Gunnar Dahlén

Bacteria as Risk Markers for Periodontitis

Specific microbial species have been closely associated with periodontitis. Through longitudinal studies, some of these microbial species have been implicated in the etiology of progressive periodontal disease. Although putative periodontal pathogens are often isolated from individuals with severe periodontitis, they also frequently inhabit the subgingival environment and are not always associated with advanced disease. In this respect, it is becoming increasingly apparent that there is no single etiology of the various periodontal diseases. Destructive periodontal diseases are the result of environmental, host, and bacterial factors. Microorganisms, however, are essential components of any model for progressive periodontitis. This paper selectively reviews bacteria as risk markers for periodontitis. Attention focuses on bacteria in conjunction with behavioral patterns (oral hygiene habits and smoking) and host response (gingival crevicular fluid substances) as risk markers for periodontitis. Prospective studies implicating specific bacteria in progressive periodontitis are addressed and a bacterial risk assessment model for progressive periodontitis is discussed with respect to the interplay between bacterial, environmental, and host markers. J Periodontol 1994; 64:498-510.

Microbiological Evaluation of One- and Two-Visit Endodontic Treatment of Teeth with Apical Periodontitis: A Randomized, Clinical Trial

The antimicrobial efficacy of endodontic procedures performed in one-visit (including a 10-min intraappointment dressing with 5% iodine-potassium-iodide) was compared with a two-visit procedure (including an interappointment dressing with calcium-hydroxide paste). Teeth with apical periodontitis (n = 96) were randomly assigned to either group. Root canal sampling and culturing were performed before and immediately after instrumentation, and after medication. Initial sampling demonstrated the presence of microorganisms in 98% of the teeth. Postinstrumentation sampling showed reduction of cultivable microbiota. Antibacterial dressing further reduced the number of teeth with surviving microbes. In the postmedication samples, residual microorganisms were recovered in 29% of the one-visit teeth and in 36% of the two-visit treated teeth. No statistically significant differences between the groups were discerned. It was concluded that from a microbiological point of view, treatment of teeth with apical periodontitis performed in two appointments was not more effective than the investigated one-visit procedure.

Clinical and microbiological characteristics of peri‐implantitis cases: a retrospective multicentre study

OBJECTIVES The aim of this study was to follow patient cases retrospectively in a longitudinal manner from the time of implant placement to the time they were diagnosed with peri-implant disease, and to identify associated clinical and microbiological features of peri-implant disease. MATERIAL AND METHODS A total of 281 patient cases were chosen from the archives of the Oral Microbiological Diagnostic Laboratory, Gothenburg, Sweden, based on bacterial samples taken from diseased implants. A form was designed and filled in separately for each case including data on patient, implant and disease profile. RESULTS Most cases were severe peri-implantitis cases (91.4%). In 41.3% of the patients, peri-implantitis was developed early, already after having implants in function less than 4 years. The type of implant surface was significantly associated with the time in years implants were in function, before disease was developed (P < 0.05). The microbiological results by both culture and checkerboard analysis, although failed to fully correspond to the severity of the disease in terms of magnitude, proved to show that peri-implantitis is a polymicrobial anaerobic infection with increased number of AGNB (aerobic Gram-negative bacilli) in 18.6% of the patients. CONCLUSIONS Peri-implantitis is a biological complication of implants in function that poses a threat to their long-term survival. It may develop earlier around implants with rough surfaces and it may represent a true infection. Microbiological sampling methods should be improved and uniformed so as to fully unveil the microbiological profile of the disease.

Caries risk assessment. A systematic review

Abstract Objective. To assess the ability of multivariate models and single factors to correctly identify future caries development in pre-school children and schoolchildren/adolescents. Study design. A systematic literature search for relevant papers was conducted with pre-determined inclusion criteria. Abstracts and full-text articles were assessed independently by two reviewers. The quality of studies was graded according to the QUADAS tool. The quality of evidence of models and single predictors was assessed using the GRADE approach. Results. Ninety original articles fulfilled the inclusion criteria. Seven studies had high quality, 35 moderate and the rest poor quality. The accuracy of multivariate models was higher for pre-school children than for schoolchildren/adolescents. However, the models had seldom been validated in independent populations, making their accuracy uncertain. Of the single predictors, baseline caries experience had moderate/good accuracy in pre-school children and limited accuracy in schoolchildren/adolescents. The period of highest risk for caries incidence in permanent teeth was the first few years after tooth eruption. In general, the quality of evidence was limited. Conclusions. Multivariate models and baseline caries prevalence performed better in pre-school children than in schoolchildren/adolescents. Baseline caries prevalence was the most accurate single predictor in all age groups. The heterogeneity of populations, models, outcome criteria, measures and reporting hampered the synthesis of results. There is a great need to standardize study design, outcome measures and reporting of data in studies on caries risk assessment. The accuracy of prediction models should be validated in at least one independent population.

Inhibitory effect of oral Lactobacillus against oral pathogens

Aims:  To determine the inhibitory effect of oral Lactobacillus against putative oral pathogens.

Site-specific O-Glycosylation on the MUC2 Mucin Protein Inhibits Cleavage by the Porphyromonas gingivalis Secreted Cysteine Protease (RgpB)

Background: MUC2 polymers form the mucus layer of colon that separates luminal bacteria from the epithelium. Results: P. gingivalis secrets a protease that cleaves the MUC2 mucin, a cleavage modulated by O-glycosylation. Conclusion: Bacteria can disrupt the MUC2 polymer via proteolytic cleavage. However, O-glycosylation can inhibit this process. Significance: Bacteria can dissolve the protective inner mucus layer, potentially triggering colitis. The colonic epithelial surface is protected by an inner mucus layer that the commensal microflora cannot penetrate. We previously demonstrated that Entamoeba histolytica secretes a protease capable of dissolving this layer that is required for parasite penetration. Here, we asked whether there are bacteria that can secrete similar proteases. We screened bacterial culture supernatants for such activity using recombinant fragments of the MUC2 mucin, the major structural component, and the only gel-forming mucin in the colonic mucus. MUC2 has two central heavily O-glycosylated mucin domains that are protease-resistant and has cysteine-rich N and C termini responsible for polymerization. Culture supernatants of Porphyromonas gingivalis, a bacterium that secretes proteases responsible for periodontitis, cleaved the MUC2 C-terminal region, whereas the N-terminal region was unaffected. The active enzyme was isolated and identified as Arg-gingipain B (RgpB). Two cleavage sites were localized to IR↓TT and NR↓QA. IR↓TT cleavage will disrupt the MUC2 polymers. Because this site has two potential O-glycosylation sites, we tested whether recombinant GalNAc-transferases (GalNAc-Ts) could glycosylate a synthetic peptide covering the IRTT sequence. Only GalNAc-T3 was able to glycosylate the second Thr in IRTT, rendering the sequence resistant to cleavage by RgpB. Furthermore, when GalNAc-T3 was expressed in CHO cells expressing the MUC2 C terminus, the second threonine was glycosylated, and the protein became resistant to RgpB cleavage. These findings suggest that bacteria can produce proteases capable of dissolving the inner protective mucus layer by specific cleavages in the MUC2 mucin and that this cleavage can be modulated by site-specific O-glycosylation.

Subgingival debridement of periodontal pockets by air polishing in comparison with ultrasonic instrumentation during maintenance therapy

AIM The objective was to determine clinical and microbiological effects and perceived treatment discomfort of root debridement by subgingival air polishing compared with ultrasonic instrumentation during supportive periodontal therapy (SPT). MATERIAL AND METHODS The trial was conducted as a split-mouth designed study of 2-month duration including 20 recall patients previously treated for chronic periodontitis. Sites with probing pocket depth (PPD) of 5-8 mm and bleeding on probing (BoP+) in two quadrants were randomly assigned to subgingival debridement by (i) glycine powder/air polishing applied with a specially designed nozzle or (ii) ultrasonic instrumentation. Clinical variables were recorded at baseline, 14 and 60 days post-treatment. Primary clinical efficacy variable was PPD reduction. Microbiological analysis of subgingival samples was performed immediately before and after debridement, 2 and 14 days post-treatment. RESULTS Both treatment procedures resulted in significant reductions of periodontitis-associated bacterial species immediately and 2 days after treatment, and in significant reduction in BoP, PPD and relative attachment level at 2 months. There were no statistically significant differences between the treatment procedures at any of the examinations intervals. Perceived treatment discomfort was lower for air polishing than ultrasonic debridement. CONCLUSION This short-term study revealed no pertinent differences in clinical or microbiological outcomes between subgingival air polishing and ultrasonic debridement of moderate deep pockets in SPT patients.

Clustering of subgingival microbial species in adolescents with periodontitis.

It has become increasingly recognized that groups of microorganisms interact within the subgingival plaque of adult subjects with periodontitis. It is much less clear, however, whether the consortia of microorganisms associated with periodontitis are different in early and more advanced cases of periodontitis. To investigate this point further, subgingival plaque was collected from six sites in 87 adolescents with periodontitis and 73 controls and the samples were analyzed for the detection of 18 microbial species using the DNA-DNA hybridization technique. Actinomyces oris accounted for the highest proportion of the flora and was more predominant among controls. Prevotella nigrescens, Prevotella intermedia, Porphyromonas gingivalis, and Tannerella forsythia were present at higher levels among the subjects with periodontitis. Factor analyses identified one factor characterized by highly positive loadings for T. forsythia, Campylobacter rectus, P. gingivalis, P. intermedia, P. nigrescens, Parvimonas micra, and Treponema denticola, and another factor characterized by highly positive loadings of A. oris, Capnocytophaga ochracea, Eikenella corrodens, Streptococcus intermedius, Selenomonas noxia, Streptococcus oralis, Streptococcus sanguinis, and Veillonella parvula. Aggregatibacter actinomycetemcomitans and Streptococcus mutans did not load on any of the two factors, while Fusobacterium nucleatum loaded on both. These findings confirm the occurrence of clustering of subgingival bacteria according to case status also among young individuals.

Bacterial flora of the human oral cavity, and the upper and lower esophagus

This reference study aims to survey the bacterial flora of the healthy lower human esophagus and to compare it with that of the upper esophagus and oral mucosa. The use of biopsies, in addition to brush samples, allows inclusion of not only transient bacteria present on the surface but also bacteria residing in the epithelia, and the yield of the two methods can be compared. Forty patients scheduled for surgery for reasons with no known influence on esophageal flora and with no symptoms or endoscopic signs of esophageal disease were included. Samples were collected from the oral, upper esophageal, and lower esophageal mucosa using sealed brushes and biopsy forceps. Colonies cultivated on agar plates were classified and semiquantified. Twenty-three different bacterial species were identified, with similar strains present at the three sites. The most common group of bacteria was viridans streptococci, with an occurrence rate in brush samples and biopsies of 98% and 95%, respectively. The median number of species occurring in the oral cavity, upper esophagus, and lower esophagus was between 3 and 4 (range 0-7). The total number of species in the oral cavity was significantly higher when compared with either level in the esophagus, while the yields obtained by brush and biopsy sampling were highly correlated. Hence, the normal human esophagus is colonized with a resident bacterial flora of its own, which has similarities to that of the oral mucosa. There are diverse species that make up this flora, although in relatively low amounts. The most frequent inhabitants of the esophagus are streptococci, with an occurrence rate in brush samples and biopsies of 95-98%. Comparative studies of patients with eosinophilic esophagitis and gastroesophageal reflux disease are warranted.

Adjunct methods for caries detection: A systematic review of literature

Abstract Objective. To assess the diagnostic accuracy of adjunct methods used to detect and quantify dental caries. Study design. A systematic literature search for relevant papers was conducted with pre-determined inclusion and exclusion criteria. Abstracts and full text articles were assessed independently by two reviewers. The study characteristics were compiled in tables and quality graded according to the QUADAS tool. The level of evidence for each diagnostic technology (fiber-optic methods, fluorescence methods, electrical methods) was based on studies of high or moderate quality according to the GRADE approach. Results. Twenty-five reports fulfilled the inclusion criteria. One study was of high quality, 10 were graded as moderate, while the remaining 14 reports were of low quality. Electrical methods (ECM) and laser fluorescence (DIAGNOdent) displayed sensitivities and specificities around 70–80% regarding occlusal dentin lesions with a mean Youdens index of 0.52–0.54. The mean accuracy of laser fluorescence for detecting enamel and dentin lesions was 0.68 and 0.91, respectively. The heterogeneity of the published reports hampered the analysis. Conclusions. There was insufficient scientific evidence for diagnostic accuracy regarding fiber-optic methods and quantitative light-induced fluorescence (+OOO). The electrical methods and laser fluorescence could be useful adjuncts to visual-tactile and radiographic examinations, especially on occlusal surfaces in permanent and primary molars, but evidence was graded as limited (++OO). No conclusions could be drawn regarding the cost-effectiveness of the methods. There is an obvious need to standardize study designs for in vitro and in vivo validation of the different methods.