Differentiation of parotid pleomorphic adenoma from Warthin tumor using signal intensity ratios on fat-suppressed T2-weighted magnetic resonance imaging.

OBJECTIVE: To investigate the value of magnetic resonance imaging (MRI) signal intensity ratios (SIRs) based on fat-suppressed T2-weighted imaging (FS-T2WI), together with demographic features, MRI anatomical characteristics, and SIRs of histopathological patterns of the tumors, in the differentiation of parotid pleomorphic adenoma (PA) from Warthin tumor (WT). STUDY DESIGN: In total, 90 patients with PA and 56 patients with WT were enrolled in the study. SIRs of tumor to normal parotid gland (SIR-T/P), spinal cord (SIR-T/S), and muscle (SIR-T/M) were calculated. Demographic and radiological features of the 2-patient groups were compared with univariate analysis and multivariate logistic regression analysis. The area under the receiver operating characteristic curve (AUC), sensitivity, and specificity were analyzed to evaluate the utility of SIRs in distinguishing between PA and WT. RESULTS: SIR-T/P exhibited outstanding discriminating ability (AUC = 0.934), SIR-T/S had excellent discrimination (AUC = 0.839), and SIR-T/M showed acceptable discrimination (AUC = 0.728). When SIR-T/P of 1.96 was selected as the cutoff value, sensitivity and specificity were 0.756 and 0.982, respectively. SIR-T/P, age, sex, and number of lesions were identified as independent predictors by multivariate logistic regression analysis. Differences in SIRs between histopathological patterns were significant. CONCLUSION: SIR-T/P based on FS-T2WI is an effective discriminator in the differential diagnosis between PA and WT. Age, sex, and number of lesions provided additional value in differentiation.

Micro-computed tomography analysis of calcium hydroxide delivery efficacy in C-shaped canal system of mandibular second molars.

BACKGROUND: Calcium hydroxide [Ca(OH)2] is widely accepted as a biocompatible interappointment intracanal medicament. This study aimed to analyze the efficacy of Ca(OH)2 placement into the C-shaped canal system of mandibular second molars using the syringe method with and without lentulo spiral utilizing micro-computed tomography (micro-CT). METHODS: Twenty-four extracted mandibular second molars were instrumented and classified into C-shaped floors (n = 12) and non-C-shaped floors (n = 12). Both groups were placed with Ca(OH)2 using the syringe system, then all teeth were scanned and cleaned, and placed with Ca(OH)2 again but with the syringe system followed by lentulo spiral and rescanned. The specimens were scanned using micro-CT to analyze the volume, volume percentage, uncontacted surface area, and uncontacted surface area percentage of Ca(OH)2 with the two delivery methods in the entire canal and at the apical 4 mm of the canal. Mann-Whitney test and Wilcoxon signed-rank test were used to determine the statistical differences among the groups. RESULTS: Syringe administration used in conjunction with lentulo spiral presented lower uncontacted surface area, a lower percentage of uncontacted surface area, larger volume, and a higher percentage of volume than syringe without lentulo spiral (P < 0.05). There was no significant difference between the C-shaped floor group and the non-C-shaped floor group (P > 0.05) in the Ca(OH)2 uncontacted surface area, volume, and percentages at different regions of canals and among different delivery techniques groups. CONCLUSIONS: The lentulo spiral and syringe technique combination can increase the volume and contacted surface area of Ca(OH)2 in the C-shaped canal system of mandibular second molars.

Bacteria debridement efficacy of two sonic root canal irrigant activation systems.

OBJECTIVE: To evaluate the bacteria debridement efficacy of two generations of sonic root canal irrigant activation systems: EndoActivator (Dentsply Sirona), the first generation, and SmartLite Pro EndoActivator, the second generation. METHODS: Instrumented, autoclaved, single-rooted human premolars were inoculated with Enterococcus faecalis (ATCC-29212) for 21 days. The bacteria biofilm-containing teeth were randomly divided into 5 groups (N=8): Group 1: Syringe-side-vented needle (S-N) delivery of saline for 1 min; Group 2: S-N delivery of 2% NaOCl for 1 min; Group 3: S-N delivery of 2% NaOCl for 5 min; Group 4: EndoActivator activation of 2% NaOCl for 1 min; Group 5: SmartLite Pro EndoActivator activation of 2% NaOCl for 1 min. The teeth were evaluated for bacterial reduction using CFU counts, and the percentages of dead bacteria within the dentinal tubules using confocal laser scanning microscopy. RESULTS: Activation of NaOCl with EndoActivator or SmartLite Pro EndoActivator significantly reduced the overall intracanal bacterial load, compared with S-N irrigant delivery (P<0.05), with no significant difference between the two agitation devices (P>0.05). Nevertheless, S-N delivery of 2% NaOCl for 5 min produced better bacteria debridement than either sonic agitation system. Different degrees of bacteria kill were identified in the coronal-middle portions and apical portion of the canal space. CONCLUSION: Delivery time of NaOCl affects the efficacy of bacteria disinfection. Activation for 1 min with the EndoActivator or SmartLite Pro EndoActivator demonstrated comparable canal wall biofilm and intracanal bacteria reduction efficacy when 2% NaOCl was used as irrigant for disinfecting E. faecalis in single-rooted teeth. CLINICAL SIGNIFICANCE: Although the sonic root canal irrigant activation devices investigated do not completely eliminate live bacteria biofilms from the canal space, they help reduce bacteria load during irrigant activation.

Effects of DJK-5 and chlorhexidine on exopolysaccharide volume and pH in oral biofilms.

BACKGROUND: Exopolysaccharides (EPS) are essential constituents of the extracellular matrix within oral biofilms and are significantly influenced by the local microenvironment. This study aimed to investigate the impact of two distinct antimicrobial agents, DJK-5 and chlorhexidine (CHX), on the EPS volume and pH levels in oral biofilms. METHODS: Oral biofilms obtained from two donors were cultured on hydroxyapatite discs for durations of 3 days, 1 week, 2 weeks, 3 weeks, and 4 weeks. Subsequently, these biofilms were subjected to treatment with 10 µg/mL DJK-5 or 2% CHX for 3 min. The impact of these antimicrobial treatments on factors such as the proportion of dead bacterial, in situ pH, and EPS volume within the biofilms was assessed using corresponding fluorescent probes. The examination was carried out utilizing confocal laser scanning microscopy, and the resulting images were analyzed with a focus on the upper and lower layers of the biofilm, respectively. RESULTS: DJK-5 exhibited a more potent bactericidal effect compared to CHX across the 3-day to 4-week duration of the biofilm (P < 0.05). The biofilms were acidic, with the upper layer being less acidic than the lower layer (P < 0.05). Both antimicrobial agents increased the pH, but DJK-5 had a greater effect than CHX (P < 0.05). The volume of EPS was significantly lower in DJK-5 treated biofilms compared to that of CHX, regardless of age or layer (P < 0.05). CONCLUSION: DJK-5 exhibited superior effectiveness in reducing viable bacteria and EPS volume, as well as in raising extracellular pH, as compared to chlorhexidine.

The effect of acidity on the physicochemical properties of two hydraulic calcium silicate-based cements and two calcium phosphate silicate-based cements.

BACKGROUND: Bioceramic cements have been widely used in endodontic treatment. This study aimed to compare the microhardness, elastic modulus, internal microstructure and chemical compositions of Biodentine, WMTA, ERRM Putty, iRoot FS and IRM after exposure to PBS, butyric acid, and butyric acid followed by PBS. METHODS: Specimens of each material were prepared and randomly divided into 5 subgroups (n = 5): subgroup A: PBS (pH = 7.4) for 4 days, subgroup B: PBS (pH = 7.4) for 14 days, subgroup C: butyric acid (pH = 5.4) for 4 days, subgroup D: butyric acid (pH = 5.4) for 14 days, subgroup E: butyric acid for 4 days followed by 10 days in contact with PBS. The surface microhardness, elastic modulus, internal morphologic and chemical compositions of specimens were analyzed. RESULTS: The microhardness and elastic modulus values of all materials were significantly higher in the presence of PBS compared to exposure to butyric acid, with the same setting time (P < 0.01). After 4-day exposure to butyric acid followed by 10-day exposure to PBS, the microhardness values returned to the same level as 4-day exposure to PBS (P > 0.05). Biodentine showed significantly higher microhardness and elastic modulus values than other materials, while IRM displayed the lowest (P < 0.01). CONCLUSION: Biodentine seems the most suitable bioceramic cements when applied to an infected area with acidic pH. Further storage at neutral pH, e.g. PBS reverses the adverse effects on bioceramic cements caused by a low pH environment.

A facile method for rejuvenating the bonding efficacy of root canal sealer-smeared dentine.

OBJECTIVES: To examine the efficacy of glycine powder air-polishing on cleaning root canal sealer-smeared dentine. METHODS: Dentine surfaces were contaminated with a smear of epoxy resin-based sealer or tricalcium silicate-based sealer. The contaminated surfaces were cleaned with saline, 75% ethanol, or air-polishing with glycine powder. Uncontaminated dentine was used as the control. The cleanliness of pulpal floor dentine was examined using scanning electron microscopy and energy dispersive X-ray analysis. The effectiveness of the three cleaning protocols was examined by testing the tensile bond strength of a self-etching adhesive to the decontaminated dentine. Resin infiltration into the dentinal tubules was identified using confocal laser scanning microscopy (CLSM). RESULTS: Morphological examination and elemental analysis indicated that glycine powder air-polishing was more effective in removing the two sealers. Tensile bond strength of adhesive-bonded dentine was significantly reduced when either sealer was cleaned with saline or ethanol. Conversely, air-polishing restored the adhesive strength of the sealer-smeared dentine to the level of the control. Longer and denser resin tags were identified with CLSM when sealers were removed with air-polishing. CONCLUSIONS: Air-polishing with glycine powder was effective in cleaning sealer-smeared dentine, as demonstrated by the rejuvenation of the tensile bond strength of a self-etching adhesive to the decontaminated dentine. CLINICAL SIGNIFICANCE: Glycine powder air-polishing improves the cleanliness of root canal sealer-smeared dentine and rejuvenates adhesive bonding effectiveness.

Predicting the Activity of Oral Lichen Planus with Glycolysis-related Molecules: A Scikit-learn-based Function.

OBJECTIVE: Oral lichen planus (OLP) is one of the most common oral mucosa diseases, and is mainly mediated by T lymphocytes. The metabolic reprogramming of activated T cells has been shown to transform from oxidative phosphorylation to aerobic glycolysis. The present study investigated the serum levels of glycolysis-related molecules (lactate dehydrogenase, LDH; pyruvic acid, PA; lactic acid, LAC) in OLP, and the correlation with OLP activity was assessed using the reticular, atrophic and erosive lesion (RAE) scoring system. METHODS: Univariate and multivariate linear regression functions based on scikit-learn were designed to predict the RAE scores in OLP patients, and the performance of these two machine learning functions was compared. RESULTS: The results revealed that the serum levels of PA and LAC were upregulated in erosive OLP (EOLP) patients, when compared to healthy volunteers. Furthermore, the LDH and LAC levels were significantly higher in the EOLP group than in the nonerosive OLP (NEOLP) group. All glycolysis-related molecules were positively correlated to the RAE scores. Among these, LAC had a strong correlation. The univariate function that involved the LAC level and the multivariate function that involved all glycolysis-related molecules presented comparable prediction accuracy and stability, but the latter was more time-consuming. CONCLUSION: It can be concluded that the serum LAC level can be a user-friendly biomarker to monitor the OLP activity, based on the univariate function developed in the present study. The intervention of the glycolytic pathway may provide a potential therapeutic strategy.

Advances in nanomaterials for the diagnosis and treatment of head and neck cancers: A review.

Nanomaterials (NMs) have increasingly been used for the diagnosis and treatment of head and neck cancers (HNCs) over the past decade. HNCs can easily infiltrate surrounding tissues and form distant metastases, meaning that most patients with HNC are diagnosed at an advanced stage and often have a poor prognosis. Since NMs can be used to deliver various agents, including imaging agents, drugs, genes, vaccines, radiosensitisers, and photosensitisers, they play a crucial role in the development of novel technologies for the diagnosis and treatment of HNCs. Indeed, NMs have been reported to enhance delivery efficiency and improve the prognosis of patients with HNC by allowing targeted delivery, controlled release, responses to stimuli, and the delivery of multiple agents. In this review, we consider recent advances in NMs that could be used to improve the diagnosis, treatment, and prognosis of patients with HNC and the potential for future research.

Covalent Immobilization of Natural Biomolecules on Chitin Nanocrystals.

As a highly crystalline and renewable natural polymer nanomaterial, chitin nanocrystals (ChNCs) have attracted intense interest in the biomedical field. The structure of a ChNC is composed of an acetylglucosamine unit containing two hydroxyl groups and an acetyl group. The acetyl group can be converted to the active amino group through deacetylation, which is under the condition of maintaining the rod-like morphology and high crystalline property and is beneficial for the following modification and potential application. We investigated the relationship between different treatments and varied crystallinities of the modified ChNC, which obtained surface amino groups and aldehyde groups and retained high crystallinity. The natural biomolecules were covalently immobilized on the surface of the ChNC. The etherification was performed based on the hydroxyl groups. Based on the amino groups and the aldehyde groups, the carboxyamine and Knoevenagel condensation reactions were realized on ChNCs. Finally, natural biomolecule-modified ChNCs showed no or low cytotoxicity, antibacterial properties, and high antioxidant properties, which extended their potential biomedical applications.

Size effect of cellulose nanocrystals in cellular internalization and exosome-packaging exocytosis.

With the purpose of investigating the bio-interaction between CNC and cells, the end-fluorescence CNC (FCNC) and surface-adsorbed glucosamine [(g)FCNC] were prepared by the region-selective modification and electrostatic adsorption strategy in this study. The cell growth was arrested in a time dependent manner when incubated with CNC in the low glucose environment. The small-size FCNC was preferred by the cells with the observation of higher affinity. Specifically, the affinity of (g)FCNC to the phagocytic cell RAW264.7 cell and kidney derived cell 293 t was generally increased in response to the "Warburg effect", which on the contrary was observed with the weak effect in the tumor cells. We confirmed the exocytosis of internalized rod-like nanocrystal was achieved by the packaging effect of exosomes. Our results revealed the underappreciated bio-interaction between CNC and different cells, which contributed the evidence of an inspiration for this natural nanomaterial in the cell-level application.

The signature based on seven genomic instability-related genes could predict the prognosis of acute myeloid leukemia patients.

BACKGROUND: Acute myeloid leukemia (AML) is the most common acute blood malignancy in adults. The complicated and dynamic genomic instability (GI) is the most prominent feature of AML. Our study aimed to explore the prognostic value of GI-related genes in AML patients. METHODS: The mRNA data and mutation data were downloaded from the TCGA and GEO databases. Differential expression analyses were completed in limma package. GO and KEGG functional enrichment was conducted using clusterProfiler function of R. Univariate Cox and LASSO Cox regression analyses were performed to screen key genes for Risk score model construction. Nomogram was built with rms package. RESULTS: We identified 114 DEGs between high TMB patients and low TMB AML patients, which were significantly enriched in 429 GO terms and 13 KEGG pathways. Based on the univariate Cox and LASSO Cox regression analyses, seven optimal genes were finally applied for Risk score model construction, including SELE, LGALS1, ITGAX, TMEM200A, SLC25A21, S100A4 and CRIP1. The Risk score could reliably predict the prognosis of AML patients. Age and Risk score were both independent prognostic indicators for AML, and the Nomogram based on them could also reliably predict the OS of AML patients. CONCLUSIONS: A prognostic signature based on seven GI-related genes and a predictive Nomogram for AML patients are finally successfully constructed.

In vitro evaluation of efficacy of two endodontic sonic-powered irrigant agitation systems in killing single-species intracanal biofilms.

OBJECTIVE: To evaluate the efficacy of two sonic-powered irrigation systems, EDDY and EndoActivator, in killing intracanal biofilms. METHODS: Eighty-three instrumented, autoclaved single-rooted human premolars were inoculated with Enterococcus faecalis (ATCC-29212) for 21 days to generate mature, single-species biofilms. The teeth were devided into four groups: irrigation with saline (N = 11); irrigation with 2% NaOCl without agitation (N = 24); irrigation with 2% NaOCl with agitation by the EndoActivaor (N = 24); irrigation with 2% NaOCl with agitation by the EDDY (N = 24). Colony-forming unit (CFU) counts and XTT assay were used to evaluate bacterial load. Additional teeth were split into root-halves for fluorescence staining to examine the percentages of live/dead bacteria in the dentinal tubules present in different canal locations (coronal, mid-root and apical portions). RESULTS: Agitation of 2% NaOCl by EDDY or EndoActivator reduced bacteria load more proficiently than the use of 2%NaOCl without agitation (p < 0.05). No significant difference was detected between the two sonic-powered irrigant agitation systems (p > 0.05). Confocal laser scanning microscopy indicated that both devices had better intratubular bacteria killing efficacy than the use of 2% NaOCl only in all parts of the canal space (p < 0.05), with no significant difference detected between EDDY and EndoActivator (p > 0.05). Elimination of intracanal and intratubular bacteria were less efficient in the apical portion of the canal space for all experimental groups. CONCLUSION: The two sonic-powered irrigant activation systems demonstrated comparable intracanal bacteria reduction efficacy when 2% NaOCl was used for disinfecting E. faecalis biofilms in single-rooted teeth. CLINICAL SIGNIFICANCE: With the use of 2% NaOCl as irrigant, the EDDY and EndoActivator sonic-powered irrigant agitation systems have improved and equivalent intracanal bacteria reduction efficacy but are incapable of completely killing all bacteria that resided within the dentinal tubules of root canals.

Surface-charged starch nanocrystals from glutinous rice: Preparation, crystalline properties and cytotoxicity.

The high-amylopectin glutinous rice is used in this study for the preparation of starch nanocrystals (SNCs) with the acid hydrolysis and enzymatic treatment. The fabricated SNC is carried out the surface modifications by phosphorylation and cationization to produce the nanocrystals with the charged surface. Four kinds of SNCs are obtained with the different surface charges involving the varied negative charges, positive charge and no charge. The chemical structures, morphologies and crystalline properties of four SNCs were investigated, together with the effect of surface charges to their cytotoxicity for two cell lines RAW267.4 and CAL27 by the cell proliferation and cell migration assay. The sulfuric acid-hydrolyzed SNC and phosphorylated SNC have more ordered regions and therefore display the higher crystallinities than the enzymatic treated SNC. Four obtained SNCs all exhibited weak cytotoxicity, indicating their good biocompatibility in the potential biomedical application.

Endocytosis of abiotic nanomaterials and nanobiovectors: Inhibition of membrane trafficking.

Humans are exposed to nanoscopical nanobiovectors (e.g. coronavirus SARS-CoV-2) as well as abiotic metal/carbon-based nanomaterials that enter cells serendipitously or intentionally. Understanding the interactions of cell membranes with these abiotic and biotic nanostructures will facilitate scientists to design better functional nanomaterials for biomedical applications. Such knowledge will also provide important clues for the control of viral infections and the treatment of virus-induced infectious diseases. In the present review, the mechanisms of endocytosis are reviewed in the context of how nanomaterials are uptaken into cells. This is followed by a detailed discussion of the attributes of man-made nanomaterials (e.g. size, shape, surface functional groups and elasticity) that affect endocytosis, as well as the different human cell types that participate in the endocytosis of nanomaterials. Readers are then introduced to the concept of viruses as nature-derived nanoparticles. The mechanisms in which different classes of viruses interact with various cell types to gain entry into the human body are reviewed with examples published over the last five years. These basic tenets will enable the avid reader to design advanced drug delivery and gene transfer nanoplatforms that harness the knowledge acquired from endocytosis to improve their biomedical efficacy. The review winds up with a discussion on the hurdles to be addressed in mimicking the natural mechanisms of endocytosis in nanomaterials design.

Recent Advances in Stimulus-Responsive Nanocarriers for Gene Therapy.

Gene therapy provides a promising strategy for curing monogenetic disorders and complex diseases. However, there are challenges associated with the use of viral delivery vectors. The advent of nanomedicine represents a quantum leap in the application of gene therapy. Recent advances in stimulus-responsive nonviral nanocarriers indicate that they are efficient delivery systems for loading and unloading of therapeutic nucleic acids. Some nanocarriers are responsive to cues derived from the internal environment, such as changes in pH, redox potential, enzyme activity, reactive oxygen species, adenosine triphosphate, and hypoxia. Others are responsive to external stimulations, including temperature gradients, light irradiation, ultrasonic energy, and magnetic field. Multiple stimuli-responsive strategies have also been investigated recently for experimental gene therapy.

Discovery of myricetin as an inhibitor against Streptococcus mutans and an anti-adhesion approach to biofilm formation.

Streptococcus mutans (S. mutans) are cariogenic microorganisms. Sortase A (SrtA) is a transpeptidase that attaches Pac to the cell surface. The biofilm formation of S. mutans is promoted by SrtA regulated Pac. Myricetin (Myr) has a variety of pharmacological properties, including inhibiting SrtA activity of Staphylococcus aureus. The purpose of this research was to investigate the inhibitory effect of Myr on SrtA of S. mutans and its subsequent influence on the biofilm formation. Here, Myr was discovered as a potent inhibitor of S. mutans SrtA, with an IC50 of 48.66 ± 1.48 µM, which was lower than the minimum inhibitory concentration (MIC) of 512 ug/mL. Additionally, immunoblot and biofilm assays demonstrated that Myr at a sub-MIC level could reduce adhesion and biofilm formation of S. mutans. The reduction of biofilm was possibly caused by the decreased amount of Pac on the cells' surface by releasing Pac into the medium via inhibiting SrtA activity. Molecular dynamics simulations and mutagenesis assays suggested that Met123, Ile191, and Arg213 of SrtA were pivotal for the interaction of SrtA and Myr. Our findings indicate that Myr is a promising candidate for the control of dental caries by modulating Pac-involved adhesive mechanisms without developing drug resistance to S.mutans.

Effects of pre-mixed hydraulic calcium silicate putties on osteogenic differentiation of human dental pulp stem cells in vitro.

OBJECTIVES: An experimental tricalcium silicate and dicalcium silicate-containing endodontic putty has been designed to overcome the issue of reduced shelf life after exposure to atmospheric moisture during repeated opening of the container for clinical retrieval. The present study examined the effects of this experimental hydraulic putty on the mineralogenic characteristics of osteogenic lineage-committed human dental pulp stem cells (hDPSCs), by comparing the cellular responses with a commercially available putty (EndoSequence BC RRM Putty). METHODS: The osteogenic potential of hDPSCs that had been exposed to the putties was examined using quantitative reverse-transcription polymerase chain reaction for osteogenic gene expressions and western blot for osteogenic protein expressions. Alkaline phosphatase activity assay and alizarin red S staining were performed to detect changes in production of the intracellular enzyme and extracellular matrix mineralization respectively. RESULTS: Osteogenic differentiation of the hDPSCs was significantly enhanced after exposure to the pre-mixed hydraulic putties, with no significant difference between these two examined putties. CONCLUSIONS: The experimental hydraulic tricalcium silicate putty enhances osteogenic differentiation of hDPSCs to the same extent as a commercially available tricalcium silicate putty. CLINICAL SIGNIFICANCE: The experimental hydraulic putty appears to be an alternative to the commercial putty when used for applications involving the regeneration of bone in endodontics. Animal models are required for validating its potential in enhancing osteogenesis in vivo.

Water redispersion and cytotoxicity of reducing end-modified cellulose nanocrystals by grafting long-chain poly(ethylene oxide).

As an ageless "nano-element" in trees, plants and other cellulose-containing species, cellulose nanocrystal (CNC) has been widely used as a renewable building block in diverse applications. Traditional modification strategy of CNC is based on the reaction with its surface hydroxyl groups, suffering the change of its surface physiochemical properties. In this study, a regio-selective and local modification strategy was performed on the reducing end of CNC with the grafting of long-chain poly(ethylene oxide) (PEO) to produce the end-grafted nanocrystals (CNC-eg-PEO). Based on thiol-ene click reaction, the terminal allyl-PEO was covalently attached on the modified nanocrystal possessing the reactive thiol groups. With the preservation of surface chemistry, the redispsersion stability of CNC-eg-PEO was promoted, attributed to the dual effect of steric stabilization and electrostatic repulsion. Furthermore, the CNC-eg-PEO exhibited the low cytotoxicity to ATCC cell lines HFF and CAL-27, indicating its promising biomedical application.

Effect of apical size on apical pressure during syringe-needle and multisonic negative pressure irrigation.

Apical pressure during root canal irrigation is regarded as a key factor affecting the risk of irrigant extrusion. The aim of this study was to examine the effect of apical size on the apical pressure by positive and negative pressure syringe-needle and multisonic negative pressure irrigation. An extracted maxillary first molar with two separate buccal roots, one palatal root and four canals was selected. The roots of the molar were fixed in a specially made apparatus to acquire the apical pressure of the four root canals separately. The apical sizes tested were from sizes 10, 30, 40, 50, 60, 70, 80, 90, 110. Multisonic negative pressure irrigation protocol was as recommended by the manufacturer (45 mL/min), syringe-needle irrigation was done using 30-G side-vented needle 3 mm from the working length at 5 mL/min as a conventional positive pressure irrigation (SNI), and as negative pressure irrigation (NPSNI) using suction. Apical pressure by SNI was measured also at 10 mL/min with an open-ended 30G needle, for the smallest and largest apical sizes. Apical pressures by SNI stayed positive, except when suction was used (NPSNI). The apical pressure by multisonic negative pressure irrigation remained negative in all situations. With increasing apical size, apical pressure by SNI decreased, whereas with multisonic negative pressure irrigation and NPSNI, it was not affected by apical size. Large apical size did not result in higher apical pressure values compared to small apical sizes.

Manoeuvrability and biocompatibility of endodontic tricalcium silicate-based putties.

OBJECTIVES: The present study evaluated the indentation depth, storage modulus and biocompatibility of an experimental endodontic putty designed for endodontic perforation repair and direct pulp-capping (NeoPutty). The results were compared with the properties associated with the commercially available EndoSequence BC RRM Putty (ES Putty). METHODS: Indentation depth was measured by a profilometer following indentation with the 1/4 lb Gilmore needle. Elastic modulus was evaluated using a strain-controlled rheometer. The effects of eluents derived from these two putties were examined on the viability and proliferation of human dental pulp stem cells (hDPSCs) and human periodontal ligament fibroblasts (hPDLFs), before (1 st testing cycle) and after complete setting (2nd testing cycle). RESULTS: The ES Putty became more difficult to ident and acquired a larger storage modulus after exposure to atmospheric moisture. Biocompatibility results indicated that both putties were relatively more cytotoxic than the bioinert Teflon negative control, but much less cytotoxic than the zinc oxide-eugenol cement negative control. NeoPutty was less cytotoxic than ES putty in the 1st testing cycle, particularly with hDPSCs. Both putties exhibited more favourable cytotoxicity profiles after complete setting. CONCLUSIONS: NeoPutty has a better window of maneuverability after exposure to atmospheric moisture. From an in vitro cytotoxicity perspective, the NeoPutty may be considered more biocompatible than ES putty. CLINICAL SIGNIFICANCE: The experimental NeoPutty is biocompatible and is capable of reducing the frustration of shortened shelf life when jar-stored endodontic putties are exposed to atmospheric moisture during repeated opening of the lid for clinical retrieval.