The root canal microbiome diversity and function. A whole-metagenome shotgun analysis.

AIM: To evaluate the root canal microbiome composition and bacterial functional capability in cases of primary and secondary apical periodontitis utilizing whole-metagenome shotgun sequencing. METHODOLOGY: Twenty-two samples from patients with primary root canal infections, and 18 samples obtained from previously treated teeth currently diagnosed with apical periodontitis were analysed with whole-metagenome shotgun sequencing at a depth of 20 M reads. Taxonomic and functional gene annotations were made using MetaPhlAn3 and HUMAnN3 software. The Shannon and Chao1 indices were utilized to measure alpha diversity. Differences in community composition were evaluated utilizing analysis of similarity (ANOSIM) using Bray-Curtis dissimilarities. The Wilcoxon rank sum test was used to compare differences in taxa and functional genes. RESULTS: Microbial community variations within a community were significantly lower in secondary relative to primary infections (alpha diversity p = .001). Community composition was significantly different in primary versus secondary infection (R = .11, p = .005). The predominant taxa observed among samples (>2.5%) were Pseudopropionibacterium propionicum, Prevotella oris, Eubacterium infirmum, Tannerella forsythia, Atopobium rimae, Peptostreptococcus stomatis, Bacteroidetes bacterium oral taxon 272, Parvimonas micra, Olsenella profusa, Streptococcus anginosus, Lactobacillus rhamnosus, Porphyromonas endodontalis, Pseudoramibacter alactolyticus, Fusobacterium nucleatum, Eubacterium brachy and Solobacterium moorei. The Wilcoxon rank test revealed no significant differences in relative abundances of functional genes in both groups. Genes with greater relative abundances (top 25) were associated with genetic, signalling and cellular processes including the iron and peptide/nickel transport system. Numerous genes encoding toxins were identified: exfoliative toxin, haemolysins, thiol-activated cytolysin, phospholipase C, cAMP factor, sialidase, and hyaluronic glucosaminidase. CONCLUSIONS: Despite taxonomic differences between primary and secondary apical periodontitis, the functional capability of the microbiomes was similar.

Taxonomic abundance in primary and secondary root canal infections.

AIM: To evaluate the root canal microbiome composition in cases of primary and secondary apical periodontitis. METHODOLOGY: Thirty-nine samples from patients with primary root canal infections obtained before root canal treatment, and 40 samples obtained during root-end resection procedures from previously filled cases with apical periodontitis were evaluated using 16S rRNA next-generation sequencing analysis (NGS). Demographic and clinical factors included age, sex, infection type, percussion sensitivity, and presence of pain. Differences in abundances of genera were evaluated using Kruskal-Wallis test. Alpha and beta diversity indices were calculated using mothur. The Shannon and Chao1 indices were used to measure alpha diversity. The Bray-Curtis dissimilarity was used to measure beta diversity. Differences in community composition were evaluated using analysis of similarity (ANOSIM) with Bonferroni correction for multiple comparisons. RESULTS: Significantly fewer operational taxonomic units values were observed from samples from secondary infections (p < .0001). While no significant differences were observed in the Chao 1 index between primary and secondary infections, the Shannon alpha diversity was significantly lower in secondary relative to primary infections (p = .008). Among samples, sex, age (adult vs. older adult), percussion sensitivity, and presence of pain all showed no significant effects on community composition via an analysis of similarity (ANOSIM). However, community composition was significantly different depending on whether the sample was from a primary or secondary infection (R = .051, p = .03). Nine microbial genera comprised the predominant taxa observed among samples (>3.3%) and included Parvimonas, Fusobacterium, Campylobacter, Arachnia, Eubacterium, Prevotella, Peptostreptococcus, Fretibacterirum, and Pseudoramibacter. Significantly greater relative abundances of Prevotella, Peptostreptococcus, Veillonella, Lactucaseibacillus, and Dialister were observed in primary infections. CONCLUSIONS: Primary endodontic infections are more diverse than secondary infections. The microbial composition is not associated with the clinical manifestations of apical periodontitis.

The effect of ultrasonic and multisonic irrigation on root canal microbial communities: An ex vivo study.

AIM: To analyse the effect of ultrasonic irrigant activation (UIA) and the GentleWave (GW) multisonic irrigation (GW) with minimal instrumentation on the root canal microbial diversity in an ex vivo model that used extracted molars with a history of pulp necrosis. METHODOLOGY: Twenty-three mandibular molars were prepared ex vivo for collection of superficial (surface control), pre-treatment and post-treatment samples 24 h after extraction. Samples were divided into two groups: UIA using 6% NaOCl (n = 11) and GW group (n = 12). All samples were processed using quantitative real-time polymerase chain reaction (qPCR) and 16S rRNA next-generation sequencing to measure microbial diversity before and after the antimicrobial treatment. For qPCR, a t-test (α = .05) was used to compare the log10 reduction. The Chao1 and Shannon indices evaluated alpha diversity. Differences in community composition (beta diversity) were evaluated by analysis of similarity (ANOSIM). Kruskal-Wallis test with Bonferroni corrections was performed to evaluate the differences in abundances genera in the samples. RESULTS: Quantitative real-time polymerase chain reaction revealed an estimated 1.6 and 2.6 log10 reduction for UIA and GW groups respectively (p = .048). An average of 5 ± 4 and 3 ± 5 operational taxonomic units (OTUs) were found in surface's samples in the UIA and GW group respectively. These values were significantly lower (p < .001) compared to the number of preoperative OTUs in those groups (155 ± 79 and 187 ± 121). In assessing beta diversity, there were no significant differences found in pre-treatment samples (R = .090, p = .070 ANOSIM with Bonferroni corrections). Also, no significant differences in community composition were observed in post-treatment samples (R = -.05, p = .829). After treatment, there was a significant reduction of Eubacterium using conventional treatment with UIA and a significant reduction of Prevotella using minimal instrumentation with GW irrigation (p = .007 and p = .002 respectively). CONCLUSION: Quantitative PCR analysis revealed a significant reduction in microbial load for GW group. Overall, diversity changes were similar between UIA and GW irrigation in this ex vivo model that used extracted teeth with a history of pulp necrosis. OTUs obtained from the surface sample were negligible and did not affect the statistical outcome of the study.

Present status and future directions: Management of curved and calcified root canals.

Root canal curvature and calcification introduce factors that increase the risk of procedural accidents during root canal treatment. The inability to achieve patency to the apical third, asymmetrical dentine removal leading to transportation, perforation, and instrument fracture inside the curved trajectories are some of the procedural problems that might jeopardize the management of intraradicular infection and result in poor treatment outcomes. In fact, curved and constricted canals introduce such complexity that total instrumentation concepts and specially designed instruments have been developed to deal with the challenge. This narrative review seeks to provide and consolidate the principles necessary for understanding the dynamics of curved and constricted canal management and to improve the understanding for future developments in this field.

A critical analysis of research methods and experimental models to study the load capacity and clinical behaviour of the root filled teeth.

The prognosis of root-filled teeth depends not only on a successful root canal treatment but also on the restorative prognosis. This critical review discusses the advantages and limitations of various methodologies used to assess the load capacity or clinical survivability of root-filled teeth and restorations. These methods include static loading, cyclic loading, finite element analysis and randomized clinical trials. In vitro research is valuable for preclinical screening of new dental materials or restorative modalities. It also can assist investigators or industry to decide whether further clinical trials are justified. It is important that these models present high precision and accuracy, be reproducible, and present adequate outcomes. Although in vitro models can reduce confounding by controlling important variables, the lack of clinical validation (accuracy) is a downside that has not been properly addressed. Most importantly, many in vitro studies did not explore the mechanisms of failure and their results are limited to rank different materials or treatment modalities according to the maximum load capacity. An extensive number of randomized clinical trials have also been published in the last years. These trials have provided valuable insight on the survivability of the root-filled tooth answering numerous clinical questions. However, trials can also be affected by the selected outcome and by intrinsic and extrinsic biases. For example, selection bias, loss to follow-up and confounding. In the clinical scenario, hypothesis-based studies are preferred over observational and retrospective studies. It is recommended that hypothesis-based studies minimize error and bias during the design phase.

Present status and future directions of intracanal medicaments.

Two fundamental goals of endodontic treatment are to prevent or treat apical periodontitis. From a predictive perspective, several variables can affect the outcome of root canal treatment. Some of these variables depend on intraoperative factors, which include irrigation technique, size of the apical preparation, use of intracanal medicaments or the number of appointments necessary to complete the treatment. However, the outcome may also be affected by host and microbial factors. The intensity of periradicular bone loss or tissue damage, the presence of preoperative pain and associated conditions such as mechanical allodynia and central sensitization, the anatomical complexity of the apical portion of the canal, and the virulence and longevity of the bacterial infection can all have a profound influence on the outcome. Furthermore, numerous medical conditions have been reported to decrease the capability of the immune system to heal the periapical tissues. It is the clinician's responsibility to analyse these variables and incorporate them into the disinfection strategy to maximize the chances of healing. This narrative review will focus on the present status of intracanal medicaments, the clinical indications for their use and future directions for research.

In vitro efficacy of a non-instrumentation technique to remove intracanal multispecies biofilm.

AIM: The aim of this study was to assess the efficacy of a non-instrumentation technique to disinfect root canals infected by a human dental plaque-derived multispecies biofilm. METHODOLOGY: Twenty-two mandibular incisors were accessed, autoclaved and inoculated with dental plaque. The Center for Disease Control biofilm reactor was used to promote contamination of the root canal space. In the conventional technique (control), the specimens were instrumented until size 35/04 and irrigated with 6% NaOCl. In the non-instrumentation technique, a glide path was established using K-files size 10-20 and specimens were immediately cleaned with the GentleWave System. Samples were obtained for culture and 16S rRNA gene sequencing. Differences in abundances of genera were evaluated using Kruskal-Wallis test, and differences in alpha diversity were compared using anova. Alpha and beta diversity indices were calculated using mothur. The Shannon and Chao1 indices were used to measure alpha diversity. The Bray-Curtis dissimilarity was used to measure beta diversity. Differences in community composition were evaluated using analysis of similarity with Bonferroni correction for multiple comparisons. RESULTS: The total numbers of reads in biological samples ranged from 126 to 45 286. Significantly fewer reads were obtained from samples following cleaning by either method (p < .0001), and significantly fewer reads were obtained in post-cleaning samples following conventional versus non-instrumentation cleaning regiment (p = .002). Communities in pre-treatment samples were similar in both groups; however, significantly greater relative abundances of Streptococcus, Veillonella and Campylobacter were observed following cleaning using non-instrumentation technique (Kruskal-Wallis p = .009, .033, and .001, respectively). Whilst no significant differences were observed in Shannon alpha diversity, the Chao1 index was significantly lower in post-cleaning samples. CONCLUSIONS: Significant shifts in composition were observed following cleaning by using both regimens, but the impact of this change was greater following a conventional cleaning technique.

Efficacy of four local anaesthesia protocols for mandibular first molars with symptomatic irreversible pulpitis: A randomized clinical trial.

AIM: To examine the efficacy rate of four anaesthetic protocols in mandibular first molars with symptomatic irreversible pulpitis (SIP). METHODOLOGY: One hundred and sixty patients with a diagnosis of SIP were included in this randomized clinical trial. Patients were randomly allocated into four treatment groups (N = 40) according to the administered technique: Group 1 (IANB): standard inferior alveolar nerve block (IANB) injection; Group 2 (IANB + IO): standard IANB followed by a supplemental intraosseous infusion (IO) injection; Group 3 (IANB + PDL): standard IANB followed by a supplemental periodontal ligament (PDL) injection; Group 4 (IANB + BI): standard IANB followed by a supplemental buccal infiltration. Patients rated pain intensity using a verbal rating scale when the root canal treatment procedure was initiated, that is, during caries removal, access preparation and pulpectomy. Heart rate changes were recorded before, during and after each injection. The anaesthetic efficacy rates were analysed using chi-square tests, age differences using one-way anova, gender differences using Fischer Exact tests whilst heart rate changes were analysed using Kruskal-Wallis tests. Statistical significances were set at p < .05 level. RESULTS: All the included patients were analysed. No differences in the efficacy rate were found in relation to the age or gender of the participants amongst the study groups (p > .05). IANB + IO injections had a significantly higher efficacy rate (92.5%) when compared to other techniques (p < .05), followed by IANB + PDL injections (72.5%), IANB + BI injections (65.0%), with no significant differences between the IANB + PDL or IANB + BI injections (p > .05). IANB injection alone had a significantly lower rate (40%) compared to the other techniques (p < .05). A transient but significant rise in the heart rate was recorded in 60% (24/40) of patients who received the IANB + IO injection compared to other groups (p < .05). CONCLUSIONS: Inferior alveolar nerve block injection alone did not reliably permit pain-free treatment for mandibular molars with SIP. The use of an additional IO supplemental injection provided the most effective anaesthesia for patients requiring emergency root canal treatment for SIP in mandibular posterior teeth.

Multispecies biofilm removal by a multisonic irrigation system in mandibular molars.

AIM: The aim of the study was to assess biofilm removal efficacy of GentleWave System and passive ultrasonic irrigation (PUI). METHODOLOGY: Twenty-two human mandibular molars with Vertucci's type II configuration in the mesial root were selected. Teeth were autoclaved, inoculated with dental plaque and incubated in a CDC biofilm reactor for two weeks. The mesial roots were instrumented up to 20.06 file (V-Taper) for the GentleWave group and up to 35.04 file (Vortex Blue) for PUI group. Irrigation was performed using GentleWave and PUI irrigation protocols (n = 11). Dentine debris on paper points samples were obtained for quantitative real-time polymerase chain reaction (qPCR) and 16S ribosomal RNA gene sequencing (next-generation aequencing-NGS). For qPCR, a non-parametric test (α = 0.05) was used. Next-generation sequencing data were analysed using mothur, with alpha diversity calculated as the Shannon and Chao1 indices and Bray-Curtis dissimilarities were used for beta diversity. Differences in alpha diversity and abundances of genera were evaluated using Kruskal-Wallis test. Differences in community composition were evaluated using analysis of similarity with Bonferroni correction for multiple comparisons. RESULTS: Quantitative real-time polymerase chain reaction results showed that the reduction estimated in percentages for both groups was equivalent (p > .05). NGS analysis showed that both techniques promoted a significant reduction in reads and OTUs number (p < .05). Shannon alpha diversity and Chao1 index showed no differences between pre- or post-treatment samples for both groups (p > .05). Additionally, pre-treatment communities differed from post-treatment samples in both groups regarding bacterial taxa reduction (ANOSIM R = 0.50 and 0.55, p < .001). CONCLUSIONS: Bacterial reduction in mesial roots of mandibular molars prepared to 35.04 with PUI was similar to those prepared to 20.06 with a multisonic irrigant activation system.

Prevalence of periapical lesions, root canal treatments and restorations in teeth adjacent to implant- or tooth-supported crowns: A multi-centre cross-sectional study.

AIM: To describe the prevalence of periapical lesions, root canal treatments and coronal restorations on teeth adjacent to either implant- or natural tooth-supported crowns using cone-beam computed tomography (CBCT) assessment compared to nonadjacent teeth. METHODOLOGY: A total of 1249 CBCT volumes were screened by five pre-calibrated observers in 11 health centres. A step-by-step screening protocol was implemented and reviewed every 3 months, and mandatory setting characteristics were established for all CBCT scans using dedicated visualization software. Intra- and inter-rater reliability tests were conducted. The prevalence of periapical lesions, root canal treatments and coronal restorations was recorded on both teeth adjacent and nonadjacent to implant- (predictor 1) or natural tooth-supported crowns (predictor 2). A binary logistic model (Generalizing Estimating Equations test) was used to verify whether the prevalence of periapical lesion, root canal filling and the tooth restorative status are altered when the assessed tooth is adjacent or not to an implant-supported crown (predictor 1); or to a natural tooth-supported crown (predictor 2). Odds ratio and confidence intervals for the dependent variables at both predictors were obtained. The significance level was set at .05. RESULTS: A global sample of 22 899 teeth was included. Compared to nonadjacent teeth, the prevalence of periapical lesion, root canals treatments and restorative procedures when adjacent to implant-supported crowns was 10.7%, 19.6% and 22.9% higher, respectively, and when adjacent to tooth-supported crowns was 19.3%, 35.6% and 37.4% higher respectively. These results were significant only for variables root canal filling and coronal restoration (p < .0001). Odds ratio to present root canal treatment is 2.57 times higher (CI 1.95-3.39, p = .0001) when the tooth is adjacent to implant-supported crown and 4.39 times (CI 3.49-5.53, p = .0001) when adjacent to tooth-supported crown, whilst for restorative procedure, the odds are, respectively, 1.63 (CI 1.29-2.06, p = .0001) and 2.30 (CI 1.92-2.76, p = .0001). CONCLUSIONS: Teeth adjacent to both implant- and natural tooth-supported crowns were associated with a higher frequency of root canal filling and coronal restorations.

PRILE 2021 guidelines for reporting laboratory studies in Endodontology: explanation and elaboration.

Guidance to authors is needed to prevent their waste of talent, time and resources in writing manuscripts that will never be published in the highest-quality journals. Laboratory studies are probably the most common type of endodontic research projects because they make up the majority of manuscripts submitted for publication. Unfortunately, most of these manuscripts fail the peer-review process, primarily due to critical flaws in the reporting of the methods and results. Here, in order to guide authors, the Preferred Reporting Items for study Designs in Endodontology (PRIDE) team developed new reporting guidelines for laboratory-based studies: the Preferred Reporting Items for Laboratory studies in Endodontology (PRILE) 2021 guidelines. The PRILE 2021 guidelines were developed exclusively for the area of Endodontology by integrating and adapting the modified CONSORT checklist of items for reporting in vitro studies of dental materials and the Clinical and Laboratory Images in Publications (CLIP) principles. The process of developing the PRILE 2021 guidelines followed the recommendations of the Guidance for Developers of Health Research Reporting Guidelines. The aim of the current document is to provide authors with an explanation for each of the items in the PRILE 2021 checklist and flowchart with examples from the literature, and to provide advice from peer-reviewers and editors about how to solve each problem in manuscripts prior to their peer-review. The Preferred Reporting Items for study Designs in Endodontology (PRIDE) website (http://pride-endodonticguidelines.org/prile/) provides a link to the PRILE 2021 explanation and elaboration document as well as to the checklist and flowchart.

PRILE 2021 guidelines for reporting laboratory studies in Endodontology: A consensus-based development.

Reproducible, skilfully conducted and unbiased laboratory studies provide new knowledge, which can inform clinical research and eventually translate into better patient care. To help researchers improve the quality and reproducibility of their research prior to a publication peer-review, this paper describes the process that was followed during the development of the Preferred Reporting Items for Laboratory studies in Endodontology (PRILE) 2021 guidelines and which used a well-documented consensus-based methodology. A steering committee was created with eight individuals (PM, RO, OP, IR, JS, EP, JJ and SP), plus the project leaders (PD, VN). The steering committee prepared an initial checklist by combining and adapting items from the modified Consolidated Statement of Reporting Trials checklist for reporting in vitro studies of dental materials and the Clinical and Laboratory Images in Publications principles as well as adding several new items. The steering committee then formed a PRILE Delphi Group (PDG) and PRILE Online Meeting Group (POMG) to provide expert advice and feedback on the initial draft checklist and flowchart. The members of the PDG participated in an online Delphi process to achieve consensus on the items within the PRILE 2021 checklist and the accompanying flowchart for clarity and suitability. The PRILE checklist and flowchart developed by the online Delphi process were discussed further by the POMG. This online meeting was conducted on 12 February 2021 via the Zoom platform. Following this meeting, the steering committee developed a final version of the PRILE 2021 guidelines and flowchart, which was piloted by several authors when writing up a laboratory study for publication. Authors are encouraged to use the PRILE 2021 guidelines and flowchart to improve the clarity, completeness and quality of reports describing laboratory studies in Endodontology. The PRILE 2021 checklist and flowchart are freely available and downloadable from the Preferred Reporting Items for study Designs in Endodontology website (http://pride-endodonticguidelines.org/prile/).

The MB3 canal in maxillary molars: a micro-CT study.

OBJECTIVES: To assess the internal and external morphologies of the mesiobuccal (MB) root of maxillary molars presenting a third root canal (MB3), using micro-computed tomography (micro-CT). MATERIAL AND METHODS: Two-hundred and sixty-five extracted maxillary first and second molars with different root configurations were imaged in a micro-CT scanner at 19.6-µm pixel size. Sixteen teeth presenting MB3 canal were selected and evaluated regarding root configuration, minimal dentine thickness 2 mm under the furcation area, canal configuration of the MB root, MB3 canal morphology (location, independent or confluent orifice, and anatomy types), and the apical anatomy (aspect ratio, number of accessory canals and foramina, presence of isthmus, and independent MB3 foramen). RESULTS: Overall, a high variability in canal configuration was detected in the MB root. MB3 canal was observed in 10 maxillary first molars and 6 maxillary second molars (n = 16). Minimal dentine thickness related to the MB3 canal at the coronal third was smaller than that of the MB1 canal. A complex internal anatomy comprising 13 different root canal configurations was observed. A high number of independent MB3 orifices at the pulp chamber floor was observed in the first molars (7 out of 10 teeth), while most of the specimens (n = 14) showed a confluent anatomy of the MB3 canal. A varied number of accessory canals and foramina were observed. At the apical third, isthmus could be observed in 6 specimens, while an independent MB3 foramen was present in 37.5% of the MB roots. CONCLUSIONS: MB3 canal is a rare anatomical variation present in maxillary first and second molars. Its presence can be associated to a complex internal anatomy of the MB root which includes the presence of isthmuses and multiple accessory canals and foramina at the apical third, but also a thin dentine thickness at the coronal third and a confluent anatomy of the MB3 with the other main canals.

Antifungal activity of 4% chlorhexidine and 2% sodium hypochlorite against Candida albicans biofilms.

The purpose of this study was to determine the antifungal efficacy of 4% chlorhexidine (CHX) and 2% sodium hypochlorite (NaOCl) on 24-hour Candida albicans biofilms. Candida albicans biofilms were developed on acrylic resin specimens, which were randomly assigned to 1 of 5 groups (n = 3 per group) exposed to 1 mL of 4% CHX for 2, 4, 6, 8, or 10 minutes. Biofilms in contact with 1 mL of distilled water or 2% NaOCl for 10 minutes were used as positive and negative controls (n = 3 per group), respectively. Specimens were analyzed with confocal laser scanning microscopy and a cell viability assay technique. The biovolume of the live subpopulation of the biofilm was calculated with biofilm image analysis software. Statistically significant differences (P < 0.05) in the biovolume of surviving cells were found among the positive control group and the 4-, 6-, 8-, and 10-minute experimental periods. The biovolumes found after 6-10 minutes of exposure to chlorhexidine were significantly different (P < 0.05) from the biovolume after 2 minutes of exposure. The most effective decrease of the biovolume was found after the use of the negative control (sodium hypochlorite) solution. Exposure to 10 minutes of 2% NaOCl removed fungal cells more effectively than all the experimental groups (P < 0.05). The 4% CHX solution showed an antifungal activity against C albicans biofilms but failed to decrease the biovolume to the levels of 2% NaOCl, which eliminated viable cells more effectively and appeared to be more effective in disrupting the attached biofilms.

An In Vitro Evaluation of the Antimicrobial Efficacy of a Novel Irrigant Using Next-Generation Sequencing.

INTRODUCTION: To evaluate the antimicrobial activity of Triton irrigation versus 4% sodium hypochlorite (NaOCl) utilizing a direct contact test and an extracted tooth model. METHODS: In the first experiment, a direct contact test was conducted to compare bacterial DNA removal and microbial diversity changes following irrigation with 4% NaOCl or Triton. Hydroxyapatite and dentin discs were inoculated with subgingival human-derived dental plaque for 2 weeks utilizing the Center for Disease Control biofilm reactor and subsequently challenged with the root canal irrigants for 5 minutes. In the second experiment, teeth contaminated with a multispecies biofilm (n = 24) were assigned into two treatment groups, NaOCl or Triton irrigation. Samples were obtained for quantitative real-time polymerase chain reaction and next-generation sequencing analysis before and after instrumentation. The Shannon and Chao1 indices were used to measure alpha diversity. The Bray-Curtis dissimilarity and ANOSIM was used to measure beta diversity. Differences in abundances of genera were evaluated using Kruskal-Wallis test with Bonferroni corrections. RESULTS: The direct contact test revealed no significant differences in the bacterial load based on 16S rRNA gene molecules/µL, reads, or differences in the Shannon index among groups. In the extracted tooth model, a bacterial load reduction of log10 3.08 ± 0.69 and 2.76 ± 0.91 were found for NaOCl and Triton, respectively (P = .348). Next-generation sequencing showed fewer reads, lower Chao1, and beta diversity values when pretreatment and post-treatment samples were assessed in both experimental groups (P < .0001). The Kruskal-Wallis analysis found that 17 genera of bacteria were over-represented in minimal values in the Triton post-treatment group, 14 of these genera represented less than 1% of the microbial community. CONCLUSIONS: Both irrigants had limited antimicrobial activity in the direct contact test. When used in conjunction with mechanical instrumentation both irrigants were able to reduce the bacterial DNA load and diversity in comparison with pretreatment communities. The NaOCl irrigation, followed by ethylenediaminetetraacetic acid flush, was more effective in decreasing DNA counts from low-abundance organisms.

The antimicrobial effect of new and conventional endodontic irrigants on intra-orally infected dentin.

OBJECTIVES: To evaluate if the incorporation of antimicrobial compounds to chelating agents or the use of chelating agents with antimicrobial activity as 7% maleic acid and peracetic acid show similar disinfection ability in comparison to conventional irrigants as sodium hypochlorite or iodine potassium iodide against biofilms developed on dentin. MATERIALS AND METHODS: The total bio-volume of live cells, the ratio of live cells and the substratum coverage of dentin infected intra-orally and treated with the irrigant solutions: MTAD, Qmix, Smear Clear, 7% maleic acid, 2% iodine potassium iodide, 4% peracetic acid, 2.5% and 5.25% sodium hypochlorite was measured by using confocal microscopy and the live/dead technique. Five samples were used for each irrigant solution. RESULTS: Several endodontic irrigants containing antimicrobials as clorhexidine (Qmix), cetrimide (Smear Clear), maleic acid, iodine compounds or antibiotics (MTAD) lacked an effective antibiofilm activity when the dentin was infected intra-orally. The irrigant solutions 4% peracetic acid and 2.5-5.25% sodium hypochlorite decrease significantly the number of live bacteria in biofilms, providing also cleaner dentin surfaces (p < 0.05). CONCLUSIONS: Several chelating agents containing antimicrobials could not remove nor kill significantly biofilms developed on intra-orally infected dentin, with the exception of sodium hypochlorite and 4% peracetic acid. Dissolution ability is mandatory for an appropriate eradication of biofilms attached to dentin.

Load capacity and fracture modes of instrumented tooth roots under axial compression.

OBJECTIVE: To investigate the influences of root canal instrumentation on the load capacity and fracture modes of tooth roots under axial compression by performing mechanical tests and finite element analysis (FEA). METHODS: Thirty bovine incisor roots were trimmed into cylinders of 5.0 mm diameter. They were randomly divided into two groups, one with root canals instrumented to ∼2.0 mm in diameter, and one without instrumentation. The specimens were fractured under uniaxial compression at a crosshead speed of 0.2 mm/min, and then micro-CT was used to reveal the fracture patterns in three dimensions. FEA was further performed, using the extended finite element method (XFEM), to compare the compression-induced stress distributions and the initiation and propagation of root fractures in both groups. RESULTS: The mean fracture load of the non-instrumented group (2334 ± 436 N) was statistically significantly higher than that of the instrumented group (1857 ± 377 N) (p < 0.01). Three types of root fractures were identified according to the path and length of the cracks: end-face crack, partial-length crack, and full-length crack. As to the fracture modes, the incidence of partial-length root fracture was the highest in both groups (60% for the non-instrumented group and 53.3% for the instrumented group), followed by that of full-length fracture (26.7% and 40%, respectively) and then end-face fracture (13.3% and 6.7%, respectively). The percentage of full-length fracture was slightly higher in the instrumented group. FEA showed that the compression induced higher Tresca stresses but lower maximum principal stresses in the canal walls of the instrumented group. The XFEM simulations predicted that the fracture of both groups initiated from the outer root surface near an end face and propagated axially to the middle third of the root and radially towards the root canal. These numerical results agreed well with our experimental findings. SIGNIFICANCE: Within the limitation of this study, it was found that root canal instrumentation could significantly decrease the load capacity of tooth roots and potentially increase their susceptibility to full-length root fracture under uniaxial compression.

Comparative study of cone beam computed tomography and intraoral periapical radiographs in diagnosis of lingual-simulated external root resorptions.

BACKGROUND: Owing to a lack of symptoms and difficult visualization in routine intraoral radiographs, diagnosis of external root resorptions can be challenging. AIM: The goal of this study was to compare two image acquisition methods, intraoral radiographs and cone beam computed tomography (CBCT), in the diagnosis of external resorption. MATERIAL AND METHODS: Thirty-four maxillary and mandibular bicuspids were divided into three groups. Perforations measuring 0.3 and 0.6 mm in diameter and 0.15 and 0.3 mm in depth, respectively, were made on the lingual root surfaces in thirty teeth, and four were used as controls. Next, teeth were mounted on an apparatus and radiographed at mesial, distal, and orthoradial angulations. CBCT images were also taken. The analysis of the intraoral radiographic and tomographic images was carried out by two experts using standardized scores. Data were then compared statistically. RESULTS: A strong agreement between the examiners was observed in both diagnosis methods, the intraoral radiographic (r = 0.93) and the tomographic analysis (r = 1.0). Tomography had higher statistically significant detection values than intraoral radiography (P < 0.05). In intraoral radiographs, the detection was significantly greater (P < 0.05) in the mandibular bicuspids, compared with their maxillary counterparts. The ability to detect 0.6-mm perforations by intraoral radiography was significantly higher than that of 0.3-mm perforations (P < 0.05). CONCLUSION: Cone beam computed tomography showed better diagnostic ability compared with intraoral radiography, regardless of the tooth or the dimensions of the resorption evaluated.

The effect of rotary instrumentation on dentin thickness in the danger zone of the MB2 canal of maxillary first molars.

The aim of this study was to measure the initial and remaining dentin thickness in the danger zone of the second mesiobuccal (MB2) canal of maxillary first molars after rotary instrumentation using cone beam computed tomography (CBCT) imaging. After determining initial dentin thickness, each sample was subjected to a standardized protocol of rotary instrumentation files: ProTaper Gold Sx Orifice Opener (maximum depth of 7 mm); Vortex Blue 15.04, 20.04, 25.04, ProTaper Gold S1, S2, F1, F2, and finally Vortex Blue 30.06. Subsequent CBCT measurements were made to compare changes in remaining dentin thickness in comparison to initial presentation. Preoperative dentin thickness in the danger zone had a mean of 0.82 ± 0.17mm. Significant levels of dentin removal in the danger zone were noted after all instrumentation groups when compared to the pre-instrumentation mean (Sx P < 0.001, 25.04 P < 0.0006, F2 P < 0.0001, 30.06 P < 0.0001). It was concluded that a thin area of dentin exists along the distal wall of the MB2 (danger zone) from the furcation to 4 mm apically.