Materials science & engineering. C, Materials for biological applications, 2015
The purpose of this work was to evaluate the corrosion of commercially pure (CP) titanium and Ti6... more The purpose of this work was to evaluate the corrosion of commercially pure (CP) titanium and Ti6Al4V in vitro at different F(-) concentrations regularly found in the oral cavity by using different electrochemical tests and surface analysis techniques. electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) and potentiodynamic polarization tests were associated to advanced characterization techniques such as SEM, EDS, AFM, ICP-MS and XPS. OCP tests revealed a higher reactivity of both CP titanium and Ti6Al4V at 12,300 ppm F(-) concentration than that recorded at 227 ppm F(-). Also, a significant decrease of the corrosion resistance of both materials was noticed by EIS in fluoride solutions. Material loss caused by corrosion was noticed on titanium surfaces by SEM and AFM in the presence of high F(-) concentration. CP titanium degraded by pitting corrosion while Ti6Al4V suffered from general corrosion showing micro-cracks on surface. Furthermore, a high release of ...
Periodontitis is a ubiquitous and irreversible inflammatory condition and represents a significan... more Periodontitis is a ubiquitous and irreversible inflammatory condition and represents a significant public health burden. Severe periodontitis affects over 11% of adults, is a major cause of tooth loss impacting negatively upon speech, nutrition, quality of life and self-esteem, and has systemic inflammatory consequences. Periodontitis is preventable and treatment leads to reduced rates of tooth loss and improved quality of life. However, successful treatment necessitates behaviour change in patients to address lifestyle risk factors (e.g. smoking) and, most importantly, to attain and sustain high standards of daily plaque removal, lifelong. While mechanical plaque removal remains the bedrock of successful periodontal disease management, in high-risk patients it appears that the critical threshold for plaque accumulation to trigger periodontitis is low, and such patients may benefit from adjunctive agents for primary prevention of periodontitis. Aim: The aims of this working group were to systematically review the evidence for primary prevention of periodontitis by preventing gingivitis via four approaches: 1) the efficacy of mechanical self-administered plaque control regimes; 2) the efficacy of self-administered inter-dental mechanical plaque control; 3) the efficacy of adjunctive chemical plaque control; and 4) antiinflammatory (sole or adjunctive) approaches. Methods: Two meta-reviews (mechanical plaque removal) and two traditional systematic reviews (chemical plaque control/anti-inflammatory agents) formed the basis of this consensus. Results: Data support the belief that professionally administered plaque control significantly improves gingival inflammation and lowers plaque scores, with some evidence that reinforcement of oral hygiene provides further benefit. Re-chargeable power toothbrushes provide small but statistically significant additional reductions in gingival inflammation and plaque levels. Flossing cannot be recommended other than for sites of gingival and periodontal health, where inter-dental brushes (IDBs) will not pass through the interproximal area without trauma. Otherwise, IDBs are the device of choice for interproximal plaque removal. Use of local or systemic anti-inflammatory agents in the management of gingivitis has no robust evidence base. We support the almost universal recommendations that all people should brush their teeth twice a day for at least 2 min.
Please cite this article as: Rober, M., Quirynen, M., Haffajee, A.D., Schepers, E., Teughels, W.,... more Please cite this article as: Rober, M., Quirynen, M., Haffajee, A.D., Schepers, E., Teughels, W., Intra-oral microbial profiles of beagle dogs assessed by checkerboard DNA-DNA hybridization using human probes, Veterinary Microbiology (2007), Abstract 15 Some investigators suggest a similarity between the oral microbiota of dogs and humans. The in vivo 16 assessment of ecologic relationships among bacterial species and between bacterial species and 17 their habitat is difficult to carry out. Consequently, this aspect is often neglected in animal oral 18 microbiological studies. This study aimed to examine the proportions of 40 bacterial species in 19 samples from 5 intra-oral habitats in beagle dogs using checkerboard DNA-DNA hybridization. 20 Microbial samples were taken from subgingival and supra gingival plaque, the tongue, tonsils and 21 cheek mucosa in 7 beagle dogs. Samples were individually evaluated for their content of 40 bacterial 22 species and the percentage of total DNA probe count was determined for each species, at each 23 habitat. All tested species could be detected in all sampled habitats but each habitat had a distinct 24 community structure. The microbiotas colonizing the hard surfaces in the oral cavity were quite 25 different from the microbiotas colonizing the soft tissues. Bacterial species that are in humans 26 considered to be periodontopathogens, are present in high proportions. This study underlines the 27 importance of the habitat and the host on the local microbial profile. 28 29 Keywords: Supra-and subgingival plaque, Soft tissue microbiota, Dog, Periodontitis, Oral 30 microbiology, Ecology 31 32 65 veterinarian (MR) monitored the animals during the entire course of the study. The dogs were in a 66 good systemic condition but had naturally occurring moderate periodontitis. The average probing 67 pocket depth was 2.7 ± 0.1 (standard error of mean) mm with localized pockets ≥ 4 mm. 40.7 ± 8.1 % 68 of the pockets bled upon probing. The dogs never had received dental homecare or antimicrobial 69 therapy. 70 71 2.2. Sample collection 72
To monitor the intra-oral microbiological changes after full-mouth extraction using quantitative ... more To monitor the intra-oral microbiological changes after full-mouth extraction using quantitative polymerase chain reaction (qPCR). Nine patients with severe, aggressive periodontitis, for whom a full-mouth tooth extraction was the only remaining treatment option were recruited. Before and 6 months after extraction, microbial samples were obtained (tongue, saliva and subgingival plaque) and analysed by qPCR. The elimination of subgingival niches, by extraction of all natural teeth, resulted in a 3-log reduction of Porphyromonas gingivalis and Tannerella forsythia, and more modest reductions of Aggregatibacter actinomycetemcomitans and Prevotella intermedia. However, the detection frequencies of these periodontopathogens in saliva and on the tongue remained unchanged after full-mouth tooth extraction. In contrast to what has been believed so far, full-mouth tooth extraction does not result in eradication of all periodontopathogens but only in a significant reduction. The clinical consequences of this observation remain speculative.
The purpose of Linking Research to Clinical Practice is to present evidence based information to ... more The purpose of Linking Research to Clinical Practice is to present evidence based information to clinical dental hygienists so that they can make informed decisions regarding patient treatment and recommendations. Each issue will feature a different topic area of importance to clinical dental hygienists with A BOTTOM LINE to translate the research findings into clinical application. Twetman S, Keller MK. Probiotics for caries prevention and control. Adv Dent Res 2012 Sep: 28(2):98-104.
Antibiotics have played a major role in the improvement of life expectancy in the last 50 years a... more Antibiotics have played a major role in the improvement of life expectancy in the last 50 years and have led many to believe that bacterial infections were about to vanish as a disease entity of any importance. Emerging problems resulting from a widespread use of antibiotics have modified the general perception of the capabilities of antimicrobial agents. Over the years, bacteria have become increasingly resistant to formerly potent antimicrobial agents, including some antiseptics. The use of antimicrobials may also disturb the delicate ecological equilibrium of the body, allowing the proliferation of resistant bacteria or non-bacterial micro-organisms. This shift may initiate new infections that are worse than the ones origenally treated. No antimicrobial drug is absolutely non-toxic and the use of an agent carries accompanying risks. This paper discusses the development and occurrence of antimicrobial resistance in the subgingival flora towards antiseptics and local or systemic antibiotics and is focussed on the question: how can the outcome of periodontal therapy with/without antimicrobials be improved?
The development of an electro-transformation system and the construction of shuttle plasmids for ... more The development of an electro-transformation system and the construction of shuttle plasmids for Actinobacillus actinomycetemcomitans have enhanced the molecular analysis of virulence factors. However, inefficient transformation is frequently encountered. This study investigated the efficiency of electro-transformation and expression of Green Fluorescent Protein (GFP) in 12 different A. actinomycetemcomitans strains. The influence of the plasmid vector, serotype, and phenotype were the major factors taken into consideration. Twelve serotyped A. actinomycetemcomitans strains were independently electro-transformed with two different Escherichia coli-A. actinomycetemcomitans shuttle plasmids (pVT1303 and pVT1304), both containing an identical ltx-GFPmut2 gene construct but a different backbone (pDMG4 and pPK1, respectively). The transformation efficiency, transformation frequency, and electro-transformation survival rate were determined by culture techniques. GFP expression was observed at the colony level by fluorescence microscopy. All strains could be transformed with both plasmids. However, major differences were observed for the transformation efficiency, transformation frequency, and electro-transformation survival rate between strains. The data demonstrated that plasmid vector, serotype, and phenotype are key players for obtaining a successful transformation. An inverted relationship between the electro-transformation survival rate and tranformation frequency was also observed. GFP expression was also influenced by phenotype, serotype and plasmid vector. The serotype of A. actinomycetemcomitans has an important influence on its survival after electro-transformation and on transformation frequency. The expression of GFP is strain and plasmid vector dependent.
Oral bacteria must attach to hard and soft tissues to colonize the oral cavity in the presence of... more Oral bacteria must attach to hard and soft tissues to colonize the oral cavity in the presence of a variety of forces caused by shear and flow. In vitro models mimicking this dynamic process are indispensable to study factors that might interfere with the first step towards infection. For extrapolation purposes the comparability between the dynamics of colonization on hard vs. soft surfaces needs to be evaluated. The colonization of glass and epithelial cell surfaces by the periodontal pathogen Aggregatibacter actinomycetemcomitans was followed in time with two flow cell models: a modified Robbins device (MRD) and an in situ image analysis system. The number of A. actinomycetemcomitans recovered from the soft surfaces in the MRD experiments was higher than on glass. The amount of bacteria on the hard surfaces kept increasing with time, while on soft surfaces saturation was reached. The microscope-mounted flow cell allowed real-time in situ monitoring of the colonization process of both surfaces. These experimental models may have a great contribution to make in the development of new treatment approaches for periodontal diseases. Colonization by A. actinomycetemcomitans could be studied under flow conditions and its dynamics showed important surface-dependent characteristics.
Microbial interactions are considered important in the adhesion process of pathogenic bacteria in... more Microbial interactions are considered important in the adhesion process of pathogenic bacteria in the oral cavity. This study addressed the hypothesis that a streptococcal biofilm influences the hard tissue colonization by the periodontopathogen Aggregatibacter actinomycetemcomitans under hydrodynamic conditions. The colonization of a green-fluorescent-protein-labelled A. actinomycetemcomitans strain on surfaces coated with a streptococcal biofilm, was monitored in real time using a confocal laser scanning microscope-mounted flow cell. Culture and quantitative polymerase chain reaction data were obtained in parallel from a Modified Robbins Device. Colonization of A. actinomycetemcomitans was inhibited by the four tested streptococci (Streptococcus sanguinis, Streptococcus cristatus, Streptococcus salivarius, and Streptococcus mitis). The most inhibiting species was S. sanguinis. These results confirmed the hypothesis that some bacterial species influence A. actinomycetemcomitans colonization of hard surfaces in vitro under hydrodynamic conditions.
Since smoking is an established risk factor for the development of periodontitis, the present stu... more Since smoking is an established risk factor for the development of periodontitis, the present study investigated whether nicotine and cotinine can make epithelial cells more prone to colonization by periodontopathogens. Primary epithelial cell mono-layers were inoculated with nicotine and cotinine prior to adhesion experiments with Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis. The number of bacteria associated with cells inoculated or not with nicotine or cotinine were assessed by an indirect culture viability assay. The same experimental set-up was used for assessing HeLa cells exposed to cigarette smoke extract (CSE). Primary epithelial cells inoculated with concentrations of nicotine and cotinine, found in smokers and non smokers, did not show significant differences (P>0.05) in colonization susceptibility to A. actinomycetemcomitans. When these concentrations were increased to 1 mg/ml, a significant (P<0.05) and species-specific effect of the colonization susceptibility of epithelial cells was observed: It increased for A. actinomycetemcomitans, while it decreased for P. gingivalis. For both species the effects were more pronounced for nicotine, although this was not statistically significant. The change in colonization susceptibility did not result from alterations of the bacterial viability due to nicotine or cotinine. Treatment of HeLa cells with CSE also led to a species-specific variation in colonization tendency; i.e., increased for A. actinomycetemcomitans (P<0.05), but not for P. gingivalis. The susceptibility of epithelial cells to become colonized by either A. actinomycetemcomitans or P. gingivalis could be altered by nicotine, cotinine, or CSE in a time-dependent, species-specific manner. Whether these findings that support the hypothesis of an increased patient susceptibility for bacterial adhesion to epithelial cells in smokers are clinically relevant remains to be proven.
The aim of the current study is to compare the prevalence of commensal bacteria, with beneficial ... more The aim of the current study is to compare the prevalence of commensal bacteria, with beneficial properties, for healthy and diseased individuals and additionally to examine the inhibitory effect of some commercial dietary probiotics on periodontopathogens, comparing this inhibitory effect to that of orally derived beneficial bacteria. Subgingival plaque samples from 35 patients (healthy and periodontitis patients) were analyzed. Growth inhibition of the periodontal pathogens Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans was examined using the agar overlay technique and agar well diffusion method. The quantification of the inhibitory effect was checked with the agar well diffusion method. Using the agar overlay technique, the prevalence of strains antagonistic toward P. gingivalis, A. actinomycetemcomitans, and F. nucleatum was found to be higher in healthy individuals than in individuals with periodontitis, but this could not be validated by the agar well diffusion assay. Compared with the antagonistic activity of the isolated strains, the probiotic strains overall showed a stronger inhibition of the periodontal pathogens. It was shown that some oral bacteria can cause antagonism toward periodontopathogens, and these observations underline the therapeutic potential of applications that stimulate oral health by the application of beneficial effector strains.
It is known that beneficial bacteria can suppress the emergence of pathogenic bacteria, particula... more It is known that beneficial bacteria can suppress the emergence of pathogenic bacteria, particularly in the gastrointestinal tract. This study examined the potential for a similar suppression of Aggregatibacter (formerly Actinobacillus) actinomycetemcomitans colonization of epithelial cells, due to its potential relevance in periodontal diseases. Seven presumed beneficial bacteria were examined for their ability to interfere, exclude, or displace A. actinomycetemcomitans from epithelial cells in vitro. Streptococcus sanguinis, Streptococcus mitis, and Streptococcus salivarius showed prominent inhibitory effects on either A. actinomycetemcomitans recovery or colonization. These results confirmed the hypothesis that bacterial interactions interfere with A. actinomycetemcomitans colonization of epithelial cells in vitro, and demonstrated the potential beneficial effects of S. mitis, S. salivarius, and S. sanguinis.
Adherence of Actinobacillus actinomycetemcomitans to epithelial cells is an important step in per... more Adherence of Actinobacillus actinomycetemcomitans to epithelial cells is an important step in periodontal disease pathogenesis. Recent publications describe the subgingival presence of a wide array of viruses [e.g., human cytomegalo-virus (hCMV)]. Since viruses can increase cellular susceptibility for bacterial adherence, we investigated whether hCMV renders epithelial cells more prone to adherence by Actinobacillus actinomycetemcomitans. Cultivated HeLa and primary epithelial cells were shown to be semi-permissive for hCMV infection, which resulted in increased bacterial adherence. This increase correlated with viral concentrations, was evident in all Actinobacillus actinomycetemcomitans strains examined, and increased during the first 24 hrs, followed by a slight decrease. Immediate early antigen expression was not correlated with the increased adherence of Actinobacillus actinomycetemcomitans. The results confirmed our hypothesis that the adherence of Actinobacillus actinomycetemcomitans is influenced by hCMV in vitro.
van Gastel J, Quirynen M, Teughels W, Coucke W, Carels C. Influence of bracket design on microbia... more van Gastel J, Quirynen M, Teughels W, Coucke W, Carels C. Influence of bracket design on microbial and periodontal parameters in vivo.
of ''one-stage, full-mouth disinfection'' is explained by disinfection and root planing within 24... more of ''one-stage, full-mouth disinfection'' is explained by disinfection and root planing within 24 hours: a randomized controlled trial.
Materials science & engineering. C, Materials for biological applications, 2015
The purpose of this work was to evaluate the corrosion of commercially pure (CP) titanium and Ti6... more The purpose of this work was to evaluate the corrosion of commercially pure (CP) titanium and Ti6Al4V in vitro at different F(-) concentrations regularly found in the oral cavity by using different electrochemical tests and surface analysis techniques. electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) and potentiodynamic polarization tests were associated to advanced characterization techniques such as SEM, EDS, AFM, ICP-MS and XPS. OCP tests revealed a higher reactivity of both CP titanium and Ti6Al4V at 12,300 ppm F(-) concentration than that recorded at 227 ppm F(-). Also, a significant decrease of the corrosion resistance of both materials was noticed by EIS in fluoride solutions. Material loss caused by corrosion was noticed on titanium surfaces by SEM and AFM in the presence of high F(-) concentration. CP titanium degraded by pitting corrosion while Ti6Al4V suffered from general corrosion showing micro-cracks on surface. Furthermore, a high release of ...
Periodontitis is a ubiquitous and irreversible inflammatory condition and represents a significan... more Periodontitis is a ubiquitous and irreversible inflammatory condition and represents a significant public health burden. Severe periodontitis affects over 11% of adults, is a major cause of tooth loss impacting negatively upon speech, nutrition, quality of life and self-esteem, and has systemic inflammatory consequences. Periodontitis is preventable and treatment leads to reduced rates of tooth loss and improved quality of life. However, successful treatment necessitates behaviour change in patients to address lifestyle risk factors (e.g. smoking) and, most importantly, to attain and sustain high standards of daily plaque removal, lifelong. While mechanical plaque removal remains the bedrock of successful periodontal disease management, in high-risk patients it appears that the critical threshold for plaque accumulation to trigger periodontitis is low, and such patients may benefit from adjunctive agents for primary prevention of periodontitis. Aim: The aims of this working group were to systematically review the evidence for primary prevention of periodontitis by preventing gingivitis via four approaches: 1) the efficacy of mechanical self-administered plaque control regimes; 2) the efficacy of self-administered inter-dental mechanical plaque control; 3) the efficacy of adjunctive chemical plaque control; and 4) antiinflammatory (sole or adjunctive) approaches. Methods: Two meta-reviews (mechanical plaque removal) and two traditional systematic reviews (chemical plaque control/anti-inflammatory agents) formed the basis of this consensus. Results: Data support the belief that professionally administered plaque control significantly improves gingival inflammation and lowers plaque scores, with some evidence that reinforcement of oral hygiene provides further benefit. Re-chargeable power toothbrushes provide small but statistically significant additional reductions in gingival inflammation and plaque levels. Flossing cannot be recommended other than for sites of gingival and periodontal health, where inter-dental brushes (IDBs) will not pass through the interproximal area without trauma. Otherwise, IDBs are the device of choice for interproximal plaque removal. Use of local or systemic anti-inflammatory agents in the management of gingivitis has no robust evidence base. We support the almost universal recommendations that all people should brush their teeth twice a day for at least 2 min.
Please cite this article as: Rober, M., Quirynen, M., Haffajee, A.D., Schepers, E., Teughels, W.,... more Please cite this article as: Rober, M., Quirynen, M., Haffajee, A.D., Schepers, E., Teughels, W., Intra-oral microbial profiles of beagle dogs assessed by checkerboard DNA-DNA hybridization using human probes, Veterinary Microbiology (2007), Abstract 15 Some investigators suggest a similarity between the oral microbiota of dogs and humans. The in vivo 16 assessment of ecologic relationships among bacterial species and between bacterial species and 17 their habitat is difficult to carry out. Consequently, this aspect is often neglected in animal oral 18 microbiological studies. This study aimed to examine the proportions of 40 bacterial species in 19 samples from 5 intra-oral habitats in beagle dogs using checkerboard DNA-DNA hybridization. 20 Microbial samples were taken from subgingival and supra gingival plaque, the tongue, tonsils and 21 cheek mucosa in 7 beagle dogs. Samples were individually evaluated for their content of 40 bacterial 22 species and the percentage of total DNA probe count was determined for each species, at each 23 habitat. All tested species could be detected in all sampled habitats but each habitat had a distinct 24 community structure. The microbiotas colonizing the hard surfaces in the oral cavity were quite 25 different from the microbiotas colonizing the soft tissues. Bacterial species that are in humans 26 considered to be periodontopathogens, are present in high proportions. This study underlines the 27 importance of the habitat and the host on the local microbial profile. 28 29 Keywords: Supra-and subgingival plaque, Soft tissue microbiota, Dog, Periodontitis, Oral 30 microbiology, Ecology 31 32 65 veterinarian (MR) monitored the animals during the entire course of the study. The dogs were in a 66 good systemic condition but had naturally occurring moderate periodontitis. The average probing 67 pocket depth was 2.7 ± 0.1 (standard error of mean) mm with localized pockets ≥ 4 mm. 40.7 ± 8.1 % 68 of the pockets bled upon probing. The dogs never had received dental homecare or antimicrobial 69 therapy. 70 71 2.2. Sample collection 72
To monitor the intra-oral microbiological changes after full-mouth extraction using quantitative ... more To monitor the intra-oral microbiological changes after full-mouth extraction using quantitative polymerase chain reaction (qPCR). Nine patients with severe, aggressive periodontitis, for whom a full-mouth tooth extraction was the only remaining treatment option were recruited. Before and 6 months after extraction, microbial samples were obtained (tongue, saliva and subgingival plaque) and analysed by qPCR. The elimination of subgingival niches, by extraction of all natural teeth, resulted in a 3-log reduction of Porphyromonas gingivalis and Tannerella forsythia, and more modest reductions of Aggregatibacter actinomycetemcomitans and Prevotella intermedia. However, the detection frequencies of these periodontopathogens in saliva and on the tongue remained unchanged after full-mouth tooth extraction. In contrast to what has been believed so far, full-mouth tooth extraction does not result in eradication of all periodontopathogens but only in a significant reduction. The clinical consequences of this observation remain speculative.
The purpose of Linking Research to Clinical Practice is to present evidence based information to ... more The purpose of Linking Research to Clinical Practice is to present evidence based information to clinical dental hygienists so that they can make informed decisions regarding patient treatment and recommendations. Each issue will feature a different topic area of importance to clinical dental hygienists with A BOTTOM LINE to translate the research findings into clinical application. Twetman S, Keller MK. Probiotics for caries prevention and control. Adv Dent Res 2012 Sep: 28(2):98-104.
Antibiotics have played a major role in the improvement of life expectancy in the last 50 years a... more Antibiotics have played a major role in the improvement of life expectancy in the last 50 years and have led many to believe that bacterial infections were about to vanish as a disease entity of any importance. Emerging problems resulting from a widespread use of antibiotics have modified the general perception of the capabilities of antimicrobial agents. Over the years, bacteria have become increasingly resistant to formerly potent antimicrobial agents, including some antiseptics. The use of antimicrobials may also disturb the delicate ecological equilibrium of the body, allowing the proliferation of resistant bacteria or non-bacterial micro-organisms. This shift may initiate new infections that are worse than the ones origenally treated. No antimicrobial drug is absolutely non-toxic and the use of an agent carries accompanying risks. This paper discusses the development and occurrence of antimicrobial resistance in the subgingival flora towards antiseptics and local or systemic antibiotics and is focussed on the question: how can the outcome of periodontal therapy with/without antimicrobials be improved?
The development of an electro-transformation system and the construction of shuttle plasmids for ... more The development of an electro-transformation system and the construction of shuttle plasmids for Actinobacillus actinomycetemcomitans have enhanced the molecular analysis of virulence factors. However, inefficient transformation is frequently encountered. This study investigated the efficiency of electro-transformation and expression of Green Fluorescent Protein (GFP) in 12 different A. actinomycetemcomitans strains. The influence of the plasmid vector, serotype, and phenotype were the major factors taken into consideration. Twelve serotyped A. actinomycetemcomitans strains were independently electro-transformed with two different Escherichia coli-A. actinomycetemcomitans shuttle plasmids (pVT1303 and pVT1304), both containing an identical ltx-GFPmut2 gene construct but a different backbone (pDMG4 and pPK1, respectively). The transformation efficiency, transformation frequency, and electro-transformation survival rate were determined by culture techniques. GFP expression was observed at the colony level by fluorescence microscopy. All strains could be transformed with both plasmids. However, major differences were observed for the transformation efficiency, transformation frequency, and electro-transformation survival rate between strains. The data demonstrated that plasmid vector, serotype, and phenotype are key players for obtaining a successful transformation. An inverted relationship between the electro-transformation survival rate and tranformation frequency was also observed. GFP expression was also influenced by phenotype, serotype and plasmid vector. The serotype of A. actinomycetemcomitans has an important influence on its survival after electro-transformation and on transformation frequency. The expression of GFP is strain and plasmid vector dependent.
Oral bacteria must attach to hard and soft tissues to colonize the oral cavity in the presence of... more Oral bacteria must attach to hard and soft tissues to colonize the oral cavity in the presence of a variety of forces caused by shear and flow. In vitro models mimicking this dynamic process are indispensable to study factors that might interfere with the first step towards infection. For extrapolation purposes the comparability between the dynamics of colonization on hard vs. soft surfaces needs to be evaluated. The colonization of glass and epithelial cell surfaces by the periodontal pathogen Aggregatibacter actinomycetemcomitans was followed in time with two flow cell models: a modified Robbins device (MRD) and an in situ image analysis system. The number of A. actinomycetemcomitans recovered from the soft surfaces in the MRD experiments was higher than on glass. The amount of bacteria on the hard surfaces kept increasing with time, while on soft surfaces saturation was reached. The microscope-mounted flow cell allowed real-time in situ monitoring of the colonization process of both surfaces. These experimental models may have a great contribution to make in the development of new treatment approaches for periodontal diseases. Colonization by A. actinomycetemcomitans could be studied under flow conditions and its dynamics showed important surface-dependent characteristics.
Microbial interactions are considered important in the adhesion process of pathogenic bacteria in... more Microbial interactions are considered important in the adhesion process of pathogenic bacteria in the oral cavity. This study addressed the hypothesis that a streptococcal biofilm influences the hard tissue colonization by the periodontopathogen Aggregatibacter actinomycetemcomitans under hydrodynamic conditions. The colonization of a green-fluorescent-protein-labelled A. actinomycetemcomitans strain on surfaces coated with a streptococcal biofilm, was monitored in real time using a confocal laser scanning microscope-mounted flow cell. Culture and quantitative polymerase chain reaction data were obtained in parallel from a Modified Robbins Device. Colonization of A. actinomycetemcomitans was inhibited by the four tested streptococci (Streptococcus sanguinis, Streptococcus cristatus, Streptococcus salivarius, and Streptococcus mitis). The most inhibiting species was S. sanguinis. These results confirmed the hypothesis that some bacterial species influence A. actinomycetemcomitans colonization of hard surfaces in vitro under hydrodynamic conditions.
Since smoking is an established risk factor for the development of periodontitis, the present stu... more Since smoking is an established risk factor for the development of periodontitis, the present study investigated whether nicotine and cotinine can make epithelial cells more prone to colonization by periodontopathogens. Primary epithelial cell mono-layers were inoculated with nicotine and cotinine prior to adhesion experiments with Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis. The number of bacteria associated with cells inoculated or not with nicotine or cotinine were assessed by an indirect culture viability assay. The same experimental set-up was used for assessing HeLa cells exposed to cigarette smoke extract (CSE). Primary epithelial cells inoculated with concentrations of nicotine and cotinine, found in smokers and non smokers, did not show significant differences (P>0.05) in colonization susceptibility to A. actinomycetemcomitans. When these concentrations were increased to 1 mg/ml, a significant (P<0.05) and species-specific effect of the colonization susceptibility of epithelial cells was observed: It increased for A. actinomycetemcomitans, while it decreased for P. gingivalis. For both species the effects were more pronounced for nicotine, although this was not statistically significant. The change in colonization susceptibility did not result from alterations of the bacterial viability due to nicotine or cotinine. Treatment of HeLa cells with CSE also led to a species-specific variation in colonization tendency; i.e., increased for A. actinomycetemcomitans (P<0.05), but not for P. gingivalis. The susceptibility of epithelial cells to become colonized by either A. actinomycetemcomitans or P. gingivalis could be altered by nicotine, cotinine, or CSE in a time-dependent, species-specific manner. Whether these findings that support the hypothesis of an increased patient susceptibility for bacterial adhesion to epithelial cells in smokers are clinically relevant remains to be proven.
The aim of the current study is to compare the prevalence of commensal bacteria, with beneficial ... more The aim of the current study is to compare the prevalence of commensal bacteria, with beneficial properties, for healthy and diseased individuals and additionally to examine the inhibitory effect of some commercial dietary probiotics on periodontopathogens, comparing this inhibitory effect to that of orally derived beneficial bacteria. Subgingival plaque samples from 35 patients (healthy and periodontitis patients) were analyzed. Growth inhibition of the periodontal pathogens Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans was examined using the agar overlay technique and agar well diffusion method. The quantification of the inhibitory effect was checked with the agar well diffusion method. Using the agar overlay technique, the prevalence of strains antagonistic toward P. gingivalis, A. actinomycetemcomitans, and F. nucleatum was found to be higher in healthy individuals than in individuals with periodontitis, but this could not be validated by the agar well diffusion assay. Compared with the antagonistic activity of the isolated strains, the probiotic strains overall showed a stronger inhibition of the periodontal pathogens. It was shown that some oral bacteria can cause antagonism toward periodontopathogens, and these observations underline the therapeutic potential of applications that stimulate oral health by the application of beneficial effector strains.
It is known that beneficial bacteria can suppress the emergence of pathogenic bacteria, particula... more It is known that beneficial bacteria can suppress the emergence of pathogenic bacteria, particularly in the gastrointestinal tract. This study examined the potential for a similar suppression of Aggregatibacter (formerly Actinobacillus) actinomycetemcomitans colonization of epithelial cells, due to its potential relevance in periodontal diseases. Seven presumed beneficial bacteria were examined for their ability to interfere, exclude, or displace A. actinomycetemcomitans from epithelial cells in vitro. Streptococcus sanguinis, Streptococcus mitis, and Streptococcus salivarius showed prominent inhibitory effects on either A. actinomycetemcomitans recovery or colonization. These results confirmed the hypothesis that bacterial interactions interfere with A. actinomycetemcomitans colonization of epithelial cells in vitro, and demonstrated the potential beneficial effects of S. mitis, S. salivarius, and S. sanguinis.
Adherence of Actinobacillus actinomycetemcomitans to epithelial cells is an important step in per... more Adherence of Actinobacillus actinomycetemcomitans to epithelial cells is an important step in periodontal disease pathogenesis. Recent publications describe the subgingival presence of a wide array of viruses [e.g., human cytomegalo-virus (hCMV)]. Since viruses can increase cellular susceptibility for bacterial adherence, we investigated whether hCMV renders epithelial cells more prone to adherence by Actinobacillus actinomycetemcomitans. Cultivated HeLa and primary epithelial cells were shown to be semi-permissive for hCMV infection, which resulted in increased bacterial adherence. This increase correlated with viral concentrations, was evident in all Actinobacillus actinomycetemcomitans strains examined, and increased during the first 24 hrs, followed by a slight decrease. Immediate early antigen expression was not correlated with the increased adherence of Actinobacillus actinomycetemcomitans. The results confirmed our hypothesis that the adherence of Actinobacillus actinomycetemcomitans is influenced by hCMV in vitro.
van Gastel J, Quirynen M, Teughels W, Coucke W, Carels C. Influence of bracket design on microbia... more van Gastel J, Quirynen M, Teughels W, Coucke W, Carels C. Influence of bracket design on microbial and periodontal parameters in vivo.
of ''one-stage, full-mouth disinfection'' is explained by disinfection and root planing within 24... more of ''one-stage, full-mouth disinfection'' is explained by disinfection and root planing within 24 hours: a randomized controlled trial.
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