Uncovering the Dynamics of Urease and Carbonic Anhydrase Genes in Ureolysis, Carbon Dioxide Hydration, and Calcium Carbonate Precipitation.

The hydration of CO2 suffers from kinetic inefficiencies that make its natural trapping impractically sluggish. However, CO2-fixing carbonic anhydrases (CAs) remarkably accelerate its equilibration by 6 orders of magnitude and are, therefore, "ideal" catalysts. Notably, CA has been detected in ureolytic bacteria, suggesting its potential involvement in microbially induced carbonate precipitation (MICP), yet the dynamics of the urease (Ur) and CA genes remain poorly understood. Here, through the use of the ureolytic bacteriumSporosarcina pasteurii, we investigate the differing role of Ur and CA in ureolysis, CO2 hydration, and CaCO3 precipitation with increasing CO2(g) concentrations. We show that Ur gene up-regulation coincides with an increase in [HCO3-] following the hydration of CO2 to HCO3- by CA. Hence, CA physiologically promotes buffering, which enhances solubility trapping and affects the phase of the CaCO3 mineral formed. Understanding the role of CO2 hydration on the performance of ureolysis and CaCO3 precipitation provides essential new insights, required for the development of next-generation biocatalyzed CO2 trapping technologies.

The Washout Resistance of Bioactive Root-End Filling Materials.

Fast-setting bioactive cements were developed for the convenience of retrograde fillings during endodontic microsurgery. This in vitro study aimed to investigate the effect of irrigation on the washout of relatively fast-setting materials (Biodentine, EndoCem Zr, and MTA HP) in comparison with MTA Angelus White and IRM in an apicectomy model. Washout resistance was assessed using artificial root ends. A total of 150 samples (30 for each material) were tested. All samples were photographed using a microscope, and half of them were also scanned. The samples were irrigated and immersed in saline for 15 min. Then the models were evaluated. Rinsing and immersing the samples immediately after root-end filling and after 3 min did not disintegrate the fillings made of all tested materials except Biodentine. Root-end fillings made of Biodentine suffered significant damage both when rinsing was performed immediately and 3 min after the filling. Quantitative assessment of washed material resulted in a slight loss of IRM, EndoCem MTA Zr, and MTA HP. MTA Angelus White showed a slightly greater washout. Rinsing and immersion of Biodentine restorations resulted in their significant destruction. Under the conditions of the current study, the evaluated materials, excluding Biodentine, showed good or relatively good washout resistance.

Evaluation of Gingival Phenotype in the Early Transitional Dentition Phase in Children-Comparison of Three Non-Invasive Methods.

Gingival phenotype (GP) is determined based on the thickness and width of the gingival tissue. An evaluation of GP is essential for adequate treatment planning and outcome monitoring, including orthodontic treatments in a paediatric population. The present study aimed to compare the reliability of the visual and TRAN methods with that of the ultrasound biometer measurements in the early transitional dentition phase. One hundred ninety three generally healthy, 7-year-old children were examined. An assessment of GP was performed by a paedodontist and a periodontist. The average thickness of the gingiva was 0.76 ± 0.36 mm, which was classified as a thin GP. The agreement between a visual assessment and the biometric ultrasound measurements reached the highest (94%) level when assessing a very thin GP (Spearman's rank correlation coefficient r = 0.37, p < 0.01). Similarly, 99% agreement in the diagnosis of a thin GP was recorded for the TRAN and ultrasound methods (Spearman's rank correlation coefficient r = 0.49, p < 0.001). In total, 86% of cases diagnosed as having a thick GP using the TRAN method turned out to be thin according to the ultrasound measurements. The dentist's specialization and professional experience in the assessment of GP were irrelevant (Spearman's rank correlation coefficient r = 0.49, p < 0.001). All methods tested in the present study were proven to be easy to perform and well accepted by the children. The visual assessment and TRAN methods, despite the fact that they enabled the diagnosis of a thin GP (crucial for treatment planning), cannot be recommended during the teeth replacement period. A misdiagnosis of thick GP may deprive a young at-risk patient of special supervision, which may develop into mucogingival deformities. A biometric ultrasound, although expensive, allows for reliable assessment of the gingiva thickness when needed.

Kinetic and Thermodynamic Enhancement of Low-Temperature Oxygen Release from Strontium Ferrite Perovskites Modified with Ag and CeO2.

The redox behavior of the nonstoichiometric perovskite oxide SrFeO3-δ modified with Ag, CeO2, and Ce was assessed for chemical looping air separation (CLAS) via thermogravimetric analysis and by cyclic release and uptake of O2 in a packed bed reactor. The results demonstrated that the addition of ∼15 wt % Ag at the surface of SrFeO3-δ lowers the temperature of oxygen release in N2 by ∼60 °C (i.e., from 370 °C for bare SrFeO3-δ to 310 °C) and more than triples the amount of oxygen released per CLAS cycle at 500 °C. Impregnation of SrFeO3-δ with Ag increased the concentration of oxygen vacancies at equilibrium, lowering (3 - δ) under all investigated oxygen partial pressures. The addition of CeO2 at the surface or into the bulk of SrFeO3-δ resulted in more modest changes, with a decrease in temperature for O2 release of 20-25 °C as compared to SrFeO3-δ and a moderate increase in oxygen yield per reduction cycle. The apparent kinetic parameters for reduction of SrFeO3-δ, with Ag and CeO2 additives, were determined from the CLAS experiments in a packed bed reactor, giving activation energies and pre-exponential factors of Ea,reduction = 66.3 kJ mol-1 and Areduction = 152 mol s-1 m-3 Pa-1 for SrFeO3-δ impregnated with 10.7 wt % CeO2, 75.7 kJ mol-1 and 623 molO2 s-1 m -3 Pa-1 for SrFeO3-δ mixed with 2.5 wt % CeO2 in the bulk, 29.9 kJ mol-1 and 0.88 molO2 s-1 m-3 Pa-1 for Sr0.95Ce0.05FeO3-δ, and 69.0 kJ mol-1 and 278 molO2 s-1 m-3 Pa-1 for SrFeO3-δ impregnated with 12.7 wt % Ag, respectively. Kinetics for reoxidation were much faster and were assessed for two materials with the slowest oxygen uptake, SrFeO3-δ, giving the activation energy Ea,oxidation = 177.1 kJ mol-1 and pre-exponential factor Aoxidation = 3.40 × 1010 molO2 s-1 m-3 Pa-1, and Sr0.95Ce0.05FeO3-δ, giving the activation energy Ea,oxidation = 64.0 kJ mol-1, and pre-exponential factor Aoxidation = 584 molO2 s-1 m-3 Pa-1.

Production of Acetaldehyde via Oxidative Dehydrogenation of Ethanol in a Chemical Looping Setup.

A novel chemical looping (CL) process was demonstrated to produce acetaldehyde (AA) via oxidative dehydrogenation (ODH) of ethanol. Here, the ODH of ethanol takes place in the absence of a gaseous oxygen stream; instead, oxygen is supplied from a metal oxide, an active support for an ODH catalyst. The support material reduces as the reaction takes place and needs to be regenerated in air in a separate step, resulting in a CL process. Here, strontium ferrite perovskite (SrFeO3-δ) was used as the active support, with both silver and copper as the ODH catalysts. The performance of Ag/SrFeO3-δ and Cu/SrFeO3-δ was investigated in a packed bed reactor, operated at temperatures from 200 to 270 °C and a gas hourly space velocity of 9600 h-1. The CL capability to produce AA was then compared to the performance of bare SrFeO3-δ (no catalysts) and materials comprising a catalyst on an inert support, Cu or Ag on Al2O3. The Ag/Al2O3 catalyst was completely inactive in the absence of air, confirming that oxygen supplied from the support is required to oxidize ethanol to AA and water, while Cu/Al2O3 gradually got covered in coke, indicating cracking of ethanol. The bare SrFeO3-δ achieved a similar selectivity to AA as Ag/SrFeO3-δ but at a greatly reduced activity. For the best performing catalyst, Ag/SrFeO3-δ, the obtained selectivity to AA reached 92-98% at yields of up to 70%, comparable to the incumbent Veba-Chemie process for ethanol ODH, but at around 250 °C lower temperature. The CL-ODH setup was operated at high effective production times (i.e., the time spent producing AA to the time spent regenerating SrFeO3-δ). In the investigated configuration with 2 g of the CLC catalyst and 200 mL/min feed flowrate ∼5.8 vol % ethanol, only three reactors would be required for the pseudo-continuous production of AA via CL-ODH.

Alkalizing Properties of Six Calcium-Silicate Endodontic Biomaterials.

INTRODUCTION: Calcium silicate-based cements (CSC), are self-setting hydraulic biomaterials widely used for reparative procedures in dentistry and endodontics. These materials possess physical properties, such as ion release, porosity, solubility, and radiopacity. Their biological properties are connected to their alkalizing activity and calcium release capacity. MATERIALS AND METHODS: Six calcium silicate-based materials were selected for this study: TheraCal LC (Bisco Inc., Schaumburg, IL, USA), MTA Plus (PrevestDenpro, Jammu, India Avalon Biomed Inc., Bradenton, FL, USA), Biodentine (Septodont, Saint-Maur-des-Fossés, France), RetroMTA (BioMTA, Seoul, Korea), MTA Flow (Ultradent Products, Inc., South Jordan, UT, USA), and OrthoMTA (BioMTA, Seoul, Korea). The pH was analyzed immediately after immersion (baseline) and after 1 h, 3 h, 1 day, 2 days, 3 days, 1 week, 2 weeks, 3 weeks, and 1 year with a pH meter, previously calibrated with solutions of known pH. All testing materials had alkaline pH. RESULTS: Analysis of the tested materials showed statistically significant differences in terms of pH changes as a function of the time showed a gradual rise in the pH of all materials. CONCLUSIONS: All tested materials exhibited continuous hydroxyl ion release resulting in a rise in pH until the end of time of experience.

Knowledge of Oral and Physical Manifestations of Anorexia Nervosa Among Polish Dentists: A Cross-Sectional Study.

Background: Anorexia nervosa is a psychosomatic disorder and is commonly associated with impaired oral health. Dentists can play a relevant role in the early diagnosis of anorexia nervosa. With the help of intra- and extraoral examinations and anamnesis, the dentist can detect characteristic signs and symptoms of this eating disorder. The purpose of this study was to determine the knowledge regarding the oral and physical manifestations of anorexia nervosa among general dental practitioners and specialist dentists of Poland. Material and Methods: A pretested online questionnaire consisting of a first part asking for the characteristics of the participant and a second part with 22 specific questions on their general knowledge of anorexia nervosa and knowledge of physical and oral manifestations of this eating disorder was used. Results: A total of 369 dentists completed the questionnaire. The Polish dentists in this study reported sufficient knowledge regarding anorexia nervosa. However, younger dentists and general dental practitioners had relatively lower knowledge scores than other groups. The dentists mainly had difficulties with the oral symptoms of anorexia nervosa. Conclusion: Despite Polish dentists having sufficient knowledge about anorexia nervosa in relation to the general symptoms of anorexia, there are deficits with regard to oral manifestations. Therefore, there is a need to increase continuing education in this field, which can improve early diagnosis of this disease by dental practitioners and referral to specialists for treatment.

Characterisation of CaCO3 phases during strain-specific ureolytic precipitation.

Numerous microbial species can selectively precipitate mineral carbonates with enhanced mechanical properties, however, understanding exactly how they achieve this control represents a major challenge in the field of biomineralisation. We have studied microbial induced calcium carbonate (CaCO3) precipitation (MICP) in three ureolytic bacterial strains from the Sporosarcina family, including S. newyorkensis, a newly isolated microbe from the deep sea. We find that the interplay between structural water and strain-specific amino acid groups is fundamental to the stabilisation of vaterite and that, under the same conditions, different isolates yield distinctly different polymorphs. The latter is found to be associated with different urease activities and, consequently, precipitation kinetics, which change depending on pressure-temperature conditions. Further, CaCO3 polymorph selection also depends on the coupled effect of chemical treatment and initial bacterial concentrations. Our findings provide new insights into strain-specific CaCO3 polymorphic selection and stabilisation, and open up promising avenues for designing bio-reinforced geo-materials that capitalise on the different particle bond mechanical properties offered by different polymorphs.

SEM and EDS study of TotalFill BC Sealer and GuttaFlow Bioseal root canal sealers.

BACKGROUND: Recently, a new generation of calcium silicate-based root canal sealers has been developed. These new types of sealers have the ability to set in wet environment, have high alkalinity and present potential antimicrobial activity. OBJECTIVES: The aim of this study was to determine the chemical composition and microstructure of 2 novel calcium silicate-containing root canal sealers - TotalFill® BC Sealer and GuttaFlow® Bioseal. MATERIAL AND METHODS: The tested sealers were prepared according to the manufacturers' instructions. Sixteen cylindrical dishes (inner diameter: 4 mm; height: 3 mm) were placed on a glass Petri dish and packed with the materials. The Petri dish was transferred to an incubator. After the sealers set, excess material was removed with diamond discs and polishing paste. The materials were assessed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) X­ray microanalysis. RESULTS: Both TotalFill BC Sealer and GuttaFlow Bioseal contained calcium, zirconium, oxygen, carbon, silicon, and a trace of sodium. In the case of TotalFill BC Sealer, trace amounts of copper and technetium were also present, and for GuttaFlow Bioseal, iron, zinc, and a trace of magnesium and hafnium were noted. No bismuth was found. Both of the assessed sealers contained fine particles embedded in the matrix; however, GuttaFlow Bioseal also had larger particles with a diameter of 2-10 µm. CONCLUSIONS: TotalFill BC Sealer represents a higher degree of purity in comparison with GuttaFlow Bioseal. The clinical implications of heavy metals present in GuttaFlow Bioseal need to be investigated. Both materials have a fine particle structure, which is desirable for root canal sealers.

The influence of two forms of chlorhexidine on the accuracy of contemporary electronic apex locators.

BACKGROUND: Accurate determination of working length (WL) is crucial for the success of endodontic therapy. The aim of this study was to determine the influence of 2% chlorhexidine digluconate solution, 2% chlorhexidine digluconate gel and 2% hypochlorite solution on the accuracy of two devices: the Raypex 5 and the ApexDal. METHODS: Twenty-nine single-rooted human teeth were used in this study. The crowns were cut horizontally and embedded in an alginate mass. In each tooth, six endodontic measurements were made using two electronic apex locators (EALs): a Raypex 5 and an ApexDal. For each EAL, measurements were taken with the following products: 2% chlorhexidine solution (CHX-S group), 2% chlorhexidine gel (CHX-G group) and 2% NaOCl (NaOCl group). After performing an endodontic measurement, the endodontic instruments were stabilized with flow resin composite. Afterwards, the roots were removed from the alginate mass, and the apical one-third of each root was cut lengthways to recover the canal system. Last, the distance between the file tip and the apical foramen was measured under a microscope at 60 x magnification. RESULTS: Statistically significant differences were found between CHX-S and NaOCl and CHX-G and NaOCl, but no significant differences were detected between CHX-S and CHX-G during the testing of both devices. No statistically significant differences were observed between the Raypex 5 and ApexDal for all intracanal media tested. CONCLUSION: The EALs Raypex 5 and ApexDal had higher accuracy in the anatomical foramen of the root containing chlorhexidine in the gel or in the solution form than in the canal containing sodium hypochlorite.

Usefulness assessment of preoperative MRI fistulography in patients with perianal fistulas.

BACKGROUND: Accurate preoperative assessment of the perianal fistulous tract is the main purpose of the diagnostics and to a large extend determines surgery effectiveness. One of the useful diagnostic methods in perianal fistulas is magnetic resonance imaging. The authors presented experiences in the application of MRI fistulography for evaluation of cases of perianal fistulas difficult to diagnose and treat. MATERIAL/METHODS: Own examination method was described; MRI fistulography findings were analyzed and compared with intraoperative conditions in 14 patients (11 men and 3 women) diagnosed in the years 2005- 2009. Eight patients had recurrent fistulas and 6 had primary fistulas. Imaging was performed with a GE SIGNA LX HS scanner with a 1.5-Tesla field strength and a dedicated surface coil placed at the level of hip joints. Contrast agent was a gadolinium-based solution. RESULTS: Intraoperative findings were consistent with radiological descriptions of 13 MRI fistulographies. Only in one case, according to surgery findings, it was a transsphincteric fistula with an abscess in the ischioanal fossa, with an orifice in the posterior crypt; the radiologist described it as a transsphincteric, internal blind fistula. CONCLUSIONS: Due to its accuracy in the assessment of the perianal fistulous tracts in soft tissues, MRI fistulography becomes a useful and recommended diagnostic method in this pathology. It shows the location of the fistula regarding the system of anal sphincters, and identifies the internal orifice and branching of the fistula. It enables precise planning of surgical treatment. Authors suggest that this diagnostic method should be improved and applied more commonly.