Newly identified pathogens associated with periodontitis: a systematic review

There is substantial evidence supporting the role of certain oral bacteria species in the onset and progression of periodontitis. Nevertheless, results of independent-culture diagnostic methods introduced about a decade ago have pointed to the existence of new periodontal pathogens. However, the data of these studies have not been evaluated together, which may generate some misunderstanding on the actual role of these microorganisms in the etiology of periodontitis. The aim of this systematic review was to determine the current weight of evidence for newly identified periodontal pathogens based on the results of "association" studies. This review was conducted and reported in accordance with the PRISMA statement. The MEDLINE, EMBASE, and Cochrane databases were searched up to September 2013 for studies (1) comparing microbial data of subgingival plaque samples collected from subjects with periodontitis and periodontal health and (2) evaluating at least 1 microorganism other than the already-known periodontal pathogens. From 1,450 papers identified, 41 studies were eligible. The data were extracted and registered in predefined piloted forms. The results suggested that there is moderate evidence in the literature to support the association of 17 species or phylotypes from the phyla Bacteroidetes, Candidatus Saccharibacteria, Firmicutes, Proteobacteria, Spirochaetes, and Synergistetes. The phylum Candidatus Saccharibacteria and the Archaea domain also seem to have an association with disease. These data point out the importance of previously unidentified species in the etiology of periodontitis and might guide future investigations on the actual role of these suspected new pathogens in the onset and progression of this infection.

Composition of supra- and subgingival biofilm of subjects with healthy and diseased implants

OBJECTIVES

The purpose of this study was to compare the microbial composition of supra- and subgingival biofilm in subjects with and without peri-implantitis.

MATERIAL AND METHODS

Forty-four subjects (mean age 48.9 +/- 13.51 years) with at least one implant restored and functional for at least 2 years were assigned to two groups: a peri-implantitis group (n=22), consisting of subjects presenting peri-implant sites with radiographic defects >3 mm, bleeding on probing and/or suppuration; and a control group (n=22), consisting of subjects with healthy implants. The clinical parameters evaluated were plaque index, gingival bleeding, bleeding on probing, suppuration, probing depth and clinical attachment level. Supra- and subgingival biofilm samples were taken from the deepest sites of each implant and analyzed for the presence of 36 microorganisms by checkerboard DNA-DNA hybridization.

RESULTS

Higher mean counts of Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia were observed in the peri-implantitis group, both supra- and subgingivally (P<0.05). The proportions of the pathogens from the red complex were elevated, while host-compatible beneficial microbial complexes were reduced in diseased compared with healthy implants. The microbiological profiles of supra- and subgingival environments did not differ substantially within each group.

CONCLUSION

Marked differences were observed in the composition of supra- and subgingival biofilm between healthy and diseased implants. The microbiota associated with peri-implantitis was comprised of more periodontal pathogenic bacterial species, including the supragingival biofilm.

Systemic antibiotics in the treatment of periodontitis

Despite the fact that several clinical studies have shown additional benefits when certain systemic antibiotics are used as adjuncts to periodontal treatment, clear guidelines for the use of these agents in the clinical practice are not yet available. Basic questions concerning the use of systemic antibiotics to treat periodontitis remain unanswered, such as: which drug(s) should be used; which patients would most benefit from treatment; which are the most effective protocols (i.e. doses and durations); and in which phase of the mechanical therapy should the drug(s) be administered? Although not all of those questions have been directly addressed by controlled randomized clinical trials, recent concepts related to the ecology of periodontal diseases, as well as the major advances in laboratory and clinical research methods that have occurred in the past decade, have significantly broadened our knowledge in this field. This article endeavored to provide a 'state of the art' overview on the use of systemic antibiotics in the treatment of periodontitis, based on the most recent literature on the topic as well as on a compilation of data from studies conducted at the Center of Clinical Trials at Guarulhos University (São Paulo, Brazil) from 2002 to 2012.

Microbiological diversity of generalized aggressive periodontitis by 16S rRNA clonal analysis

BACKGROUND/AIM

The purpose of this study was to determine the bacterial diversity in the subgingival plaque of subjects with generalized aggressive periodontitis by using culture-independent molecular methods based on 16S ribosomal DNA cloning.

METHODS

Samples from 10 subjects with generalized aggressive periodontitis were selected. DNA was extracted and the 16S rRNA gene was amplified with the universal primer pairs 9F and 1525R. Amplified genes were cloned, sequenced, and identified by comparison with known 16S rRNA sequences.

RESULTS

One hundred and ten species were identified from 10 subjects and 1007 clones were sequenced. Of these, 70 species were most prevalent. Fifty-seven percent of the clone (40 taxa) sequences represented phylotypes for which no cultivated isolates have been reported. Several species of Selenomonas and Streptococcus were found at high prevalence and proportion in all subjects. Overall, 50% of the clone libraries were formed by these two genera. Selenomonas sputigena, the species most commonly detected, was found in nine of 10 subjects. Other species of Selenomonas were often present at high levels, including S. noxia, Selenomonas sp. EW084, Selenomonas sp. EW076, Selenomonas FT050, Selenomonas sp. P2PA_80, and Selenomonas sp. strain GAA14. The classical putative periodontal pathogens, such as, Aggregatibacter actinomycetemcomitans, was below the limit of detection and was not detected.

CONCLUSION

These data suggest that other species, notably species of Selenomonas, may be associated with disease in generalized aggressive periodontitis subjects.

Short-term benefits of the adjunctive use of metronidazole plus amoxicillin in the microbial profile and in the clinical parameters of subjects with generalized aggressive periodontitis

AIM

The aim of this study was to evaluate the clinical and microbiological effects of scaling and root planing (SRP) alone or combined with metronidazole (MTZ) and amoxicillin (AMX) in the treatment of subjects with generalized aggressive periodontitis (GAgP).

MATERIALS AND METHODS

A double-blind, placebo-controlled, randomized clinical trial was conducted in 30 subjects receiving SRP alone or combined with MTZ (400 mg 3 x per day) and AMX (500 mg 3 x per day) for 14 days. Clinical and microbiological examinations were performed at baseline and 3 months post-SRP. Nine subgingival plaque samples per subject were analysed using checkerboard DNA-DNA hybridization.

RESULTS

Subjects receiving MTZ and AMX showed the greatest improvements in the mean full-mouth probing depth and clinical attachment level and at initially intermediate and deep sites. The most beneficial changes in the microbial profile were also observed in the MTZ+AMX group, which showed the lowest proportions of the red complex as well as a significant decrease in the proportions of the orange complex after treatment. The antibiotic therapy also reduced the levels of Aggregatibacter actinomycetemcomitans at initially deep sites.

CONCLUSION

Subjects with GAgP significantly benefit from the adjunctive use of MTZ and AMX. The short-term advantages are observed in the clinical and microbiological parameters.

The subgingival periodontal microbiota of the aging mouth

Different mechanisms have been hypothesized to explain the increase in prevalence and severity of periodontitis in older adults, including shifts in the periodontal microbiota. However, the actual impact of aging on the composition of subgingival biofilms remains unclear. In the present article, we provide an overview of the composition of the subgingival biofilm in older adults and the potential effects of age on the oral microbiome. In particular, this review covers the following topics: (i) the oral microbiota of an aging mouth; (ii) the effects of age and time on the human oral microbiome; (iii) the potential impact of inflammaging and immunosenescence in the host-oral microbiota interactions; and (iv) the relationship of the aging oral microbiota and Alzheimer's disease. Finally, we present analyses of data compiled from large clinical studies that evaluated the subgingival microbiota of periodontally healthy subjects and patients with periodontitis from a wide age spectrum (20-83 years of age).

Microbiological profile of untreated subjects with localized aggressive periodontitis

AIM

The microbial profile of localized aggressive periodontitis (LAgP) has not yet been determined. Therefore, the aim of this study was to evaluate the subgingival microbial composition of LAgP.

MATERIAL AND METHODS

One hundred and twenty subjects with LAgP (n=15), generalized aggressive periodontitis (GAgP, n=25), chronic periodontitis (ChP, n=30) or periodontal health (PH, n=50) underwent clinical and microbiological assessment. Nine subgingival plaque samples were collected from each subject and analysed for their content of 38 bacterial species using checkerboard DNA-DNA hybridization.

RESULTS

Red complex and some orange complex species are the most numerous and prevalent periodontal pathogens in LAgP. The proportions of Aggregatibacter actinomycetemcomitans were elevated in shallow and intermediate pockets of LAgP subjects in comparison with those with GAgP or ChP, but not in deep sites. This species also showed a negative correlation with age and with the proportions of red complex pathogens. The host-compatible Actinomyces species were reduced in LAgP.

CONCLUSION

A. actinomycetemcomitans seems to be associated with the onset of LAgP, and Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Campylobacter gracilis, Eubacterium nodatum and Prevotella intermedia play an important role in disease progression. Successful treatment of LAgP would involve a reduction in these pathogens and an increase in the Actinomyces species.

Mechanisms of action of systemic antibiotics used in periodontal treatment and mechanisms of bacterial resistance to these drugs

Antibiotics are important adjuncts in the treatment of infectious diseases, including periodontitis. The most severe criticisms to the indiscriminate use of these drugs are their side effects and, especially, the development of bacterial resistance. The knowledge of the biological mechanisms involved with the antibiotic usage would help the medical and dental communities to overcome these two problems. Therefore, the aim of this manuscript was to review the mechanisms of action of the antibiotics most commonly used in the periodontal treatment (i.e. penicillin, tetracycline, macrolide and metronidazole) and the main mechanisms of bacterial resistance to these drugs. Antimicrobial resistance can be classified into three groups: intrinsic, mutational and acquired. Penicillin, tetracycline and erythromycin are broad-spectrum drugs, effective against gram-positive and gram-negative microorganisms. Bacterial resistance to penicillin may occur due to diminished permeability of the bacterial cell to the antibiotic; alteration of the penicillin-binding proteins, or production of β-lactamases. However, a very small proportion of the subgingival microbiota is resistant to penicillins. Bacteria become resistant to tetracyclines or macrolides by limiting their access to the cell, by altering the ribosome in order to prevent effective binding of the drug, or by producing tetracycline/macrolide-inactivating enzymes. Periodontal pathogens may become resistant to these drugs. Finally, metronidazole can be considered a prodrug in the sense that it requires metabolic activation by strict anaerobe microorganisms. Acquired resistance to this drug has rarely been reported. Due to these low rates of resistance and to its high activity against the gram-negative anaerobic bacterial species, metronidazole is a promising drug for treating periodontal infections.

Levels of Candidate Periodontal Pathogens in Subgingival Biofilm

In recent years, several new periodontal taxa have been associated with the etiology of periodontitis. A recent systematic review provides further support for the pathogenic role of 17 species/phylotypes. Thus, the aim of this study was to assess the prevalence and levels of these species in subjects with generalized chronic periodontitis (GChP; n = 30), generalized aggressive periodontitis (GAgP; n = 30), and periodontal health (PH; n = 30). All subjects underwent clinical and microbiological assessment. Nine subgingival plaque samples were collected from each subject and analyzed for their content of 20 bacterial species/phylotypes through the RNA-oligonucleotide quantification technique. Subjects from the GChP and GAgP groups presented the highest mean values for all clinical parameters in comparison with the PH group (P < 0.05). Subjects with GChP and GAgP showed significantly higher mean levels of Bacteroidetes sp. human oral taxon (HOT) 274, Fretibacterium sp. HOT 360, and TM7 sp. HOT 356 phylotypes, as well as higher mean levels of Filifactor alocis, Fretibacterium fastidiosum, Porphyromonas gingivalis, Tannerella forsythia, and Selenomonas sputigena species than PH subjects (P < 0.05). GAgP subjects presented higher mean levels of TM7 sp. HOT 356 and F. alocis than GChP subjects (P < 0.05). A significantly higher mean prevalence of Bacteroidales sp. HOT 274, Desulfobulbus sp. HOT 041, Fretibacterium sp. HOT 360, and Fretibacterium sp. HOT 362 was found in subjects with GChP and GAgP than in PH subjects. Mean levels of P. gingivalis (r = 0.68), T. forsythia (r = 0.62), F. alocis (r = 0.51, P = 0.001), and Fretibacterium sp. HOT 360 (r = 0.41) were correlated with pocket depth (P < 0.001). In conclusion, Bacteroidales sp. HOT 274, Desulfobulbus sp. HOT 041, Fretibacterium sp. HOT 360, Fretibacterium sp. HOT 362, and TM7 sp. HOT 356 phylotypes, in addition to F. alocis, F. fastidiosum, and S. sputigena, seem to be associated with periodontitis, and their role in periodontal pathogenesis should be further investigated.

Relationships between subgingival microbiota and GCF biomarkers in generalized aggressive periodontitis

AIM

To examine relationships between subgingival biofilm composition and levels of gingival crevicular fluid (GCF) cytokines in periodontal health and generalized aggressive periodontitis (GAP).

MATERIALS AND METHODS

Periodontal parameters were measured in 25 periodontally healthy and 31 GAP subjects. Subgingival plaque and GCF samples were obtained from 14 sites from each subject. Forty subgingival taxa were quantified using checkerboard DNA-DNA hybridization and the concentrations of eight GCF cytokines were measured using Luminex. Cluster analysis was used to define sites with similar subgingival microbiotas in each clinical group. Significance of differences in clinical, microbiological and immunological parameters among clusters was determined using the Kruskal-Wallis test.

RESULTS

GAP subjects had statistically significantly higher GCF levels of interleukin-1beta (IL-1beta) (p<0.001), granulocyte-macrophage colony-stimulating factor (GM-CSF) (p<0.01) and IL-1beta/IL-10 ratio (p<0.001) and higher proportions of Red and Orange complex species than periodontally healthy subjects. There were no statistically significant differences in the mean proportion of cytokines among clusters in the periodontally healthy subjects, while the ratio IL-1beta/IL-10 (p<0.05) differed significantly among clusters in the aggressive periodontitis group.

CONCLUSIONS

Different subgingival biofilm profiles are associated with distinct patterns of GCF cytokine expression. Aggressive periodontitis subjects were characterized by a higher IL-1beta/IL-10 ratio than periodontally healthy subjects, suggesting an imbalance between pro- and anti-inflammatory cytokines in aggressive periodontitis.

Simultaneous analysis of T helper subsets (Th1, Th2, Th9, Th17, Th22, Tfh, Tr1 and Tregs) markers expression in periapical lesions reveals multiple cytokine clusters accountable for lesions activity and inactivity status

Previous studies demonstrate that the balance between pro- and anti-inflammatory mediators determines the stable or progressive nature of periapical granulomas by modulating the balance of the osteoclastogenic factor RANKL and its antagonist OPG. However, the cytokine networks operating in the development of periapical lesions are quite more complex than what the simple pro- versus anti-inflammatory mediators' paradigm suggests. Here we simultaneously investigated the patterns of Th1, Th2, Th9, Th17, Th22, Thf, Tr1 and Tregs cytokines/markers expression in human periapical granulomas.

METHODS

The expression of TNF-α, IFN-γ, IL-17A, IL23, IL21, IL-33, IL-10, IL-4, IL-9, IL-22, FOXp3 markers (via RealTimePCR array) was accessed in active/progressive (N=40) versus inactive/stable (N=70) periapical granulomas (as determined by RANKL/OPG expression ratio), and also to compare these samples with a panel of control specimens (N=26). A cluster analysis of 13 cytokine levels was performed to examine possible clustering between the cytokines in a total of 110 granulomas.

RESULTS

The expression of all target cytokines was higher in the granulomas than in control samples. TNF-α, IFN-γ, IL-17A and IL-21 mRNA levels were significantly higher in active granulomas, while in inactive lesions the expression levels of IL-4, IL-9, IL-10, IL-22 and FOXp3 were higher than in active granulomas. Five clusters were identified in inactive lesion groups, being the variance in the expression levels of IL-17, IL-10, FOXp3, IFN-γ, IL-9, IL-33 and IL-4 statistically significant (KW p<0.05). Three clusters were identified in active lesions, being the variance in the expression levels of IL-22, IL-10, IFN-γ, IL-17, IL-33, FOXp3, IL-21 and RANKL statistically significant (KW p<0.05).

CONCLUSION

There is a clear dichotomy in the profile of cytokine expression in inactive and active periapical lesions. While the widespread cytokine expression seems to be a feature of chronic lesions, hierarchical cluster analysis demonstrates the association of TNF-α, IL-21, IL-17 and IFN-γ with lesions activity, and the association of FOXP3, IL-10, IL-9, IL-4 and IL-22 with lesions inactivity.

Assessment of the reproducibility and precision of milling and 3D printing surgical guides

BACKGROUND

Technology advancement has rising in the past decade and brought several innovations and improvements. In dentistry, this advances provided more comfortable and quick procedures to both the patient and the dental surgeon, generating less predictability in the final result. Several techniques has been developed for the preparation of surgical guides aiming at the optimization of surgical procedures. The present study aimed to evaluate the reproducibility and precision of two types of surgical guides obtained using 3D printing and milling methods.

METHODS

A virtual model was developed that allowed the virtual design of milled (n = 10) or 3D printed (n = 10) surgical guides. The surgical guides were digitally oriented and overlapped on the virtual model. For the milling guides, the Sirona Dentsply system was used, while the 3D printing guides were produced using EnvisionTEC's Perfactory P4K Life Series 3D printer and E-Guide Tint, a biocompatible Class I certified material. The precision and trueness of each group during overlap were assessed. The data were analyzed with GraphPad software using the Kolmogorov-Smirnov test for normality and Student's t test for the variables.

RESULTS

The Kolmogorov-Smirnov test showed a normal distribution of the data. Comparisons between groups showed no statistically significant differences for trueness (p = 0.529) or precision (p = 0.3021). However, a significant difference was observed in the standard deviation of mismatches regarding accuracy from the master model (p < 0.0001).

CONCLUSIONS

Within the limits of this study, surgical guides fabricated by milling or prototyped processes achieved similar results.

Microbiological diversity of peri-implantitis biofilm by Sanger sequencing

BACKGROUND AND OBJECTIVE

To examine the microbial diversity associated with implants with or without peri-implantitis and to identify differences between the bacterial communities in these clinical conditions.

MATERIAL AND METHODS

Twenty subjects were assigned to a Control group consisting of subjects with healthy implants and a Test group consisting of subjects with peri-implantitis sites, as well as a healthy implant site (n = 10/group). In the Test group, subgingival biofilm samples were taken from the deepest sites of the diseased implant. In both groups, samples were collected from one site around a healthy implant. DNA was extracted and the 16S rRNA gene was amplified and sequenced, and the phylotypes were identified by comparison with known 16S rRNA sequences.

RESULTS

The phylogenetic identity of 1387 16S rRNA gene clones was determined. Healthy implants demonstrated higher proportions of Actinomyces, Atopobium, Gemella, Kingella and Rothia and lower levels of Campylobacter, Desulfobulbus, Dialister, Eubacterium, Filifactor, Mitsukella, Porphyromonas and Pseudoramibacter (Mann-Whitney U-test; P < 0.05). Fusobacterium nucleatum, Dialister invisus, Streptococcus sp. human oral taxon (HOT) 064, Filifactor alocis and Mitsuokella sp. HOT 131 presented a higher mean proportion, while Veillonella dispar, Actinomyces meyeri, Granulicatella adiacens showed lower mean proportions in the peri-implantitis sites when compared with healthy implants in both the Control and Test groups (Mann-Whitney U-test; P < 0.05).

CONCLUSION

Marked differences were observed in the composition of the subgingival biofilm between healthy and diseased implants. The biofilm associated with peri-implantitis harbored more pathogenic bacterial species from the orange complex and other "unusual" putative pathogens, such as F. alocis, D. invisus and Mitsuokella sp. HOT 131.

Metronidazole and amoxicillin as adjuncts to scaling and root planing for the treatment of type 2 diabetic subjects with periodontitis: 1-year outcomes of a randomized placebo-controlled clinical trial

AIM

To evaluate the clinical and microbiological effects of the use of metronidazole (MTZ) + amoxicillin (AMX) as adjuncts to scaling and root planing (SRP) for the treatment of chronic periodontitis (ChP) in type 2 diabetic subjects.

MATERIAL AND METHODS

Fifty-eight type 2 diabetic subjects (n = 29/group) with generalized ChP were randomly assigned to receive SRP alone or with MTZ [400 mg/thrice a day (TID)]+AMX (500 mg/TID) for 14 days. Subgingival biofilm samples were analyzed by qPCR for the presence of seven periodontal pathogens. Subjects were monitored at baseline, 3, 6 and 12 months post-therapies.

RESULTS

The group receiving SRP+MTZ+AMX presented greater mean probing depth (PD) reduction and clinical attachment gain, a lower number of sites with PD ≥5 mm (primary outcome variable) and a reduced number of subjects with ≥9 of these residual pockets than the control group at 1-year post-therapy (p < 0.05). The antibiotic-treated group also presented reduced levels and greater decreases of the three red complex species, Eubacterium nodatum and Prevotella intermedia, compared to the control group at 1 year (p < 0.05).

CONCLUSIONS

The adjunctive use of MTZ+AMX significantly improved the clinical and microbiological outcomes of SRP in the treatment of type 2 diabetic subjects with ChP.

Prevalence and microbiological diversity of Archaea in peri-implantitis subjects by 16S ribosomal RNA clonal analysis

BACKGROUND AND OBJECTIVE

This study evaluated the prevalence and the molecular diversity of Archaea in the subgingival biofilm samples of subjects with peri-implantitis.

MATERIAL AND METHODS

Fifty subjects were assigned into two groups: Control (n = 25), consisting of subjects with healthy implants; and Test (n = 25), consisting of subjects with peri-implantitis sites, as well as a healthy implant. In the Test group, subgingival biofilm samples were taken from the deepest sites of the diseased implant. In both groups, subgingival biofilm was collected from one site with a healthy implant and from one site with a periodontally healthy tooth. DNA was extracted and the 16S ribosomal RNA gene was amplified with universal primer pairs for Archaea. Amplified genes were cloned and sequenced, and the phylotypes were identified by comparison with known 16S ribosomal RNA sequences.

RESULTS

In the Control group, Archaea were detected in two and three sites of the implant and the tooth, respectively. In the Test group, Archaea were detected in 12, 4 and 2 sites of diseased implants, healthy implants and teeth, respectively. Diseased implants presented a significantly higher prevalence of Archaea in comparison with healthy implants and natural teeth, irrespective of group. Over 90% of the clone libraries were formed by Methanobrevibacter oralis, which was detected in both groups. Methanobacterium congelense/curvum was detected in four subjects from the Test group and in two subjects from the Control group.

CONCLUSION

Although M. oralis was the main species of Archaea associated with both healthy and diseased implant sites, the data indicated an increased prevalence of Archaea in peri-implantitis sites, and their role in pathogenesis should be further investigated.