[Medicaments and oral care: Is there still a rationale for clinical periodontal microbiology?]

Clinical microbiology now occupies an important place in periodontics and oral implant dentistry as a supplementary diagnostic tool and in planning treatment, particularly with respect to the rational use of antibiotics. This view is in line with the emphatic call by the World Health Organization and the European Union for the prudent use of antibiotics due to the global increase in resistance to antibiotics. Furthermore side effects may occur, such as the disturbance of the microbial intestinal and oral microflora, sometimes leading to serious pathological conditions. Hyposalivation following the use of antibiotics may lead to an oral environmental condition in which caries may develop faster than usual.

[A renewed focus on extra-oral manifestations of oral infections]

Dental focal infections are extraoral manifestations caused by oral pathogens. Pathological oral conditions, such as periapical inflammation and periodontitis, can cause bacteremia. Dissemination of oral pathogens to nonoral sites can subsequently cause infections in extraoral tissues and organs. Cardiovascular infections and brain abscesses are the most common of these. The course of such infections can be lethal. In order to improve patient care, a closer collaboration between dental and medical caregivers is necessary.

Conserved Citrullinating Exoenzymes in Porphyromonas Species

Porphyromonas gingivalis is one of the major oral pathogens implicated in the widespread inflammatory disorder periodontitis. Moreover, in recent years, P. gingivalis has been associated with the autoimmune disease rheumatoid arthritis. The peptidylarginine deiminase enzyme of P. gingivalis (PPAD) is a major virulence factor that catalyzes the citrullination of both bacterial and host proteins, potentially contributing to production of anticitrullinated protein antibodies. Considering that these antibodies are very specific for rheumatoid arthritis, PPAD appears to be a link between P. gingivalis, periodontitis, and the autoimmune disorder rheumatoid arthritis. PPAD was thus far considered unique among prokaryotes, with P. gingivalis being the only bacterium known to produce and secrete it. To challenge this hypothesis, we investigated the possible secretion of PPAD by 11 previously collected Porphyromonas isolates from a dog, 2 sheep, 3 cats, 4 monkeys, and a jaguar with periodontitis. Our analyses uncovered the presence of secreted PPAD homologues in 8 isolates that were identified as Porphyromonas gulae (from a dog, monkeys, and cats) and Porphyromonas loveana (from sheep). In all 3 PPAD-producing Porphyromonas species, the dominant form of the secreted PPAD was associated with outer membrane vesicles, while a minor fraction was soluble. Our results prove for the first time that the citrullinating PPAD exoenzyme is not unique to only 1 prokaryotic species. Instead, we show that PPAD is produced by at least 2 other oral pathogens.

Bacterial colonization of the peri-implant sulcus in dentate patients: a prospective observational study

OBJECTIVES

The aim of the present study was to compare the composition of the periodontal microflora at baseline (T0) with the submucosal microflora at least 1 year after implant placement (T1) in periodontally healthy patients.

MATERIAL AND METHODS

For all 169 consecutive patients that visited our clinic during 1 year, we determined their periodontal parameters, implant mucosal index, and presence of implant calculus. At T0, self-reported smoking status was recorded and subgingival and submucosal biofilm samples were obtained and analyzed for the presence and numbers of selected periodontal pathogens. All measurements were repeated at T1.

RESULTS

One hundred twenty patients completed the study. Periodontal parameters were stable or had improved at T1. The total bacterial load was lower at implant sites (P < 0.05). The prevalence of Porphyromonas gingivalis was low at baseline, but at T1, detection rate and numbers were higher at implant sites compared to dentate sites. At T1, the frequency of detection of P. gingivalis (P = 0.01), Parvimonas micra (P = 0.018), and Fusobacterium nucleatum (P = 0.035) was higher in smoking patients (n = 23) than in non-smokers (n = 97).

CONCLUSIONS

Colonization of the submucosal peri-implant area is similar to the composition of subgingival microbiota. Smoking has a measurable effect on the colonization of implant-associated biofilms and may select for P. gingivalis, P. micra, and F. nucleatum.

CLINICAL RELEVANCE

The colonization of implants by well-known periodontal pathogens is very similar to that in normal dentition, also in a healthy cohort. Smoking status was related with the prevalence of periodontal pathogens where smokers harbored more often periodontal pathogens such as P. gingivalis, P. micra, and F. nucleatum.

The optimization and validation of the Biotyper MALDI-TOF MS database for the identification of Gram-positive anaerobic cocci

Gram-positive anaerobic cocci (GPAC) account for 24%-31% of the anaerobic bacteria isolated from human clinical specimens. At present, GPAC are under-represented in the Biotyper MALDI-TOF MS database. Profiles of new species have yet to be added. We present the optimization of the matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) database for the identification of GPAC. Main spectral profiles (MSPs) were created for 108 clinical GPAC isolates. Identity was confirmed using 16S rRNA gene sequencing. Species identification was considered to be reliable if the sequence similarity with its closest relative was ≥98.7%. The optimized database was validated using 140 clinical isolates. The 16S rRNA sequencing identity was compared with the MALDI-TOF MS result. MSPs were added from 17 species that were not yet represented in the MALDI-TOF MS database or were under-represented (fewer than five MSPs). This resulted in an increase from 53.6% (75/140) to 82.1% (115/140) of GPAC isolates that could be identified at the species level using MALDI-TOF MS. An improved log score was obtained for 51.4% (72/140) of the strains. For strains with a sequence similarity <98.7% with their closest relative (n = 5) or with an inconclusive sequence identity (n = 4), no identification was obtained by MALDI-TOF MS or in the latter case an identity with one of its relatives. For some species the MSP of the type strain was not part of the confined cluster of the corresponding clinical isolates. Also, not all species formed a homogeneous cluster. It emphasizes the necessity of adding sufficient MSPs of human clinical isolates.

Anaerococcus nagyae sp. nov., isolated from human clinical specimens

We describe a new Anaerococcus species isolated from human clinical specimens. Analyses of 16S rRNA gene sequences of three strains showed <98% similarity with its closest relative Anaerococcus octavius. Phylogenetically the isolated strains form a cluster and can be differentiated from other species of the genus Anaerococcus based on its phenotypic characteristics and its MALDI-TOF MS profile. We propose the name Anaerococcus nagyae, with A. nagyae DSM101193 (accession number KU043522) as the type strain.

[Periodontitis and systemic diseases: from science to clinical practice]

The evidence for an association between systemic diseases and periodontitis is strongest with diabetes mellitus type 2 and cardiovascular disease. There is a moderate association of periodontitis with adverse pregnancy outcomes and rheumatoid arthritis. Periodontal treatment has, on average, a positive effect on reducing systemic infection and improving the condition of the vascular system. For diabetes patients, periodontal treatment can also have a positive effect on metabolic regulation. There is insufficient evidence that periodontal treatment prevents adverse pregnancy outcomes and rheumatoid arthritis.

In vitro antimicrobial effects of two antihalitosis mouth rinses on oral pathogens and human tongue microbiota

OBJECTIVES

The aim of the study was to compare the antimicrobial activity of a mouth rinse containing chlorhexidine and cetylpyridinium chloride (MR1) with a stannous fluoride-based mouth rinse (MR2) in vitro.

MATERIALS AND METHODS

Samples of the tongues from 10 subjects with and 10 subjects without halitosis were inoculated on blood agar plates. The agar was perforated, and the cylindrical holes were filled either with mouth rinse MR1 or with mouth rinse MR2. After incubation, inhibition zones of the whole tongue microbiota and Fusobacterium nucleatum were measured. In addition, MR1 and MR2 were applied in a short interval killing test (SIKT) on four oral pathogens Porphyromonas gingivalis, Prevotella intermedia, F. nucleatum and Aggregatibacter actinomycetemcomitans. Total viable cell counts were made after two minutes of incubation with increasing concentrations of MR1 and MR2.

RESULTS

MR1 showed a significantly higher in vitro antimicrobial activity against the whole tongue microbiota and F. nucleatum than MR2 in both groups of subjects. In the SIK test, MR1 showed a significantly greater killing capacity than MR2. The results show that a mouth rinse with low concentrations of chlorhexidine and 0.05% cetylpyridinium chloride appears to be more effective in inhibiting growth of the human tongue microbiota in vitro than a fluoride/stannous fluoride-containing mouth rinse.

CONCLUSION

This in vitro observation supports the use of chlorhexidine and cetylpyridinium chloride in the treatment of oral halitosis.

Evaluation of three selective media for isolation of Aggregatibacter actinomycetemcomitans

BACKGROUND AND OBJECTIVE

Aggregatibacter actinomycetemcomitans is a pathogen in oral and nonoral infections. Detection and quantification of this pathogen can be performed using selective culture techniques. The aim of this study was to establish the efficacy of two known selective media in their ability to select and support the growth of A. actinomycetemcomitans.

MATERIAL AND METHODS

Trypticase soy bacitracin vancomycin (TSBV) medium and brain-heart infusion agar with vancomycin (Dentaid-1), as well as a modified Dentaid-1 medium (in which the brain-heart infusion agar was substituted with brain-heart infusion broth), were compared. Two-hundred and eighteen clinical samples were used to establish the recovery rate, the number of colony-forming units (CFUs) of A. actinomycetemcomitans as well as the total number of CFUs on the three different types of medium. In addition, the numbers of gram-negative aerobic rods and yeasts were determined.

RESULTS

Both types of Dentaid-1 medium showed a higher recovery of A. actinomycetemcomitans compared with TSBV. However, these differences did not reach statistical significance. The total number of CFUs of A. actinomycetemcomitans recovered was significantly higher on Dentaid-1 compared with TSBV (p = 0.029). The mean number of gram-negative aerobic rods recovered was statistically higher on both types of Dentaid-1 medium in comparison with TSBV. Low numbers of yeasts were recovered occasionally on all test plates.

CONCLUSION

Dentaid-1 is a low-cost effective alternative to TSBV for the isolation and growth of A. actinomycetemcomitans from clinical samples, such as dental plaque, which contain a complex microflora.

[Effect of periodontal treatment on rheumatoid arthritis and vice versa]

The pathogenesis of periodontitis and of rheumatoid arthritis show remarkable similarities. There is a distinct degree of co-existence between the 2 diseases. The prevalence of periodontitis is more pronounced in rheumatoid arthritis patients and the prevalence of rheumatoid arthritis is more pronounced in periodontitis patients. At present, a positive influence of periodontal treatment on the rheumatoid arthritis disease activity or of rheumatoid arthritis drug treatment on periodontitis is not sufficiently supported by clinical research. Periodontitis may play a role in unsatisfactory therapy response in some rheumatoid arthritis patients.

[Dissertations 25 years after date 31. Black-pigmented oral bacteria in human oral infections]

In 1986, oral microbiology, and especially the microbiology of periodontal infections, was of central importance. Interest in periodontology was growing rapidly and with it, interest in developments in microbiology and the immunology of infectious diseases of the periodontium. At national and international meetings discussions took place concerning the role of the newly discovered bacterial species Actinobacillus actinomycetemcomitans and the role of antibiotics in the treatment of severe periodontitis. Since the 1980s, much has changed in periodontology, not least of all as a result of a new specialism: oral implantology. With it, a new disease also came into existence: peri-implantitis.

Rheumatoid arthritis and periodontitis; a possible link via citrullination

Rheumatoid Arthritis (RA) and chronic and aggressive periodontitis are chronic inflammatory disorders characterized by deregulation of the host inflammatory response. Increased secretion of pro-inflammatory mediators results in soft and hard tissue destruction of the synovium and periodontium respectively. Both diseases share risk factors and have pathological pathways in common, resulting in loss of function and disability as a final clinical outcome. This article discusses possible interactions, particularly related to the periodontal pathogen Porphyromonas gingivalis, which could explain the observed association between these two prevalent diseases.

[Consensus on peri-implant infections]

In 2008, in a workshop of the European Federation on Periodontology, a consensus was reached concerning oral peri-implant infections on the basis of the state of the art in the relevant sciences. Important conclusions were that peri-implant mucositis occurs in 80% of subjects with oral implants, and that peri-implantitis occurs in 28-56% of subjects studied. Important risk factors for developing peri-implant infections seem to be insufficient oral hygiene, a history of periodontitis and cigarette smoking. There are insufficient research findings available to support a definitive conclusion about the role of genetic factors, diabetes mellitus, alcohol consumption and implant surface properties. Mechanical treatment in combination with antimicrobial oral mouth rinses may be effective in the treatment of mucositis. No evidence has been found that mechanical treatment of peri-implantitis is effective. To control the infection of peri-implantitis, surgical treatment, often in combination with the use of local or systemic antibiotics, is necessary. Validated protocols for the treatment of peri-implant infections are not available due to lack of clinical scientific evidence.

Comparison of periodontal pathogens between cats and their owners

The periodontal pathogens Porphyromonas gingivalis and Tannerella forsythia are strongly associated with periodontal disease and are highly prevalent in humans with periodontitis. Porphyromonas and Tannerella spp. have also been isolated from the oral cavity of cats. The oral microflora in animals was compared with those in humans in earlier studies, but no studies are available on the comparison of the oral microflora from pets and their respective owners. The aim of this study was to determine the presence of these bacteria in the oral microflora of cats and their owners, since animal to human transmission, or vice versa, of oral pathogens could have public health implications. This study investigated the prevalence of Porphyromonas gulae, P. gingivalis, and T. forsythia in the oral microflora of cats and their owners, using culture and polymerase chain reaction (PCR). All Porphyromonas isolates from cats (n=64) were catalase positive, whereas the Porphyromonas isolates from owners (n=7) were catalase negative, suggesting that the isolates from cats were P. gulae whereas those from the owners were P. gingivalis. T. forsythia was recovered from both cats (n=63) and owners (n=31); the proportion of T. forsythia relative to the total CFU was higher in cats with periodontitis than in cats without periodontal disease. Genotyping of T. forsythia isolates (n=54) in six cat/owner couples showed that in one cat/owner couple the T. forsythia isolates (n=6) were identical. These T. forsythia isolates were all catalase positive, which led us to hypothesize that transmission from cats to owners had occurred and that cats may be a reservoir of T. forsythia.

[Stress and periodontal health]

Periodontitis and periimplant infections are complex manifestations associated with several disease-modifying factors, such as causative pathogens and smoking. Although research into these factors has led to important progressions in the treatment of these infections in recent decades, the contribution of mental stress in the absence of pathogens or smoking is still unclear. Qualitative and quantitative assessment of mental stress might be an important instrument in periodontal and periimplant therapy.

Gingival and periodontal ligament fibroblasts differ in their inflammatory response to viable Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

Porphyromonas gingivalis is an oral pathogen strongly associated with destruction of the tooth-supporting tissues in human periodontitis. Gingival fibroblasts (GF) and periodontal ligament fibroblasts (PDLF) are functionally different cell types in the periodontium that can participate in the host immune response in periodontitis. This study aimed to investigate the effects of viable P. gingivalis on the expression of genes associated with inflammation and bone degradation by these fibroblast subsets.

MATERIAL AND METHODS

Primary human GF and PDLF from six healthy donors were challenged in vitro with viable P. gingivalis W83 for 6 h. Gene expression of inflammatory cytokines in GF and PDLF was analyzed using real-time PCR, and protein expression was analyzed using ELISA.

RESULTS

Viable P. gingivalis induced a strong in vitro inflammatory response in both GF and PDLF. We found increased gene expression of interleukin (IL)-1beta, IL-6, IL-8, tumor necrosis factor-alpha, monocyte chemotactic protein-1 and regulated upon activation, normal T-cell expressed and secreted (RANTES). Macrophage colony-stimulating factor was induced and the expression of osteoprotegerin was decreased in GF, but not in PDLF. In nonchallenged cells, a higher level of expression of IL-6 was observed in GF than in PDLF. Between individual donors there was large heterogeneity in responsiveness to P. gingivalis. Also, in each individual, either GF or PDLF was more responsive to P. gingivalis.

CONCLUSION

Considerable heterogeneity in responsiveness to P. gingivalis exists both between GF and PDLF and between individuals, which may be crucial determinants for the susceptibility to develop periodontitis.

[Pitfalls in diagnosis and treatment of periodontal diseases]

In the present article the complex aetiology of periodontal diseases is explained. Furthermore risk factors are identified for making mistakes in diagnosis and failing treatment of periodontal infections. This includes patient and treatment factors such as incomplete anamnesis, improper screening and documentation as well as insufficient plaque and smoking control, improper use of antibiotics and insufficient pocket-elimination and maintenance care. The use of a strict diagnostic and treatment protocol including evaluation is emphasized in order to obtain optimal treatment results. Patients should minimally expect to be regularly screened by their dentist or dental hygienist for periodontal diseases, to be informed about the further diagnostic steps and possible treatment options and to get periodontal care organised. Providers of oral health care can, in this way, reduce the risk of negligent practice and significantly limit their liability.

[Infectious complications with dental implants]

Dental implantology represents an essential step in the rehabilitation of function, stability and aesthetics of the human dentition.The introduction of dental implantology has at the same time created a problem: peri-implant infections. Putative risk factors for this disorder are, among others, smoking, a history of periodontitis, genetic traits, and uncontrolled diabetes mellitus. Since no validated protocol for the treatment of peri-implantitis exists, clinicians have to rely on their own experience and knowledge and on the experience of others.

Host and microbiological factors related to dental caries development

Studies on dental caries suggest that in severe cases it may induce a systemic immune response. This occurs particularly when caries progresses into pulpal inflammation and results in abscess or fistula formation (AFF). We hypothesized that severe dental caries will affect the general health of children. The acute phase proteins alpha-1-acid glycoprotein (AGP), C-reactive protein (CRP) and the cytokine neopterin were chosen as parameters to monitor general health. Also, a polymorphism in the bacterial ligand CD14 (-260) was studied to investigate the relationship between genotype sensitivity for bacterial infections and AFF. In Suriname, children aged 6 years were recruited and enrolled into a dental care scheme, randomly assigned to 4 groups with different treatment strategies and monitored longitudinally. 348 children were included in the present study. Blood and saliva samples were taken at baseline and 1 year, and concentrations of serum AGP, CRP, neopterin, salivary Streptococcus mutans and CD14-260 C>T polymorphism were determined. There was no significant association between different treatment strategies and the serum parameters. Binary logistic regression analyses revealed a significant association between AFF as the outcome variable and the CD14 genotype and the concentrations of CRP and of neopterin as factors (p < 0.05). A significant negative association was found between the CD14-260 TT and AFF (p = 0.035, OR = 3.3) for the whole population. For children who had 4 or more carious lesions at baseline, the significance increased (p = 0.005, OR = 4.8), suggesting that the CD14-260 TT genotype was protective for AFF as a consequence of dental caries.

[Post-academic dental specialties 19. The effect of periodontal treatment on the degree of de novo plaque formation]

In order to determine whether the quantity of bacteria in saliva and the degree of periodontal infection influence the speed of de novo plaque formation in periodontitis patients, 23 patients rinsed with 10 ml sterile saline. All teeth were then supragingivally and professionally cleaned, after which the patients were not allowed to undertake any form of oral hygiene for 24 hours. After this period, the rinsing procedure was repeated and the amount of de novo plaque was assessed. Three months after the initial periodontal therapy was completed the experiment was repeated. Both before and after treatment, the periodontal parameters were evaluated. The results showed that the quantity of the de novo plaque in healthy areas was less than in infected areas. In order to determine the influence of the quantity of bacteria in the saliva, only the areas which were already healthy before the treatment and the same areas after treatment were inspected. It was concluded that the degree of periodontal infection was the most important parameter for the degree of de novo plaque formation, but that the number of bacteria in the saliva also played a role.

Genotypic characterization of Porphyromonas gingivalis isolated from Swedish patients with periodontitis and from periodontal abscesses

INTRODUCTION

A significant genetic polymorphism has been shown for Porphyromonas gingivalis isolates from different geographical areas. It is, however, possible that genetic similarities can be found among isolates obtained from a more specific population. The aim of the present study was to evaluate genetic heterogeneity among P. gingivalis isolates obtained from Swedish subjects with chronic periodontitis and from periodontal abscess lesions.

METHODS

A total of 78 P. gingivalis strains, including 55 fresh clinical isolates obtained from 52 Swedish periodontitis subjects, eight isolates from eight Swedish periodontal abscess subjects and 15 reference strains, were subjected to amplified fragment length polymorphism (AFLP) and random amplified polymorphic DNA (RAPD) genotyping assays.

RESULTS

A total of 62 AFLP genotypes and 70 RAPD genotypes were identified among the 78 P. gingivalis strains. Forty-six strains were clustered at 70% similarity level into 15 clusters. Six identical RAPD genotypes were identified among the strains. The AFLP/RAPD profiles were compared for identical genotypes. A total of 56 AFLP/RAPD genotypes were found. Four pairs of identical AFLP/RAPD genotypes were found for two strains obtained from two different periodontal pockets each of four subjects. Interestingly, two strains showed an RAPD/AFLP genotype, which was identical to the type strain W83.

CONCLUSION

The present study demonstrated that Swedish P. gingivalis isolates exhibit a wide variety of genotypes with only a weak clustering pattern. No predominant genotype at the whole chromosomal DNA level was present among Swedish P. gingivalis strains.

Activation of toll-like receptors 2 and 4 by gram-negative periodontal bacteria

BACKGROUND/AIMS

Periodontitis is a chronic infectious disease associated with a gram-negative subgingival microflora. Bacterial components stimulate, among other receptors, Toll-like receptor (TLR) 2 and/or TLR4. Accumulating evidence indicates that both qualitatively and quantitatively distinct immune responses result from the triggering of TLR2 as compared to TLR4 triggering. The aim was to study the interaction of Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Tannerella forsythensis, Prevotella intermedia, Prevotella nigrescens, Fusobacterium nucleatum and Veillonella parvula with TLR2 and TLR4. We investigated all known serotypes (K(-), K1-K6) of P. gingivalis and A. actinomycetemcomitans serotype a-e strains for their potency to stimulate cytokine production.

METHODS

Human embryonic kidney (HEK) cells, stably transfected with CD14, CD14-TLR2, or CD14-TLR4 and whole blood were stimulated with bacterial sonicates. Cytokine production (interleukin-6, -8, -10 and -12) was measured in the supernatant by enzyme-linked immunosorbent assay.

RESULTS

All test bacteria stimulated HEK-CD14-TLR2, but only A. actinomycetemcomitans and V. parvula stimulated HEK-CD14-TLR4. No differences were found in the activation of HEK-CD14-TLR2/4, or cytokine production in whole blood between serotypes of P. gingivalis and A. actinomycetemcomitans.

CONCLUSION

Gram-negative periodontal bacteria predominantly stimulated TLR2, which may be of importance for the Th1/Th2 cell orientation of the immune response in periodontitis.

Java project on periodontal diseases: a study on transmission of Porphyromonas gingivalis in a remote Indonesian population

AIM

To study transmission of Porphyromonas gingivalis in a population living in a remote area in Southern Java, Indonesia.

MATERIAL AND METHODS

Subgingival plaque samples from 167 subjects with varying degrees of periodontal breakdown were obtained and cultured for the presence of P. gingivalis. After extraction and purification of bacterial DNA, amplified fragment length polymorphism technique was applied to genotype the bacterial isolates. Computer-assisted analysis of the bacterial DNA profiles was used to study distribution of P. gingivalis genotypes within family units.

RESULTS

One hundred and five of the 167 (63%) subjects were culture positive for P. gingivalis. In total, 371 P. gingivalis isolates were obtained from the 105 subjects. Of the 105 subjects, 30 were siblings representing 13 families. In six of the 13 families (46%), identical P. gingivalis genotypes were found among siblings. In the study group of 105 subjects, 13 married couples were identified of which both spouses were culture positive for P. gingivalis. None of the 13 couples shared an identical P. gingivalis genotype. Twenty P. gingivalis-positive subjects had spouses that were culture negative for P. gingivalis.

CONCLUSIONS

In this study population, vertical transmission of P. gingivalis has occurred within family units, most likely from parents to children. Transmission of P. gingivalis between spouses could not be established.

Microbiology in diagnosis and treatment planning in periodontics

Periodontitis is considered a multifactorial infectious disease in which bacteria play an essential role. It has become clear that not all patients with periodontitis harbour the same subgingival microflora, and so far, a limited number of species have been recognised as indicators for progression of periodontal breakdown. These findings are the basis for the use of clinical periodontal microbiology. Microbiological information can assist in diagnosis and treatment planning in periodontics, and is essential for the rational use of topical and systemic antimicrobial treatment. Different antimicrobial regimes have been proposed as adjuncts to mechanical periodontal treatment. This article reviews the current knowledge on periodontal microbiology, different techniques to test for marker bacteria and the use of antibiotics in the treatment of severe periodontitis.

Antibiotics in periodontics: are we getting somewhere?

van Winkelhoff AJ. Antibiotics in periodontics: are we getting somewhere? J Clin Periodontol 2005; 32: 1094-1095. doi: 10.1111/j.1600-051X.2005.00830.x. (c) Blackwell Munksgaard 2005.

Antimicrobial profiles of periodontal pathogens isolated from periodontitis patients in the Netherlands and Spain

BACKGROUND AND AIM

Antimicrobial resistance of periodontal pathogens towards currently used antibiotics in periodontics has been investigated in a previous study. Microbial resistance in the periodontal microflora was more frequently observed in Spanish patients in comparison with Dutch patients. The aim of the present study was to compare antimicrobial susceptibility profiles of five periodontal bacteria isolated from periodontitis patients in Spain and in The Netherlands.

MATERIAL AND METHODS

Subgingival plaque samples from adult patients with periodontitis were collected and cultured on selective and non-selective plates. Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum and Micromonas micros were isolated and used for minimal inhibitory concentration tests using the Epsilometer (E-test) technique. Eight different antibiotics were tested on all bacterial isolates. MIC50 and MIC90 values for each antibiotic and each species were determined and the percentage of resistant strains was calculated.

RESULTS

Significantly higher MIC values were noted in Spanish strains of F. nucleatum for penicillin, ciprofloxacin, of P. intermedia for penicillin, amoxicillin and tetracycline, of M. micros for tetracycline, amoxicillin and azithromycin, and of P. gingivalis for tetracycline and ciprofloxacin. Based on breakpoint concentrations, a higher number of resistant strains in Spain were found in F. nucleatum for penicillin, amoxicillin and metronidazole, in Prevotella intermedia for tetracycline and amoxicillin, and in A. actinomycetemcomitans for amoxicillin and azithromycin. Resistance of P. gingivalis strains was not observed for any of the antibiotics tested both in Spain and The Netherlands.

CONCLUSIONS

Differences exist in the susceptibility profiles of periodontal pathogens isolated from periodontitis patients in Spain and in The Netherlands. This implicates that antibiotic susceptibility testing is necessary to determine efficacy of antimicrobial agents. Also, clinical studies with antibiotics should take these differences into account. The information from the present study indicates that it may not be possible to develop uniform protocols for usage of antibiotics in the treatment of severe periodontitis in the European Union.

[Effectiveness of feeding large kibbles with mechanical cleaning properties in cats with gingivitis]

Periodontal disease is the most common acquired oral disease in cats. It starts with plaque accumulation and gingivitis. The aim of this study was to evaluate the effectiveness of different types of kibble and teeth brushing after professional dental cleaning. To this end, the ratio of facultative anaerobic and obligate anaerobic bacteria was determined, and the amount of plaque and tartar and the severity of gingivitis were measured. Eighty-eight cats with gingivitis and tartar were randomly divided into four groups and given different treatments after professional dental cleaning. The dental treatments were: group 1, cats were fed on small kibbles with mechanical cleaning qualities; group 2, cats were fed on small kibbles without mechanical cleaning qualities, and owners were instructed to brush the cats' teeth; group 3, cats were fed on large kibbles with mechanical cleaning qualities; and group 4, cats were fed on the same kibbles as group 2, but owners were not asked to brush their cats' teeth. A supragingival plaque sample was taken, and used for bacteriological analysis scores for tartar, plaque, and gingivitis were determined at the initial presentation and at 3 and 6 months after professional dental cleaning. Cats fed on the large kibbles with mechanical cleaning qualities (group 3) had significantly less gingivitis and tartar.

[Impact of antibiotics on the indication for periodontal surgery]

The present paper describes the use of oral antibiotics in the treatment of severe periodontitis based on the composition of the subgingival flora. Antimicrobial therapy is applied within the concept of the three basic steps in periodontal treatment. It is demonstrated in the literature that the use of antibiotics based on clinical and microbiological parameters, can reduce the need of periodontal access surgery. Proper infection control is also related to favourable outcome of regenerative periodontal procedures and periodontal plastic surgery. Therefore, the proper use of antibiotics may result in a shift in indication for different modalities of periodontal surgery.

CARD15 gene mutations in periodontitis

OBJECTIVES

The CARD15 gene encodes the Nod2 protein, which is involved in intracellular recognition of bacterial products like peptidoglycan, activates inflammation and regulates apoptosis through nuclear factor-kappa B, a transcription factor that plays a central role in the innate immunity. Two functional mutations, an insertion mutation at nucleotide 3020 (3020insC) and a missense mutation C2104T in the CARD15 gene (originally NOD2 gene) have been reported to be associated with Crohn's disease. Our aim was to investigate the occurrence of CARD15 gene polymorphisms in adult patients with periodontitis taking into account smoking and presence of putative periodontal pathogens as additional variables.

MATERIAL AND METHODS

A case-control study was performed in 104 Dutch Caucasian patients with severe adult periodontitis (54 non-smokers and 50 smokers, mean age 46 years) and in 97 ethnically matched, periodontal healthy controls (73 non-smokers and 24 smokers, mean age 40 years). DNA isolated from a mouthwash was typed with PCR technology. Presence of putative periodontal pathogens was established by culture technique.

RESULTS

Frequencies of the CARD15 3020insC and 2104T mutations were similar in the periodontitis group and in the control group (5.1% and 13.3%; 5.2% and 10.3%, respectively). The highest carrier frequency of CARD15 mutations was found in non-smoking patients without Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans (29.4% versus 17.4% in controls); however it did not reach statistical significance.

CONCLUSION

Our results suggest no role for CARD15 3020insC and C2104T mutations in adult periodontitis.

Atmospheric contamination during ultrasonic scaling

OBJECTIVE

The aim of this study was to determine the microbial atmospheric contamination during initial periodontal treatment using a piezoelectric ultrasonic scaler in combination with either high-volume evacuation (HVE) or conventional dental suction (CDS).

METHODS

The study included 17 treatment sessions, consisting of a 40-min episode of continuous plaque and calculus removal using an ultrasonic unit (EMS). The treatment sessions were carried out in six patients with generalized adult periodontitis and ranged from two to four sessions per patient according to their needs. The use of HVE and CDS was randomly assigned over the sessions within each patient. Before each treatment, the operating room was not used for 15 h. To measure baseline microbial air pollution two Petri dishes containing blood agar were exposed for 10 min to the air. At the start of each treatment session, two Petri dishes were exposed for 5 min at a distance of 40 cm from the mouth of the patients. After 20 min, this procedure was repeated. At a distance of 150 cm, two Petri dishes were exposed for 20 min followed by exposure of two new Petri dishes for the rest of the session. The plates were cultured aerobically and anaerobically for 3 and 7 days, respectively.

RESULTS

The mean colony forming units (CFU) before treatment never exceeded 0.6 colonies per plate. At 40 cm, the mean CFU, when considering a period of 40 min, was 8.0 for HVE and 17.0 for CDS. The mean CFU at 150 cm during this period was 8.1 with HVE and 10.3 with the CDS. With reference to the Air Microbial Index the operatory atmosphere was considered to be in a good condition during 40 min of continuous use of the ultrasonic scaler in combination with both HVE and CDS.

CONCLUSION

Within the restrictions of this study, only limited atmospheric microbial contamination is produced when using a piezoelectric ultrasonic scaler.

Plasma antibody levels in periodontitis patients and controls

BACKGROUND

A major aspect of the adaptive host response in periodontitis is the production of antibodies. Several risk and susceptibility factors for periodontitis, including smoking, age and composition of the subgingival microflora, have also been suggested to influence antibody production.

AIM

The present study was conducted to investigate plasma levels of immunoglobulin (Ig) G, A and M antibodies in periodontitis patients of Caucasian European heritage in relation to disease severity, smoking, diagnosis and prevalence of periodontopathogens.

METHODS

In this study, 29 patients with severe periodontitis, 51 with moderate periodontitis and 55 controls without periodontal destruction were enrolled. From the total of 80 patients, 18 were diagnosed with aggressive periodontitis and 62 with chronic periodontitis. Total IgG, IgA and IgM as well as IgG isotypes were analyzed in plasma samples.

RESULTS

Levels of total IgG, IgA and IgM were not different between patients and controls; however, in periodontitis, higher levels of IgG1 and IgG2 were observed. Smoking appeared to be significantly and inversely related to antibody levels in periodontitis, in particular for total IgG and IgG2. The absence of an elevated total IgG and IgG2 in smoking patients was irrespective of severity, prevalence of periodontal pathogens and diagnosis. The elevation of total IgG and IgG1 and IgG2 in non-smoker periodontitis patients was observed in patients with moderate periodontitis and even greater in patients with severe periodontitis, but was independent whether patients were infected with Actinobacillus actinomycetemcomitans or Porphyromonas gingivalis and independent of diagnosis. Clinically, it was observed that patients who smoked had more periodontal bone loss; the current findings on antibody levels may be one of several mechanisms related to more extensive periodontal breakdown in smoker patients.

CONCLUSION

The current study shows that non-smoker periodontitis patients have higher levels of total IgG and IgG2 than smoker periodontitis patients.

Pharmacokinetics and effects on bowel and throat microflora of oral levofloxacin as antibacterial prophylaxis in neutropenic patients with haematological malignancies

Gram-positive breakthrough infections pose a major drawback to the use of quinolones for antibacterial prophylaxis in neutropenic patients. Levofloxacin offers the advantage of an augmented Gram-positive spectrum and may potentially overcome this problem. In an open-label, clinical pilot study, we investigated the effects on throat and bowel microflora and pharmacokinetics of a once-daily oral dose of 500 mg levofloxacin, during neutropenia in 20 patients with haematological malignancies. Gram-negative bowel flora and Staphylococcus aureus were successfully eradicated. No Gram-negative infections occurred. Minimal inhibitory concentration values for viridans group (VG) streptococci tended to increase, in four patients over 8 mg/l, indicating resistance to levofloxacin. Four patients developed blood-stream infections with levofloxacin-resistant Gram-positive cocci. No significant changes in numbers of anaerobic microorganisms were observed. Pharmacokinetic parameters of levofloxacin, including the maximum serum concentration (C(max)), time to C(max) (T(max)), area under the concentration-time curve (AUC), volume of distribution at steady state (V(ss)/F) and clearance (CL/F) were not statistically different at first dose and during neutropenia. In conclusion, levofloxacin eradicates Gram-negative microorganisms and S. aureus and spares the anaerobic flora. Its pharmacokinetic profile is unaltered during neutropenia. However, prolonged administration of levofloxacin as antibacterial prophylaxis may be hampered by the emergence of levofloxacin-resistant VG streptococci.

Porphyromonas gingivalis, Bacteroides forsythus and other putative periodontal pathogens in subjects with and without periodontal destruction

BACKGROUND AND AIMS

Bacteria play an essential role in the pathogenesis of destructive periodontal disease. It has been suggested that not all bacteria associated with periodontitis may be normal inhabitants of a periodontally healthy dentition. In particular, Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans have been isolated infrequently from subjects without periodontitis. The aim of the present study was to compare prevalence and proportions of a number of periodontal bacteria in periodontitis patients and control subjects.

MATERIAL AND METHODS

In all, 116 consecutive subjects diagnosed with moderate to severe periodontitis (mean age 42.4) and 94 subjects without radiographic evidence of alveolar bone loss (mean age 40.4) were recruited for the study. The gingival condition in the control group varied between gingival health and various degrees of gingivitis. In patients, the deepest pocket in each quadrant was selected for microbiological sampling. In control subjects all mesial and distal sites of all first molars were selected for sampling. All paper points from a patient were pooled and processed for anaerobic cultivation within 6 h after sampling. Clinical variables of sampled sites included bleeding index, probing pocket depth and clinical attachment level.

RESULTS

A. actinomycetemcomitans, P. gingivalis, Prevotella intermedia, Bacteroides forsythus, Fusobacterium nucleatum and Peptostreptococcus micros were significantly more often prevalent in patients than in controls. The highest odds ratios were found for P. gingivalis and B. forsythus (12.3 and 10.4 resp.). Other odds ratios varied from 3.1 to 7.7 for A. actinomycetemcomitans and P. micros, respectively. Absolute numbers of target bacteria were all higher in patients, but only the mean percentage of B. forsythus was significantly higher in patients in comparison to controls (P < 0.001).

CONCLUSIONS

A. actinomycetemcomitans, P. gingivalis, P. intermedia, B. forsythus, F. nucleatum and P. micros are all significant markers for destructive periodontal disease in adult subjects. Based on calculated odds ratios, B. forsythus and P. gingivalis are the strongest bacterial markers for this disease and are infrequently cultured from subjects without periodontal bone loss.

[Risk factors in adult periodontitis: polymorphism in the interleukin-1 gene family]

Interleukin (IL)-1 alpha, IL-1 beta and IL-1 receptor antagonist (ra) play a major role in regulation of the inflammatory response in periodontal tissues. The aim of this study was to investigate the distribution of genetic variation in the IL-1 gene family among periodontitis patients and controls, taking into account smoking and microbiology as additional variables. There were 53 non-smoking and 52 smoking patients with severe adult periodontitis and 53 periodontal healthy controls genotyped for genetic variation in the IL-1 gene family. The presence of Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans was established by culture techniques. A higher frequency of genotype+ (IL-1A*2 + IL-1B*2 + IL-1RN*2) was found in non-smoking periodontitis patients in whom P. gingivalis and A. actinomycetemcomitans could not be detected (42.1% vs. 11.3% in controls; p = 0.0068; or 5.7, 95% ci: 1.6-19.8). This data provide evidence that polymorphisms in genes of the IL-1 family are associated with severe adult periodontitis and may be a risk factor for severe periodontitis.

Combinations of bacterial species in endodontic infections

AIM

This study was undertaken to investigate combinations of bacteria found in root-canal infections of teeth with periapical bone destruction without clinical signs and symptoms.

METHODOLOGY

Endodontic samples from 58 root canals were cultured anaerobically and microorganisms were counted and identified. Eighty-one combinations of microorganisms were found and tested for a symbiotic relationship using the Fisher's exact test and Odds ratio calculation.

RESULTS

All samples contained microorganisms with a median CFU mL(-1) of 8x10(4) per sample. Strict anaerobic species accounted for 87% of the microflora. The most prevalent bacteria were Prevotella intermedia, Peptostreptococcus micros and Actinomyces odontolyticus, present in 33, 29 and 19%, respectively, of the cultured canals. A significant relationship (P<0.05) and an Odds ratio >2 were found between P. intermedia and P. micros, P. intermedia and P. oralis, A. odontolyticus and P. micros, Bifidobacterium spp. and Veillonella spp.

CONCLUSIONS

These results indicate that endodontic pathogens do not occur at random but are found in specific combinations.

Effects of instrumentation, irrigation and dressing with calcium hydroxide on infection in pulpless teeth with periapical bone lesions

AIM

The aim of this study was to evaluate the fate of microorganisms in root canals of teeth with infected pulps and periapical bone lesions with and without the use of calcium hydroxide medication.

METHODOLOGY

Endodontic samples were cultured and microorganisms were counted and identified in 43 teeth before (sample 1) and after (sample 2) treatment during the first visit and before (sample 3) and after (sample 4) treatment during the second visit. In the first visit teeth were instrumented and half of the teeth were filled with a thick slurry of calcium hydroxide in sterile saline. The other teeth were obturated with gutta-percha and AH-2 6 sealer. After 4 weeks the teeth with calcium-hydroxide were accessed again and after microbiological sampling they were obturated with gutta-percha and AH-26 sealer.

RESULTS

The mean total colony forming unit (CFU) counts of positive samples dropped significantly as a result of canal preparation during the first visit from 1.0 x 10(6) to 1.8 x 10(3) (between samples 1 and 2) but increased to 9.3 x 10(3) in the period between the two visits (sample 2 and 3). There was no difference in mean total CFU counts of positive samples between the end of the first (sample 2) and the end of the second visit (sample 4). The most frequently isolated species were Prevotella intermedia, Capnocytophaga spp.. Actinomyces odontolyticus. Propionibacterium acnes and Peptostreptococcus micros.

CONCLUSIONS

Although a calcium hydroxide paste was placed in the prepared canals, the number of positive canals had increased in the period between visits. However, the number of microorganisms had only increased to 0.93% of the original number of CFU (sample 1). It is concluded that a calcium hydroxide and sterile saline slurry limits but does not totally prevent regrowth of endodontic bacteria.

Absence of a specific subgingival microflora in adults with Down's syndrome

BACKGROUND

Periodontal disease in Down's syndrome (DS) is generally characterized by a high degree of bone loss. Bone loss of 5 mm or more is observed in 70% of these subjects. Among DS subjects, considerable differences in disease progression occur. So far, no studies have been conducted in which specific properties of the subgingival microflora have been related to the condition observed.

AIMS

To investigate (1) the subgingival microflora in DS subjects and other mentally retarded (control) individuals which were matched to the utmost and (2) to investigate the subgingival microflora of a "low-risk" and a " high-risk" group formed in DS subjects.

MATERIAL AND METHODS

17 DS subjects and 17 control subjects were matched with respect to age, plaque level and bleeding on probing. In addition, the DS group was divided in a "low-risk" group (0-2 teeth lost due to periodontal disease n=6) and a "high-risk"group (6-13 teeth lost due to periodontal disease n=11). Prevalence and proportions of the putative periodontal pathogens Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Bacteroides forsythus, Peptostreptococcus micros, Fusobacterium nucleatum and Campylobacter rectus in the subgingival plaque were determined using anaerobic culture techniques. No differences in the prevalence of distinct suspected periodontopathic bacteria and bacterial subgingival composition between the DS group and the control group could be established. Also no differences in the prevalence of the seven investigated microbial species between the "low-risk" and the "high-risk" group were observed.

CONCLUSIONS

Because of the lack of differences in microflora between the DS group and the control group, a specific effect of the microbiological composition in the periodontal status of subjects with DS can be excluded in this population. Host factors constitute the more likely explanation of the differences observed in DS.

Polymorphisms of the interleukin-1 gene family, oral microbial pathogens, and smoking in adult periodontitis

Interleukin (IL)-1alpha, IL-1beta, and IL-1ra contribute to regulation of the inflammatory response in periodontal tissues. We aimed to investigate the distribution of polymorphisms in the IL-1 gene family among periodontitis patients and controls, taking into account smoking and microbiology as additional variables. Fifty-three non-smoking and 52 smoking patients with severe adult periodontitis and 53 controls were genotyped for bi-allelic IL-1A(-889), IL-1B(-3954), and a penta-allelic 86-bp VNTR IL-1RN gene polymorphisms. The presence of Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans was established by culture techniques. We found a higher frequency of allele 2 carriage in IL-1A, IL-1B, and IL-1RN in periodontitis patients who were non-smokers and in whom P. gingivalis and A. actinomycetemcomitans could not be detected (42.1% vs. 11.3% in controls; P = 0.0068; OR 5.7, 95% CI: 1.6-19.8). Our results provide evidence that polymorphisms in genes of the IL-1 family are associated with severe adult periodontitis in the absence of other risk factors tested in this patient population.

Mutans streptococci in subgingival plaque of treated and untreated patients with periodontitis

BACKGROUND

The etiology of root caries is thought to be identical to coronal caries, though root caries seem to be more complicated because of the higher susceptibility of exposed roots (dentin) by periodontal therapy to demineralization than intact enamel. This implies that mutans streptococci are the most likely pathogens in the development of root caries. Although it is known that both the numbers of mutans streptococci and the frequency of isolation in root caries lesions are negatively correlated with the distance from the gingival margin, the subgingival sulcus has not been considered a possible habitat for mutans streptococci. However, subgingival occurrence of mutans streptococci in both untreated and treated periodontal patients has not been documented well in the literature.

OBJECTIVE

To investigate the presence and levels of mutans streptococci in the subgingival plaque of patients (n=154) in different stages of periodontal therapy. The subgingival sulcus may be a possible habitat for mutans streptococci. This localisation of mutans streptococci may be of importance in the development of root caries after periodontal surgery.

MATERIALS AND METHODS

In this cross-sectional study, subgingival plaque samples from 154 consecutive adult periodontitis patients were tested for presence and levels of mutans streptococci and putative periodontal pathogens by anaerobic cultures. These patients were divided into 4 groups based on their stage of periodontal treatment: (1) untreated patients; (2) patients after initial periodontal therapy only; (3) patients in the maintenance phase who not underwent periodontal surgery; (4) patients after periodontal surgery.

RESULTS

The prevalence of mutans streptococci in the 4 study groups varied from 82% in untreated patients to 94% in maintenance patients. The mean proportion of mutans streptococci was 6.65% in maintenance patients versus 1.86% in untreated patients (p=0.005) and 2.51% in patients after scaling and root planing (p=0.041).

CONCLUSIONS

The subgingival area is a microbial habitat for mutans streptococci that may be of importance in the development of root caries in periodontitis patients.

Smoking affects the subgingival microflora in periodontitis

BACKGROUND

Tobacco smoking has been identified as one major risk factor for destructive periodontal disease. Scaling and root planing have been shown to be less effective in smokers with periodontitis. The aim of the present study was to compare the subgingival microbial flora of treated and untreated smokers and non-smokers.

METHODS

Four independent adult patient groups with periodontitis were included in this investigation: 88 untreated smokers (U-S); 90 untreated non-smokers (U-NS); 119 treated non-smokers (T-NS); and 171 treated smokers (T-S). Clinical variables included cumulative plaque index (CPI), probing depth (PD), clinical attachment level (CAL), cumulative bleeding index (CBI), and cumulative suppuration index (CSI). Paper point samples from the deepest bleeding pocket in each quadrant of the dentition were analyzed for the presence and levels of 6 periodontal bacterial pathogens using anaerobic culture techniques.

RESULTS

U-S showed a higher mean cumulative plaque index than U-NS (3.5 versus 2.7). Mean PD and mean CAL were higher in the T-S in comparison to the T-NS group (7.0 versus 6.6 mm and 5.6 versus 4.7 mm, respectively). Microbiological characteristics of U-S were a higher prevalence of Prevotella intermedia/nigrescens and higher mean levels of Peptostreptococcus micros (Pm) and Fusobacterium nucleatum (Fn). T-S patients were characterized by higher prevalence of Bacteroides forsythus (Bf), Pm, and Campylobacter rectus (Cr) and higher mean levels of Pm and Fn. The mean percentage of B. forsythus tended to be higher in the T-S group than in the T-NS group (6.9% versus 5.6%). The relative risk to be infected with Bf, Pm, and Cr was statistically higher in smokers (odds ratios: 1.9, 1.9, and 1.6, respectively). The chance to find > or =10% of Bf, Pm, and/or Fn was 3.3 higher in smokers when A. actinomycetemcomitans and P gingivalis were absent. Detection of > or =20% Pm/Fn in treated patients was strongly associated with smoking (odds ratio 13.8, P= 0.002).

CONCLUSIONS

Smoking is a determining factor for the composition of the subgingival microflora in adult patients with periodontitis and may select for a specific cluster of periodontal pathogens, notably Bf, Pm, Fn, and Cr. On the basis of these observations, smoking, among other criteria, may be one parameter to use in deciding to treat refractory periodontitis in smokers with a systemic antibiotic therapy directed against smoking-associated periodontal bacteria.

[Periodontitis: a hidden chronic infection]

Periodontitis is a chronic inflammatory disease of the tooth supporting tissues which has a prevalence of 35% in the adult population. Risk factors are dental plaque, calculus, smoking, diabetes mellitus, stress and genetic traits. In parallel with chronic intestinal inflammatory diseases and stomach cancer, gene polymorphisms in the interleukin-I gene family are associated with severity of periodontitis. Periodontitis is usually painless. Symptoms of the disease are bleeding, redness and swelling of the gums, suppuration and migration of teeth. Halitosis may be present. Treatment of periodontitis involves supra- and subgingival mechanical debridement, oral hygiene instruction and surgical elimination of residual deepened and bleeding pockets on indication. Microbiological testing can be used to select patients who may benefit from additional systemic antimicrobial therapy. Periodontal lesions may act as a portal of entry for dissemination of periodontal bacteria into the blood stream, which may result in extraoral infections. For this reason it is recommended to include diagnosis of periodontitis in focal examination. Associations have been documented between periodontitis and cardiovascular diseases, arthritis and premature low birth weight infants.

Viable bacteria in root dentinal tubules of teeth with apical periodontitis

Two sets of teeth with apical periodontitis were collected at different geographic locations to study the identity of bacteria left in the root dentinal tubules. Root dentin of 20 of these teeth was cultured from three locations between pulp and cementum (A, B, and C). In addition dentin from eight teeth was examined histologically. Using the culturing technique bacteria were found in 77% of the dentin samples from set 1 (Amsterdam) and in 87.5% of the dentin samples from set 2 (Glasgow). At greater distance, in layer C, from the pulp bacteria were found in 62% (13 of 21) of the dentin samples. Twenty-three percent (3 of 13) of set 1 and 25% (2 of 8) of set 2 contained >50,000 colony-forming units/mg of dentin in layer C. In layers closer to the pulp higher numbers of anaerobic bacteria and gram-positive rods were found, as well as a larger number of bacterial species. Histological sections showed bacterial penetration in dentinal tubules in 5 of 8 teeth. In the other three teeth where the colony-forming units/mg recovered was <10,000, no histological signs of tubule penetration was seen. It seems clear that, in more than half of the infected roots, bacteria are present in the deep dentin close to the cementum and that anaerobic culturing of dentin is more sensitive than histology to detect these bacteria.