Pre-incubation of PMNL with monoclonal antibodies to CD11a and CD18 that recognize alpha- and beta-chains of the LFA-1 integrin, a leukotoxin receptor on PMNL, inhibited the cytolysis, but not the release of granule components. The present results demonstrate the ability of A. actinomycetemcomitans leukotoxin to trigger a rapid release of lysosomal compounds in human PMNL. The release is due to an active process stimulated by the interaction of PMNL with the toxin or toxin-carrying bacteria.

Anaerobic neutrophil-dependent killing of Actinobacillus actinomycetemcomitans in relation to the bacterial leukotoxicity

The effect of leukotoxin on the interaction of Actinobacillus actinomycetemcomitans with human polymorphonuclear leukocytes (PMNL) was studied under anaerobic conditions with strains able to produce high or low amounts of leukotoxin. PMNL morphology, phagocytosis and killing were examined by transmission electron microscopy and bioassays, respectively. At ratios of > or =25 bacteria/PMNL, a highly toxic A. actinomycetemcomitans strain completely destroyed the PMNL within 7 min, resulting in bacterial survival. Lowering the bacteria/PMNL-ratio enabled phagocytosis and killing of this highly toxic strain. A. actinomycetemcomitans strains with low leukotoxicity were effectively killed by PMNL under any condition. Presence of specific antibodies against A. actinomycetemcomitans or of anti-leukotoxin serum protected PMNL from being injured and allowed phagocytosis to occur. Pre-incubation of the leukotoxic strain with Porphyromonas gingivalis, a bacterium that destroys leukotoxin, abolished lysis of PMNL and inhibited phagocytosis of A. actinomycetemcomitans. The results show that leukotoxin may protect A. actinomycetemcomitans against phagocytosis by human PMNL. The protection occurs at a population level and in relation to the bacterial load. The size of the bacterial population required to counteract phagocytosis is dependent on the leukotoxin production of the strain.

Description of Mogibacterium pumilum gen. nov., sp. nov. and Mogibacterium vescum gen. nov., sp. nov., and reclassification of Eubacterium timidum (Holdeman et al. 1980) as Mogibacterium timidum gen. nov., comb. nov

A new genus, Mogibacterium, is proposed for anaerobic, non-spore-forming, Gram-positive, rod-shaped bacteria which have been isolated from the periodontal pockets of adult human patients with periodontal disease and infected root canals. The novel isolates, strains D2-18T, BA11a-f and D5-2T, were inert in most of the conventional biochemical tests and phenotypically resemble asaccharolytic Eubacterium species. The protein profiles of whole cells on SDS-PAGE gels and Western immunoblotting reaction analysis distinguished these organisms from type strains belonging to the previously described Eubacterium species. The G + C content of the DNA is 45-46 mol% for Mogibacterium pumilum and 46 mol% for Mogibacterium vescum. The levels of DNA-DNA relatedness of these new species to other Eubacterium species, including Eubacterium limosum, Eubacterium brachy, Eubacterium lentum, Eubacterium nodatum, Eubacterium saphenum, and the more recently proposed Eubacterium minutum and Eubacterium exiguum (reclassified as Slackia exigua), are less than 2%. The DNA-DNA hybridization value between M. pumilum and M. vescum was 30%. Eubacterium timidum exhibited DNA homologies with Mogibacterium species which were low (17 and 18%) but clearly higher than with all the other Eubacterium species. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the closest phylogenetic neighbour of Mogibacterium species was E. timidum, and that these three species represent a novel lineage distinct from the previously described genera of Gram-positive, rod-shaped bacteria. On the basis of phenotypic characteristics and 16S rRNA gene sequence comparisons, it is also proposed that E. timidum is transferred to the genus Mogibacterium gen. nov. as Mogibacterium timidum gen. nov., comb. nov. (type strain ATCC 33093T).

Cryptobacterium curtum gen. nov., sp. nov., a new genus of gram-positive anaerobic rod isolated from human oral cavities

Novel Eubacterium-like isolates, strains 12-3T and KV43-B, which were isolated from the periodontal pocket of an adult patient with periodontal disease and necrotic dental pulp, respectively, were studied taxonomically and phylogenetically. The morphological and differential biochemical characteristics of these organisms are also described in this paper. These organisms were Gram-positive, anaerobic, non-spore-forming, rod-shaped bacteria that were inert in most of the conventional biochemical tests and closely resembled members of asaccharolytic oral Eubacterium species. On the other hand, protein profiles of whole cells in SDS-PAGE and Western immunoblotting reaction analysis distinguished these isolates from strains of the previously described genus Eubacterium. The G+C content of the DNAs from the novel isolates was 50 and 51 mol%, respectively. The levels of DNA-DNA relatedness to other asaccharolytic oral Eubacterium species, including Eubacterium brachy, Eubacterium lentum, Eubacterium nodatum, Eubacterium timidum, Eubacterium saphenum, Eubacterium minutum and Eubacterium exiguum, was less than 11%. These organisms also exhibited a very low level of reassociation with the DNA of Eubacterium limosum, the type species of the genus Eubacterium. The results of 16S rDNA sequence comparisons revealed that these organisms represent a novel lineage distinct from all previously described genera of Gram-positive, rod-shaped bacteria. On the basis of our results, it is suggested that strains 12-3T and KV43-B should be classified in a new genus and species, for which the name Cryptobacterium curtum gen. nov., sp. nov. is proposed. The type strain of Cryptobacterium curtum is 12-3T (= ATCC 700683T).

Tissue necrosis after subgingival irrigation with fluoride solution

Irrigation of periodontal pockets with fluoride solution after scaling and root planing is occasionally recommended to inhibit the growth of pathogenic bacteria in the periodontal pocket. At the same time, irrigation enables mechanical removal of loosely adhering plaque and debris. Due to its toxicity, fluoride solution deposited in the periodontium may lead to tissue damage. We report in this paper, a case of extensive periodontal tissue necrosis and permanent loss of alveolar bone after irrigation of periodontal pockets with stannous fluoride solution. The literature on the toxic effects of fluoride on the local tissues is briefly reviewed and arguments for a re-evaluation of the use of stannous fluoride for pocket irrigation are provided.

Characterization of the proteinase-dependent cytotoxicity of Porphyromonas gingivalis

Cytotoxicity of proteins from Porphyromonas gingivalis towards gingival fibroblasts and epithelial cells was studied by methods measuring vital dye uptake, DNA synthesis, release of cytoplasmic components, and apoptosis. Microscopic examination of the cells was also performed for detection of morphological changes. Experiments were made with dialyzed culture supernatants of P. gingivalis as well as supernatant fractions obtained by isoelectric focusing. The main cell damage observed was rounding of the cells and detachment from each other and the underlying surface. The cell-damaging activity correlated with the cystein-dependent proteolytic activity of the various supernatant preparations as well as with the occurrence of gelatinolytic protein bands with molecular weights previously reported for the cysteine proteinases gingipains R and K of P. gingivalis. The activity was abolished by heat treatment or by the addition of cysteine proteinase inhibitors. The results indicate that the main cytotoxic effect towards fibroblasts and epithelial cells is degradation of the intercellular matrix. The gingipains released in P. gingivalis culture supernatants are the responsible factors for this degradation.

Ribotype diversity of Actinomyces with similar intraoral tropism but different types of N-acetyl-beta-D-galactosamine binding specificity

Sixty-three isolates of Actinomyces naeslundii genospecies 1 and 2 and Actinomyces odontolyticus from three subjects clustered into 22 ribotypes. Unique ribotypes were found in the subjects and within individual tissue sites (bucca, tooth and tongue). A odontolyticus ribotypes shared tongue-specific binding properties, while those of genospecies 1 and 2 from buccal and tooth surfaces shared different types of N-acetyl-beta-D-galactosamine binding specificity.

Restriction fragment-length polymorphism analysis of 16S rDNA from oral asaccharolytic Eubacterium species amplified by polymerase chain reaction

Restriction fragment-length polymorphism (RFLP) analysis of 16S rDNA amplified by polymerase chain reaction was used to generate restriction profiles of the type strains of oral asaccharolytic Eubacterium species, that is, Eubacterium brachy, Eubacterium exiguum, Eubacterium lentum, Eubacterium minutum, Eubacterium nodatum, Eubacterium saphenum, Eubacterium timidum and 33 asaccharolytic Eubacterium strains isolated from oral sites. The 16S rRNA gene sequences from isolated genomic DNA samples were amplified by polymerase chain reaction (PCR). PCR products were purified and characterized by single digestions with 7 restriction endonucleases. Among the 7 endonucleases, HpaII was found to discriminate the respective reference strains. Twenty-three isolates, out of 33, were assigned to one of the reference species, on the basis of their restriction profiles by digestion with HpaII. The remaining 10 isolates could not be assigned to any of the established species and constituted 4 distinct groups, each of which may be a new species.

Characterization of the lactoferrin-dependent inhibition of the adhesion of Actinobacillus actinomycetemcomitans, Prevotella intermedia and Prevotella nigrescens to fibroblasts and to a reconstituted basement membrane

Lactoferrin was previously shown to inhibit the adhesion of A. actinomycetemcomitans, P. intermedia and P. nigrescens to human cells. Lactoferrin was also shown to competitively inhibit the binding of these bacteria to the basement membrane protein laminin. The present study aimed to determine the type of interactions inhibited by lactoferrin. Lactoferrin binds to fibroblast monolayers and Matrigel, a reconstituted basement membrane, through ionic interactions. The adhesion of A. actinomycetemcomitans to these substrata was mainly dependent on the ionic strength of the environment. P. intermedia and P. nigrescens also adhere to fibroblasts mainly by ionic interactions, while their adhesion to Matrigel seems to be mediated by specific mechanisms. Lectin-type interactions were not found to be involved in the binding of these bacteria to the substrata. Treatment of either A. actinomycetemcomitans or fibroblasts with lactoferrin decreased the adhesion in a dose-dependent manner, while lactoferrin treatment of Matrigel alone had no adhesion-counteracting effect. Adhesion of P. intermedia and P. nigrescens to Matrigel was not significantly affected by the ionic strength, but the presence of lactoferrin inhibited the adhesion. Lactoferrin bound to Matrigel, P. intermedia and P. nigrescens was rapidly released, while lactoferrin bound to A. actinomycetemcomitans and fibroblasts was retained. These findings indicate that lactoferrin-dependent inhibition of the adhesion of A. actinomycetemcomitans, P. intermedia and P. nigrescens to fibroblasts and Matrigel can involve binding of lactoferrin to both the bacteria and substrata. The decreased adhesion may be due to blocking of both specific adhesin-ligand as well as non-specific charge-dependent interactions.

Fluoride and mutans streptococci levels in plaque on aged restorations of resin-modified glass ionomer cement, compomer and resin composite

The use of fluoride-releasing restoratives such as glass ionomer cements (GICs) has increased during the last decade. The antibacterial effect of released fluoride is thought to be a possible caries-preventive effect of these restorations. In this study fluoride concentrations in plaque on 1-year old resin-modified GIC, compomer and resin composite restorations were compared intraindividually and related to the occurrence of caries-associated bacteria. Plaque from class III restorations of the three restorative materials and from a proximal enamel surface in 18 individuals was analysed. Low fluoride levels were detected in all the samples, while the resin-modified GIC samples showed significantly higher amounts. The distribution of oral streptococci, mutans streptococci and lactobacilli did not differ significantly among the surfaces and did not correlate to the fluoride levels in the samples. A good correlation was found between the counts of mutans streptococci in saliva and their proportions in the plaque. The results indicate that the fluoride concentrations released in vivo from 1-year-old restoratives are not high enough to affect the plaque levels of the caries-associated bacteria mutans streptococci and lactobacilli.

Degradation of lactoferrin by periodontitis-associated bacteria

The degradation of human lactoferrin by putative periodontopathogenic bacteria was examined. Fragments of lactoferrin were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and measured by densitometry. The degradation of lactoferrin was more extensive by Porphyromonas gingivalis and Capnocytophaga sputigena, slow by Capnocytophaga ochracea, Actinobacillus actinomycetemcomitans and Prevotella intermedia, and very slow or absent by Prevotella nigrescens, Campylobacter rectus, Campylobacter sputorum, Fusobacterium nucleatum ssp. nucleatum, Capnocytophaga gingivalis, Bacteroides forsythus and Peptostreptococcus micros. All strains of P. gingivalis tested degraded lactoferrin. The degradation was sensitive to protease inhibitors, cystatin C and albumin. The degradation by C. sputigena was not affected by the protease inhibitors and the detected lactoferrin fragments exhibited electrophoretic mobilities similar to those ascribed to deglycosylated forms of lactoferrin. Furthermore a weak or absent reactivity of these fragments with sialic acid-specific lectin suggested that they are desialylated. The present data indicate that certain bacteria colonizing the periodontal pocket can degrade lactoferrin. The presence of other human proteins as specific inhibitors and/or as substrate competitors may counteract this degradation process.

Laminin binding to a heat-modifiable outer membrane protein of Actinobacillus actinomycetemcomitans

The interaction of Actinoabacillus actinomycetemcomitans with the basement membrane protein, laminin, was examined in a 125I-labeled protein-binding assay. The binding of laminin increased by lowering the pH. The ability to bind laminin was decreased in cells at the stationary phase of growth and by the presence of blood in the culture medium. Laminin binding to this bacterium was saturable, and the affinity constant was 4.6 nM. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Western blot (ligand blot) analysis of cell-envelope and outer membrane of A. actinomycetemcomitans displayed a 125I-laminin-reactive protein band with a molecular weight of 29 k. The laminin-binding protein was the previously described outer membrane protein A of A. actinomycetemcomitans. It was identified by its heat-modifiable property, detergent-solubility profile and reactivity with outer membrane protein A-specific polyclonal antiserum. At acidic pH, 25I laminin bound to several cell-envelope components of A. actinomycetemcomitans, but at neutral pH, laminin bound only to the heat-modifiable protein. Despite the existence of the laminin-binding protein, cells grown in blood-containing media did not bind laminin. Several mammalian proteins interfered with laminin-bacterial interaction, including lactoferrin, which binds to the same bacterial protein that inhibited and displaced the laminin-bacterial interaction.

Effect of acetate on sorbitol fermentation by oral lactobacilli

The rate of acid production and end-products from sorbitol were measured under anaerobic conditions in washed-cell suspensions of oral strains of Lactobacillus casei subsp. casei and Lactobacillus casei subsp. rhamnosus. The enzymatic activities were assayed in cell extracts of these strains. The cells fermented sorbitol to lactate, formate, ethanol and acetate under anaerobic conditions. Exposure of the cells to air (oxygen) led to inactivation of pyruvate formate-lyase and inhibition of anaerobic sorbitol fermentation. In the presence of acetate, air-exposed cells fermented sorbitol with a concomitant consumption of acetate and production of ethanol and lactate. Acetate also enhanced acid production from sorbitol in cells kept under anaerobic conditions and resulted in formation of lactate and ethanol. Cell extracts of all the strains had NADH-coupled acetate-reducing activity, which consisted of sequential reactions of acetate kinase, phosphotransacetylase, acylating aldehyde dehydrogenase and alcohol dehydrogenase. These findings indicate that oral lactobacilli can utilize acetate as an electron acceptor for maintaining their intracellular redox balance during anaerobic sorbitol fermentation in the absence of pyruvate formate-lyase activity.

Phosphorylating enzymes involved in glucose fermentation of Actinomyces naeslundii

Enzymatic activities involved in glucose fermentation of Actinomyces naeslundii were studied with glucose-grown cells from batch cultures. Glucose could be phosphorylated to glucose 6-phosphate by a glucokinase that utilized polyphosphate and GTP instead of ATP as a phosphoryl donor. Glucose 6-phosphate was further metabolized to the end products lactate, formate, acetate, and succinate through the Embden-Meyerhof-Parnas pathway. The phosphoryl donor for phosphofructokinase was only PPi. Phosphoglycerate kinase, pyruvate kinase, and acetate kinase coupled GDP as well as ADP, but P(i) compounds were not their phosphoryl acceptor. Cell extracts showed GDP-dependent activity of phosphoenolpyruvate carboxykinase, which assimilates bicarbonate and phosphoenolpyruvate into oxaloacetate, a precursor of succinate. Considerable amounts of GTP, polyphosphate, and PPi were found in glucose-fermenting cells, indicating that these compounds may serve as phosphoryl donors or acceptors in Actinomyces cells. PPi could be generated from UTP and glucose 1-phosphate through catalysis of UDP-glucose synthase, which provides UDP-glucose, a precursor of glycogen.

Lactoferrin interaction with Actinobacillus actinomycetemcomitans

The interaction of lactoferrin with Actinobacillus actinomycetemcomitans was examined in a 125I-labeled protein binding assay. The binding of human and bovine lactoferrins reached maximum within 1 h. Lactoferrin binding to the bacterium was pH-dependent and reversible. Scatchard analysis indicated the existence of two different types of binding sites on the bacterium, one with a high affinity constant k alpha approximately 8.8 x 10(-7) M) and the other with a low one (k alpha approximately 1.8 x 10(-6) M). Bacteria in the exponential phase of growth showed higher binding than cells in the stationary phase. Bacteria grown in medium containing serum and/or lysed erythrocytes bound lactoferrin to a lesser extent. Heat-inactivated serum, lysed erythrocytes and other proteins such as mucin and laminin inhibited lactoferrin binding to A. actinomycetemcomitans in a competitive binding assay. Sodium dodecyl sulfate polyacrylamide-gel electrophoresis and Western blot analysis of the cell envelope as well as the outer membrane of A. actinomycetemcomitans revealed lactoferrin-reactive protein bands at 29 kDa and 16.5 kDa. The 29-kDa band displayed a heat-modifiable lactoferrin-reactive form with a molecular weight of 34 kDa. Neither proteinase K-treated cell envelope nor lipopolysaccharide of this bacterium showed reactivity with lactoferrin. These data suggests a specific interaction of lactoferrin with outer membrane proteins of A. actinomycetemcomitans.

Inhibitory effect of lactoferrin on the adhesion of Actinobacillus actinomycetemcomitans and Prevotella intermedia to fibroblasts and epithelial cells

Adhesion of the periodontitis-associated bacteria Actinobacillus actinomycetemcomitans and Prevotella intermedia to monolayers of fibroblasts, HEp-2, KB and HeLa cells was quantified with radiolabeled bacteria. Bacterial adhesion was also examined microscopically with Giemsa-stained non-radioactive preparations. The degree of bacterial adherence was dependent on the growth phase of the bacteria. Strains at the exponential phase adhered to a greater extent than those at the stationary phase of growth. Both human and bovine lactoferrins competitively inhibited the adhesion of A. actinomycetemcomitans and P. intermedia to all tested cell monolayers. The inhibitory effect was dose-dependent in the concentration range 0.5-2500 micrograms/ml and not related to the bacterial growth phase. In the presence of lactoferrin, decreased association of bacteria with the cell monolayers was also found by microscopic examination of the preparations. The present findings indicate that lactoferrin may prevent the establishment of bacteria in periodontal tissues through adhesion-counteracting mechanisms in addition to its bacteriostatic and bactericidal properties.

Initial catabolism of sorbitol in Actinomyces naeslundii and Actinomyces viscosus

The initial steps of sorbitol catabolism were studied in 4 strains of Actinomyces naeslundii and Actinomyces viscosus that had been isolated from human dental plaque. Cell-free extracts were prepared from cells grown in the presence of either sorbitol, xylitol or glucose. The extracts from all strains grown on sorbitol had nicotinamide adenine dinucleotide-linked dehydrogenase activities for sorbitol and xylitol and reduced nicotinamide adenine dinucleotide-linked reductase activities for fructose and xylulose. Two of the strains also exhibited these activities when grown in the presence of xylitol, and all glucose-grown cells lacked them. The results indicate that sorbitol metabolism in oral actinomyces involve oxidation of sorbitol to fructose by an inducible enzyme, nicotinamide adenine dinucleotide-linked sorbitol dehydrogenase. This step is followed by the phosphorylation of fructose with guanosine triphosphate as a main phosphoryl donor. Thus, the initial catabolic pathway of sorbitol in A. naeslundii and A. viscosus is different from those described for other oral bacteria.