Web-Based Survey on Regenerative Endodontic Practices among Members of the American Association of Endodontists.

INTRODUCTION: The American Association of Endodontics (AAE) Regenerative Endodontics Committee reports here the web-based survey data of regenerative endodontic procedures performed by the AAE members from 2008 to 2019. METHODS: The web-based survey consisted of 2 questionnaires, a revascularization and a follow-up, including clinical and radiographic data at 3, 6, 12 or >12 months after treatment. Data from demographics, etiology, clinical protocols, radiographic, and clinical outcome as perceived by the clinicians were recorded. From 927 entries, 184 full cases were submitted and 126 were suitable for radiographic analysis. The data were divided into cases with 6-12 months and cases with >12 months recall time. Descriptive statistics and univariate analyses were performed. RESULTS: Predominantly patients were male (63%), average 10 years-old with anterior teeth (77.2%) due to trauma (69.6%). A wide variation in regenerative endodontic procedures protocols was reported by the AAE members. The most common clinical protocols used minimal instrumentation (75.5%), 2.5% or higher concentrations of sodium hypochlorite (83.7%), and antibiotic paste as intracanal medication (58.7%). The majority reported blood clot formation (56%) and most common coronal capping material was white mineral trioxide aggregates (50.5%). Increases in radiographic root length, and radiographic root area were proportional to the time lapsed after treatment. Overall, case outcomes were categorized by clinicians as successful (54.3%), uncertain (23.9%), and unsuccessful (3.8%). CONCLUSIONS: This web-based survey provides a valuable perspective on case selection, clinical protocols, and perceived outcomes for regenerative endodontic procedures and supports the need for future higher level evidence studies.

Role of (p)ppGpp in biofilm formation by Enterococcus faecalis.

Enterococcus faecalis strain OG1RF and its (p)ppGpp-deficient ΔrelA, ΔrelQ, and ΔrelA ΔrelQ mutants were grown in biofilms and evaluated for growth profiles, biofilm morphology, cell viability, and proteolytic activity. E. faecalis lacking (p)ppGpp had a diminished capacity to sustain biofilm formation over an extended period of time and expressed abundant proteolytic activity.

Conservative Management of Mature Permanent Teeth with Carious Pulp Exposure.

Vital pulp therapy (VPT) in mature permanent teeth with carious pulp exposure has been a matter of debate, with root canal therapy being the conventional standard of care. Previously reported negative outcomes for VPT in these teeth were based on data from studies that have used calcium hydroxide in direct pulp capping and partial and full pulpotomy. The introduction of hydraulic calcium silicate-based materials with sealing and bioactive potentials have opened a new era in VPT with more favorable results. Understanding the histopathology and histobacteriology of the cariously exposed pulp and the healing potential of the inflamed pulp could guide the decision-making process toward an ultraconservative management of these teeth. However, proper case selection, strict aseptic condition, capping material, and good coronal seal are crucial for long-term success.

Outcome assessment of orthodontic clear aligner vs fixed appliance treatment in a teenage population with mild malocclusions.

OBJECTIVE: To assess the efficacy and efficiency of treatment in adolescents presenting with mild malocclusions, comparing outcomes using clear aligners to fixed appliances. MATERIALS AND METHODS: Patients identified retrospectively and consecutively from one private practice had been treated with either clear aligners (Invisalign, Align Technology, Santa Clara, Calif) or fixed appliances (0.022 Damon, Ormco, Orange, Calif; n = 26/group). Assessments of occlusion were made using the American Board of Orthodontics Discrepancy Index (DI) for initial records and Cast-Radiograph Evaluation (CRE) for final records. Number of appointments, number of emergency visits, and overall treatment time were determined from chart reviews. Data were analyzed using Pearson's correlation, Wilcoxon rank tests, unpaired t-tests, and Chi-square tests, with significance set to P ≤ .05. RESULTS: Pretreatment, the aligner and fixed groups showed no significant difference in overall severity (DI: 11.9 ± 5.3 vs 11.6 ± 4.8) or in any individual DI category. Posttreatment scores showed finishes for the aligner group had fewer discrepancies from ideal relative to the fixed appliance group (CRE: 30.1 ± 8.3 vs 37.0 ± 9.3; P < .01). Patients treated with aligners had fewer appointments (13.7 ± 4.4 vs 19.3 ± 3.6; P < .0001), fewer emergency visits (0.8 ± 1.0 vs 3.6 ± 2.5; P < .0001), and shorter overall treatment time (16.9 ± 5.7 vs 23.4 ± 4.4 months; P < .0001). CONCLUSIONS: Outcomes for treatment of mild malocclusions in adolescents showed equivalent effectiveness of clear aligners compared to fixed appliances, with significantly improved results for clear aligner treatment in terms of tooth alignment, occlusal relations, and overjet. Assessment of the number of appointments, number of emergency visits, and overall treatment time showed better outcomes for treatment with clear aligners.

Accuracy of Presurgical Limited Field of View Cone-beam Computed Tomography in Predicting Intraoperative Buccal Cortical Bone.

INTRODUCTION: Limited field of view cone-beam computed tomography (LFOV CBCT) is the primary imaging modality recommended for treatment planning before endodontic microsurgery (EMS). Persistent apical periodontitis, often treated with EMS, results in changes in the buccal cortical plate that may detrimentally impact prognosis. The accuracy of a preoperative LFOV CBCT to predict intraoperative findings is unclear. METHODS: Electronic health records (EHRs) of EMS performed at 2 endodontic offices between 2016 and 2018 were reviewed retrospectively. EHR data extracted were documented for surgical findings of intact buccal cortical plate, fenestration, dehiscence, and height of remaining buccal collar of bone. Two calibrated, independent reviewers evaluated presurgical LFOV CBCTs in the multiplanar paraxial and parasagittal planes at 2 different reconstructed viewing plane thicknesses. Reviewer findings were compared with EHR documentation. Data were analyzed by using χ2, logistic regression, and multivariable analysis. Significance was set at P < .05. RESULTS: Within the 125 EMS cases included in the study, the EHR prevalence of intact buccal cortical plate was 49%, dehiscence 7%, and fenestration 44%. The imaging predictive value, whether it was negative (NPV) or positive (PPV), was higher when predicting presence of buccal bone (PPV of intact buccal cortical plate = 86.5%; NPV of dehiscence = 96%; NPV of fenestration = 89%). Sensitivity and specificity ranged from 80%-90%. Accuracy in prediction was high for all variables, exceeding 80%. Accuracy was not significantly influenced by reconstructed viewing slice thickness, viewing plane, or reviewer. CONCLUSION: Preoperative LFOV CBCT was highly discriminatory and accurately predicted intraoperative buccal cortical bone status, especially intact buccal cortical plate and fenestration.

Plasmid pAMS1-encoded, bacteriocin-related "Siblicide" in Enterococcus faecalis.

The Enterococcus faecalis class IIa bacteriocin MC4-1 encoded by the sex pheromone-responding, multiple-antibiotic resistance plasmid pAMS1 exhibits "siblicidal" (sibling-killing) activity under certain conditions. Stabs of plasmid-containing cells on solid medium containing lawns of bacteria of the same (plasmid-containing) strain give rise to zones of inhibition. If the plasmid-containing host also produces gelatinase, bacteriocin cannot be detected.

The impact of the Affordable Care Act on provision of endodontic services within a dental school setting in Oregon.

OBJECTIVES: In January 2014 implementation of the Medicaid expansion of the Affordable Care Act (EACA) in Oregon increased the number of children and adults qualifying for the Oregon Health Plan (OHP). Simultaneously, dental care benefits for adult Medicaid members were restored in Oregon after a period of noncoverage. This study evaluated the impact of these changes on the receipt of endodontic services in the Graduate Endodontic Clinic (GEC) at Oregon Health & Science University. METHODS: A retrospective electronic health records (EHRs) database review was conducted from July 2010 through June 2017, a seven-year period covering 3.5 years before (pre-EACA) and 3.5 years after (post-EACA) implementation of EACA. The number of completed anterior, premolar and molar non-surgical root canal therapies (NS-RCT) was retrieved from de-identified EHRs by targeting dental codes. Pre- and post-EACA frequencies were compared and analyzed by patient age [<21 years (children) versus adults], payer mix [OHP versus non-Medicaid (self-pay and private insurance)], and tooth type (anterior, premolar and molar) using Chi-square tests (P < 0.05). RESULTS: The number of procedures provided for patients covered by OHP post-EACA compared to pre-EACA was increased by 363 percent. There was an 18 percent decline in NS-RCT provided for non-OHP patients (P < 0.0001). Post-EACA increases in frequency applied to anterior, premolar, and molar NS-RCT (P < 0.0001), with the greatest increase in frequency post-EACA occurring for premolar NS-RCT procedures (666 percent). CONCLUSIONS: By eliminating barriers to care greater numbers of vulnerable people in Oregon sought and received endodontic services at the GEC.

Opioid-prescribing Practices in a Graduate Endodontic Clinic before and after Implementation of the Federal Schedule II Prescribing Mandate.

INTRODUCTION: Opioid prescriptions have the potential for misuse. In October 2014, the federal schedule II prescribing mandate reclassified hydrocodone combination products from schedule III to schedule II drugs that required a written prescription. The aim of this study was to evaluate the opioid-prescribing practices in a graduate endodontic clinic (GEC) before and after the mandate. METHODS: Electronic health records from all patients treated in the GEC from 2010 to 2018 were reviewed retrospectively for opioid prescribing, the date of prescription, and the Current Dental Terminology code. Where opioid prescribing was documented in the electronic health record, additional data were extracted about pulpal and periapical diagnosis, pain level, opioid type, and prescription details. Prescribing rates were calculated and analyzed by using chi-square, analysis of variance, logistic regression, and multivariable analysis. Significance was set at P < .05. RESULTS: Overall, 4851 patients underwent 7841 procedures; 92.2% of patients were never prescribed opioids. The remaining 380 patients underwent 420 procedures, and 509 prescriptions were provided. Prescribing rates were 7.5% (228/3021) before versus 4.0% (192/4820) after the mandate (P < .001). Hydrocodone combinations were the most prescribed opioid (77%, 392/509). Tramadol prescribing increased after the mandate (P = .023). Multivariable analysis showed significantly higher prescribing for apicoectomy procedures (P < .001). Preoperative pulpal and periapical diagnosis and pain level were not significantly associated with opioid prescribing. CONCLUSIONS: An overall reduction in opioid-prescribing rates occurred coincidentally with the 2014 federal mandate. The lack of correlation between prescribing and pain level highlighted the need for evidence-based rather than habitual prescribing protocols in the GEC.

The prevalence and impact of lysogeny among oral isolates of Enterococcus faecalis.

Bacterial phenotypic properties are frequently influenced by the uptake of extrachromosomal genetic elements, such as plasmids and bacteriophage genomes. Such modifications can result in enhanced pathogenicity due to toxin production, increased toxin release, altered antigenicity, and resistance to antibiotics. In the case of bacteriophages, the phage genome can stably integrate into the bacterial chromosome as a prophage, to produce a lysogenic cell. Oral enterococcal strains have been isolated from subgingival plaque and the root canals of endodontically-treated teeth that have failed to heal. Previously, we isolated a bacteriophage, phage ɸEf11, induced from a lysogenic Enterococcus faecalis strain recovered from the root canal of a failed endodontic case. PCR analysis using phage ɸEf11-specific oligonucleotide primers, disclosed that lysogens containing ɸEf11 prophages were commonly found among oral E. faecalis strains, being detected in 19 of 61 (31%) strains examined. Furthermore, in comparison to an isogenic cured strain, cultures of a lysogen harboring an ɸEf11 prophage exhibited altered phenotypic characteristics, such as increased persistence at high density, enhanced biofilm formation, and resistance to a bacteriophage lytic enzyme. From these results we conclude that lysogeny is common among oral E. faecalis strains, and that it alters properties of the lysogenic cell.

The influence of root canal sealer on extended intracanal survival of Enterococcus faecalis with and without gelatinase production ability in obturated root canals.

Enterococcus faecalis can survive for extended periods in obturated root canals. In this study, the hypotheses tested were that long-term survival of E. faecalis is dependent on (1) the type of endodontic sealer and (2) the capacity for microbial gelatinase activity, a potential "virulence" trait identified previously in clinical isolates. Root canals of extracted human canines (n=95) were inoculated with either E. faecalis OG1RF or its gelatinase-negative mutant E. faecalis TX5128. After 48 hours of incubation at 37 degrees C, canals were obturated with gutta-percha and either the epoxy-resin-based AH-Plus (Dentsply, De Trey, Konstanz, Germany), the silicone-based RoekoSeal (Coltène/Whaledent, Langenau, Germany), or zinc oxide eugenol-based Roth's sealer (Root Canal Cement Type 801; Roth International Ltd, Chicago, IL). Access cavities were sealed. After 8 months of incubation at 37 degrees C, viable E. faecalis was recovered from more teeth sealed with RoekoSeal (95%) compared with AH-Plus (40%) (p=0.0004, Fisher's exact test) and Roth's sealer (45%) (p=0.0012, Fisher's exact test). In the RoekoSeal groups, viable counts of E. faecalis OG1RF were higher than E. faecalis TX5128 (p=0.03, Mann-Whitney U test) suggesting that gelatinase activity plays a role in long-term survival of E. faecalis in obturated root canals.

Biofilm formation of oral and endodontic Enterococcus faecalis.

Biofilms are complex aggregations of microorganisms attached to a surface. The formation of biofilms might facilitate certain survival and virulence characteristics under some situations. This study tested the hypothesis that the ability of Enterococcus faecalis to form biofilms is related to the source of the strains. E. faecalis strains recovered from root canals (n = 33), the oral cavity (n = 21), and non-oral/non-endodontic sources (n = 16) were studied. Biofilms were grown in tryptic soy broth in 96-well plates for 24 hours at 37 degrees C, fixed with Bouin's fixative, and stained with 1% crystal violet. Optical density at 570 nm (OD(570)) was measured by using a microtiter plate reader. Experiments were performed in quadruplicate on three occasions and mean OD(570) readings determined for each strain. There were no statistically significant differences between groups (p = 0.066, Kruskal-Wallis). Within the root canal and oral isolates there were no significant associations between biofilm formation and the presence of the virulence determinants asa, cylA, esp, and gelE.

Antibiotic Use in 2016 by Members of the American Association of Endodontists: Report of a National Survey.

INTRODUCTION: This study surveyed the antibiotic prescribing practices of endodontists, and data were compared with previous surveys conducted in 1994 and 1999. METHODS: A 17-question survey was sent via www.surveymonkey.com to 3000 active members of the American Association of Endodontists for responses about antibiotic prescribing practices and demographics. The data were analyzed using descriptive statistics, chi-square tests, and linear regression analyses. RESULTS: Six hundred eighty-six participants (22.86%) completed the survey. The most frequently prescribed antibiotics were amoxicillin (60.71%) followed by penicillin V (30.43%) and clindamycin for patients with allergies (95.4%). Respondents reported prescribing antibiotics for irreversible pulpitis with mild symptoms (1.75%), irreversible pulpitis with moderate symptoms (6.41%), necrotic pulp with symptomatic apical periodontitis (43.59%), chronic apical abscess without (10.50%) or with symptoms (29.74%), acute apical abscess (95.92%), avulsion (70.26%), endodontic surgery (41.69%), retreatment (silver point [23.76%] or gutta-percha [15.60%]), postoperative pain after instrumentation or obturation (12.39%), and perforation repair (5.98%). The type of practice (solo/group) and geographic region (Southeast) were significant predictors of increased antibiotic prescribing; 36.89% of respondents reported prescribing antibiotics that are not necessary, most commonly because of patient expectations. CONCLUSIONS: Since 1999, there has been a significant shift from prescribing penicillin V to amoxicillin as endodontists' first choice of antibiotic and a significant increase in the use of clindamycin for penicillin-allergic patients. Antibiotics continue to be prescribed in clinical situations for which they are typically not indicated, most commonly because of patient expectations. Regional differences in antibiotic prescribing practices by endodontists exist in the United States.

A Novel Strategy to Engineer Pre-Vascularized Full-Length Dental Pulp-like Tissue Constructs.

The requirement for immediate vascularization of engineered dental pulp poses a major hurdle towards successful implementation of pulp regeneration as an effective therapeutic strategy for root canal therapy, especially in adult teeth. Here, we demonstrate a novel strategy to engineer pre-vascularized, cell-laden hydrogel pulp-like tissue constructs in full-length root canals for dental pulp regeneration. We utilized gelatin methacryloyl (GelMA) hydrogels with tunable physical and mechanical properties to determine the microenvironmental conditions (microstructure, degradation, swelling and elastic modulus) that enhanced viability, spreading and proliferation of encapsulated odontoblast-like cells (OD21), and the formation of endothelial monolayers by endothelial colony forming cells (ECFCs). GelMA hydrogels with higher polymer concentration (15% w/v) and stiffness enhanced OD21 cell viability, spreading and proliferation, as well as endothelial cell spreading and monolayer formation. We then fabricated pre-vascularized, full-length, dental pulp-like tissue constructs by dispensing OD21 cell-laden GelMA hydrogel prepolymer in root canals of extracted teeth and fabricating 500 µm channels throughout the root canals. ECFCs seeded into the microchannels successfully formed monolayers and underwent angiogenic sprouting within 7 days in culture. In summary, the proposed approach is a simple and effective strategy for engineering of pre-vascularized dental pulp constructs offering potentially beneficial translational outcomes.

Nonsteroidal Anti-inflammatory Drugs for Managing Postoperative Endodontic Pain in Patients Who Present with Preoperative Pain: A Systematic Review and Meta-analysis.

INTRODUCTION: Nonsteroidal anti-inflammatory drugs (NSAIDs) have been commonly used to treat endodontic postoperative pain. The purpose of this study was to address the following Population, Intervention, Comparator, Outcome, Timing, Study design and setting question: in patients with preoperative pain who undergo initial orthograde endodontic treatment, what is the comparative efficacy of NSAIDS compared with non-narcotic analgesics or placebo in reducing postoperative pain and the incidence of adverse events. METHODS: Ovid MEDLINE (1946-December 15, 2015), the Cochrane Database of Systematic Reviews (2005-December 15, 2015), and the Cochrane Central Register of Controlled Trials (to December 15, 2015) were searched using included drugs, indications, and study designs as search terms. Hand searches in texts were also conducted. Two independent reviewers assessed eligibility for inclusion, extracted data, and assessed quality using the risk of bias tool. L'Abbe plots were used for qualitative review. Where applicable, meta-analysis was conducted on the pooled effect size (ES). RESULTS: Two thousand two hundred eighty-four studies were identified through the database searches; 405 full-text articles were assessed. Fifteen articles met the inclusion criteria; qualitative analysis revealed all studies had a moderate to high risk of bias. Ibuprofen was the most studied NSAID. The L'Abbe plots showed that NSAIDS are effective at relieving postoperative endodontic pain overall. Meta-analysis showed that ibuprofen 600 mg is more effective than placebo at 6 hours postoperatively (ES = 10.50, P = .037), and ibuprofen 600 mg + acetaminophen 1000 mg combination is more effective than placebo (ES = 34.89, P = .000) but not significantly different than ibuprofen (ES = 13.94, P = .317). Five studies reported patients experiencing adverse events such as drowsiness, dizziness, nausea, and emesis; 2 studies reported that patients experienced no adverse events. CONCLUSIONS: A combination of ibuprofen 600 mg and acetaminophen 1000 mg is more effective than placebo but not significantly different than ibuprofen 600 mg at 6 hours postoperatively. Ibuprofen 600 mg is more effective than placebo at 6 hours postoperatively; however, there are insufficient data to recommend the most effective NSAID, dose amount, or dose interval for the relief of postoperative endodontic pain of longer duration in patients with preoperative pain.

The influence of canal curvature on the mechanical efficacy of root canal irrigation in vitro using real-time imaging of bioluminescent bacteria.

There are no quantitative data on the mechanical efficacy of irrigation in the removal of bacteria from curved canals. This study quantitatively analyzed the effects of root canal curvature and preparation size on the mechanical efficacy of irrigation using 33 mandibular single-rooted bicuspids allocated to groups according to root canal curvatures, group 1 (straight) 4 to 8 degrees, group 2 (intermediate curvature) 15 to 19 degrees, and group 3 (greatest curvature) 24 to 28 degrees. Teeth were sequentially instrumented to sizes 27/.04, 36/.04, and 46/.04 using a crown-down technique. Suspensions of the bioluminescent reporter strain Pseudomonas fluorescens 5RL (1.5 x 10(6) cells) were inoculated into canals of sterilized teeth after each sequential instrumentation. Canals were irrigated with 6 ml of irrigant delivered 1 mm from working length using a 30-gauge needle. Remaining bacteria were quantified using real-time bioluminescent imaging. Irrigation was significantly less effective in 24 to 28 degrees curvature canals prepared to size 27/.04 compared to 46/.04 (p < 0.007, repeated-measures ANOVA).

Prevalence of Enterococcus faecalis at multiple oral sites in endodontic patients using culture and PCR.

There are conflicting data on the occurrence of Enterococcus faecalis in the oral cavity of endodontic patients. This study investigated the prevalence of E. faecalis in multi-site oral samples (n = 136) from 41 endodontic patients using culture and polymerase chain reaction (PCR). Additionally, culturable strains were investigated for virulence traits. Overall, E. faecalis was detected in at least one tongue, oral rinse, or gingival sulcus sample in 68% of patients and in the root canals only in 5% of patients. In 21 patients from whom samples were obtained from all four sites, E. faecalis was detected in more tongue than gingival sulcus, oral rinse, and root canal samples (43, 14, 10, and 10%, respectively; p = 0.0148, chi(2)), and in proportionally greater numbers of patients with gingivitis/periodontitis compared to healthy periodontium (73% versus 20%; p = 0.03, Fisher's exact test). PCR was more sensitive than culture in detecting E. faecalis in oral samples (32% and 4%, respectively; p < 0.0001, McNemar's test). Multiple virulence traits were identified in culturable strains.

Coaggregation interactions between oral and endodontic Enterococcus faecalis and bacterial species isolated from persistent apical periodontitis.

Interactions between Enterococcus faecalis and other species found in root canal infections might be important for the development and persistence of periapical disease. The aim of this study was to investigate the coaggregation interactions between E. faecalis clinical isolates and species previously shown to survive and induce apical periodontitis in monkeys: Peptostreptococcus anaerobius, Prevotella oralis, Fusobacterium nucleatum, and Streptococcus anginosus. Intergeneric coaggregation assays were conducted in duplicate with observations scored immediately at 0 h, 1 h and 24 h after mixing of combinations of strains. All E. faecalis strains (n = 53) coaggregated with F. nucleatum; E. faecalis did not coaggregate with P. anaerobius or S. anginosus. One strain, E. faecalis E1, coaggregated with P. oralis, with aggregates visible at 1 h. Coaggregation interactions between E. faecalis and F. nucleatum observed in this study suggest a potential role for this combination in endodontic infections.

Real-time quantitative polymerase chain reaction and culture analyses of Enterococcus faecalis in root canals.

Reports on the prevalence of Enterococcus faecalis in root canals vary considerably, potentially because of variations in clinical sampling and sample analysis methods. This study compared culture and real-time quantitative polymerase chain reaction (qPCR) to detect and quantify E. faecalis in the same root canal sample. Consecutive root canal samples obtained from primary infection (n = 40) and retreatment (n = 48) cases were divided into two equal aliquots that were independently analyzed using culture and qPCR by investigators blinded to the analysis results of the other sample. E. faecalis was detected in 10.2% and 79.5% of samples by culture and qPCR, respectively (p < 0.0001; McNemar's test). E. faecalis was detected in more retreatment than primary infection samples (89.6% versus 67.5%; p = 0.01, Fisher's exact test). qPCR reported a significantly higher prevalence of E. faecalis in endodontic samples than culture techniques.

Oral microbiota species in acute apical endodontic abscesses.

BACKGROUND AND OBJECTIVES: Acute apical abscesses are serious endodontic diseases resulting from pulpal infection with opportunistic oral microorganisms. The objective of this study was to identify and compare the oral microbiota in patients (N=18) exhibiting acute apical abscesses, originating from the demographic region in Portland, Oregon. The study hypothesis is that abscesses obtained from this demographic region may contain unique microorganisms not identified in specimens from other regions. DESIGN: Endodontic abscesses were sampled from patients at the Oregon Health & Science University (OHSU) School of Dentistry. DNA from abscess specimens was subjected to polymerase chain reaction amplification using 16S rRNA gene-specific primers and Cy3-dCTP labeling. Labeled DNA was then applied to microbial microarrays (280 species) generated by the Human Oral Microbial Identification Microarray Laboratory (Forsyth Institute, Cambridge, MA). RESULTS: The most prevalent microorganisms, found across multiple abscess specimens, include Fusobacterium nucleatum, Parvimonas micra, Megasphaera species clone CS025, Prevotella multisaccharivorax, Atopobium rimae, and Porphyromonas endodontalis. The most abundant microorganisms, found in highest numbers within individual abscesses, include F. nucleatum, P. micra, Streptococcus Cluster III, Solobacterium moorei, Streptococcus constellatus, and Porphyromonas endodontalis. Strong bacterial associations were identified between Prevotella multisaccharivorax, Acidaminococcaceae species clone DM071, Megasphaera species clone CS025, Actinomyces species clone EP053, and Streptococcus cristatus (all with Spearman coefficients >0.9). CONCLUSIONS: Cultivable and uncultivable bacterial species have been identified in endodontic abscesses obtained from the Portland, Oregon demographic region, and taxa identifications correlated well with other published studies, with the exception of Treponema and Streptococcus cristae, which were not commonly identified in endodontic abscesses between the demographic region in Portland, Oregon and other regions.