Molecular Analysis of Persistent Periradicular Lesions and Root Ends Reveals a Diverse Microbial Profile

Apical root canal microbiome associated with primary and posttreatment apical periodontitis: A systematic review

BACKGROUND

Microorganisms colonizing the apical root canal system are conceivably the ones directly involved with the causation and maintenance of apical periodontitis.

OBJECTIVES

This article systematically reviews the reports on the microbiome occurring exclusively at the apical root canal of teeth with primary and posttreatment apical periodontitis.

METHODS

The electronic databases PubMed, Embase, Web of Science, Science Direct, and Proquest were searched up to August 2023. Clinical studies using culture and molecular microbiology methods to identify the microbial taxa present exclusively in the apical root canal segment of infected teeth with apical periodontitis were included. Studies were critically assessed using the Joanna Briggs Institute Critical Prevalence Assessment Checklist.

RESULTS

From 2277 articles initially detected, 52 were selected for full reading and 21 were eventually included in this review. Of these, molecular methods were used in 19 and culture in 2 studies. Ten studies evaluated primary infections, 8 evaluated posttreatment infections, and 3 included both. Cryopulverization of the apical root specimens was conducted in 11 studies. All studies evaluated the prevalence and diversity of bacteria, and only one also reported on fungi. Overall, the most frequent/abundant bacterial taxa found in the apical canal of primary infections were Pseudoramibacter alactolyticus, Olsenella uli, Fusobacterium species, Streptococcus species, Porphyromonas endodontalis, Prevotella species, Actinomyces species, Parvimonas micra, Treponema denticola, Synergistetes species, and an as-yet uncharacterized taxon. In posttreatment infections, the most prevalent/abundant bacterial taxa included species of Streptococcus, Enterococcus, Fusobacterium, Actinomyces, Pseudoramibacter, Pseudomonas, and Propionibacterium. At the phylum level, Firmicutes was the most represented. The average apical bacterial load ranged from 105 to 106 in primary infections and from 103 to 104 in posttreatment infections.

DISCUSSION

Microbial diversity in the apical part of the root canal system was examined encompassing data from both primary and posttreatment infections. Heterogeneity amongst the studies, especially in sample collection and microbial identification methods, is an important limitation that prevented a meta-analysis.

CONCLUSIONS

There is a pronounced bacterial diversity in the infected apical canal, with a high interindividual variability. Different microbiome compositions at the species/genus level are observed according to the infection type.

REGISTRATION

PROSPERO CRD42021275886.

A novel endolysin from an Enterococcus faecalis phage and application

Enterococcus faecalis is the primary species detected in cases of secondary persistent infection resulting from root canal therapy failure. Due to the overuse of antibacterial agents, E. faecalis has developed resistance to these drugs, making it challenging to treat clinical diseases caused by E. faecalis infection. Therefore, there is an urgent need to explore new alternative drugs for treating E. faecalis infections. We aimed to clone and express the genes of phage endolysins, purify the recombinant proteins, and analyze their antibacterial activity, lysis profile, and ability to remove biofilm. The crude enzyme of phage endolysin pEF51 (0.715 mg/mL), derived from phage PEf771 infecting E. faecalis, exhibited superior bacterial inhibitory activity and a broader bactericidal spectrum than its parental phage PEf771. Furthermore, pEF51 demonstrated high efficacy in eliminating E. faecalis biofilm. Therapeutic results of the infected Sprague-Dawley (SD) rat model indicated that among 10 SD rats, only one developed a thoracic peritoneal abscess and splenic peritoneal abscess after 72 h of treatment with pEF51. This suggests that pEF51 could provide protection against E. faecalis infection in SD rats. Based on the 16S rDNA metagenomic data of the intestinal microbial community of SD rats, endolysin pEF51 exerted a certain influence on the diversity of intestinal microorganisms at the genus level. Thus, pEF51 may serve as a promising alternative to antibiotics in the management of E. faecalis infection.

Unraveling the Endodontic Archaeome: A Systematic Review with Meta-Analysis

INTRODUCTION

The controversial issue of whether the Archaea domain plays a role in endodontic infections is the focus of this systematic review with meta-analysis. The aim is to emphasize the significance of minority microbial domains in oral dysbiosis by evaluating the prevalence of archaea in root canals and its association with clinical parameters such as symptomatology and type of endodontic infection.

METHODS

The search strategy involved researching 6 databases and the gray literature. Publications were accepted in any year or language that identified archaea in samples from endodontic canals. A 2-step selection process narrowed the final choice to 16 articles. The methodological quality of the studies was evaluated using tools from the Joanna Briggs Institute, and the certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach.

RESULTS

The results showed that archaea were present in 20% (95% [confidence interval] CI = 8%-32%) of individuals with endodontic samples analyzed. The samples were about twice as likely to be archaeal-positive if collected from individuals with primary vs. persistent/secondary infection (odds ratio = 2.33; 95% CI = 1.31-4.14; I2 = 0%), or individuals with self-reported vs. symptom-free infections (odds ratio = 2.67; 95% CI = 1.47-4.85; I2 = 0%). Methanogenic archaea were reported in 66% of the included studies. Representative members of phyla Thaumarchaeota and Crenarchaeota were also identified.

CONCLUSIONS

Archaea are present in about one-fifth of the infected root canals. Recognized biases in experimental approaches for researching archaea must be addressed to understand the prevalence and roles of archaea in endodontic infections, and to determine whether the decontamination process should include the elimination or neutralization of archaea from root canals (International Prospective Register of Systematic Reviews protocol = CRD42021264308).

Prevalence of Enterococcus species in adults with periodontal health or with periodontitis: a systematic review

The aim of this study was to evaluate the prevalence of Enterococcus species in the mouth of adults with periodontal health and periodontitis. A systematic search was made in databases in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The search for articles was conducted in Medline/PubMed, Latin American and Caribbean Health Sciences Literature Database (LILACS), Cochrane Library, Scopus, Embase, Web of Science databases and in the System of Information on Grey Literature in Europe (SINGLE) and included articles published in English up to April 25th, 2021. Observational studies in humans with and without periodontitis were evaluated to identify the prevalence of Enterococcus species. Articles that met the inclusion criteria were analyzed and classified to determine the quality rating in good, fair, and poor. A new detailed checklist for quality assessment was developed based on the information required for applicable data extraction in reviews. The study design, sample size, demographic data, periodontal clinical parameters, microbial analysis method, biological sample, prevalence of Enterococcus spp., and correlations with periodontal clinical parameters were assessed. After screening and full-text reading, 8 articles met the inclusion criteria. All selected studies showed a significantly higher prevalence of Enterococcus spp. in patients with periodontitis compared with periodontally healthy patients. Thus, the present systematic review suggests that the prevalence of Enterococcus faecalis in the mouth of periodontitis individuals is higher than that of periodontally healthy individuals.

Microbiome in paired root apices and periapical lesions and its association with clinical signs in persistent apical periodontitis using next-generation sequencing

AIM

To assess and compare the microbiome of paired root apices and periapical lesions from cases with failed endodontic treatment and to associate the microbiome and bacterial metabolic pathways in both sites with asymptomatic apical periodontitis (AAP) and symptomatic apical periodontitis (SAP), using next-generation sequencing (NGS).

METHODOLOGY

Matched root apices and periapical lesions of patients with failed root canal treatments were surgically extracted. Specimens were cryopulverized, bacterial DNA was extracted and the V3-V4 hypervariable regions of the 16 S rRNA gene were amplified and sequenced using the Illumina Miseq platform. Diversity and community composition were studied in the paired samples, as well as in AAP and SAP cases. Diversity indices were compared in each case by means of the Wilcoxon matched-pairs signed rank and Mann-Whitney U tests. Differences in the community composition were explored with multivariate statistical analysis and Linear discriminant analysis Effect Size (LEfSe). Bacterial functional study was performed through the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis.

RESULTS

Twenty-one paired apices and lesions were successfully sequenced and analysed, identifying a total of 21 phyla and 600 genera. A higher alpha-diversity was observed in the periapical lesions, although no global differences in the community composition between the two sites were found (p = .87), the most prevalent genera being Fusobacterium, Porphyromonas and Streptococcus. Prevotella, Clostridiales_vadinBB60_group, Bosea, Phreatobacter, Afipia and Xanthobacteriaceae_unclassified were enriched in SAP samples, while Pseudopropionibacterium, Campylobacter and Peptoniphilus were significantly more abundant in AAP cases (p < .05). Metabolic pathways involved in the amino acid metabolism or degradation and flagellum assembly were more abundant in SAP samples, whereas glucose metabolism-related pathways were associated with AAP.

CONCLUSIONS

The bacterial community composition was similar in the apices and periapical lesions. The microbiome was different in AAP and SAP samples, gram-negative bacteria showing higher relative abundances in SAP cases. An association was observed between amino acid degradation and flagellum assembly pathways, and the development of tenderness to percussion or palpation.

The Preventive Effect of A Magnetic Nanoparticle-Modified Root Canal Sealer on Persistent Apical Periodontitis

Persistent apical periodontitis is a critical challenge for endodontists. Developing root canal filling materials with continuous antibacterial effects and tightly sealed root canals are essential strategies to avoid the failure of root canal therapy and prevent persistent apical periodontitis. We modified the EndoREZ root canal sealer with the antibacterial material dimethylaminododecyl methacrylate (DMADDM) and magnetic nanoparticles (MNPs). The mechanical properties of the modified root canal sealer were tested. The biocompatibility of this sealer was verified in vitro and in vivo. Multispecies biofilms were constructed to assess the antibacterial effects of the modified root canal sealer. We applied magnetic fields and examined the extent of root canal sealer penetration in vitro and in vivo. The results showed that EndoREZ sealer containing 2.5% DMADDM and 1% MNP had biological safety and apical sealing ability. In addition, the modified sealer could increase the sealer penetration range and exert significant antibacterial effects on multispecies biofilms under an external magnetic field. According to the in vivo study, the apices of the root canals with the sealer containing 2.5% DMADDM and 1% MNP showed no significant resorption and exhibited only a slight increase in the periodontal ligament space, with a good inhibitory effect on persistent apical periodontitis.

Enterococcus faecalis-Induced Macrophage Necroptosis Promotes Refractory Apical Periodontitis

The persistence of residual bacteria, particularly Enterococcus faecalis, contributes to refractory periapical periodontitis, which still lacks effective therapy. The role of receptor-interacting protein kinase 3 (RIPK3)- and mixed lineage kinase domain-like protein (MLKL)-mediated necroptosis, a highly proinflammatory form of regulated cell death, has recently drawn much attention. However, the role of necroptosis in the pathogenesis of refractory periapical periodontitis remains unclear. We investigated whether the RIPK3/MLKL signaling pathway was activated in periapical lesion specimens obtained from patients diagnosed with refractory periapical periodontitis. RIPK3-deficient mice were then used to determine the role of necroptosis under this condition in vivo. We found that the phosphorylation levels of RIPK3 and MLKL were elevated in periapical lesion specimens of patients with refractory periapical periodontitis. In addition, necroptosis was induced in an E. faecalis-infected refractory periapical periodontitis mouse model, in which inhibition of necroptosis by RIPK3 deficiency could markedly alleviate inflammation and bone destruction. Moreover, double-labeling immunofluorescence suggested that macrophage necroptosis may be involved in the development of refractory periapical periodontitis. Then, we established an in vitro macrophage infection model with E. faecalis. E. faecalis infection was found to induce necroptotic cell death in macrophages through the RIPK3/MLKL signaling pathway, which was markedly alleviated by the RIPK3- or MLKL-specific inhibitor. Our study revealed that RIPK3/MLKL-mediated macrophage necroptosis contributes to the development of refractory periapical periodontitis and suggests that inhibitors or treatments targeting necroptosis represent a plausible strategy for the management of refractory periapical periodontitis. IMPORTANCE Oral infectious diseases represent a major neglected global population health challenge, imposing an increasing burden on public health and economy. Refractory apical periodontitis (RAP), mainly caused by Enterococcus faecalis, is a representative oral infectious disease with considerable therapeutic challenges. The interplay between E. faecalis and the host often leads to the activation of programmed cell death. This study identifies an important role of macrophage necroptosis induced by E. faecalis in the pathogenesis of RAP. Manipulating RIPK3/MLKL-mediated necroptosis may represent novel therapeutic targets, not only for RAP but also for other E. faecalis-associated infectious diseases.

How is working length determination taught? A survey to assess what is recommended in undergraduate Schools of Dentistry in Brazil

INTRODUCTION

To analyse what are the methods for working length (WLD) determination taught for undergraduate students in Brazilian Dental Schools and the perception of professors about the use of electronic WL determination in the clinical practice.

METHODS

An online questionnaire with eighteen closed questions was sent to 209 Schools of Dentistry in Brazil using the Google Forms Platform. The questionnaire was structured to analyse the perception of professors in the department of endodontics about the method of working length determination taught in undergraduate courses in Dentistry. The data collected in the questionnaires were transferred to an Excel^® spreadsheet and analysed using absolute and relative frequencies. The non-parametric Mann-Whitney test was used to compare groups.

RESULTS

Of the 209 schools contacted, 41 (19.61%) returned answers to the questionnaire. According to professors, electronic working length (WL) determination had a shorter length of time to perform it (p < .001), WL measurement accuracy (p < .001) and ease of performance (p < .001). Professors felt safer when maintaining patency when using electronic WL determination (p = .0020).

CONCLUSIONS

Both radiographic and electronic methods of WL determination are taught in Brazilian Schools of Dentistry. The electronic method was used more frequently, especially in undergraduate clinical courses.

Applications of Plasma-Activated Water in Dentistry: A Review

The activation of water by non-thermal plasma creates a liquid with active constituents referred to as plasma-activated water (PAW). Due to its active constituents, PAW may play an important role in different fields, such as agriculture, the food industry and healthcare. Plasma liquid technology has received attention in recent years due to its versatility and good potential, mainly focused on different health care purposes. This interest has extended to dentistry, since the use of a plasma–liquid technology could bring clinical advantages, compared to direct application of non-thermal atmospheric pressure plasmas (NTAPPs). The aim of this paper is to discuss the applicability of PAW in different areas of dentistry, according to the published literature about NTAPPs and plasma–liquid technology. The direct and indirect application of NTAPPs are presented in the introduction. Posteriorly, the main reactors for generating PAW and its active constituents with a role in biomedical applications are specified, followed by a section that discusses, in detail, the use of PAW as a tool for different oral diseases.

Microbial Communities in the Extraradicular and Intraradicular Infections Associated With Persistent Apical Periodontitis

Microorganisms in the complex root canal system and the extraradicular regions, including the periapical lesions and extraradicular biofilm may cause root canal treatment failures. However, few studies described the difference between the intraradicular and extraradicular infections from the same tooth associated with persistent apical periodontitis. This study aimed to characterize the microbiome present in the root canal, extraradicular biofilm, and periapical lesions associated with persistent apical periodontitis. The microbial communities in the root canal, extraradicular biofilm, and periapical lesions were investigated by Illumina high-throughput sequencing using Illumina Hiseq 2500 platform. The dominant phyla in the extraradicular and intraradicular infections associated with persistent apical periodontitis were Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria, and the genera Fusobacterium, Morganella, Porphyromonas, Streptococcus, and Bifidobacterium dominated across all samples. Although extraradicular infection sites showed higher OTU richness and β-diversity compared to intraradicular samples, the occurrence of sinus tract rather than the sampling sites demarcated the microbial communities in the infections associated with persistent apical periodontitis. PERMANOVA analysis confirmed that the samples with or without sinus tracts contained significantly different microbial communities. Porphyromonas, Eubacterium, Treponema, and Phocaeicola were found in significantly higher levels with sinus tracts, whilst Microbacterium and Enterococcus were more abundant in samples without sinus tracts. In conclusion, diverse bacteria were detected in both intraradicular and extraradicular infections associated with persistent apical periodontitis, which might be influenced by the occurrence of the sinus tract. The results may provide new insight into the pathogenesis of persistent apical periodontitis.

Present status and future directions - microbiology of endodontic infections

Apical periodontitis has a microbial aetiology and is one of the most common inflammatory diseases that affect humans. Fungi, archaea and viruses have been found in association with apical periodontitis, but bacteria are by far the most prevalent and dominant microorganisms in endodontic infections. Bacterial infection of the root canal system only occurs when the pulp is necrotic or was removed for previous treatment. In some specific cases, including acute and chronic abscesses, the bacterial infection may reach the periradicular tissues. Intracanal bacteria are usually observed as sessile multispecies communities (biofilms) attached to the dentinal root canal walls. Infection in the main root canal lumen can spread to other areas of the root canal system. Although more than 500 bacterial species have been detected in endodontic infections, a selected group of 20 to 30 species are most frequently detected and may be considered as the core microbiome. There is a high interindividual variability in the endodontic microbiome in terms of species composition and relative abundance. Obligate anaerobic species are more abundant in the intraradicular bacterial communities of teeth with primary apical periodontitis, while both anaerobes and facultatives dominate the communities in post-treatment apical periodontitis. Bacterial interactions play an essential role in determining the overall virulence of the community, which has been regarded as the unit of pathogenicity of apical periodontitis. This article reviews the microbiologic aspects of endodontic infections and provides perspectives for future research and directions in the field.

A critical analysis of research methods and experimental models to study the root canal microbiome

Endodontic microbiology deals with the study of the microbial aetiology and pathogenesis of pulpal and periradicular inflammatory diseases. Research in endodontic microbiology started almost 130 years ago and since then has mostly focussed on establishing and confirming the infectious aetiology of apical periodontitis, identifying the microbial species associated with the different types of endodontic infections and determining the efficacy of treatment procedures in eradicating or controlling infection. Diverse analytical methods have been used over the years, each one with their own advantages and limitations. In this review, the main features and applications of the most used technologies are discussed, and advice is provided to improve study designs in order to properly address the scientific questions and avoid setbacks that can compromise the results. Finally, areas of future research are described.

Diverse bacterial profile in extraradicular biofilms and periradicular lesions associated with persistent apical periodontitis

AIM

To characterize the bacterial community present in the extraradicular biofilm and periradicular lesions associated with persistent apical periodontitis.

METHODOLOGY

Eighteen adult patients who presented with persistent periradicular lesions after root canal treatment and scheduled for endodontic surgery were selected. During surgery, extraradicular samples of biofilms and periradicular lesions were collected. Ten pairs of periradicular lesions and extraradicular biofilm samples were randomly selected for ribosomal 16S rRNA cloning and sequencing. A Wilcoxon's rank-sum test was used to compare total bacterial counts and the levels of individual genera and species between the two groups (P < 0.05).

RESULTS

Overall, seventy-three phylotypes belonging to six different phyla were identified from 1000 sequenced clones. Mogibacterium timidum, Streptococcus intermedius and Enterococcus faecalis predominated in both extraradicular biofilm and periapical lesions. Propionibacterium propionicus, Abiotrophia adiacens, Peptostreptococcus prevotii, Campylobacter gracilis and Pseudomonas aeruginosa were found in significantly higher levels in the extraradicular biofilm than periapical lesions, whilst Parvimonas micra and Atopobium rimae were more abundant in periapical lesions (P < 0.05).

CONCLUSIONS

The microbial profile of extraradicular biofilms differed from periapical lesions, indicating the presence of diverse bacterial populations in these regions. Several genera and species were significantly associated with the formation of extraradicular biofilms.

Effect of photobiomodulation on post-operative symptoms in teeth with asymptomatic apical periodontitis treated with foraminal enlargement: A randomized clinical trial

AIM

To assess the efficacy of photobiomodulation in reducing post-operative symptoms and use of analgesics in teeth with asymptomatic apical periodontitis treated with foraminal enlargement in a single visit.

METHODOLOGY

This prospective double-blind, controlled, superiority, randomized clinical trial enrolled 70 patients requiring root canal treatment of one single-rooted tooth with asymptomatic apical periodontitis. The participants were randomized into one of the following two groups: 35 patients in the control group (C.G) - root canal treatment with foraminal enlargement, without any additional treatment and 35 patients in the photobiomodulation group (PBM.G) - root canal treatment with foraminal enlargement associated with photobiomodulation (antimicrobial photodynamic therapy and low-level laser therapy). The outcome variables were post-operative pain, tenderness, oedema and the use of analgesics. Pain intensity was measured using a visual analogue scale (recorded every day for 7 days, then the 14th and 30th days after root canal treatment). Facial oedema was assessed subjectively by two independent evaluators using photographs taken by one of the researchers at 48 h, 72 h and 7 days after the procedures. Data were tabulated and analysed using the Mann-Whitney U, Chi-Square, Fisher`s Exact, Student T and Ordinal Logistic Regression by Generalized Estimating Equations tests in SPSS software.

RESULTS

There were no significant differences in post-operative pain and tenderness between the groups at any observation period (p > .05). Photobiomodulation (beta = -0.77 / p = .01), time (beta = -0.23 / p < .01), and male gender (beta = -1.20 / p < .01) were associated with decreased post-operative pain. Only time (beta: -0.10; p < .01) and male gender (beta: -1.04; p < .01) were associated with decreased tenderness. For oedema and use of analgesics, there was no difference between the groups (p > .05).

CONCLUSIONS

Photobiomodulation had no significant effect on post-operative pain, tenderness, oedema and the use of analgesics after root canal treatment with foraminal enlargement, in single-rooted teeth treated in a single visit. Register of Clinical Trials: NCT03704857. Research Ethics Committee: no 2.353.996 / CAAE 74185417.9.0000.5626.

Antimicrobial susceptibility and virulence of Enterococcus spp. isolated from periodontitis-associated subgingival biofilm

BACKGROUND

This study evaluated the prevalence, virulence and antimicrobial susceptibility of enterococci isolated from the subgingival microbiota of patients with different periodontal status.

METHODS

Subgingival biofilm was obtained from individuals with periodontal health (PH) (n = 139), gingivitis (n = 103), and periodontitis (n = 305) and cultivated on selective media. Isolated strains were identified by mass spectrometry. Antimicrobial sensitivity was determined by disk diffusion, virulence genes by polymerase chain reaction, and the subgingival microbiota by checkerboard. Differences among groups were assessed by Kruskal-Wallis, Mann-Whitney, and Chi-square tests.

RESULTS

Enterococcus spp. were isolated from 7.4% of all samples; 53.7% were Enterococcus faecalis. They were more prevalent in periodontitis (9.8%) and gingivitis (7.8%) than PH (2.2%; P <0.05), but no differences among stages of disease severity were observed. High rates of low susceptibility/resistance (>64%) to at least one antimicrobial were observed. Predominant virulence factors included ace (64.3%), asa (39.3%), and esp (35.7%). Fusobacterium nucleatum was prevalent in the subgingival microbiota of enterococci+ individuals, whereas Dialister pneumosintes was found in low frequency in patients with bopD+ enterococci. Oral streptococci were prevalent (>70%) in patients carrying enterococci susceptible to doxycycline (P <0.05), usually bopD- and esp- (P <0.01).

CONCLUSIONS

E. faecalis is increased in periodontitis-associated biofilm. Oral enterococci carry virulence genes and express resistance to some antibiotics commonly used in dentistry, such as ciprofloxacin and erythromycin. Specific subgingival taxa are associated with oral enterococci, suggesting they may interact with species of the dysbiotic periodontitis biofilm, constituting a potential source of factors to tissue destruction, antibiotic resistance dissemination, and poor response to periodontal therapy.

Antimicrobial effect of photodynamic therapy on intracanal biofilm: A systematic review of in vitro studies

BACKGROUND

Antimicrobial photodynamic therapy (A-PDT), is one of the adjunctive therapies developed to improve the effectiveness of root canal disinfection.. The aim of this study was to analyze the antimicrobial effect of PDT on intracanal biofilm.

METHODS

Two reviewers conducted a literature search in PubMed, MEDLINE, Lilacs, SciELO, EMBASE and Google Scholar using the following search strategy: photochemotherapy "[Mesh] OR (photodynamic therapy) AND" dental plaque "[Mesh] OR (dental biofilm) AND (root canal). The following data were collected: publication year, author's name, study site, type of study, participant number, type of photosensitizer, type of laser, method of data collection, application time and results. Study quality was assessed using the Methodological Index for Non-Randomized Studies (MINORS).

RESULTS

After selection based on title, abstract and full text, 27 studies were included in this systematic review. PDT reduced bacterial viability in most studies when combined with conventional endodontic techniques.

CONCLUSION

PDT reduced bacterial counts in most studies, especially when used as an adjunct to the conventional endodontic technique to treat refractory infection. However, PDT effects on in vitro bacterial biofilm were not accurately quantified because of the numerous biases in the studies reviewed.

Radiographic and Clinical Findings of Single-Visit Root Canal Treatments with Apical Enlargement in Necrotic Teeth: A Retrospective Cohort Study

This study evaluated the long-term clinical outcomes of single-visit root canal treatments with apical enlargement on patients with necrotic pulp tissue retrospectively. A total of 137 teeth with necrotic pulp tissue which underwent single-visit root canal treatments were included. The root canals were shaped up until the apical constriction, which was determined by an apex locator. The outcomes were evaluated by two independent and calibrated endodontists clinically and radiographically. Teeth were dichotomized into healed (PAI ≤ 2, no signs or symptoms) and nonhealed (PAI > 2, with/without signs or symptoms) groups. Each patients' preoperative PAI and lesion size were recorded to evaluate the preoperative periapical status as well as several other prognostic factors. Statistical analyses were performed (p = 0.05) on ninety teeth. The mean observation time was 60 months. Out of ninety teeth, 87 (96.7%) were healed and 3 (3.3%) were nonhealed. No correlations were found between the prognostic factors and the outcomes (p > 0.05). Cohen's kappa and Gwet's agreement coefficient scores between the preoperative PAI scores and preoperative lesion sizes showed good agreements, with values of 0.834 and 0.898, respectively. Apical enlargement is a viable treatment option for single-visit root canal treatments.

Identification of bacteria associated with periapical abscesses of primary teeth by sequence analysis of 16S rDNA clone libraries

OBJECTIVE

This study aims to detect the predominant bacteria in acute periapical abscesses of primary teeth using culture-independent molecular methods based on 16S ribosomal DNA cloning.

METHODS

Purulent material was collected from nine children diagnosed with abscesses of endodontic origin. DNA was extracted and the 16S rRNA gene amplified with universal primer pairs 27F and 1492R. Amplified genes were cloned, sequenced by Applied Biosystems, and identified by comparison with known 16S rRNA gene sequences.

RESULTS

Bacterial DNA was present in all nine purulence samples. A total of 681 clones were classified into 8 phyla, 78 genera, and 125 species/phylotypes. The phyla were Firmicutes, Proteobacteria, Fusobacteria, Bacteroidetes, Actinobacteria, Tenericutes, Deinococcus-Thermus, and Spirochaetes. The most dominant genera were Streptococcus (13.3%), Fusobacterium (11.8%), Parvimonas (7.8%), Prevotella (6.7%), Sphingomonas (5.8%), and Hafnia (5.2%). Fusobacterium nucleatum (11.5%), Parvimonas micra (7.8%), Streptococcus intermedius (6.6%), Sphingomonas echinoides (5.3%), Hafnia alvei (5.2%), and Citrobacter freundii (4.9%) were the most common species/phylotypes. Among these species/phylotypes, F.nucleatum was the most prevalent (7/9). C. freundii, Carnobacterium maltaromaticum, and H. alvei were seldom detected species in acute periapical abscesses but had relatively high abundance and prevalence.

CONCLUSION

Acute periapical abscesses are polymicrobial with certain prevalent bacteria, especially anaerobic bacterium. The most predominant and prevalent bacteria of acute periapical abscesses in children was F. nucleatum.

Mucosal-associated invariant T cells and oral microbiome in persistent apical periodontitis

Opportunistic bacteria in apical periodontitis (AP) may pose a risk for systemic dissemination. Mucosal-associated invariant T (MAIT) cells are innate-like T cells with a broad and potent antimicrobial activity important for gut mucosal integrity. It was recently shown that MAIT cells are present in the oral mucosal tissue, but the involvement of MAIT cells in AP is unknown. Here, comparison of surgically resected AP and gingival tissues demonstrated that AP tissues express significantly higher levels of Vα7.2-Jα33, Vα7.2-Jα20, Vα7.2-Jα12, Cα and tumour necrosis factor (TNF), interferon (IFN)-γ and interleukin (IL)-17A transcripts, resembling a MAIT cell signature. Moreover, in AP tissues the MR1-restricted MAIT cells positive for MR1–5-OP-RU tetramer staining appeared to be of similar levels as in peripheral blood but consisted mainly of CD4⁺ subset. Unlike gingival tissues, the AP microbiome was quantitatively impacted by factors like fistula and high patient age and had a prominent riboflavin-expressing bacterial feature. When merged in an integrated view, the examined immune and microbiome data in the sparse partial least squares discriminant analysis could identify bacterial relative abundances that negatively correlated with Vα7.2-Jα33, Cα, and IL-17A transcript expressions in AP, implying that MAIT cells could play a role in the local defence at the oral tissue barrier. In conclusion, we describe the presence of MAIT cells at the oral site where translocation of oral microbiota could take place. These findings have implications for understanding the immune sensing of polymicrobial-related oral diseases.

Does Maintaining Apical Patency during Instrumentation Increase Postoperative Pain or Flare-up Rate after Nonsurgical Root Canal Treatment? A Systematic Review of Randomized Controlled Trials

INTRODUCTION

The concept of maintaining apical patency (AP) is a controversial issue in endodontics. The primary objectives of this systematic review of randomized controlled trials (RCTs) were to determine the influence of maintaining AP during instrumentation on postoperative pain severity and the prevalence of flare-ups. A second objective was to assess the effect of maintaining AP on the use of analgesics.

METHODS

RCTs and controlled clinical trials were searched for in MEDLINE (Ovid), Embase (Ovid), and the Cochrane Library. Four reviewers independently screened all identified articles for eligibility. The included studies were assessed for bias using the Cochrane Risk of Bias Tool. The Grading of Recommendations Assessment, Development and Evaluation approach was used to rate the quality of the body of evidence. Because of the considerable heterogeneity of the studies, a meta-analysis was not possible. Therefore, the results were analyzed narratively.

RESULTS

Five RCTs that included a total of 848 patients were found eligible and included in the review. An assessment of the risk of bias in the included studies provided results that classified the studies as showing a low risk (n = 1), high risk (n = 1), or unclear risk (n = 3) of bias. The available evidence indicated that maintaining AP (1) did not increase postoperative pain in teeth with nonvital pulp, (2) did not increase postoperative pain in teeth with vital pulp, and (3) did not cause (0%) flare-ups. The available evidence also indicated that maintaining AP did not increase analgesic use. The available evidence indicated that maintaining AP did not increase postoperative pain when a single-visit or 2-visit root canal treatment approach was used.

CONCLUSIONS

In light of the current evidence, maintaining AP does not increase postoperative pain in teeth with vital/nonvital pulp when compared with nonapical patency (low to moderate quality evidence). Furthermore, maintaining AP did not cause flare-ups (low evidence) and did not increase analgesic use (moderate evidence).

Antibacterial efficacy of an endodontic sonic-powered irrigation system: An in vitro study

OBJECTIVE

To evaluate the efficacy of EDDY, a new sonic-powered irrigation system, in reducing intracanal bacteria load.

METHODS

Thirty-eight instrumented, autoclaved single-rooted human premolars were inoculated with Enterococcus faecalis (ATCC-29212) for 21 days. Two teeth were used as negative control without bacterial contamination. For the bacteria-inoculated teeth, 6 were used as positive control without irrigation. The remaining 30 teeth were randomly divided into 2 groups (N = 15), using 3% NaOCl as irrigant: (A) 30-gauge syringe needle irrigation (SNI), (B) EDDY (VDW, Munich, Germany). Twelve teeth per group and 4 teeth in the positive control were evaluated for bacterial reduction using MTT assay. The remaining teeth were split for BacLight LIVE/DEAD staining to examine the percentages of live/dead bacteria present in the dentinal tubules from different canal locations (coronal, mid-root and apical portions of the canal space) using confocal laser scanning microscopy (CLSM).

RESULTS

MTT assay indicated that both SNI and EDDY significantly reduced overall intracanal bacterial load compared with the positive control, with no significant difference between the two techniques. CLSM indicated that EDDY had better intratubular bacterial killing efficacy than SNI in the coronal and mid-root portions of the canal space only but not in the apical portion. In all canal locations (coronal, mid-root apical), both systems failed to eliminate bacteria that proliferated deep within the dentinal tubules.

CONCLUSION

With the use of 3% NaOCl, sonic-powered irrigant activation with EDDY tips did not provide additional advantage over SNI in killing Enterococcus faecalis from deep intraradicular dentin.

CLINICAL SIGNIFICANCE

Both the sonic-powered root canal irrigant activation system and syringe needle irrigation can reduce intracanal bacteria load but are incapable of completely killing all bacteria that resided deep within the dentinal tubules of root canals infected with Enterococcus faecalis.

Factors that cause endodontic failures in general practices in Japan

BACKGROUND

Bacterial biofilms that develop on root surfaces outside apical foramens have been found to be associated with refractory periapical periodontitis. However, several other factors cause endodontic failures apart from extraradicular biofilms. The aim of this study was to identify the factors causing endodontic failures in general practices in Japan.

METHODS

Patients diagnosed as having refractory periapical periodontitis by general practitioners and who requested endodontic treatment at Osaka University Dental Hospital were selected by checking medical records from April 2009 to March 2013. Factors causing endodontic failures were identified.

RESULTS

A total of 103 teeth were selected, and 76 teeth completed root-canal treatment. Tooth extractions were required for 18 teeth after or without endodontic treatment. Six teeth required apicoectomy after endodontic treatment. One tooth needed hemisection. One tooth needed intentional replantation. One tooth needed adhesion and replantation. The main causes of treatment failure were open apices (24 teeth), perforation (18 teeth), and root fracture (13 teeth). In six teeth with open apices that required apicoectomy or extraction, extraradicular biofilms may have been related to endodontic failure.

CONCLUSIONS

Most endodontic cases diagnosed with refractory periapical periodontitis by general practitioners were compromised by any other factors rather than extraradicular biofilms.

Bacterial diversity of symptomatic primary endodontic infection by clonal analysis

The aim of this study was to explore the bacterial diversity of 10 root canals with acute apical abscess using clonal analysis. Samples were collected from 10 patients and submitted to bacterial DNA isolation, 16S rRNA gene amplification, cloning, and sequencing. A bacterial genomic library was constructed and bacterial diversity was estimated. The mean number of taxa per canal was 15, ranging from 11 to 21. A total of 689 clones were analyzed and 76 phylotypes identified, of which 47 (61.84%) were different species and 29 (38.15%) were taxa reported as yet-uncultivable or as yet-uncharacterized species. Prevotella spp., Fusobacterium nucleatum, Filifactor alocis, and Peptostreptococcus stomatis were the most frequently detected species, followed by Dialister invisus, Phocaeicola abscessus, the uncharacterized Lachnospiraceae oral clone, Porphyromonas spp., and Parvimonas micra. Eight phyla were detected and the most frequently identified taxa belonged to the phylum Firmicutes (43.5%), followed by Bacteroidetes (22.5%) and Proteobacteria (13.2%). No species was detected in all studied samples and some species were identified in only one case. It was concluded that acute primary endodontic infection is characterized by wide bacterial diversity and a high intersubject variability was observed. Anaerobic Gram-negative bacteria belonging to the phylum Firmicutes, followed by Bacteroidetes, were the most frequently detected microorganisms.

The cultivable microbiota of primary and secondary infected root canals, their susceptibility to antibiotics and association with the signs and symptoms of infection

AIM

To examine the presence of microbial species in primary and secondary infections and identify the signs and symptoms associated with them.

METHODOLOGY

A total number of 37 root canals from 33 patients undergoing root canal treatment were selected. Samples were taken using a sterile paper point following chemomechanical canal instrumentation. Microbiological identification was performed by macromorphological, micromorphological and commercial biochemical tests (ATB system). The antibiotic susceptibility profile of isolated Enterococcus, Streptococcus and Propionibacterium spp. was evaluated.

RESULTS

A total number of 54 species were isolated. The most common was E. faecalis followed by Propionibacterium acnes and Streptococcus spp. Five multidrug-resistant enterococcal strains were isolated. However, resistance to linezolid or glycopeptides was not found. Radiolucency was observed significantly more often in symptomatic infections (P = 0.0061) caused by Actinomyces spp. than in asymptomatic ones.

CONCLUSIONS

Enterococci and streptococci were the most commonly isolated bacteria from root canals. The resistance of enterococci to many antimicrobials may pose a problem in their eradication.

Novel Coating of Surgical Suture Confers Antimicrobial Activity Against Porphyromonas gingivalis and Enterococcus faecalis

BACKGROUND

The oral cavity is colonized by >10(9) bacteria, many of which can increase heart disease risk when seeded into the bloodstream. Most dentoalveolar surgeries require the use of surgical sutures. Suture placement and removal can increase the risk of postoperative infection and bacteremia. The aim of this study is to evaluate the antimicrobial activity of a novel quaternary ammonium compound, K21, when coated on different suture materials.

METHODS

The periodontal pathogen Porphyromonas gingivalis and the endodontic species Enterococcus faecalis were grown to early log phase and inoculated on enriched Brucella blood agar, on which were placed identical lengths of surgical suture (chromic gut, polyester suture, silk, and nylon suture) and control unwaxed dental floss impregnated with K21 at 5%, 10%, 20%, and 25% volume/volume in ethanol vehicle. Controls included the following: 1) sutures treated with vehicle; 2) untreated sutures; and 3) unwaxed floss. Zones of inhibition in millimeters were measured at five randomized sites per suture/floss for each concentration and material used. Mean ± SD of zones of inhibition were calculated, and analysis of variance (P <0.05) was used to determine whether differences were statistically significant.

RESULTS

The results indicate that K21-coated suture at concentrations ranging from 5% to 25%, depending on the type of suture, have antimicrobial activity for P. gingivalis and E. faecalis. Nylon suture coated with K21 at 5%, 10%, 20%, and 25% resulted in zones ranging from 3 to 11 mm. Polyester suture was more effective at lower K21 concentrations with 5% (P = 0.0031), 10% (P = 0.0011), and 20% (P = 0.0002), yielding 7.5, 8.3, and 10.5 mm zones of inhibition. K21-coated silk suture yielded significant zones of inhibition at 25% (P <0.0001), whereas chromic gut was effective at K21 concentrations of 5% (P = 0.0081) and 25% (P <0.0001).

CONCLUSION

It is concluded that K21-coated surgical sutures have antimicrobial activity for bacterial species of direct relevance to postoperative infection and bacteremia.

Antimicrobial peptide-based treatment for endodontic infections--biotechnological innovation in endodontics

The presence/persistence of microorganisms in the pulp and periapical area corresponds to the maintenance of an exacerbated immune response that leads to the start of periradicular bone resorption and its perpetuation. In endodontic treatment, the available intracanal medications do not have all the desirable properties in the context of endodontic infection and apical periodontitis; they need to include not only strong antimicrobial performance but also an immunomodulatory and reparative activity, without host damage. In addition, there are various levels of resistance to root canal medications. Thus, antimicrobial agents that effectively eliminate resistant species in root canals could potentially improve endodontic treatment. In the emergence of new therapies, an increasing number of studies on antimicrobial peptides (AMPs) have been seen over the past few years. AMPs are defense biomolecules produced in response to infection, and they have a wide spectrum of action against many oral microorganisms. There are some studies that correlate peptides and oral infections, including oral peptides, neuropeptides, and bacterial, fish, bovine and synthetic peptides. So far, there are around 120 published studies correlating endodontic microbiota with AMPs but, according to our knowledge, there are no registered patents in the American patent database. There are a considerable number of AMPs that exhibit excellent antimicrobial activity against endodontic microbiota at a small inhibitory concentration and modulate an exacerbated immune response, down-regulating bone resorption. All these reasons indicate the antimicrobial peptide-based endodontic treatment as an emerging and promising option.

Extraradicular infection as the cause of persistent symptoms: a case series

INTRODUCTION

This article describes 3 cases that presented persistent symptoms after appropriate endodontic treatment. Histopathologic and histobacteriologic investigation were conducted for determination of the cause.

METHODS

Three cases are reported that presented with persistent symptoms after endodontic retreatment (cases 1 and 2) or treatment (case 3). Periapical surgery was indicated and performed in these cases. The biopsy specimens, consisting of root apices and the apical periodontitis lesions, were subjected to histopathologic and histobacteriologic analyses.

RESULTS

Case 1 was an apical cyst with necrotic debris, heavily colonized by ramifying bacteria, in the lumen. No bacteria were found in the apical root canal system. Case 2 was a granuloma displaying numerous bacterial aggregations through the inflammatory tissue. Infection was also present in the dentinal tubules at the apical root canal. Case 3 was a cyst with bacterial colonies floating in its lumen; bacterial biofilms were also seen on the external apical root surface, filling a large lateral canal and other apical ramifications, and between layers of cementum detached from the root surface. No bacteria were detected in the main root canal.

CONCLUSIONS

Different forms of extraradicular infection were associated with symptoms in these cases, leading to short-term endodontic failure only solved by periapical surgery.

Supplementary sampling of obturation materials enhances microbial analysis of endodontic treatment failures: a proof of principle study

OBJECTIVES

Root canal treatment failures often correlate with persistent biomaterial-associated endodontic infections. The aim of the present study was to assess the impact of endodontic obturation material sampling from root canals with posttreatment apical periodontitis on improving standard study protocols.

MATERIALS AND METHODS

Samples from previously filled root canals and their corresponding endodontic filling materials were obtained from five root-filled teeth with posttreatment periradicular lesions. After cultivation, the isolated microorganisms were quantified and biochemically identified. Moreover, clone libraries were constructed after the amplification of bacterial 16S ribosomal DNA (rDNA) from the same samples. DNA from selected clones was sequenced to identify microbial species. Transmission electron microscopy (TEM) aided visualization of the detected bacteria.

RESULTS

Overall, 22 taxa of the phyla Firmicutes, Actinobacteria, and Bacteroidetes were detected in both obturation and root canal samples by culture-dependent and culture-independent methods. Root canal fillings sheltered 17 species (3.30-7.50 × 10(3) CFU/ml). Of these, nine were detected solely in the retrieved obturation materials. The reinfected root canals harbored 13 taxa (3.48-7.36 × 10(3) CFU/ml). Obligate and facultative anaerobic bacteria prevailed. The number of different species ranged from 1 to 5 within a single sample. Fungi were not detected.

CONCLUSIONS

Bacteria can colonize both root canals and endodontic fillings in vivo.

CLINICAL RELEVANCE

Integrating the sampling of obturation materials with standard root canal sample collection offers a clearer insight into the actual microbial flora of reinfected root canals and improves the study protocols of secondary/persistent endodontic infections.

Comparison of the bacterial composition and structure in symptomatic and asymptomatic endodontic infections associated with root-filled teeth using pyrosequencing

Residual microorganisms and/or re-infections are a major cause for root canal therapy failure. Understanding of the bacterial content could improve treatment protocols. Fifty samples from 25 symptomatic and 25 asymptomatic previously root-filled teeth were collected from Sudanese patients with periradicular lesions. Amplified 16S rRNA gene (V1-V2) variable regions were subjected to pyrosequencing (FLX 454) to determine the bacterial profile. Obtained quality-controlled sequences from forty samples were classified into 741 operational taxonomic units (OTUs) at 3% dissimilarity, 525 at 5% dissimilarity and 297 at 10% dissimilarity, approximately corresponding to species-, genus- and class levels. The most abundant phyla were: Firmicutes (29.9%), Proteobacteria (26.1%), Actinobacteria (22.72%), Bacteroidetes (13.31%) and Fusobacteria (4.55%). Symptomatic patients had more Firmicutes and Fusobacteria than asymptomatic patients, while asymptomatic patients showed more Proteobacteria and Actinobacteria. Interaction of disease status and age was observed by two-way ANOSIM. Canonical correspondence analysis for age, tooth restoration and disease status showed a correlation of disease status with the composition and prevalence of different members of the microbial community. The pyrosequencing analysis revealed a distinctly higher diversity of the microbiota compared to earlier reports. The comparison of symptomatic and asymptomatic patients showed a clear association of the composition of the bacterial community with the presence and absence of symptoms in conjunction with the patients’ age.

Analysis of the secondary endodontic lesions focusing on the extraradicular microorganisms: an overview

The present study aimed at reviewing the literature on extraradicular infections of endodontically treated teeth, summarizing the main hypotheses on etiopathogenesis and describing the most suitable techniques to identify the composition of pathogenic extraradicular microorganisms. Medline database was searched using the keywords "Apical biofilm," "extraradicular infection," "secondary endodontic lesion," "endodontic retreatment," "biofilm" either alone or combined with AND. A further hand search was performed on the main endodontic journals. The most frequent bacterial species identified in different studies and with different techniques may vary considerably. Although the presence of some species of microorganisms seems to be determinant, the true origin of extraradicular infection is still undetermined. The literature analysis showed marked differences in methodology, materials, aims, and techniques adopted, which led to highly heterogeneous outcomes. The picture emerging from this review is that extraradicular infection is likely a multifactorial disease that requires further systematic investigation using standardized techniques.

As-yet-uncultivated oral bacteria: breadth and association with oral and extra-oral diseases

It has been shown that 40–60% of the bacteria found in different healthy and diseased oral sites still remain to be grown in vitro, phenotypically characterized, and formally named as species. The possibility exists that these as-yet-uncultivated bacteria play important ecological roles in oral bacterial communities and may participate in the pathogenesis of several oral infectious diseases. There is also a potential for these as-yet-uncultivated oral bacteria to take part in extra-oral infections. For a comprehensive characterization of physiological and pathogenic properties as well as antimicrobial susceptibility of individual bacterial species, strains need to be grown in pure culture. Advances in culturing techniques have allowed the cultivation of several oral bacterial taxa only previously known by a 16S rRNA gene sequence signature, and novel species have been proposed. There is a growing need for developing improved methods to cultivate and characterize the as-yet-uncultivated portion of the oral microbiome so as to unravel its role in health and disease.

Comparison of endotoxin levels found in primary and secondary endodontic infections

INTRODUCTION

This clinical study was conducted to compare the levels of endotoxins (lipopolysaccharides [LPSs]) found in primary and secondary endodontic infections with apical periodontitis by correlating LPS contents with clinical/radiographic findings. In addition, the presence of target gram-negative anaerobic bacteria was also investigated.

METHODS

Samples were taken from 15 root canals with primary infections and 15 with secondary infections by using paper points. The limulus amebocyte lysate assay was used to quantify endotoxins, and the polymerase chain reaction technique (16S rDNA) was used for bacterial investigation.

RESULTS

Endotoxins were detected in 100% of the root canal samples collected from primary (15/15) and secondary (15/15) infections with median values of 7.49 EU/mL and 3.96 EU/mL, respectively (P < .05). The median value of endotoxins found in the presence of clinical symptoms was significantly higher than in asymptomatic teeth with primary infections (P < .05). A positive correlation was found between endotoxin contents and a larger size of the radiolucent area (>3 mm) (P < .05). Prevotella nigrescens (10/15, 4/15), Fusobacterium nucleatum (5/15, 1/15), Treponema denticola (3/15, 1/15), and Treponema socranskii (5/15, 1/15) were detected in teeth with primary and secondary infections, respectively. P. endodontalis was present only in teeth with primary infections (5/15).

CONCLUSIONS

Teeth with primary endodontic infections had higher contents of endotoxins and a more complex gram-negative bacterial community than teeth with secondary infections. Moreover, the levels of endotoxins were related to the severity of bone destruction in periapical tissues as well as the development of clinical features in teeth with primary infections.

Comprehensive analysis of secondary dental root canal infections: a combination of culture and culture-independent approaches reveals new insights

Persistence of microorganisms or reinfections are the main reasons for failure of root canal therapy. Very few studies to date have included culture-independent methods to assess the microbiota, including non-cultivable microorganisms. The aim of this study was to combine culture methods with culture-independent cloning methods to analyze the microbial flora of root-filled teeth with periradicular lesions. Twenty-one samples from previously root-filled teeth were collected from patients with periradicular lesions. Microorganisms were cultivated, isolated and biochemically identified. In addition, ribosomal DNA of bacteria, fungi and archaea derived from the same samples was amplified and the PCR products were used to construct clone libraries. DNA of selected clones was sequenced and microbial species were identified, comparing the sequences with public databases. Microorganisms were found in 12 samples with culture-dependent and -independent methods combined. The number of bacterial species ranged from 1 to 12 in one sample. The majority of the 26 taxa belonged to the phylum Firmicutes (14 taxa), followed by Actinobacteria, Proteobacteria and Bacteroidetes. One sample was positive for fungi, and archaea could not be detected. The results obtained with both methods differed. The cloning technique detected several as-yet-uncultivated taxa. Using a combination of both methods 13 taxa were detected that had not been found in root-filled teeth so far. Enterococcus faecalis was only detected in two samples using culture methods. Combining the culture-dependent and –independent approaches revealed new candidate endodontic pathogens and a high diversity of the microbial flora in root-filled teeth with periradicular lesions. Both methods yielded differing results, emphasizing the benefit of combined methods for the detection of the actual microbial diversity in apical periodontitis.