Microbiota association and profiling o 1 fgingival sulci and root canals of teeth with primary or secondary/persistent endodontic infections.

INTRODUCTION: Microbiota associated with primary (PEI) and secondary/persistent (SPEI) endodontic infections must be characterized to elucidate pathogenesis in apical periodontitis and bacterial biomarkers identified for diagnostic and therapeutic applications. METHODS: This study analyzed the microbial community profiles of root canals and gingival sulci (sulcus-E) for teeth with PEI (n = 10) or SPEI (n = 10), using the Illumina MiSeq platform. Bacterial samples from gingival sulci (sulcus-C) of healthy contralateral teeth served as controls. RESULTS: There were 15 phyla, 177 genera, and 340 species identified. The number and diversity of bacteria in root canals did not differ significantly between PEI and SPEI. Proteobacteria, Firmicutes, Fusobacteria, Bacteroidetes, and Actinobacteria were the dominant phyla in both groups. At the genus level, Lancefieldella, Bifidobacterium, Stomatobaculum, and Schaalia were enriched in root canals with SPEI. Of significance, Lancefieldella was observed in both root canals and sulcus-E of teeth with SPEI. At the species level, Neisseria macacae, Streptococcus gordonii, Bifidobacterium dentium, Stomatobaculum longum, and Schaalia odontolytica were increased significantly in root canals with SPEI compared to PEI. Oribacterium species, Streptococcus salivarius, Lancefieldella parvula, Prevotella denticola, and Oribacterium asaccharolyticum were more abundant in sulcus-E of teeth with SPEI compared to PEI. CONCLUSIONS: There were distinctive and differing predominant bacterial species associated with the root canals and gingival sulci between teeth with PEI and SPEI. Specific bacteria identified in sulcus-E and root canals of teeth with SPEI could serve as non-invasive diagnostic biomarkers for detecting SPEI.

3D finite element analysis of stress distribution on the shape of resected root-end or with/without bone graft of a maxillary premolar during endodontic microsurgery.

Background/purpose: Apical root resection pattern affects the stress distribution behavior in the apical region of the resected tooth. The purpose of the study was to compare the biomechanical responses of resected teeth between endodontic microsurgery (horizontal resection) and targeted endodontic microsurgery (round resection). Materials and methods: Five different models were developed. The basic model without resection (NR) was regarded as the control model, and the others involved: horizontal resection without bone grafting (HN), horizontal resection with bone grafting (HG), round resection without bone grafting (RN), and round resection with bone grafting (RG) models. A static load of 100 N was applied to the buccal and palatal cusps of all the teeth in a 30° oblique direction. The maximum von-Mises stress and tooth displacement values were analyzed and compared. Results: Both the HN and RN models exhibited lower stress distribution values on bone compared with the NR (control) model. Regarding maximum stress distribution at the root apex, the stress value of the RN model was slightly higher compared to the HN model, whereas the RG model displayed a slightly lower stress value in comparison with the HG model. For maximum tooth displacement value, there were no significant differences between the HN and RN models, as well as the HG and RG models. Conclusion: The round resection pattern had comparable stress distribution behaviors at the root apex and tooth displacement values with the horizontal resection pattern. Targeted endodontic microsurgery might provide better biomechanical response of the resected tooth after root-end resection.

Endodontic Microsurgery Outcomes over 10 Years and Associated Prognostic Factors: A Retrospective Cohort Study.

INTRODUCTION: This retrospective cohort study aimed to evaluate long-term healing outcomes (10-17.5 years) after contemporary endodontic microsurgery (EMS) and identify the associated prognostic factors. METHODS: Clinical and radiographic data of an EMS cohort (2006-2013) from the electronic database of the dental hospital were reviewed retrospectively by 2 independent examiners to determine their survival and healing outcomes, and potential prognostic factors were analyzed by Cox proportional hazards regression and logistic regression (α = 0.05). RESULTS: Through strict inclusion and exclusion criteria and 721 EMS-treated teeth in the cohort, 309 (42.9%) were included (male = 35.0%; female = 65.0%; age = 45.83 ± 15.53 years) with a mean final follow-up of 152.26 ± 26.37 months (range, 120-211 months; median = 148 months). Clinical and radiographic assessments found an 80.5% 10-year survival rate with 63.4% of success. Collectively, tooth type, tooth mobility, preoperative lesion size, clinical crown-to-root ratio, and crown restorations at follow-up were significantly associated with long-term success and survival over 10 years. CONCLUSIONS: The preoperative status and condition of the tooth including its alveolar bone support and adequate full-crown restorations may be relevant prognostic determinants of success and survival after EMS over time.

Stress Distribution on Trephine-Resected Root-end in Targeted Endodontic Microsurgery: A Finite Element Analysis.

INTRODUCTION: This study aimed to determine if stress distribution from occlusal loads after targeted endodontic microsurgery (TEMS) differed for trephine-resected flat and curved root-ends, with and without bone graft. METHODS: Finite element analysis models were constructed from cone-beam computed tomography data of a TEMS-treated maxillary central incisor. Models included flat and curved resected root-ends, with and without apical bone graft, and normal or root canal filled controls. In centric occlusion, axial force was directed on mesial and distal lingual marginal ridges at 120° angle. For lateral excursion, additional mesiodistal forces were applied from centric occlusion. For edge biting, axial force was directed on the incisal edge. Under occlusal loads, stress distribution patterns on tooth and root-end circumference were analyzed. RESULTS: In normal and root filled controls, occlusal stress was distributed on labial and palatal root surfaces, concentrated in the labial cervical area, and maximized at the apex. For resected root-ends, occlusal loads concentrated stress on the labial cervical area. With bone graft, maximum stress concentration shifted to the apex, which implied stress relief and dispersion from the cervical root area. Stress patterns on the root-end were more widely spread in models with apical bone graft, whereas curved root-end showed stress concentrating arc especially when without apical bone support. The mean stress values on root-end circumference were significantly higher in curved than flat root-end (P < .05), especially with apical bone support (P < .05). CONCLUSIONS: Occlusal stress patterns on a maxillary central incisor were markedly affected by root-end resection configuration and apical bone support. Trephine-resected curved root-end had stress pattern concentrated on its circumference. Curved and flat root-ends had labial cervical stress that was relieved by bone graft. TEMS resected root-ends should be flattened and bone grafted to disperse stress from occlusal loads.

Evolutionary trends in human mandibles and dentition from Neolithic to current Chinese.

OBJECTIVES: This study aimed to systematically compare Neolithic mandibles and dentition with modern Chinese, and thereby discern human evolutionary trends. MATERIALS AND METHODS: Neolithic remains of 45 adults unearthed at the Zhangqiu Jiaojia site, were compared with clinical records of 48 patients at Shandong University. All samples were scanned by cone beam computed tomography (CBCT) using identical parameters. Digital imaging and communications in medicine images were collected, three-dimensional models reconstructed, and morphology measurements obtained using Mimics software. RESULTS: Neolithic mandibles were significantly larger in their vertical and sagittal dimensions (P < .05), but similar in horizontal width to modern humans. Their condyles had fewer bird beak and crooked finger shaped morphologies than modern mandibles (P < .05). Neolithic third molars were more often erupted than in modern mandibles, and their Position A, class I and II, and vertical impactions were more common (P < .05). Neolithic teeth were generally smaller in crown lengths and in cross-sectional areas, than their modern counterparts (P < .05). CONCLUSIONS: Neolithic mandibles were larger than modern humans, who have refined diets and mandibular atrophy. They had fewer abnormally shaped condylar morphologies, and much fewer third molar impactions than in modern humans. However, modern dentition particularly their crowns are larger, likely through genetic influx from migrations.

Root canals shaped by nickel-titanium instrumentation with automated computerized numerical control systems.

BACKGROUND: To investigate the efficacy of a nickel-titanium (NiTi) file with an automated computerized numerical control (CNC) system for root canal shaping. METHODS: The movement of the automated device and the insertion angle were investigated. In Experiment 1, simulated resin root canals were randomly divided into four groups (n = 20): manual downward movement using a handpiece (Group 1), vertical downward movement by CNC (Group 2), reciprocating up and down movement by CNC (Group 3), and spiral up and down movement by CNC (Group 4). In Experiment 2, five different insertion angles of the NiTi file were evaluated (n = 20). Four parameters were used to evaluate the shaping ability: change in the working length, central axis offset, curvature variation, and preparation time. Groups were compared using one-way analysis of variance (ANOVA) with significance was set at P < 0.05. RESULTS: The change in central axis position in the curved part of the root canal was found to be smaller in Group 4 than in other groups (P < 0.05). The curvature changes and preparation time of Groups 1 and 4 were significantly reduced compared with Groups 2 and 3 (P < 0.05). The variation in working length and curvature in the 5° insertion angle group was significantly smaller than in the other groups (P < 0.05). CONCLUSIONS: A spiral up and down movement, controlled by the CNC machine, and 5° insertion angle, maintained original root canal shape more precisely than other methods.

Characterization of Histopathology and Microbiota in Contemporary Regenerative Endodontic Procedures: Still Coming up Short.

INTRODUCTION: This study aimed to investigate microbiota and the histopathology of infected immature teeth microenvironments after disinfection with calcium hydroxide, triple antibiotic paste, and a synthetic antimicrobial peptide (synthetic human beta-defensin-3-C15) for regenerative endodontic procedures (REPs). The null hypothesis was that there is no difference among intracanal medications on disinfection in REPs. METHODS: Pulp necrosis and periapical lesions were induced in immature beagle dog premolars. Block randomized teeth were uninfected (negative control, n = 6), left infected (positive control, n = 6), or medicated with a disinfectant (n = 6/group). After disinfection (2 weeks), teeth were reaccessed, irrigated with 17% EDTA, blood clot induced, sealed with ProRoot MTA (Dentsply Tulsa Dental, Tulsa, OK), and restored with resin-modified glass ionomer. Animals were monitored radiographically and euthanized (12 weeks) for histopathologic and metagenomic analyses. RESULTS: REP-treated roots showed radiographic repair of periapical radiolucency (67.65%, 23/34), continued root development (73.53%, 25/34), and apical closure (70.59%, 24/34) regardless of the disinfectant used (P > .05). Canal microenvironments histologically devoid of bacteria contained new mineralized and pulp-like tissues in characteristic patterns that varied by disinfectant. Next-generation sequencing (16S ribosomal RNA) identified Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes as dominant phyla of microbiota in immature teeth. Infection-induced teeth showed changes in diversity and richness of microbiota from negative controls. Compared with positive controls, all treated teeth exhibited depleted operational taxonomic units, with lower phylogenic diversity from synthetic human beta-defensin-3-C15-treated teeth. CONCLUSIONS: There were no differences among the medicaments investigated in radiologic treatment outcomes, but disinfectants in REPs showed altered microbiota from normal and diseased immature teeth with different histologic patterns of regeneration.

Internal Resorption of Multiple Posterior Teeth in a Patient Diagnosed with Hyperparathyroidism: A Case Report.

This case reports a 46-year-old man with end-stage renal disease and internal resorption (IR) affecting multiple posterior teeth. IR involves odontoclast's removal of dentin within pulp chambers and root canal space. Typically, asymptomatic until detected on radiographs, IR is relatively rare, so the etiology and pathogenesis are poorly understood. Patients' radiographs with cone-beam computed tomography revealed extensive IR in multiple premolars and all remaining molar teeth. Blood tests and hormonal assay measured elevated phosphorus and parathyroid hormone levels consistent with secondary hyperparathyroidism. Histopathology showed highly vascularized and inflamed pulp tissues with numerous odontoclast-like multinucleated giant cells along dentinal walls and in resorption lacunae. Immunohistochemistry showed that multinucleated giant cells and adjacent mononuclear precursors stained strongly for tartrate-resistant acid phosphatase like osteoclasts. Extraction of crown-root fractures and endodontic treatment with crown restorations for all IR teeth effectively arrested disease progression at 9 months' follow-up. Elevated parathyroid hormone from secondary hyperparathyroidism that promotes bone osteoclast activity may also stimulate odontoclasts causing IR.

Guidance for dental treatment of patients with disabilities during COVID-19 pandemic.

People with disabilities are challenged managing their oral hygiene and more often burdened with oral diseases. They often require immediate dental treatment for severe pain and greater precautions are needed to cope with COVID-19. The potential for COVID-19 infection can be relatively high in patients with disabilities due to concomitant systemic diseases, unique individual circumstances, relationship with caregivers and the living conditions of long-term care facilities, which make them vulnerable to the virus. For behavior management, dental treatment is often provided under general anesthesia with meticulous preoperative evaluation and the use of high-quality viral filters. In response to COVID-19, additional considerations should be taken for dental procedures on patients with special needs. These recommendations for dental treatment of the disabled are based on 6 months of authors COVID-19 pandemic experience.

Effect of mineral trioxide aggregate plug location on root development in regenerative endodontic procedure.

This retrospective study investigated the effect of mineral trioxide aggregate (MTA) plug location on treatment outcome and root maturation after regenerative endodontic procedures (REP) in immature permanent teeth. Thirty-three roots (n = 33) in cohort that underwent REP consistently according to AAE guideline were included to trace radiographic changes for the root and canal dimensions. Based on intraoral radiographs, roots were divided into two groups depending on the location of MTA plug within whole root length: coronal group (n = 14), within the upper half; apical group (n = 19), within the lower half. Periapical radiographs were standardized to assess treatment outcomes and root maturation including root development stages and digital measurements on the change ratios of root length, apex width, radiographic root area (RRA), modified RRA (mRRA), and periapical rarefaction area. The data were statistically analysed using the Mann-Whitney test. The patients' average age was 11 years and 10 months, with no significant between-group difference in sex. Premolars were the most prevalent tooth type (62.1%), followed by incisiors and molars. Pre-existing symptoms and signs subsided within 6 months in all cases. The teeth showed similar radiographic root development in both groups (P > 0.05). However, mRRA increase ratio was significantly higher in apical group than that in coronal group at early (< 6 months) and late (< 24 months) periods of follow-up (P < 0.05). Significant changes of root development stage were observed at early period for apical group and at late period for coronal group (P < 0.05). All the observed cases showed continuing root development after REP. Significant changes in root developments occurred at different follow-up periods according to the location of MTA plugs.

Sealing Ability of AH Plus and GuttaFlow Bioseal.

The objective of root canal obturation is to achieve a fluid-tight seal. Recently, GuttaFlow bioseal (GB), a root canal sealer composed of polydimethylsiloxane, gutta-percha particles, and bioactive glass ceramics, has been developed, to enhance the sealing ability of root canal filling material. The objective of this study was to assess the sealing ability of GB using a subnanoliter-scaled fluid-flow measuring device and to compare with that of AH Plus (AH). The fluid flow in root canal-filled teeth using either gutta-percha cone (GP) with AH (GAR; n = 10) or GP with GB (GBR; n = 10) and in GP inserted in AH blocks (GA; n = 10) or GP inserted in GB blocks (GB; n = 10) was measured. In addition, fluid flow in sealer blocks of AH (A; n = 10) and GB (B; n = 10), which served as negative controls, was measured. Root canal-filled teeth using GP without any sealer (GR) acted as positive controls (n = 10). The leakage was obtained by calculating the volume of moved water by time (s), after stabilization of the fluid flow was achieved. Statistical analysis was performed using the Kruskal-Wallis test and Mann-Whitney U-test with Bonferroni correction. A p value less than 0.00238 (0.05/21) was considered significantly different. The mean leakages (nL/s) in the groups are as follows: GAR, 0.0958 ± 0.0543; GBR, 0.0223 ± 0.0246; GA, 0.0644 ± 0.0803; GB, 0.0267 ± 0.0182; A, 0.0055 ± 0.0057; B, 0.0052 ± 0.005; and GR, 0.2892 ± 0.3018. The mean leakage in the GBR group was lower than that in the GAR group (p = 0.001), while the mean leakages in the GA and GB groups were not significantly different. GuttaFlow bioseal can be useful in single-cone obturation technique.

Candida albicans Virulence Factors and Pathogenicity for Endodontic Infections.

Candida albicans (C. albicans) is the fungus most frequently isolated from endodontic root canal infections. Although recognized by dental pulp and periradicular tissue cells that elicit immune responses, it eludes host defenses and elicits cell death. Then, C. albicans binds tooth dentin, forms biofilms, and invades dentinal tubules to resist intracanal disinfectants and endodontic treatments. Insensitive to most common medicaments, it survives sequestered within biofilms and intratubular dentin. Thus, C. albicans has been associated with cases of persistent or refractory root canal infections. Its treatment strategies may require alternative intracanal irrigants, intracanal medicaments such as chlorhexidine gel or human beta defensin-3 (HBD3), Ca-Si-based obturating materials, and microsurgical procedures.

Prognostic Factors of Long-Term Outcomes in Endodontic Microsurgery: A Retrospective Cohort Study over Five Years.

The aim of this study was to analyze the long-term outcomes of endodontic microsurgeries in a cohort and identify their association with prognostic factors. A cohort of endodontic microsurgeries followed up periodically with complete clinical and radiographic records for at least 5 years were reviewed retrospectively. Their survival and healing status and profile characteristics were analyzed by Pearson chi-square test and logistic regression (α = 0.05) to identify prognostic factors that influenced outcomes. Of 652 cases in the cohort, 225 (34.5%) were included. The mean follow-up period was 90.4 months (range, 60-168 months). The long-term success rate was 80.5%, and the 5-year survival rate was 83.5%. Logistic regression showed higher success in anteriors compared to molars (OR = 5.405, (95% CI, 1.663-17.571; p = 0.005)) and in teeth with crown restorations (OR = 10.232, (95% CI, 3.374-31.024; p < 0.001)). Conversely, lower success was found in teeth with periodontal disease (OR = 0.170, (95% CI, 0.032-0.900; p = 0.037)) and maxillary sinus involvement (OR = 0.187, (95% CI, 0.035-0.994; p = 0.049)). Endodontic microsurgery has a highly favorable long-term outcome. Tooth position, crown restoration, periodontal disease, and maxillary sinus involvement were identified as main prognostic factors.

Mandibular molar C-shaped root canals in 5th millennium BC China.

OBJECTIVE: The aim of this study was to analyze the occurrence and variations in C-shaped canals in ancient Chinese teeth and compare the differences of these features between ancient and age-matched modern populations. DESIGN: Approximately 5000-year-old craniofacial bone remains were collected from the fossils of 38 individuals (total: 68 mandibular second molars) excavated from the Jiaojia site. The control group comprised of an equal number of randomly selected modern samples. We used cone-beam computed tomography to scan the mandible along the apex-crown axis and analyzed the canal morphology, based on Fan's categorization criterion, at 2 mm, 5 mm, and 8 mm to the apical level. Grooves on the lingual and buccal sides were also recorded. RESULTS: The proportion of C-shaped roots among ancient samples on the left and right sides were 48.57 % (17/35 teeth) and 54.55 % (18/33 teeth), respectively, and 51.47 % (35/68 teeth) in the total sample. Conversely, in the control group, 44.12 % (15/34) and 38.24 % (13/34) occurred on the left and right sides, respectively, and 41.18 % (28/68) in the total sample. Among the C-shaped canals from the Jiaojia site samples, the classification type changed between two adjacent levels in 84.31 % of samples. Approximately 35 (51.5 %) teeth had a fused root, 20 (29.41 %) had one shallow buccal and one deep lingual groove. The occurrence of C-shape variation was not significantly correlated with time (p＞0.05). CONCLUSIONS: This study identified a high rate of C-shaped root canals among individuals of Jiaojia who lived approximately 5000 years ago.

Effect of Pretreatment and Activation Mode on the Interfacial Adaptation of Nanoceramic Resin Inlay and Self-adhesive Resin Cement.

OBJECTIVES: The first objective of this study was to determine if the luting material used for resin nanoceramic inlay affects interfacial adaptation. The second was to investigate whether pretreatment and the adhesive curing method before cementation affects interfacial adaptation. The final objective was to compare activation modes of luting material. METHODS: Class I cavities were prepared on extracted human third molars. Resin nanoceramic inlays were fabricated using Lava Ultimate CAD/CAM block (3 M). For the control groups, inlays were cemented using Panavia V5 (Kuraray Noritake). For the experimental groups, teeth were randomly divided into five experimental groups with four subgroups using different self-adhesive cements (SACs). Cement in Group I was dual-cured without pretreatment. In Group II, the cement was dual-cured after polyacrylic acid treatment of the tooth cavity. In Groups III and IV, the cement was dual-cured after universal dentin adhesive treatment with pre-cure and co-cure methods. In Group V, the inlay was cemented in self-cure mode. After thermocycling, interfacial adaptation at the inlay-tooth interface was measured using swept-source optical coherence tomography (SS-OCT) imaging. Finally, polymerization shrinkage strain of the luting material was measured and compared. RESULTS: Interfacial adaptation differed depending on the luting material. After application of a universal adhesive, some subgroups showed improved interfacial adaptation. Interfacial adaptation and polymerization shrinkage strain differed significantly depending on activation mode. SIGNIFICANCE: Interfacial adaptation for a resin nanoceramic inlay can differ according to the type of SAC and activation mode. For some SACs, application of a universal adhesive before cementation improves interfacial adaptation.

Lipoteichoic acid of Enterococcus faecalis interferes with Porphyromonas gingivalis lipopolysaccharide signaling via IRAK-M upregulation in human periodontal ligament cells.

Periodontitis is a chronic inflammatory disease of the gum caused by infection with multispecies oral bacteria. Since the periodontopathic bacteria, Porphyromonas gingivalis together with Enterococcus faecalis are frequently detected in patients with a severe form of periodontitis, interactions between their virulence factors might play an important role in progression of the disease. P. gingivalis and E. faecalis possess lipopolysaccharide (Pg.LPS) and lipoteichoic acid (Ef.LTA), respectively, as the major virulence factors inducing inflammatory responses. However, the combinatorial effect of these virulence factors on chemokine expression was poorly understood. Here, we examined the interaction between Ef.LTA and Pg.LPS on IL-8 induction in human periodontal ligament (PDL) cells. Pg.LPS, but not Ef.LTA, induced IL-8 expression at both mRNA and protein levels, which was suppressed in the presence of Ef.LTA. Although Ef.LTA and Pg.LPS could stimulate Toll-like receptor 2 (TLR2), Ef.LTA did not interfere with Pg.LPS induced-TLR2 activation. However, Ef.LTA decreased Pg.LPS-induced phosphorylation of ERK, JNK, and p38 kinase. Furthermore, Ef.LTA suppressed Pg.LPS-induced IL-8 promoter activity as well as AP-1, NF-IL6 and NF-κB transcription factors, which are indispensable for IL-8 expression. Interestingly, Ef.LTA enhanced only IL-1 receptor-associated kinase-M (IRAK-M) expression among the tested negative regulators of TLR intracellular signaling cascades in the presence of Pg.LPS. In addition, silencing IRAK-M restored the decreased IL-8 expression by Ef.LTA in the presence of Pg.LPS. Collectively, these results suggest that Ef.LTA inhibits Pg.LPS-induced IL-8 expression in human PDL cells via inducing the expression of a negative regulator of TLR signaling cascades, IRAK-M.

Morphological measurements of two separate mesiobuccal canals in maxillary first molars using micro-computed tomography.

OBJECTIVES: To obtain radicular measurements of two separate mesiobuccal (MB) root canals in maxillary first molars using micro-computed tomography (µCT) with customized software. MATERIALS AND METHODS: Human maxillary first molar MB roots (N = 36) with two separate canals (MB1, MB2) and apical foramina were scanned by µCT and analyzed with Kappa2 software to reconstruct three-dimensional (3D) surface models of roots and canals. These models were sectioned at 0.1 mm intervals perpendicular to the central axis of each canal. Canal widths, 3D curvatures, and surrounding dentine thicknesses were measured concurrently on each section. Dentine thicknesses were analyzed statistically for differences between each direction and the different levels of both canals. RESULTS: Dentine walls around MB1 were thicker than MB2 (p < 0.05). Thinnest dentine was most often located at disto-inside direction in both canals. Canal widths were significantly smaller in MB2 than MB1 (p < 0.01). Apical constrictions were smaller (p < 0.05) and further (p < 0.05) from the apex in MB2 than MB1. Canal curvatures were greatest in the apical third of both canals (p < 0.001), and they were greater in MB2 than MB1 (p < 0.05). CONCLUSIONS: MB2 canals had shorter lengths, smaller widths, and more severe curvatures and were surrounded by thinner dentine walls. In MB2, apical constrictions were between 1 and 2 mm from the apex, compared to about 1 mm for MB1. CLINICAL RELEVANCE: These detailed measurements and in-depth 3D analyses of maxillary first molar MB roots with two separate canals and apical foramina provide morphologic references for root canal therapy.

Lactobacillus plantarum lipoteichoic acid disrupts mature Enterococcus faecalis biofilm.

Apical periodontitis is caused by biofilm-mediated root canal infection. Early phase oral bacterial biofilms are inhibited by Lactobacillus plantarum lipoteichoic acid (Lp.LTA). However, mature biofilms that develop over 3 weeks are more resistant to traditional endodontic medicaments. Therefore, this study examined the effectiveness of Lp.LTA on disrupting mature Enterococcus faecalis biofilms, and on enhancing the effects of endodontic medicaments. LTA was purified from L. plantarum through butanol extraction followed by hydrophobic and ion-exchange chromatography. E. faecalis biofilms were formed over 3 weeks on glass bottom dishes and in dentin blocks obtained from human single-rooted premolars. These mature biofilms were treated with or without Lp.LTA for 1 h, followed by additional treatment with either chlorhexidine digluconate (CHX), calcium hydroxide (CH), or triple antibiotics for 24 h. Biofilms on glass were live/dead stained and quantified by ZEN through confocal laser microscopy. Bio-films in dentin were fixed, sputter coated and analyzed by ImageJ with scanning electron microscopy. Preformed E. faecalis mature biofilms on the culture dishes were dose-dependently disrupted by Lp.LTA. Lp.LTA potentiated the effects of CHX or CH on the disruption of mature biofilm. Interestingly, CHX-induced disruption of preformed E. faecalis mature biofilms was synergistically enhanced only when pre-treated with Lp.LTA. Furthermore, in the dentin block model, Lp.LTA alone reduced E. faecalis mature biofilm and pre-treatment with Lp.LTA promoted the anti-biofilm activity of CHX. Lp.LTA could be an anti-biofilm or supplementary agent that can be effective for E. faecalis-biofilm-induced diseases.

Bending resistance and cyclic fatigue resistance of WaveOne Gold, Reciproc Blue, and HyFlex EDM instruments.

BACKGROUND/PURPOSE: Several single-file systems manufactured using different heat treatment and operated by different kinematics have been released. This study compared the bending resistance and cyclic fatigue resistance of three NiTi files, and examined their phase-transformation behavior. MATERIALS AND METHODS: WaveOne Gold Primary (WOG), Reciproc Blue R25 (RPB), and HyFlex EDM OneFile (HDM) were tested (N = 40/instrument). A vertical load was applied to a point 3 mm from the tip, and the stress was measured until a displacement of 3 mm. Tests were conducted at either room temperature (RT: 22 °C) or body temperature (BT: 37 °C) (n = 10). Cyclic fatigue resistance tests were performed in an artificial canal, which had a curvature angle of 40° and a 5-mm radius. Tests were conducted at either RT or BT (n = 10). Instruments were operated according to the manufacturers' instructions. Test results were analyzed using the Kruskal-Wallis and the Mann-Whitney tests. Additional three instruments of each brand were subjected to differential scanning calorimetry (DSC). RESULTS: At RT the bending resistance of three files were not significantly different. However, at BT the bending resistance of RPB was highest, followed by WOG, and HDM (P < 0.05). At RT, RPB demonstrated the longest fracture time, followed by HDM, and WOG (P < 0.05). At BT, HDM had the longest fracture time, followed by RPB, and WOG (P < 0.05). The WOG, RPB consisted of austenite in a considerable proportion, whereas HDM was mainly martensite state at BT. CONCLUSION: HDM presented superior flexibility and cyclic fatigue resistance at BT.

Effect of autoclave sterilization on cyclic fatigue and torsional fracture resistance of NiTi rotary instruments.

The purpose of this study is to assess the effect of autoclave sterilization on the cyclic fatigue and torsional fracture resistance of ProTaper Universal (PTU), K3XF, HyFlex EDM (EDM), and TF adaptive (TFA). Sixty instruments from each file type were divided into two categories for cyclic fatigue group (CGr) and torsional fracture group (TGr). CGr and TGr were divided into three subgroups, respectively, consisting of ten instruments from each file type. Cyclic fatigue fracture test was performed using artificial canal made of stainless steel, and the mean number of cycles to failure (NCF) were determined. CGr1, the files were tested to establish baseline for NCF; CGr2, the files were tested cyclic fatigue after 10 cycles of autoclave; CGr3, instruments were autoclaved after being cycled to 25, 50, and 75% of corresponding NCF determined in CGr1, followed by cyclic fatigue test. The torsional fracture test was performed without autoclave (TGr1), after 3-cycle autoclave (TGr2), and 7-cycle autoclave (TGr3), respectively, which evaluated maximum torque and angular deflection. NCF, maximum torque and angular deflection were compared using one-way ANOVA with Bonferroni test. Two-way ANOVA was performed to determine the interaction between 'autoclave treatment' and 'type of NiTi file'. EDM showed highest NCF within the same autoclave treatment. TFA presented the lowest maximum torque and the highest angular deflection, and PTU presented the lowest angular deflection. Within the same NiTi file systems, most of NCF, maximum torque and angular deflection of tested files were not significantly influenced by autoclave condition.