Treated periodontitis and recurrent events after first-time myocardial infarction: A Danish nationwide cohort study

AIM

To investigate the association between previous periodontal treatment and recurrent events after first-time myocardial infarction (MI).

MATERIALS AND METHODS

From the Danish nationwide registries, patients with first-time MI between 2000 and 2015 were divided into three groups according to oral health care within 1 year prior to first-time MI. A multiple logistic regression model provided adjusted odds ratios (ORs) with 95% confidence intervals (CIs) to assess the 3-year risk of major adverse cardiovascular events (MACE).

RESULTS

A total of 103,949 patients were included. Patients with treated periodontitis (PD) prior to first-time MI had an adjusted 3-year risk of MACE similar to patients presumed periodontally healthy (OR 0.97 [95% CI 0.92-1.03]). Patients with no prior dental visits were significantly older, had more comorbidities and showed significantly increased adjusted 3-year risks of MACE (OR 1.47 [95% CI 1.42-1.52]), cardiovascular death (OR 1.71 [95% CI 1.64-1.78]) and heart failure (OR 1.13 [95% CI 1.07-1.20]) compared with patients presumed periodontally healthy.

CONCLUSIONS

Patients with treated PD 1 year prior to first-time MI had a similar risk of recurrent cardiovascular events as patients presumed periodontally healthy. No dental visit prior to first-time MI was an independent risk factor for recurrent events.

Suitability of machine learning models for prediction of clinically defined Stage III/IV periodontitis from questionnaires and demographic data in Danish cohorts

AIM

To evaluate if, and to what extent, machine learning models can capture clinically defined Stage III/IV periodontitis from self-report questionnaires and demographic data.

MATERIALS AND METHODS

Self-reported measures of periodontitis, demographic data and clinically established Stage III/IV periodontitis status were extracted from two Danish population-based cohorts (The Copenhagen Aging and Midlife Biobank [CAMB] and The Danish Health Examination Survey [DANHES]) and used to develop cross-validated machine learning models for the prediction of clinically established Stage III/IV periodontitis. Models were trained using 10-fold cross-validations repeated three times on the CAMB dataset (n = 1476), and the resulting models were validated in the DANHES dataset (n = 3585).

RESULTS

The prevalence of Stage III/IV periodontitis was 23.2% (n = 342) in the CAMB dataset and 9.3% (n = 335) in the DANHES dataset. For the prediction of clinically established Stage III/IV periodontitis in the CAMB cohort, models reached area under the receiver operating characteristics (AUROCs) of 0.67-0.69, sensitivities of 0.58-0.64 and specificities of 0.71-0.80. In the DANHES cohort, models derived from the CAMB cohort achieved AUROCs of 0.64-0.70, sensitivities of 0.44-0.63 and specificities of 0.75-0.84.

CONCLUSIONS

Applying cross-validated machine learning algorithms to demographic data and self-reported measures of periodontitis resulted in models with modest capabilities for the prediction of Stage III/IV periodontitis in two Danish cohorts.

Additional information of bitewings to first time clinical examination of caries and restoration status in permanent dentition

OBJECTIVES

Identifying additional information obtained by X-rays combined with clinical examination concerning primary caries, caries adjacent to restorations and quality of restorations.

MATERIAL AND METHODS

A total of 240 adult patients, equally distributed in gender and six age-groups, were randomly selected from an original study population of 4,402 subjects (DANHES). Clinical and radiographical registrations on occlusal and approximal surfaces in posterior teeth were categorized into unrestored surfaces (sound/primary caries) and restored surfaces (without/with caries adjacent to restorations). Material and quality of restorations were also recorded. Chi-square and Fisher-exact tests were used for statistical analyses.

RESULTS

Of potentially 11,520 surfaces, 3,015 occlusal and 5,112 approximal surfaces were analysed. Occlusal: Of 907 unrestored surfaces, 110 had primary caries and 53% were detected radiographically. A total of 183 of 2,108 restored surfaces had caries adjacent to restorations, and 99% were found radiographically. A total of 190 restorations were over/under-extended, and 89% were registered radiographically. Approximal: Of 2,649 unrestored surfaces 648 had primary caries, and 92% were registered radiographically. A total of 565 of 2,463 restored surfaces had caries adjacent to restorations, and 99% were found radiographically. A total of 638 restorations were over/under-extended, and 98% were found radiographically. For all restorations, material and depth influenced quality of restorations and incidence of caries adjacent to restorations. At least one independent variable (gender/age group/tooth-type/jaw/side/mesial-distal surface) influenced frequencies of primary caries, caries adjacent to restorations and quality of restorations.

CONCLUSIONS

First-time clinical examination must be supplemented with X-rays to obtain a complete impression of caries status in posterior regions regarding diagnostics of caries, assessment of lesion depth and quality of restorations.

Immunoglobulin G antibodies against Porphyromonas gingivalis or Aggregatibacter actinomycetemcomitans in cardiovascular disease and periodontitis

Objectives: The aim was to elucidate whether levels of circulating antibodies to Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis correlate to loss of attachment, as a marker for periodontitis and cardiovascular disease (CVD). Design: Sera were collected from 576 participants of the Danish Health Examination Survey (DANHES). Immunoglobulin G antibodies against lipopolysaccharide (LPS) and protein antigens from the a, b and c serotypes of A. actinomycetemcomitans and P. gingivalis were quantified by titration in ELISA plates coated with a mixture of antigens prepared by disintegration of bacteria. Results: Levels of antibodies against P. gingivalis (OR = 1.48) and A. actinomycetemcomitans (1.31) associated with periodontitis, as determined by univariable logistic regression analysis. These antibody levels also associated with CVD (1.17 and 1.37), respectively, However, after adjusting for other risk factors, including age, smoking, gender, alcohol consumption, overweight, and level of education using multivariable logistic regression analysis, only increasing body mass index (BMI; 1.09), previous smoking (1.99), and increasing age (decades) (2.27) remained associated with CVD. Increased levels of antibodies against P. gingivalis (1.34) remained associated with periodontitis after adjusting for other risk factors. Conclusions: CVD and periodontitis were associated with levels of IgG antibodies to P. gingivalis or A. actinomycetemcomitans in univariable analyses, but only the association of P. gingivalis antibody levels with periodontitis reached statistical significance after adjustment for common confounders. Age, in particular, influenced this relationship.

Dental biofilm infections - an update

Teeth are colonized by oral bacteria from saliva containing more than 700 different bacterial species. If removed regularly, the dental biofilm mainly comprises oral streptococci and is regarded as resident microflora. But if left undisturbed, a complex biofilm containing up to 100 bacterial species at a site will build up and may eventually cause development of disease. Depending on local ecological factors, the composition of the dental biofilm may vary considerably. With access to excess carbohydrates, the dental biofilm will be dominated by mainly gram-positive carbohydrate-fermenting bacteria causing demineralization of teeth, dental caries, which may further lead to inflammation and necrosis in the pulp and periapical region, i.e., pulpitis and periapical periodontitis. In supra- and subgingival biofilms, predominantly gram-negative, anaerobic proteolytic bacteria will colonize and cause gingival inflammation and breakdown of supporting periodontal fibers and bone and ultimately tooth loss, i.e., gingivitis, chronic or aggressive periodontitis, and around dental implants, peri-implantitis. Furthermore, bacteria from the dental biofilm may spread to other parts of the body by bacteremia and cause systemic disease. Basically, prevention and treatment of dental biofilm infections are achieved by regular personal and professional removal of the dental biofilm.

Impact of Periodontitis Case Criteria: A Cross-Sectional Study of Lifestyle

BACKGROUND

Associations of risk factors/indicators with periodontitis may depend on the included case criterion. The objective of the current study is to evaluate differences in outcome by applying five periodontitis case definitions for cross-sectional associations with lifestyle factors among participants of the Danish Health Examination Survey (DANHES).

METHODS

A total of 4,402 adults aged 18 to 96 years from the general health examination of DANHES had a periodontal examination consisting of half-mouth registration at six sites per tooth including probing depth (PD) and clinical attachment level (CAL). Periodontitis was defined according to severe periodontitis, European Workshop of Periodontology (EWP)-specific, meanCAL ≥2.55 mm, CAL-tertile, and PD-CAL definitions. Multivariable logistic regression models fitted the association of age, sex, smoking status, diabetes mellitus, educational level, alcohol consumption, body mass index, physical activity, body fat percentage, waist circumference, triglycerides, total cholesterol, and C-reactive protein with periodontitis.

RESULTS

Number of cases captured by the five periodontitis case definitions ranged from 337 (9.2%) to 1,136 (31.0%). A total of 224 participants were defined as periodontitis cases by all five criteria. Analyses on 3,665 participants with complete data revealed statistically significant associations of age and smoking with all periodontitis case definitions and of male sex with severe periodontitis and EWP-specific definitions. Educational level (two lowest groups) was related to three periodontitis criteria. Among obesity and hyperlipidemia measures no factors were related to periodontitis.

CONCLUSION

Regression analyses showed little difference in odds ratio across the five periodontitis case definitions; however, the level of significance did show some variation.

Salivary microbiota in individuals with different levels of caries experience

This study compared salivary bacterial profiles in two groups having a 10-fold difference in levels of caries experience, as it was hypothesized that the composition of the salivary microbiota might associate with the levels of caries experience.

Bacterial profiles in stimulated saliva samples from 85 individuals with low levels of caries experience (healthy group) and 79 individuals with high levels of caries experience (caries group) were analyzed by means of the Human Oral Microbiome Identification Next Generation Sequencing (HOMINGS) technique. Subsequently, saliva samples from caries-free individuals in the healthy group (n = 57) and the caries group (n = 31) were compared.

A significantly higher α-diversity (p < 0.0001) and a twofold higher relative abundance of Neisseria, Haemophilus, and Fusobacterium were recorded in saliva samples from the healthy group compared with the caries group. Differences observed were more pronounced when limiting the analyses to caries-free individuals in each group.

Data from this cross-sectional analysis suggest that low levels of caries experience might associate with a characteristic salivary bacterial composition different from that in individuals with high caries experience. Consequently, longitudinal studies are required to determine if the composition of the salivary microbiota might be a predictive factor of caries risk at the individual level.

Comparative analysis of bacterial profiles in unstimulated and stimulated saliva samples

Background and objective

The microbial profiles of stimulated saliva samples have been shown to differentiate between patients with periodontitis, patients with dental caries, and orally healthy individuals. Saliva was stimulated to allow for easy and rapid collection; however, microbial composition may not reflect the more natural, unstimulated state. The purpose of this study was to validate whether stimulated saliva is an adequate surrogate for unstimulated saliva in determining salivary microbiomes.

Design

Unstimulated (n=20) and stimulated (n=20) saliva samples were collected from 20 orally and systemically healthy, non-smoking participants. Salivary bacterial profiles were analyzed by means of the Human Oral Microbe Identification using Next Generation Sequencing (HOMINGS), and statistical analysis was performed using Mann–Whitney test with Benjamini–Hochberg's correction for multiple comparison, cluster analysis, principal component analysis, and correspondence analysis.

Results

From a total of 40 saliva samples, 496 probe targets were identified with a mean number of targets per sample of 203 (range: 146–303), and a mean number of probe targets of 206 and 200 in unstimulated and stimulated saliva samples, respectively (p=0.62). Based on all statistical methods used for this study, the microbial profiles of unstimulated and stimulated saliva samples collected from the same person were not statistically significantly different.

Conclusions

Analysis of bacterial salivary profiles in unstimulated and stimulated saliva samples collected from the same individual showed comparable results. Thus, the results verify that stimulated saliva is an adequate surrogate of unstimulated saliva for microbiome-related studies.

Temporal Stability of the Salivary Microbiota in Oral Health

Objectives

Saliva is a biological fluid suitable for biomarker analysis, and differences in the salivary microbiota in oral health and disease have been reported. For such comparative analyses, time of sampling is critical since the bacterial composition may vary throughout the day, i.e., diurnal variation. The purpose of this study is to compare the salivary microbiome over time to determine the optimal time for sampling.

Design

Stimulated saliva samples were collected from 5 orally healthy individuals in 4 h intervals for 24 h, and collection was repeated 7 days later (number of samples per person, n = 12, total number of samples, n = 60). Salivary microbiota was analyzed using the Human Oral Microbe Identification using Next Generation Sequencing (HOMINGS), and statistical analysis was performed using the Kruskal-Wallis test with Benjamini-Hochberg’s correction for multiple comparisons, cluster analysis, principal component analysis and correspondence analysis.

Results

From a total of 60 saliva samples, 477 probe targets were collectively identified with a mean number of probes per sample of 207 (range: 153–307). Little or no variation in microbial profiles within subjects was observed over time.

Conclusions

Although there was considerable variation between subjects, microbial profiles within subjects were stable throughout a 24 hour period and after 1 week. Since there is little or no evidence of diurnal variation of the salivary microbiome, time of sampling of saliva is not critical for perturbation or other microbial studies.

Salivary bacterial fingerprints of established oral disease revealed by the Human Oral Microbe Identification using Next Generation Sequencing (HOMINGS) technique

Background and objective

The composition of the salivary microbiota, as determined using various molecular methods, has been reported to differentiate oral health from diseases. Thus, the purpose of this study was to utilize the newly developed molecular technique HOMINGS (Human Oral Microbe Identification using Next Generation Sequencing) for comparison of the salivary microbiota in patients with periodontitis, patients with dental caries, and orally healthy individuals. The hypothesis was that this method could add on to the existing knowledge on salivary bacterial profiles in oral health and disease.

Design

Stimulated saliva samples (n=30) were collected from 10 patients with untreated periodontitis, 10 patients with untreated dental caries, and 10 orally healthy individuals. Salivary microbiota was analyzed using HOMINGS and statistical analysis was performed using Kruskal–Wallis test with Benjamini–Hochberg's correction.

Results

From a total of 30 saliva samples, a mean number of probe targets of 205 (range 120–353) were identified, and a statistically significant higher mean number of targets was registered in samples from patients with periodontitis (mean 220, range 143–306) and dental caries (mean 221, range 165–353) as compared to orally healthy individuals (mean 174, range 120–260) (p=0.04 and p=0.04). Nine probe targets were identified with a different relative abundance between groups (p<0.05).

Conclusions

Cross-sectional comparison of salivary bacterial profiles by means of HOMINGS analysis showed that different salivary bacterial profiles were associated with oral health and disease. Future large-scale prospective studies are needed to evaluate if saliva-based screening for disease-associated oral bacterial profiles may be used for identification of patients at risk of acquiring periodontitis and dental caries.

Root caries, root surface restorations and lifestyle factors in adult Danes

AIM

To investigate selected lifestyle factors in relation to active caries and restored root surface lesions in adults.

MATERIALS AND METHODS

Based on clinical examinations and questionnaires, data on root caries, socioeconomic status, body mass index, dietary habits, alcohol consumption, tobacco use and oral hygiene routines were collected from 4369 adults aged 21-89 who took part in a survey covering 13 municipalities across Denmark. Uni- and multivariate logistic regression analyses were applied to analyse the relationship between the independent lifestyle variables and active caries and restored root surface lesions, respectively.

RESULTS

The prevalence of active root caries was 4%, while 26% displayed restored root surfaces. The sugar intake was not related to root caries. A multivariate logistic regression analysis revealed that, in subjects aged 45 or over, smoking and wearing dentures were significantly associated with presence of active root caries (p<0.01). The intake of 15 drinks or more per week was associated with higher odds of root surface restorations compared with no alcohol intake (OR=1.7; p<0.001).

CONCLUSIONS

Lifestyle factors such as tobacco use and alcohol consumption, as well as wearing dentures, were significantly associated with the occurrence of untreated caries and restored root surface lesions, especially in persons over 45. Thus, such lifestyle factors should be taken into consideration, identifying persons with a need of preventive dental services. In addition, oral health education should focus on the possible risks of smoking and a high alcohol intake.

Differentiation of salivary bacterial profiles of subjects with periodontitis and dental caries

Bacterial profiles of saliva in subjects with periodontitis and dental caries have been demonstrated to differ from that of oral health. The aim of this comparative analysis of existing data generated by the Human Oral Microbe Identification Microarray (HOMIM) from 293 stimulated saliva samples was to compare bacterial profiles of saliva in subjects with periodontitis and dental caries.

Bacterial profiles of saliva in relation to diet, lifestyle factors, and socioeconomic status

BACKGROUND AND OBJECTIVE

The bacterial profile of saliva is composed of bacteria from different oral surfaces. The objective of this study was to determine whether different diet intake, lifestyle, or socioeconomic status is associated with characteristic bacterial saliva profiles.

DESIGN

Stimulated saliva samples from 292 participants with low levels of dental caries and periodontitis, enrolled in the Danish Health Examination Survey (DANHES), were analyzed for the presence of approximately 300 bacterial species by means of the Human Oral Microbe Identification Microarray (HOMIM). Using presence and levels (mean HOMIM-value) of bacterial probes as endpoints, the influence of diet intake, lifestyle, and socioeconomic status on the bacterial saliva profile was analyzed by Mann-Whitney tests with Benjamini-Hochberg's correction for multiple comparisons and principal component analysis.

RESULTS

Targets for 131 different probes were identified in 292 samples, with Streptococcus and Veillonella being the most predominant genera identified. Two bacterial taxa (Streptococcus sobrinus and Eubacterium [11][G-3] brachy) were more associated with smokers than non-smokers (adjusted p-value<0.01). Stratification of the group based on extreme ends of the parameters age, gender, alcohol consumption, body mass index (BMI), and diet intake had no statistical influence on the composition of the bacterial profile of saliva. Conversely, differences in socioeconomic status were reflected by the bacterial profiles of saliva.

CONCLUSIONS

The bacterial profile of saliva seems independent of diet intake, but influenced by smoking and maybe socioeconomic status.

Smoking and Drinking as Risk Indicators for Tooth Loss in Middle-Aged Danes

Objectives: To investigate tobacco and alcohol consumption as risk indicators for missing teeth in late middle-aged Danes. Method: In all, 1,517 Copenhagen Aging and Midlife Biobank (CAMB) participants received a clinical oral examination that included number of teeth. Information on smoking, drinking, and various covariates was obtained using self-administered, structured questionnaires. Descriptive statistics and logistic regression (dependent variable: 6+ vs. <6 missing teeth) were used to investigate smoking and drinking in relation to missing teeth. Results: Current smokers, persons who currently or previously smoked >15 tobacco units/day, and persons who had smoked for 27+ years had elevated mean scores of missing teeth and associated odds ratios (OR) compared with never smokers. Relative to nondrinkers, alcohol consumption was associated with reduced odds of missing 6+ teeth. Discussion: Our findings suggest that smoking is positively associated, while alcoholic beverage consumption is inversely related to tooth loss in middle-aged Danes.

Findings from the oral health study of the Danish Health Examination Survey 2007-2008

OBJECTIVE

The aims of the oral part of the Danish Health Examination Survey (DANHES 2007-2008) were (1) to establish an oral health database for adult Danes and (2) to explore the influence of general diseases and lifestyle on oral health. This paper presents the study population, examination methods, questionnaire and baseline results.

MATERIALS AND METHODS

The study population comprised 4402 subjects, aged 18-96, consecutively enrolled from 18 065 DANHES participants from 13 municipalities in Denmark. The oral part consisted of a validated questionnaire and a clinical examination, carried out in mobile units by three trained and calibrated dental hygienists. The data were processed with descriptive statistics and mono- and bivariate analyses.

RESULTS

The mean age was 54.1 years and 60% were women. The mean number of natural teeth was 26.6; the mean DMFT/DMFS values were 18.9 and 61.0, and varied with age (DMFT 8.7-24.3). A higher proportion of females suffered from dental erosion in the younger age groups. Forty per cent of all subjects had a mean clinical attachment loss ≥ 3 mm, varying from 4% among those aged 18-34 to 80% in those over 75. A sub-optimal saliva secretion rate was more common among females than males (17.7% vs 10.4%) and this was reflected by the reported frequency of dry mouth.

CONCLUSION

This extensive cross-sectional study provides a platform for obtaining future knowledge of the impact of health- and lifestyle-related factors on oral diseases. The validated questionnaire and the clinical characteristics enable robust analyses, although the conclusions may be hampered by limited external validity.

Bacterial sex in dental plaque

Genes are transferred between bacteria in dental plaque by transduction, conjugation, and transformation. Membrane vesicles can also provide a mechanism for horizontal gene transfer. DNA transfer is considered bacterial sex, but the transfer is not parallel to processes that we associate with sex in higher organisms. Several examples of bacterial gene transfer in the oral cavity are given in this review. How frequently this occurs in dental plaque is not clear, but evidence suggests that it affects a number of the major genera present. It has been estimated that new sequences in genomes established through horizontal gene transfer can constitute up to 30% of bacterial genomes. Gene transfer can be both inter- and intrageneric, and it can also affect transient organisms. The transferred DNA can be integrated or recombined in the recipient's chromosome or remain as an extrachromosomal inheritable element. This can make dental plaque a reservoir for antimicrobial resistance genes. The ability to transfer DNA is important for bacteria, making them better adapted to the harsh environment of the human mouth, and promoting their survival, virulence, and pathogenicity.

Changing the curriculum and the role of the teacher and the students in the classroom--an analysis of the process of reforming a course in oral microbiology

In 2005, a new curriculum was introduced at the School of Dentistry at the University of Copenhagen. Amongst many changes, the pedagogical concept behind theoretical teaching was changed. The main emphasis was previously on lectures and teacher controlled teaching, but the emphasis has now shifted to a more dialogue-based teaching style for smaller groups where the students became much more active. Thus, the learning principle was now given the pride of place. The present article focuses on the pedagogical reorganisation of the course in oral microbiology where, based on interviews with students and teachers, an evaluation is made regarding how the changes were implemented and developed. Despite the fact that the students themselves wanted to abandon the lecture-based teaching style, there was great dissatisfaction with the new dialogue-based teaching style as the students did not think that it was possible for them to take responsibility for their learning. They would much rather listen to teachers who know the material. Initially, the teachers were very surprised by the negative attitude of the students and had to change the teaching style to more traditional teaching in groups whilst still maintaining the dialogue principle to a certain degree. In this article, the need to enter into a teaching contract between students and teachers prior to introducing new pedagogical principles is discussed.

Low calcium intake is related to increased risk of tooth loss in men

Our aim was to investigate the association between calcium (Ca) intake and number of teeth and tooth loss. The Danish Monica (Monitoring Trends and Determinants in Cardiovascular Disease) study is a prospective observational study from 1982-83 to 1993-94. The study population included 1602 adults (30-60 y) with information on dietary Ca intake and number of teeth and a subset of 511 participants with information on tooth loss from 1987-88 to 1993-94. Ca intake less than the recommendations, estimated by a 7-d food record or a diet history interview in 1982-83, was more frequent among females (55%) than males (45%; P < 0.001). Low Ca intake was associated with low number of teeth (1-25 vs. 26-32 teeth) in males [odds ratio (OR) = 1.57 (95% CI = 1.10-2.29)] and females [OR = 1.44 (95% CI = 1.10-2.05)] after adjustment for age, education, smoking, alcohol and sucrose consumption, subjective oral dryness, and time since last dental care visit. The reference group (26-32 teeth) and edentulous participants did not significantly differ. A Ca intake below recommendations was significantly associated with increased risk of subsequent tooth loss in males [incidence-rate ratio = 1.70 (95% CI = 1.15-2.48)]. There was no association in women. Ca intake below recommendations was significantly associated with fewer teeth in both sexes. However, there was a significant, negative association between Ca intake below recommendations and tooth loss in males only. Given the high percentage of individuals with Ca intake below recommendations, consumption of foods rich in Ca should be promoted to preserve oral health.

Coaggregation between probiotic bacteria and caries-associated strains: an in vitro study

OBJECTIVE

To evaluate the in vitro abilities of probiotic bacteria derived from consumer products to coaggregate with caries-associated mutans streptococci.

MATERIAL AND METHODS

Six lactobacillus strains (L. acidophilus (CCUG 5917), L. plantarum 299v, L. rhamnosus GG and LB21, L. paracasei F19, L. reuteri PTA5289) were cultivated under anaerobic conditions at 37°C in Man Rogosa Sharpe (MSB) broth for 24 h. Four strains of human streptococci (S. mutans Ingbritt, S. mutans (ATCC 25175), S. mutans GS-5, S. sobrinus (ATCC 33478) were similarly grown in Brain Heart Infusion (BHI) broth. A gastrointestinal pathogen (Escherichia coli) was aerobically cultivated on BHI broth as a positive control. After incubation, the bacteria were aerobically harvested, washed, and suspended in 10 mmol/l phosphate-buffered saline (pH 7.2). The probiotic strains were characterized with the API 50 CH system to confirm their identity. Coaggregation was determined by spectrophotometry in mixtures and bacterial suspensions alone after 1, 2, 4, and 24 h and expressed as the aggregation ratio (%).

RESULTS

All probiotic strains showed coaggregation abilities with the oral pathogens and the results were strain specific and dependent on time. S. mutans GS-5 exhibited a significantly higher ability to coaggregate with all the probiotic strains than the other mutans streptococci and E. coli. The differences among the probiotic strains were modest with L. acidophilus being the most prone and L. rhamnosus LB21 the least prone to coaggregate with the oral streptococci.

CONCLUSIONS

The results demonstrated different abilities of lactobacilli-derived probiotic bacteria to coaggregate with selected oral streptococci. Aggregation assays may be a useful complement for screening of probiotic candidates with possible anti-caries properties.

Identification of periodontal pathogens in atherosclerotic vessels

BACKGROUND

Epidemiological studies have shown that periodontitis may be associated with presence of atherosclerosis. DNA from periodontal pathogens has been detected in atherosclerotic lesions, but viable oral bacteria have not yet been isolated from atherosclerotic plaques. The purpose of the present study was to determine if viable oral bacteria could be isolated from atherosclerotic lesions and if DNA from periodontal pathogens could be detected by use of polymerase chain reaction (PCR) techniques.

METHODS

Seventy-nine specimens of atherosclerotic plaque removed from carotid or femoral arteries during surgery were immediately transferred to reduced transport fluid and brought to the laboratory. The calcified tissue was meticulously cut into fine pieces and used for cultivation of Porphyromonas gingivalis, Prevotella intermedia, P. nigrescens, Campylobacter rectus, Actinobacillus actinomycetemcomitans, Tannerella forsythensis, and oral streptococci. The material from 24 of the specimens was homogenized, DNA was extracted, and PCR amplification of 16S rDNA with universal and specific primers was carried out. Finally, the PCR products were sequenced.

RESULTS

None of the samples yielded growth of the oral bacteria under investigation. In all the 24 specimens bacterial DNA was detected and likewise DNA of P. intermedia was found in the samples. P. nigrescens and P. gingivalis were found sporadically.

CONCLUSIONS

Viable oral bacteria could not be isolated from the atheromas, but the data confirm that DNA of periodontal pathogens can be detected in atherosclerotic plaques. However, the finding that DNA from P. intermedia constantly occured in the examined samples was new. Further studies may focus on the simultaneous occurrence of identical clones of this species in subgingival plaque and atherosclerotic plaques.

The effect of Sterilex Ultra for disinfection of dental unit waterlines

AIM

To evaluate the effect of a disinfectant agent based on hydrogen peroxide (Sterilex Ultra, Sterilex Corporation, Maryland, USA) on the microbiological water quality in dental unit waterlines (DUWL).

SETTING

Six older dental units were disinfected with Sterilex Ultra and another six units with sodium hypochlorite. The results were compared to six non-disinfected units examined during a period without patient treatment.

OUTCOME MEASURE

The number of colony forming units of bacteria (cfu)/ml of water was determined according to European Standards on water quality.

DESIGN

The water quality was initially determined during a six week period, and subsequently in more detail for two weeks. Finally, the effect of prolonged administration of Sterilex Ultra was investigated for six weeks.

RESULTS

Instillation of Sterilex Ultra according to the recommendations of the manufacturer initially reduced the number of bacteria in DUWL to <10(2) cfu/ml. However, following daily, as well as prolonged administration of Sterilex Ultra a gradual recolonisation was observed resulting in bacterial numbers >10(4) cfu/ml in a number of units. Major differences between the number of cfu/ml in individual units were observed.

CONCLUSION

Neither daily nor extended administration of Sterilex Ultra was capable of maintaining an acceptable water quality in these older dental units.

Oral infections and systemic diseases

An association between periodontal infection and CVD has been revealed in some epidemiologic studies, whereas other studies were unable to demonstrate such an association. A link between the two diseases may be explained by shared established or nonestablished risk factors. Future studies with extended control of confounding factors and intervention studies may add to the understanding of a possible relationship between the diseases. In some cases, IE is caused by dental plaque bacteria. Several studies are suggestive of oral bacteria causing respiratory infection. The pathogenesis and course of a number of other diseases including DM and rheumatoid arthritis have been associated wish periodontitis, but more research is necessary to elucidate possible pathogenic interactions.

Perspectives on dental education in the Nordic countries

The object of this review is to discuss the state of dental education and describe current developments at dental schools in the Nordic countries. The main focus is the undergraduate dental education; however, the postgraduate system will also be addressed. The curriculum model for undergraduate dental education in the Nordic countries is based upon the odontological tradition. The influence of biomedicine on dental education is increasing at present due to scientific and medico-technological developments and the altered disease profiles of oral and systemic diseases. These circumstances create new possibilities for dental education, but at the same time they raise some problems. In the long-term, the strong biomedical influence on dental education will be an advantage to future dentists' function and tasks in health care systems in the Nordic countries. In the short term, it may result in an identity crisis for dental schools, students, and our profession, as we experience the evolution from the traditional odontological curriculum model to one significantly influenced by ongoing changes in the biomedical field. Continuing professional education and advanced training in clinical specialties are likely to play important roles in this evolution.

The effect of drying dental unit waterline biofilms on the bacterial load of dental unit water

AIM

To evaluate drying of the dental unit waterlines (DUWL) as a new method of controlling the bacterial biofilm therein and thereby to reduce the number of living bacteria in dental unit water.

SETTING

18 dental units were incorporated into the study. Six units constituted the experimental units, which were emptied for stagnant water in the DUWL every night; six units were chlorinated every night (positive controls), and six units were left untreated (negative controls).

OUTCOME MEASURE

Water samples from the ultrasonic scaler were examined microbiologically according to the guidelines from the Danish Standard Association and the number of colony forming units (cfu) per ml of water was determined.

RESULT

Drying of DUWL did not reduce the number of cfu per ml in dental unit water below the levels found in DUWL left untreated.

CONCLUSION

The drying of the waterlines for about 16 hours per day during a 19-day period did not result in reduced counts of bacteria in water samples from the experimental units.

Probing around implants and teeth with healthy or inflamed peri-implant mucosa/gingiva. A histologic comparison in cynomolgus monkeys (Macaca fascicularis)

The purpose of this study was to obtain a better understanding of probing measurements around osseointegrated oral implants. A comparison was made of probe tip position around Astra Tech implants and teeth of eight cynomolgus monkeys (Macaca fascicularis) in conditions of i) healthy peri-implant mucosa/gingiva, ii) mild mucositis/gingivitis, iii) severe mucositis/gingivitis or iv) peri-implantitis/periodontitis. Histological sections of 128 probes that were attached to implants or teeth with surrounding tissues were prepared by the cutting-grinding technique. No systematic differences were identified in the clinical and histological estimates of the distance between the mucosal/gingival margin and the probe tip. The differences were mainly smaller than 0.5 mm, and in no case were they larger than 0.7 mm. For implants and teeth with healthy peri-implant mucosa/gingiva, the distance between the probe tip and the alveolar bone was similar and ranged from 0.5 to 1.5 mm (P = 0.97). However, the probe tip was closer to bone around implants than around teeth in conditions of mild mucositis/gingivitis (P = 0.034), severe mucositis/gingivitis (P < or = 0.0001) and peri-implantitis/periodontitis (P < or = 0.0001). Around implants with severe mucositis and peri-implantitis, the distance was generally smaller than 0.5 mm, whereas teeth with severe gingivitis and periodontitis showed distances that mainly ranged from 0.5 to 1.5 mm. In conclusion, the probing measurements around osseointegrated oral implants and teeth were different. Even mild marginal inflammation was associated with deeper probe penetration around implants in comparison to teeth.

3.2 Ensuring research productivity in the future faculty

The group concluded that the research productivity of a dental school depended to a large extent on the availability of resources, human and economic. Firstly it requires a group of individuals trained and educated to conduct independent research. Secondly, it requires that these individuals had time to spend on research activities. Thirdly, appropriate space and equipment in which to conduct the research were considered prerequisites. Fourthly, they require an ongoing and appropriate budget. Fifthly, it is essential to have an appropriate climate in the school that encourages and rewards research achievement.

Disinfection of dental impressions and occlusal records by ultraviolet radiation

As chemical disinfection of dental impressions may cause adverse effects on materials and the dental personnel this study examined disinfection by ultraviolet radiation. Alginate, addition silicone rubber and red wax contaminated by Streptococcus salivarius, Fusobacterium nucleatum and five other bacteria in different suspension media were radiated for up to 18 min, and the number of colony forming units was compared to non-radiated controls. The effect of ultraviolet radiation differed among bacterial species and depended on the organic content in the suspension. Generally, the bacterial reduction after ultraviolet radiation was below 4 log steps and thus insufficient for disinfection of dental impressions.

Bacterial binding to extracellular matrix proteins -- in vitro adhesion

A binding assay was developed and used to study the binding of oral streptococcus to immobilized human fibronectin, laminin, vitronectin, fibrinogen, heparin, and collagen IV. The protein binding was dependent on the broth used for bacterial growth. The binding after growth in brain heart infusion broth, trypticase soy broth, Todd-Hewitt broth, and Dulbecco's modified Eagle's medium was examined. Most of the strains were able to bind to immobilized fibronectin and laminin, and to a minor extent vitronectin. Binding was not observed on immobilized fibrinogen, collagen IV, or heparin. Measured surface hydrophobicity correlated well with the bacterial binding strength to the proteins. Streptococcal incubation with putative inhibitors indicates multiple binding mechanisms of a lectin-like and protein nature, possibly involving protein receptors.

Current status of taxonomic groups of oral streptococci in endocarditis. Can virulence factors discriminate between endocarditis and non-endocarditis strains?

OBJECTIVE: Infective endocarditis is frequently caused by oral streptococci, especially Streptococcus sanguis. In this group, many strains have recently been reclassified on the basis of new taxonomic schemes. The purpose of this study was to classify oral streptococci from patients with infective endocarditis and, further, to assess the importance of specific virulence factors for the development of streptococcal endocarditis. METHODS: Twenty-eight previously identified and 10 new streptococcal isolates from infective endocarditis were classified according to Kilian et al (1989) and compared to 30 streptococcal isolates from the oral cavities of periodontal patients without endocarditis. Subsequently, surface hydrophobicity was assessed by hydrophobic interaction chromatography, production of extracellular dextran was determined by precipitation, and non-specific proteolytic activity was evaluated by determination of hydrolysis of gelatin, and casein-precipitating activity. RESULTS: Eight streptococcal species were represented in the endocarditis isolates. Most strains were highly hydrophobic and none showed non-specific proteolytic activity. Dextran was produced with similar frequency in endocarditis and non-endocarditis isolates. CONCLUSIONS: The present study showed that infective endocarditis may be caused by a variety of oral streptococcal species. The possible virulence factors investigated were found in the same proportions in endocarditis and non-endocarditis isolates, and thus did not seem to be crucial for development of endocarditis.

Effect of steam sterilization inside the turbine chambers of dental turbines

OBJECTIVE

It has been demonstrated that contamination of the insides of high-speed dental turbines occurs and that bacteria as well as viruses may remain infectious when expelled from such turbines during subsequent use. Consequently, it has been widely recommended that a high-speed turbine be sterilized after each patient. The purpose of this study was to evaluate the effect of steam autoclaving on a high-speed dental turbine with a contaminated turbine chamber.

STUDY DESIGN

Streptococcus salivarius and endospores of Bacillus stearothermophilus were used as test organisms to determine the effectiveness of 4 different small non-vacuum autoclaves and one vacuum autoclave.

RESULTS

The study demonstrated different efficiencies among the small non-vacuum autoclaves, the best showing close to a 6 log reduction of the test organisms inside the turbine chamber. When cleaning and lubrication of the high-speed dental turbine was carried out before autoclaving, this level of reduction was observed for all the examined non-vacuum autoclaves.

CONCLUSIONS

It is concluded that cleaning before sterilization is essential for safe use of high-speed dental turbines and that small non-vacuum autoclaves should be carefully evaluated before being used for the reprocessing of hollow instruments such as high-speed turbines.

The basic science teaching experience in the Nordic countries

The article concerns the dental education at 10 different faculties in Denmark, Iceland, Norway, Sweden, and Finland. The information is based upon a questionnaire to the faculties concerning the definition, the structure and succession of the basic science subjects/courses/themes/topics in the dental curriculum, the time span of the basic science teaching, and the methods of teaching. Furthermore, there is information about integration among the basic science subjects and the coordination/integration between the basic science teaching and the clinical teaching. Finally, the teachers' educational background and the cowork with the medical education is elucidated. The main findings are: the basic science teaching is structured in different ways in the Nordic countries. In Reykjavik, Bergen, and Aarhus this teaching is subject specific, while in Copenhagen it is mainly subject specific, as it has few integrated courses. In Gothenburg, Stockholm, and Umeå, the basic science teaching consists of a mixture of integrated courses and subject specific teaching. In Helsinki, Oslo and Malmö the basic sciences are theme and topic based, and for the two last-mentioned institutions, integrated with the clinic, except at the faculty in Malmö. Here the basic science teaching is totally integrated in the clinical teaching throughout the study. Usually, the basic science teaching is placed mainly in the first part of the curriculum; however, in Umeå, Copenhagen, and Oslo, some integration takes place.

Evaluation of a new device for sterilizing dental high-speed handpieces

Dental high-speed turbines and handpieces can take up and expel microorganisms during operation and thus need regular sterilization. This study established a method for validating devices used to sterilize high-speed turbines and handpieces. The air and water channels and turbine chambers were contaminated with suspensions of Streptococcus salivarius or endospores of Bacillus stearothermophilus. The effect of flushing and/or autoclaving performed by a new device combining both procedures was evaluated by counting the number of viable bacteria recovered from these devices. Further, the effect on clinically used handpieces was evaluated. In an initial experiment, the device partially reduced S. salivarius, and the endospores survived. In a second experiment, a 5 to 6 log reduction of S. salivarius in air and water channels was obtained. No growth was observed in clinically used high-speed handpieces, and both S. salivarius and endospores were eliminated from the turbine chambers. Thus, the method of validation proved capable of discriminating between different levels of bacterial reduction.

Epidemiology of Pseudomonas aeruginosa in cystic fibrosis and the possible role of contamination by dental equipment

Cystic fibrosis (CF) patients often suffer from Pseudomonas aeruginosa lung infection yet the source of this organism is not known. In order to determine whether CF patients might be contaminated with P. aeruginosa from dental equipment, a total of 103 water samples from 25 dental sessions in Frederiksberg Municipal Oral Health Care Service were examined. Three samples (2.9%) were positive for P. aeruginosa. Three hundred and twenty-seven water samples from 82 dental sessions from various other Municipal Oral Health Services in Denmark, attended by CF patients, were also examined. Eighteen of 327 samples (5.5%) from nine sessions (11%) were positive for P. aeruginosa. In one case, genotypically identical (RFLP, pulsed-field gel electrophoresis) P. aeruginosa strains were found both in water from the dental equipment and in the CF patients sputum. This indicates a small risk for acquiring P. aeruginosa from dental sessions, which is however equal to the yearly 'natural background' incidence (1-2%) of acquisition of P. aeruginosa in our CF centre.

Development of resistance to metronidazole and minocycline in vitro

By local delivery of antibiotics to periodontal pockets, very high initial concentrations are often quickly succeeded by subinhibitory concentrations, which may facilitate development of bacterial resistance. The purpose of the present study was to investigate possible development of resistance in suspected periodontal pathogens after exposure to subinhibitory concentrations of metronidazole and minocycline. The minimal inhibitory concentration (MIC) of 18 reference strains and 12 clinical isolates was determined by a broth dilution method. Subsequently, all strains with MIC < 8 micrograms/ml were exposed to serial passage on plates containing subinhibitory and gradually increasing concentrations of antibiotics, until growth was inhibited. Initially, most strains were inhibited at < or = 0.250 microgram/ml of minocycline and < or = 0.5 microgram/ml of metronidazole, though A. actinomycetemcomitans was resistant to metronidazole. After growth at subinhibitory concentrations, 8 strains survived 1-2 x and 11 stains survived 8-32 x their initial MIC of metronidazole, growing at up to 8 micrograms/ml. All A. actinomycetemcomitans survived 8-64 x their initial MIC of minocycline, growing at > or = 2 micrograms/ml, while all other strains were inhibited at < or = 0.250 microgram/ml, corresponding to a 1-8 x increase in their initial MIC. Thus, development of resistance was observed for periodontal bacteria growing at up to 64 x their initial MIC, but the final level of resistance was moderate.

Microbiology of ligature-induced marginal inflammation around osseointegrated implants and ankylosed teeth in cynomolgus monkeys (Macaca fascicularis)

The microbiota associated with ligature-induced marginal inflammation around osseointegrated dental implants, ankylosed teeth, and normal control teeth was investigated in 8 cynomolgus monkeys (Macaca fascicularis). Submucosal/subgingival plaque was sampled with paper points on the day of literature placement and after 7 weeks. The samples were evaluated by phase-contrast microscopy and by cultivation on enriched non-selective and various solid media. The submucosal/subgingival flora was changed 7 weeks after ligation. The total number of cultivable bacteria and the proportions of motile rods, anaerobic Gram-negative rods, black-pigmented rods, Porphyromonas gingivalis, and Prevotella intermedia increased significantly around implants, ankylosed teeth, and normal control teeth. Except for a significantly higher proportion of anaerobic Gram-positive cocci around implants compared to ankylosed teeth and normal control teeth at the end of the study, no significant microbiological differences were observed between implants, ankylosed teeth, and normal control teeth neither at baseline nor at the end of the study. Consequently, the microbiota associated with marginal inflammation around implants, ankylosed teeth, and normal control teeth appears to be rather similar in cynomolgus monkeys.

Resistance of Streptococcus sanguis biofilms to antimicrobial agents

Bacteria living in biofilms as dental plaque on tooth surfaces are generally more resistant to antimicrobial agents than bacteria in batch culture normally used for in vitro susceptibility testing. In order to compare the resistance of free-living and surface-grown oral bacteria, the MIC of Streptococcus sanguis 804 and ATCC 10556 to amoxicillin, doxycycline and chlorhexidine was determined by a broth dilution method. Subsequently, S. sanguis biofilms established in an in vitro flow model were perfused with the antimicrobial agents for 48 h at concentrations equal to and up to 500 times the MIC, and biofilm cell number was determined during this period. The antibiotics at the MIC did not affect the cell number of S. sanguis biofilms compared to the starting point, and only after 48 h at 500 times the MIC were the biofilm bacteria eliminated. At intermediate concentrations biofilm cell number gradually decreased. Chlorhexidine also gradually reduced biofilm cell number, but was inhibitory at concentrations closer to the MIC than was the case for the antibiotics. Thus S. sanguis in biofilms survived up to 500 times the MIC found in batch culture for up to 48 h.

Identity of 1:2:1 and 2:4:2 subgingival spirochetes by DNA hybridization

A group of 1:2:1 and 2:4:2 subgingival spirochetes, well characterized by transmission electron microscopy, biochemical tests, cellular fatty acid and carbohydrate analyses, and ribotyping, was recently suggested to represent new treponemal species. The present study used DNA hybridization to examine this possibility. When DNA of a representative strain (no. 16) of the 8 1:2:1 spirochetes examined was labeled by iodination, it showed, after S1 nuclease treatment, from 58 to 104% (average 76%) homology with DNA from the 1:2:1 spirochetes, 94% homology with DNA from the type strain of Treponema socranskii and of T. socranskii subsp. socranskii, i.e., ATCC 35536T, and 62% homology with DNA from T. socranskii subsp. buccale, strain ATCC 35534T. Similarly treated DNA from a representative strain (no. 3) of 8 2:4:2 spirochetes exhibited from 90 to 105% (average 97%) homology with DNA from the 2:4:2 spirochetes, and 85% and 87% homology, respectively, with DNA from Treponema denticola strains ATCC 33520 and FDC T1. There was a negligible degree of homology between the 1:2:1 and 2:4:2 spirochetes. Thus, all the 2:4:2 spirochetes belonged to T. denticola. 1:2:2 strains with DNA homology levels >70% (5 strains) belonged to T. socranskii or T. socranskii subsp. socranskii, while those with homology levels from 58 to 63% (3 strains) most likely belonged to other subspecies of T. socranskii.

Identity of streptococcal blood isolates and oral isolates from two patients with infective endocarditis

The purpose of this study was to isolate streptococcal strains from the oral cavities of streptococcal endocarditis patients and compare these strains biochemically and genetically with the corresponding streptococcal blood isolates. Total identity was observed between the blood and oral cavity isolates from the two patients studied.

Development of a flow method for susceptibility testing of oral biofilms in vitro

Bacteria in biofilms are known to be more resistant than bacteria in batch cultures to antimicrobial agents. The purpose of the present study was to develop a flow method for formation of oral biofilms permitting susceptibility testing of plaque bacteria. A brain heart infusion (BHI) Streptococcus sanguis 804 culture was pumped through a modified Robbins Device (MRD) with 25 exchangeable silicone disks at 40 ml/h. After 24-48 h disks were removed and biofilm cells dispersed by vortex mixing and low-output ultrasonication. Colony forming units (cfu)/cm2 were determined after aerobic incubation on blood agar plates. Optimal biofilm formation was found after growth for 48 h at 37 degrees C in BHI + 1% sucrose, using saliva-coated silicone disks in inverted MRDs, yielding on average 4.4 x 10(5) cfu/cm2. Similar results were obtained for S. sanguis ATCC 10556 and five clinical isolates. Testing the susceptibility of S. sanguis to chlorhexidine gluconate showed increased resistance of biofilms compared to batch culture. Thus an appropriate biofilm model for susceptibility testing of oral microorganisms has been established.

Restriction fragment length polymorphism of rRNA genes for molecular typing of members of the family Legionellaceae

Typing of Legionella pneumophila remains important in the investigation of outbreaks of Legionnaires' disease and in the control of organisms contaminating hospital water. We found that the discriminatory power of a nonradioactive ribotyping method could be improved by combining results obtained with four restriction enzymes (HindIII, NciI, ClaI, and PstI). Fifty-eight clinical and environmental L. pneumophila strains including geographically unrelated as well as epidemiologically connected isolates were investigated. Epidemiologically related strains had the same ribotypes independent of the combinations of enzymes used. Some strains belonging to the same serogroup were assigned to different ribotypes, and some ribotypes contained members of different serogroups, indicating, as others have found, that serogroup and genotype are not always related. The discriminatory power of the method was estimated by calculating an index of discrimination (ID) for individual enzymes and combinations thereof. The combined result with all four enzymes was highly discriminatory (ID = 0.97), but results for three enzymes also yielded ID values acceptable for epidemiological purposes. In addition, the testing of 27 type strains and 6 clinical isolates representing Legionella species other than L. pneumophila indicated that ribotyping might be of value for species identification within this genus, as previously suggested.

Ribotyping on small-sized spirochetes isolated from subgingival plaque

In the present study DNA restriction patterns and corresponding ribotypes of 17 subgingival small-sized spirochetes (1:2:1 and 2:4:2 isolates), 2 Treponema socranskii strains and two Treponema denticola strains were examined. Purified chromosomal DNA was digested by BamHI, HindIII, PstI and ClaI. The DNA fragments were separated in a horizontal slab of 0.7% agarose containing ethidium bromide and transferred by nylon membranes. Hybridization was carried out with digoxigenin-labelled copy DNA of 16S and 23S ribosomal RNA from Escherichia coli. Depending on the restriction endonuclease used, up to 4 distinct bands were observed for the 2:4:2 isolates and the T. denticola strains. For each of the endonucleases used, identical band patterns were always observed for this group of isolates, and these patterns differed persistently from the T. denticola strains. For the 1:2:1 strains, up to 11 distinct bands were observed after digestion with HindIII, whereas a maximum of 6 bands were observed when PstI or ClaI was used. By using ClaI, the examined 1:2:1 isolates were separated into 8 groups, whereas PstI and HindIII separated these isolates into 5 groups. The ribotyping showed that the tested 1:2:1 spirochetes were more heterogeneous than the 2:4:2 spirochetes examined.

Decontamination of dental equipment. A validation of three devices designed for cleaning, disinfecting, and lubricating of dental high-speed turbines and handpieces

This study deals with the decontamination of dental turbines and handpieces (DTH) aiming at eliminating the cross-infection risk in dental practice. Three types of equipment designed for cleaning/lubricating DTH were validated. The effect of the three devices was determined for four different types of DTH, which were artificially contaminated with Streptococcus salivarius ATCC 13419 in a controlled manner. Sampling was carried out by collecting one ml water flushed through the DTH connected to a dental unit. The study resulted in a model for testing the decontamination potential of a cleaning/lubrication device for DTH. One of the devices could not reduce the contamination, while two others were able to reduce the bioburden with at least 3.9 logarithmic steps. However none of the devices tested could constantly eliminate the contamination, for which reason an additional heat treatment of the DTH is recommended.

Ribotyping for differentiating Flavobacterium meningosepticum isolates from clinical and environmental sources

On the basis of DNA-DNA hybridization data, two main genomic relatedness groups (I and II) have been reported for a geographically varied collection of 52 strains of Flavobacterium meningosepticum. Herein, we have shown that genomic group II can be further divided into four subgroups (II:1 to II:4). To examine the taxonomic relevance of the ribosomal patterns of the 52 F. meningosepticum strains, the patterns were compared with existing DNA-DNA hybridization data with restriction enzymes PstI and HindIII. Ribotyping of the 52 F. meningosepticum strains showed banding patterns that could identify them correctly to one of the five genomic groups or subgroups. To assess the value of ribotyping for the interpretation of epidemiological data, the discriminatory power of the method was investigated for the 52 F. meningosepticum strains. With one to four restriction enzymes (PstI, HindIII, ClaI, EcoRI), a discriminatory index of 0.95 to 0.97 was found. The value of ribotyping in an epidemiological setting was assessed for three clinical isolates of F. meningosepticum from an outbreak of meningitis and bacteremia in the neonatal intensive care unit, Rigshospitalet, Copenhagen, Denmark. The three clinical isolates were shown to belong to the same ribotype, characteristic of genomic subgroup II:1. This ribotyping method will prove to be a useful tool for epidemiological studies concerning F. meningosepticum in the future.

Physical and microbiological quality of five different examination and surgical gloves before and after use in dental practice

The purpose of the present study was to compare five different types of examination and surgical gloves physically and microbiologically before and after use in clinical dentistry. The prevalence of perforations was examined by the water inflation technique, and adhesion of bacteria to the glove surfaces was determined by use of a standard procedure with Streptococcus salivarius ATCC 13419. The effect of handwashing with a non-medicated soap and disinfectant soaps was finally examined. About 3% of the unused latex--and Elastyren gloves had perforations, while 6-7% of the unused vinyl gloves showed pinholes. Ten handwashes with a non-medicated soap did not affect the physical integrity of any of the glove types, while the disinfectant soap BLIX deteriorates about one third of the Elastyren gloves after 10 washes. In contrast, another disinfectant soap Hibiscrub did not affect these gloves. After use in clinical dentistry all vinyl gloves had perforations, while the other four types seemed unchanged. S. salivarius adhered to unused gloves of all types except for the hypoallergenic latex glove Biogel D. Highest numbers of cultivable bacteria were found for the non-sterile latex gloves and Elastyren gloves. The bacterial contamination was easily removed from all types by handwashing. Repeated handwashing decreased the adherence of S. salivarius to the non-sterile latex gloves and Elastyren gloves. After use in dental practice the adherence of S. salivarius seemed to be unchanged in relation to the situation, when the gloves were only washed up to 10 times. For the Biogel D gloves an increase in adherence of S. salivarius from zero before clinical use to a level comparable with the other glove types after clinical use was observed. Based on the findings in this study and compared with previous studies general recommendations for use of gloves in dental practice are formulated.

Periodontal bone loss in Porphyromonas gingivalis-infected specific pathogen-free rats after preinoculation with endogenous Streptococcus sanguis

Anaerobic Gram-negative bacteria dominate in periodontitis locations, while Gram-positive bacteria characterize healthy sites. A well-established Gram-positive flora might therefore inhibit the colonization of Gram-negative pathogens. The purpose of the present investigation was to examine whether endogenous S. sanguis could prevent, or reduce, periodontal bone loss in rats infected with a virulent P. gingivalis strain. Sixty specific pathogen-free Wistar rats were divided into 6 groups. Doxycycline was administered in the drinking water for 2 weeks to the groups A, B, C, and D to suppress the preexisting microflora in the mouth. Rats in groups A and C were subsequently inoculated with an S. sanguis strain, isolated from one of the rats, once a day for 5 d. Infection with P. gingivalis 381 was then carried out for 5 d in groups A, B, and E. Group F was not treated with doxycycline nor infected with bacteria and served as untreated control. Six weeks after the P. gingivalis inoculation, the rats were killed. Periodontal bone levels were assessed radiographically and morphometrically, and serum antibody against P. gingivalis 381 was determined by a fluorescence immunoassay. Periodontal bone support, determined radiographically, was reduced in group B (doxycycline-treated, P. gingivalis-inoculated) compared with the other groups. In contrast, the morphometric determination showed no differences between the groups. In group B antibody levels against two different P. gingivalis 381 cell surface antigens were significantly elevated.(ABSTRACT TRUNCATED AT 250 WORDS)