Effect of additions of chemicals on properties of endodontic cements

Tricalcium silicate (TCS)-based materials are vastly applied in vital pulp therapy, mainly due to the calcium hydroxide release which is responsible for their biological and antimicrobial activity. Recently, alterations have been introduced in their formulation, namely incorporation of calcium phosphate, micro-silica or resins to improve potential limitations. The current study investigated whether different additives affect calcium ion release and in turn modify biological and antimicrobial properties by testing prototype and commercial TCS-based cements. The water: powder ratio in the prototype formulations was determined with a rheological assessment. Hydration was monitored with scanning electron microscopy and x-ray diffraction analysis. Materials’ eluates were evaluated for pH, calcium release, biocompatibility and antimicrobial potential. Modifications altered the water demand, hydration and leaching profile of the prototype cements in different extent. Calcium phosphate did not alter calcium ion release significantly, albeit an initial stronger antibacterial effect was induced. Micro-silica replacement resulted in a decreased long-term calcium hydroxide formation, which was correlated with neutralised cytotoxicity and antibacterial activity. Hydration of commercial TCS-based materials was faster and calcium release was enhanced, except for a resin-modified cement. Overall, incorporation of compounds in hydraulic cements can alter calcium ion release and consequently modify their biological and antimicrobial properties

Endodontic sealers after exposure to chlorhexidine digluconate:An assessment of physicochemical properties

Objectives Final root canal irrigation should ideally maintain the physicochemical stability of root canal sealers. We seek to assess the effect of contact with 2% chlorhexidine digluconate (CHX) on the physicochemical properties of AH Plus, BioRoot™ RCS, and Pulp Canal Sealer (PCS). Methods Mixed sealers were placed in cylindrical teflon molds and allowed to set for 1.5x the manufacturers’ setting time. Half of the specimens had their free surface in contact with CHX for the first minute of their setting period. Solubility, radiopacity, surface roughness, microhardness and wettability of the sealers were assessed up to 28 days after setting. Elemental analysis of sealer surfaces and their leachates together with pH measurements were also performed. Appropriate parametric and non-parametric analysis with post hoc tests were performed (p < 0.05). Results Exposure to CHX had no effect on solubility and radiopacity of all sealers. CHX altered the surface roughness of PCS and BioRoot RCS (p < 0.05). Contact with CHX reduced the microhardness of AH Plus and PCS (p < 0.05). AH Plus was more hydrophilic after CHX contact, whereas PCS became more hydrophobic (p < 0.05). AH Plus and PCS surfaces appeared to adsorb CHX as exhibited by chlorine peaks after contact with CHX. Sealer leachates’ alkalinity was not affected. CHX increased elution of silicon and zirconium for BioRoot and zinc for PCS leachates. Significance In our study, CHX affected sealers’ physicochemical properties to various extents. Further studies are needed to confirm the obtained results by investigating various final irrigation strategies and correlating to biological properties

Effect of chlorhexidine digluconate on antimicrobial activity, cell viability and physicochemical properties of three endodontic sealers

ObjectiveAssess the biological and physicochemical properties of AH Plus, BioRoot RCS and Pulp Canal Sealer (PCS) leachates with and without chlorhexidine (CHX).MethodsThe sealers were studied in no contact and 1-minute contact with CHX. For biological properties (antibacterial activity and cytotoxicity), leachates were formed in saline of freshly mixed, 1-, 7- and 28 days set sealers. The antibacterial properties of sealer leachates were investigated for planktonic and biofilm growth of E. faecalis, S. mutans, S.epidermidis and S.aureus. The 3-(4,5 dimethylthiazolyl-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was used to evaluate murine fibroblast cell viability after exposure to the leachates. The physical properties (water uptake, sorption, solubility, porosity, surface characteristics) of sealers and the pH of the immersion liquid (saline or distilled water) were also assessed over a 28-days period.ResultsCHX improved the antibacterial properties of the sealer leachates and reduced cell viability for all sealer leachates, except for freshly mixed PCS. BioRoot RCS leachates presented the highest antibacterial properties and cell viability with and without CHX contact. PCS was the material most affected by CHX in terms of physical properties, whereas for AH Plus, solubility was increased. CHX did not affect the physical properties of BioRoot RCS, except for solubility that was decreased. CHX contact did not change sealers’ alkalinity in distilled water whereas it increased it for AH Plus and BioRoot RCS in saline.SignificanceCHX improved the antibacterial efficacy of sealer leachates and either compromised or did not affect cell viability. CHX affected to various extent sealers’ physicochemical properties

Machine Learning Classification of Sphalerons and Black Holes at the LHC

In models with large extra dimensions, "miniature" black holes (BHs) might be produced in high-energy proton-proton collisions at the Large Hadron Collider (LHC). In the semi-classical regime, those BHs thermally decay, giving rise to large-multiplicity final states with jets and leptons. On the other hand, similar final states are also expected in the production of electroweak sphaleron/instanton-induced processes. We investigate whether one can discriminate these scenarios when BH or sphaleron-like events are observed in the LHC using Machine Learning (ML) methods. Classification among several BH scenarios with different numbers of extra dimensions and the minimal BH masses is also examined. In this study we consider three ML models: XGBoost algorithms with (1) high- and (2) low-level inputs, and (3) a Residual Convolutional Neural Network. In the latter case, the low-level detector information is converted into an input format of three-layer binned event images, where the value of each bin corresponds to the energy deposited in various detector subsystems. We demonstrate that only a few detected events are sufficient to effectively discriminate between the sphaleron and BH processes. Separation among BH scenarios with different minimal BH masses is also possible with a reasonable number of events, that can be collected in the LHC Run-2, -3 and the high-luminosity LHC (HL-LHC). We find, however, that a large number of events is needed to discriminate between BH hypotheses with the same minimal BH mass, but different numbers of extra dimensions.Comment: 18 pages, 5 figure

Technical Quality and Associated Iatrogenic Errors of Endodontic Treatments Performed in Extracted Anterior Single-Rooted Teeth by Preclinical Undergraduate Students

Aim: To evaluate technical quality of root canal treatments performed in extracted anterior single-rooted teeth in an undergraduate dental clinic, and to record the associated iatrogenic errors

Investigation of the effect of the water to powder ratio on hydraulic cement properties

Objective: The use of rheological properties to determine the optimal water: powder ratio of tricalcium silicate-based prototype materials incorporating alternative radiopacifiers and fillers. Determination of how the proportion of water incorporated affected the physicochemical behaviour of the materials. Methods: Endodontic cements replaced with 30% radiopacifier, and additions of calcium phosphate and micro-silica were tested. The unmodified cements were mixed with a 0.35 water: powder ratio which served as control. At this water: powder ratio, unmodified Portland cement without any addition had an adequate consistency and furthermore it has been well characterized. Assessment of material rheological properties enabled adjustment of the water: powder ratio in each material to provide comparable viscosity values to those of the pure cement. The flowability, phase analysis and calcium release were measured for both viscosity-matched and the standard 0.35 water: powder ratio blends. The prototype materials with the adjusted water: powder ratios were also characterized by scanning electron microscopy, energy-dispersive spectroscopy and evaluated for radio-opacity. Results: The use of the 0.35 water: powder ratio is not appropriate when changing the radiopacifier and incorporating additives. Zirconium oxide did not vary the water: powder ratio but tantalum oxide and calcium tungstate resulted in an increase and decrease in water demand respectively. Using the standard 0.35 ratio when the mixture had a low water demand resulted in higher flowability values and calcium release in solution. Micro-silica and calcium phosphate altered the hydration of the materials. All materials were adequately radiopaque. Significance: Rheological assessment is an easy reproducible way to determine the water: powder ratios of materials with varying amounts of additives and radiopacifiers during development. Modifications to the water: powder ratio affects material properties