Effect of phase transition on the electrochemical behavior of ferredoxin embedded in an artificial lipid membrane film

The effect of the phase transition of a bilayer membrane on the electrochemical behavior of ferredoxin embedded in a cast film of artificial lipid, 2C₁₈N⁺Br⁻, was investigated. The redox potential of ferredoxin embedded in the lipid film showed a linear, positive shift from −510 (± 2) to −466 (± 3) mV (vs. Ag|AgCl|saturated KCl) with increasing temperature from 25 to 53 °C. The diffusion coefficient (D) and heterogeneous electron transfer rate constant (k°^′) were evaluated at various temperatures by means of analyzing cyclic voltammograms. The overall shape of the simulated voltammograms fitted well with the experimentally observed voltammograms at various potential sweep rates, when the estimated D and k°^′ values were used for the simulation. The results of the temperature dependence of the estimated D and k°^′ values indicated that D and k°^′ were enhanced near the phase transition temperature (T_c), 46 °C, of the lipid film. The D and k°^′ values at temperatures above the T_c were approximately two-orders and one-order of magnitude larger than those estimated at temperatures under the T_c, respectively. The estimated D and k°^′ values were 2.1–5.8 × 10⁻¹⁰ cm² s⁻¹ and 1.2–1.6 × 10⁻⁴ cm s⁻¹ at 25 °C, and 3.5–3.7 × 10⁻⁸ cm² s⁻¹ and 1.1–1.2 × 10⁻³ cm s⁻¹ at 50 °C, respectively. The electrochemical behavior of ferredoxin in the lipid film changed drastically near the T_c.     

Efficacy of doxycycline release collagen membrane on surgically created and contaminated defects in rat tibiae: A histopathological and microbiological study

BackgroundThe effects of systemic antibiotics on controlling infective pathogens after guided bone regeneration(GBR) procedures especially in membrane exposures are limited. However, local administrations of antibiotics are rare in GBR techniques.AimThe aim of this study was to investigate the osteogenesis potential and the antibacterial effect of a doxycycline releasing collagen membrane in surgically created and contaminated defects in rat tibiae.Material and methodsDefects were created in 20 rats that were randomly divided in to two groups: control group (defect contaminated by Porphyromonas gingivalis, filled with bone graft and covered by collagen membrane); test group (defect contaminated by P. gingivalis filled with bone graft and covered by collagen membrane containing 1 mg/cm² doxycycline. Animals were sacrificed post surgically on the 14th day for microbiologic evaluation and on the 28th day for histopathological evaluation.ResultsThe degree of osteogenesis in the test group was seen to be significantly higher than control group (p: 0.011; p < 0.05). Furthermore in test group, no bacterial growth was observed. The bacteria counts were determined between 1 × 104 and 268 × 104 CFU/g with a median of 1.32 × 104 for control group.ConclusionsWithin the limitations of this study, the results of the present study suggests that the use of a doxycycline releasing membrane has a positive effect on contaminated GBR procedures for limiting P. gingivalis infections leading to bone formation following GBR procedures in a rat model.     

Initial oral biofilm formation on titanium implants with different surface treatments: An in vivo study

ObjectiveThe aim of this study was to examine in vivo the initial bacterial adhesion on titanium implants with different surface treatments.DesignTen subjects wore oral splints containing machined pure titanium disks (Ti-M), acid-etched titanium (Ti-AE) and anodized and laser irradiated disks (Ti-AL) for 24 h. After this period, disks were removed from the splints and adherent bacteria were quantified by an enzymatic assay to assess total viable bacteria and by Real Time PCR to evaluate total bacteria and Streptococcus oralis levels. Additionally, the initial adherent microorganisms were visualized by scanning electron microscopy (SEM). Titanium surface morphology was verified using SEM, and roughness was evaluated by profilometer analysis.ResultsRegarding titanium surface roughness, Ti-AL (1.423 ± 0.397) showed significantly higher Ra values than did Ti-M (0.771 ± 0.182) and Ti-AE (0.735 ± 0.196) (p < 0.05, ANOVA – Tahame). Ti-AE and Ti-AL presented roughened micro-structure surfaces characterized by open pores, whereas Ti-M showed long grooves alternating with planed areas. Comparing the Ti-M, Ti-AE and Ti-AL groups for viable bacteria (MTT assay), total bacteria and S. oralis quantification (qPCR), no significant differences were observed among these three groups (p > 0.05, ANOVA – Tahame). SEM images showed similar bacterial adhesion on the three titanium surfaces, predominantly characterized by cocci and several bacilli, indicating an initial colonization of the oral biofilm.ConclusionIn conclusion, roughness and microtopography did not stimulate initial biofilm formation on titanium surfaces with different surface treatments.     

Influence of a Brazilian wild green propolis on the enamel mineral loss and Streptococcus mutans’ count in dental biofilm

ObjectiveThis study investigated the anti-demineralizing and antibacterial effects of a propolis ethanolic extract (EEP) against Streptococcus mutans dental biofilm.DesignBlocks of sound bovine enamel (n = 24) were fixed on polystyrene plates. S. mutans inoculum (ATCC 25175) and culture media were added (48 h–37 °C) to form biofilm. Blocks with biofilm received daily treatment (30 μL/1 min), for 5 days, as following: G1 (EEP 33.3%); G2 (chlorhexidine digluconate 0.12%); G3 (ethanol 80%); and G4 (Milli-Q water). G5 and G6 were blocks without biofilm that received only EEP and Milli-Q water, respectively. Final surface hardness was evaluated and the percentage of hardness loss (%HL) was calculated. The EEP extract pH and total solids were determined. S. mutans count was expressed by log₁₀ scale of Colony-Forming Units (CFU/mL). One way ANOVA was used to compare results which differed at a 95% significance level.ResultsG2 presented the lowest average %HL value (68.44% ± 12.98) (p = 0.010), while G4 presented the highest (90.49% ± 5.38%HL) (p = 0.007). G1 showed %HL (84.41% ± 2.77) similar to G3 (87.80% ± 6.89) (p = 0.477). Groups G5 and G6 presented %HL = 16.11% ± 7.92 and 20.55% ± 10.65; respectively (p = 0.952). G1 and G4 differed as regards to S. mutans count: 7.26 ± 0.08 and 8.29 ± 0.17 CFU/mL, respectively (p = 0.001). The lowest bacterial count was observed in chlorhexidine group (G2 = 6.79 ± 0.10 CFU/mL) (p = 0.043). There was no difference between S. mutans count of G3 and G4 (p = 0.435). The EEP showed pH 4.8 and total soluble solids content = 25.9 Brix.ConclusionThe EEP seems to be a potent antibacterial substance against S. mutans dental biofilm, but presented no inhibitory action on the de-remineralization of caries process.     

Antibacterial and antibiofilm efficacy of k21-E in root canal disinfection

ObjectivesThe aim of the current project was to study the antimicrobial efficacy of a newly developed irrigant, k21/E against E. faecalis biofilm.MethodsRoot canals were instrumented and randomly divided into the following groups: irrigation with saline, 6% NaOCl (sodium hypochlorite), 6% NaOCl + 2% CHX (Chlorhexidine), 2% CHX, 0.5% k21/E (k21 - quaternary ammonium silane) and 1% k21/E. E. faecalis were grown (3-days) (1 × 10⁷ CFU mL⁻¹), treated, and further cultured for 11-days. Specimens were subjected to SEM, confocal and Raman analysis and macrophage vesicles characterized along with effect of lipopolysaccharide treatment. 3T3 mouse-fibroblasts were cultured for alizarin-red with Sortase-A active sites and Schrödinger docking was performed. TEM analysis of root dentin substrate with matrix metalloproteinases profilometry was also included. A cytotoxic test analysis for cell viability was measured by absorbance of human dental pulp cells after exposure to different irrigant solutions for 24 h. The test percentages have been highlighted in Table 1.ResultsAmong experimental groups, irrigation with 0.5% k21/E showed phase separation revealing significant bacterial reduction and lower phenylalanine 1003 cm⁻¹ and Amide III 1245 cm⁻¹ intensities. Damage was observed on bacterial cell membrane after use of k21/E. No difference in exosomes distribution between control and 0.5%k21/E was observed with less TNFα (*p < 0.05) and preferential binding of SrtA. TEM images demonstrated integrated collagen fibers in control and 0.5%k21/E specimens and inner bacterial membrane damage after k21/E treatment. The k21 groups appeared to be biocompatible to the dental pulpal cells grown for 24 h.SignificanceCurrent investigations highlight potential advantages of 0.5% k21/E as irrigation solution for root canal disinfection.     

Effect of biomimetic mineralization on enamel and dentin: A Raman and EDX analysis

ObjectiveTo investigate the effect of an experimental biomimetic mineralization kit (BIMIN) on the chemical composition and crystallinity of caries-free enamel and dentin samples in vitro.MethodsEnamel and dentin samples from 20 human teeth (10 for enamel; 10 for dentin) were divided into a control group without treatment and test samples with BIMIN treatment. Quantitative analysis of tissue penetration of fluoride, phosphate, and calcium was performed using energy-dispersive X-ray spectroscopy (EDX). Mineralization depth was measured by Raman spectroscopy probing the symmetric valence vibration near 960 cm⁻¹ as a marker for crystallinity. EDX data was statistically analyzed using a paired t-test and Raman data was analyzed using the Student’s t-test.ResultsEDX analysis demonstrated a penetration depth of fluoride of 4.10 ± 3.32 μm in enamel and 4.31 ± 2.67 μm in dentin. Calcium infiltrated into enamel 2.65 ± 0.64 μm and into dentin 5.58 ± 1.63 μm, while the penetration depths for phosphate were 4.83 ± 2.81 μm for enamel and 6.75 ± 3.25 μm for dentin. Further, up to 25 μm of a newly mineralized enamel-like layer was observed on the surface of the samples. Raman concentration curves demonstrated an increased degree of mineralization up to 5–10 μm into the dentin and enamel samples.SignificanceBiomimetic mineralization of enamel and dentin samples resulted in an increase of mineralization and a penetration of fluoride into enamel and dentin.     

Bis-GMA co-polymerizations: Influence on conversion,flexural properties,fracture toughness and susceptibility to ethanol degradation of experimental composites

ObjectivesThe aim of this study was to evaluate the influence of monomer content on fracture toughness (K_Ic) before and after ethanol solution storage, flexural properties and degree of conversion (DC) of bisphenol A glycidyl methacrylate (Bis-GMA) co-polymers.MethodsFive formulations were tested, containing Bis-GMA (B) combined with TEGDMA (T), UDMA (U) or Bis-EMA (E), as follows (in mol%): 30B:70T; 30B:35T:35U; 30B:70U; 30B:35T:35E; 30B:70E. Bimodal filler was introduced at 80 wt%. Single-edge notched beams for fracture toughness (FT, 25 mm × 5 mm × 2.5 mm, a/w = 0.5, n = 20) and 10 mm × 2 mm × 1 mm beams for flexural strength (FS) and modulus (FM) determination (10 mm × 2 mm × 1 mm, n = 10) were built and then stored in distilled water for 24 h at 37 °C. All FS/FM beams and half of the FT specimens were immediately submitted to three-point bending test. The remaining FT specimens were stored in a 75%ethanol/25%water (v/v) solution for 3 months prior to testing. DC was determined with FT-Raman spectroscopy in fragments of both FT and FS/FM specimens at 24 h. Data were submitted to one-way ANOVA/Tukey test (α = 5%).ResultsThe 30B:70T composite presented the highest K_Ic value (in MPa m^1/2) at 24 h (1.3 ± 0.4), statistically similar to 30B:35T:35U and 30B:70U, while 30B:70E presented the lowest value (0.5 ± 0.1). After ethanol storage, reductions in K_Ic ranged from 33 to 72%. The 30B:70E material presented the lowest reduction in FT and 30B:70U, the highest. DC was similar among groups (69–73%), except for 30B:70U (52 ± 4%, p < 0.001). 30B:70U and 30B:35T:35U presented the highest FS (125 ± 21 and 122 ± 14 MPa, respectively), statistically different from 30B:70T or 30B:70E (92 ± 20 and 94 ± 16 MPa, respectively). Composites containing UDMA or Bis-EMA associated with Bis-GMA presented similar FM, statistically lower than 30B:35T:35U.SignificanceComposites formulated with Bis-GMA:TEGDMA:UDMA presented the best compromise between conversion and mechanical properties.     

“Metabolism of Odontoblast-like cells submitted to transdentinal irradiation with blue and red LED”

ObjectivesThe present study evaluated the trans-dentinal effect of light emitting diodes (LEDs) irradiation on the metabolism of odontoblast-like cells.MethodsSeventy-two dentin discs (0.2 mm thick) were obtained from human molar teeth. MDPC-23 cells (20,000 cells/disc) were seeded on the pulpal side of the discs using DMEM, supplemented with 10% fetal bovine serum (FBS). After 12 h, the culture medium was replaced with DMEM containing 0.5% FBS. After additional 12 h, blue (455 ± 10 nm) or red (630 ± 10 nm) LEDs were used at irradiances of 80 and 40 mW/cm², respectively, to irradiate the occlusal side of the discs. The energy doses were fixed at 2 or 4 J/cm². Cell viability, alkaline phosphatase activity (ALP), total protein production and collagen synthesis were evaluated 72 h after irradiation. Data were submitted to Kruskal-Wallis and Mann-Whitney tests (α=0.05).ResultsRed light promoted proliferative effects at the energy dose of 4 J/cm²_. Conversely, cell cultures irradiated with 2 J/cm² emitted by the blue light showed reduced viability. ALP production was stimulated by red light in comparison with blue light at 4 J/cm². Total protein production was reduced after exposure to blue light at 4 J/cm², while no effect was observed on collagen production.ConclusionsIrradiation with red LED at 4 J/cm² bio-stimulated the viability of odontoblast-like cells, whilst blue light had unfavorable effects on the cellular metabolism.     

Amazonian delicacy tucupi is as erosive as a cola-based soft drink

ObjectiveAcidic diets are advocated as main risk factor for tooth erosion, which could be prevented, or at least controlled, if patients were early advised. It is important to identify, hence, if possible dietary constituents regionally consumed on large scale, such as tucupi, a low-pH yellowish-green color and strong flavor delicacy made from the juice of a bitter cassava, may explain its occurrence in specific patient groups. This cross-over in situ/ex vivo study evaluated tucupi's ability to promote erosion of bovine enamel by assessing its percentage of surface microhardness change (%SMHC), taking a cola-based soft drink and human saliva as positive and negative controls.DesignFor three 7-days spaced out legs of 7 days each, nine volunteers wore palatal devices with three bovine enamel blocks, which were challenged with one of the following solutions: TUC—tucupi (n = 27); COL—cola-based soft drink (n = 27); SAL—saliva (n = 27). Erosive challenges were performed extra-orally (4×/day) by dropping TUC or COL at room temperature on specimens. After 5 min, palatal devices were replaced into the mouth. SAL permanently acted as the negative control while volunteers solely wore the device. One-way ANOVA followed by Tukey’s post-hoc tests (α = 0.05) were applied.ResultsTUC promoted an enamel %SMHC (−21.56 ± 10.08^a) similar than that promoted by COL (−18.19 ± 12.99^a; p = 0.275), which were both significantly higher than that promoted by SAL (−1.86 ± 13.65^b; p < 0.0001).ConclusionsBesides the most worldwide appreciated cola-based soft drink, the greatly consumed Amazonian delicacy tucupi can be considered a potential risk factor for tooth erosion.     

Rinsing with antacid suspension reduces hydrochloric acid-induced erosion

ObjectiveMouthrinsing with antacids, following erosive episodes, have been suggested as a preventative strategy to minimize tooth surface loss due to their neutralizing effect. The purpose of this in situ study was to evaluate the effect of an antacid suspension containing sodium alginate, sodium bicarbonate and calcium carbonate in controlling simulated erosion of enamel of intrinsic origin.DesignThe experimental units were 48 slabs (3 × 3 × 2 mm) of bovine enamel, randomly divided among 12 volunteers who wore palatal appliances with two enamel slabs. One of them was exposed extra-orally twice a day to 25 mL of a hydrochloric acid (HCl) solution (0.01 M, pH 2) for 2 min. There were two independent phases, lasting 5 days each. In the first phase, according to a random scheme, half of the participants rinsed with 10 mL of antacid suspension (Gaviscon^®, Reckitt Benckiser Healthcare Ltd.), while the remainder was rinsed with deionized water, for 1 min. For the second phase, new slabs were inserted and participants switched to the treatment not received in the first stage. Therefore, the groups were as follows: (a) erosive challenge with HCl + antacid suspension; (b) erosive challenge with HCl + deionized water (DIW); (c) no erosive challenge + antacid suspension; (d) no erosive challenge + DIW. Specimens were assessed in terms of surface loss using optical profilometry and Knoop microhardness. The data were analyzed using repeated measures two-way analysis of variance and Tukey’s tests.ResultsCompared to DIW rinses, surface loss of enamel was significantly lower when using an antacid rinse following erosive challenges (p = 0.015). The Knoop microhardness of the enamel was significantly higher when the antacid rinse was used (p = 0.026).ConclusionsThe antacid suspension containing sodium alginate, sodium bicarbonate and calcium carbonate, rinsed after erosive challenges of intrinsic origin, reduced enamel surface loss.     

Maxillary sinus floor augmentation and dental implant placement using dentin matrix protein-1 gene-modified bone marrow stromal cells mixed with deproteinized boving bone: A comparative study in beagles

ObjectiveThe aim of the study was to evaluate the effects of the combined use of dentin matrix protein-1 (DMP1) gene-modified bone marrow stromal cells (BMSCs) and Bio-Oss^® for maxillary sinus floor augmentation (MSFA) implant placement in dogs.Materials and methodsBMSCs were derived from bone marrow of six beagles and cultured. The cells were transduced with a lentiviral vector overexpressing the DMP1 gene and enhanced green fluorescent protein (EGFP) gene (Lenti-DMP1/EGFP) in test group, and with a lentiviral vector encoding EGFP gene (Lenti-EGFP) in control group. Six dogs received sinus augmentations using the bilateral approach with a simultaneous implant placement at each site respectively. At the same concentration, 2 × 10⁷ cells/ml, one sinus was grafted using a mixture of autologous DMP1/EGFP gene-modified BMSCs and Bio-Oss^® (DMP1 group), and the contralateral sinus was grafted with autologous EGFP gene-modified bMSCs and Bio-Oss^® (EGFP group). After a 3 month healing period, bone regeneration and osseointegration were evaluated using histologic and histomorphometric methods.ResultsThe bone-implant contact (BIC) and the bone area fraction in the DMP1 group (BIC: 34.67% ± 8.23%, bone area fraction: 35.16% ± 3.32%) were significantly greater compared with the EGFP group (BIC: 26.06% ± 5.16%, bone area fraction: 20.74% ± 1.63%) (P < 0.05). No significant difference between the residual bone substitute material volume (BSMV) in the DMP1 group (35.86 ± 7.35) and the EGFP group (32.16 ± 9.16) was found in our study (P > 0.05).ConclusionBMSCs modified with the DMP1 gene can be used as an adjunct to Bio-Oss^® to enhance new bone formation and the osseointegration of dental implants in MSFA of dogs.     

Elevation of white blood cells and platelet counts in patients having chronic periodontitis

Background and aimMany risk factors that might contribute to the pathogenesis of atherosclerosis have been proposed, including chronic inflammation and infection. Furthermore, systemic inflammatory responses to periodontal bacteria have been suggested as a pathogenetic link between periodontal disease and atherosclerosis. The purpose of this study was to estimate the white blood cell (WBC) and platelet counts in chronic periodontitis patients.Materials and methodsFifty patients with chronic periodontitis and 50 patients with healthy periodontium were included in this study. Oral hygiene status, pocket probing depth (PPD) and clinical attachment level (CAL) were measured. During clinical evaluation, venous blood samples were taken to analyze the WBC and platelet counts. Statistical analysis was utilized to compare differences across groups.ResultsPeriodontitis patients demonstrated a significantly higher WBC count (7.22 ± 1.42 × 10⁹ cells/L) than that of control patients (5.64 ± 1.56 × 10⁹ cells/L; P < 0.001). The platelet count of patients with chronic periodontitis (290.73 ± 56.56 × 10⁹ cells/L) was also significantly higher compared to the healthy group (223.37 ± 50.27 × 10⁹ cells/L; P < 0.001).ConclusionLevels of WBCs and platelets are elevated in periodontitis patients compared to healthy controls.     

Differences in the biomechanical behaviors of natural teeth and dental implants

ObjectiveThe lack of a PDL, which acts as an energy absorber, is a contributor to implants’ early failure; however, these discrepancies are not well understood because of limited in vivo research. This study investigated the discrepancy in biomechanical behaviors between natural teeth and dental implants by detecting micro-movements in vivo.MethodsWe designed a device that could measure precisely mechanical behaviors such as creep, stress relaxation, and hysteresis by using load–control displacement on teeth and implants. We also compared energy dissipation between natural teeth and dental implants by subtracting the area of the hysteresis loop of natural teeth from that of dental implants.ResultsBiphasic curves with an initial phase of rapid response and a subsequent phase of slow response were confirmed in creep and stress relaxation curves for the load–time relationship in natural teeth. By contrast, the behavior of creep or stress relaxation was less prominent when the dental implants were tested. We observed that the periodontal ligament under an axial intrusive load of 300 g in a loading rate 3 g/s could dissipate the energy of 7.35 ± 1.18 × 10^?2 mJ, approximately 50 times that of the dental implants (1.47 ± 1.22 × 10^?3) with statistically significant (p < 0.05).SignificanceWe confirmed natural teeth could achieve greater energy dissipation compared to dental implants, which owe to that natural teeth exhibited fluid and viscoelastic properties.     

Effect of chlorhexidine application on long-term shear bond strength of resin cements to dentin

PurposeThe purpose of this study was to investigate the effect of chlorhexidine [CH] on dentin bond strength of three resin cements after 1 year of water storage.MethodsA flat middle dentin surface was prepared on 120 extracted premolars. The teeth were randomly divided into 6 groups of 20 specimens each according to the resin cement used: Panavia F2.0, Variolink II, and RelyX Unicem, with or without CH application. After cementation of an indirect composite rod [Z250], one subgroup [n = 10] was tested after 24 h in water at 37 °C and the other subgroup [n = 10] was tested after 1 year storage in water plus thermocycling. A shear bond strength [SBS] test was performed. The data [in MPa] were analyzed with ANOVA and Tukey tests [P < 0.05].ResultsThree-way ANOVA [resin cement, CH and time] indicated that Variolink II had the highest strength [16.65 ± 3.60] and RelyX Unicem had the lowest strength [9.30 ± 4.07]. Chlorhexidine application increased SBS [13.31 ± 4.61] compared to samples without CH [12.16 ± 5.04] [P = 0.04]. Initial SBS [15.63 ± 4.37] was significantly higher than after 1 year of storage [9.85 ± 3.36] [P < 0.001]. Separate two-way ANOVA for 24-h and 1-year data showed that cement had a significant effect but CH and its interaction had no significant effect at 24 h, whereas at 1 year the two factors and their interaction differed significantly [P ≤ 0.001].ConclusionsChlorhexidine 2% can diminish the loss of bonding effectiveness over time associated to etch-and-rinse and self-etch cements, although it appears not have any effect on self-adhesive cement.     

Impact of thermal misfit on shear strength of veneering ceramic/zirconia composites

ObjectivesThermal misfit is discussed as one reason for chipping of veneered zirconia restorations. The aim of the investigation was to assess the effect of thermal misfit on the shear strength of zirconia/veneering ceramic composites.MethodsShear strengths of 12 different veneering ceramic/zirconia composites were measured (n = 10). The veneering ceramics were fired onto polished Y-TZP. In order to create a strong thermal mismatch, one of the veneering ceramics was intended for use on alumina and one for the metal–ceramic technique. The glass transition temperatures of the veneering ceramics and the coefficients of thermal expansion of all ceramics were measured (n = 6). Statistical analysis was performed with one-way ANOVA and a post hoc Bonferroni test (p < 0.05).ResultsShear strength ranged from 21.9 ± 6.2 to 31.0 ± 7.1 MPa. The ceramic for the metal–ceramic technique showed spontaneous debonding. The differences in the coefficients of thermal expansion of core and veneer (Δα) were calculated. In addition the differences between glass transition temperatures of the veneering ceramics and room temperature (ΔT) as the effective temperature range for stress formation were calculated. Highest shear strength was observed when ΔαΔT ≈ 1000 × 10^?6.ConclusionsThermal expansion and glass transition temperature of the veneering ceramic have an impact on the shear strength of veneer/zirconia composites.     

Denaturing gradient gel electrophoresis profiles of bacteria from the saliva of twenty four different individuals form clusters that showed no relationship to the yeasts present

ObjectivesThe aim was to investigate the relationship between groups of bacteria identified by cluster analysis of the DGGE fingerprints and the amounts and diversity of yeast present.MethodsBacterial and yeast populations in saliva samples from 24 adults were analysed using denaturing gradient gel electrophoresis (DGGE) of the bacteria present and by yeast culture.ResultsEubacterial DGGE banding patterns showed considerable variation between individuals. Seventy one different amplicon bands were detected, the band number per saliva sample ranged from 21 to 39 (mean ± SD = 29.3 ± 4.9). Cluster and principal component analysis of the bacterial DGGE patterns yielded three major clusters containing 20 of the samples. Seventeen of the 24 (71%) saliva samples were yeast positive with concentrations up to 10³ cfu/mL. Candida albicans was the predominant species in saliva samples although six other yeast species, including Candida dubliniensis, Candida tropicalis, Candida krusei, Candida guilliermondii, Candida rugosa and Saccharomyces cerevisiae, were identified. The presence, concentration, and species of yeast in samples showed no clear relationship to the bacterial clusters.ConclusionDespite indications of in vitro bacteria-yeast interactions, there was a lack of association between the presence, identity and diversity of yeasts and the bacterial DGGE fingerprint clusters in saliva. This suggests significant ecological individual-specificity of these associations in highly complex in vivo oral biofilm systems under normal oral conditions.     

Maxillary sensory nerve responses induced by different types of dentures

PurposeThe purpose of this study was to investigate whether different types of dentures induced different responses to stimulations in sensory nerve underlying the denture-supporting mucosa using current perception threshold (CPT).Materials and methodsThe study population comprised 45 complete denture wearers with a mean age of 69.7 years (CD), 30 partial denture wearers (PD) with a mean age of 67.1 years, and 40 dentulous participants with a mean age of 69.0 years (Dent). Current perception threshold (CPT) on the greater palatine nerve at 2000 Hz, 250 Hz, and 5 Hz, corresponding to A-beta, A-delta, and C fibers respectively, were measured by the Neurometer^® NS3000 device. The differences CPTs among CD, PD, and Dent groups were analyzed by Kruskal–Wallis test and Mann–Whitney U test with adjusting the multiple comparisons’ inflation of type 1 error rate by a Bonferroni correction.ResultsCPTs of CD, PD, and Dent group at 2000 Hz were 61.5 ± 45.8, 53.5 ± 25.3, 33.0 ± 11.4 (10^?2 mA) respectively. CPTs of CD, PD, and Dent group at 250 Hz were 29.2 ± 28.2, 20.1 ± 13.2, 14.3 ± 5.9 (10^?2 mA) respectively. CPTs of CD, PD, and Dent group at 5 Hz were 28.9 ± 23.4, 17.8 ± 12.2, 12.2 ± 5.6 (10^?2 mA) respectively. The CPTs at all frequencies increased in the following order: Dent < PD < CD wearer. The statistical analyses showed that the different types of dentures significantly affected CPTs at 2000 Hz (p < 0.0001), 250 Hz (p < 0.0001), and 5 Hz (p < 0.0001).ConclusionThe different types of dentures induce different responses to stimulations in the sensory nerve underlying the denture-supporting mucosa.     

Effect of Inula viscosa on the pellicle’s protective properties and initial bioadhesion in-situ

ObjectivesThe present in situ study investigated the effect of Inula viscosa tea on the pellicle’s acid protective properties and on initial oral biofilm formation.DesignBiofilm formation was performed on bovine enamel slabs on individual maxillary splints. Following 1 min of pellicle formation, eight subjects rinsed for 10 min with Inula viscosa tea and the splints remained for 8 h intraorally. Samples carried after 1-min rinsing with CHX (0.2%) or without rinse served as controls. BacLight™ staining, 4′,6-diamidino-2-phenylindole (DAPI)-staining and fluorescence in situ hybridization (FISH) were used for fluorescence microscopic detection of adherent bacteria. For investigation of acid protective properties, three subjects rinsed for 10 min with Inula viscosa tea after 1 min pellicle formation and kept the splints intraorally for further 19 min. Physiological 30-min pellicles and native enamel samples served as controls. After HCl incubation of the samples ex-vivo over 120 s (pH 2.0, 2.3, 3.0) calcium- and phosphate release were quantified photometrically. Potential influences on the pellicle’s ultrastructure by Inula viscosa tea were evaluated by transmission electron microscopy (TEM).ResultsApplication of Inula viscosa tea yielded a significant reduction of adherent bacteria on all enamel samples as detected by fluorescence microscopy. For calcium- and phosphate release no significant effect was recorded. TEM investigation indicated a modification of the pellicle’s ultrastructure, but no enhanced protection against erosive noxae.ConclusionRinsing with Inula viscosa tea influences the bacterial colonization on enamel in situ over 8 h but has no impact on acid protective properties of the pellicle.     

A voltammetric sensor based on graphene-modified electrode for simultaneous determination of catechol and hydroquinone

In this report, a voltammetric sensor for simultaneous determination of hydroquinone (HQ) and catechol (CC) was developed at a glassy carbon electrode modified with graphene (GR/GCE). The separation of oxidation and reduction peak (ΔE) is decreased from 281 to 31 mV for HQ and from 250 to 26 mV for CC at GR/GCE, respectively. Separation of the oxidation peak potentials for HQ and CC was about 112 mV in 0.10 M acetate buffer solution (pH 4.5), and the anodic currents for the oxidation of both HQ and CC are greatly increased at GR/GCE, which makes it suitable for simultaneous determination of these compounds. Under the optimized condition, the anodic peak current of HQ is linear with the concentration of HQ from 1 × 10^?6 to 5 × 10^?5 M in the presence of 5 × 10^?5 M CC. A detection limit of 1.5 × 10^?8 M (S/N = 3) can be achieved. At the same time, the anodic current of CC is linear with the concentration of CC from 1 × 10^?6 to 5 × 10^?5 M with a detection limit of 1.0 × 10^?8 M (S/N = 3) in the presence of 5 × 10^?5 M HQ. The proposed sensor was successfully applied to the simultaneous determination of HQ and CC in tap water, and the results are satisfactory.     

Diffusion-weighted imaging with histogram analysis of the apparent diffusion coefficient maps in the diagnosis of parotid tumours

The aim of this study was to investigate the role of diffusion-weighted imaging (DWI) with histogram analysis of apparent diffusion coefficient (ADC) maps in the characterization of parotid tumours. This prospective study included 39 patients with parotid tumours. All patients underwent magnetic resonance imaging with DWI, and ADC maps were generated. The whole lesion was selected to obtain histogram-related parameters, including the mean (ADC_mean), minimum (ADC_min), maximum (ADC_max), skewness, and kurtosis of the ADC. The final diagnosis included pleomorphic adenoma (PA; n = 18), Warthin tumour (WT; n = 12), and salivary gland malignancy (SGM; n = 9). ADC_mean (×10^?3 mm²/s) was 1.93 ± 0.34 for PA, 1.01 ± 0.11 for WT, and 1.26 ± 0.54 for SGM. There was a significant difference in whole lesion ADC_mean among the three study groups. Skewness had the best diagnostic performance in differentiating PA from WT (P = 0.001; best detected cut-off 0.41, area under the curve (AUC) 0.990) and in discriminating WT from SGM (P = 0.03; best detected cut-off 0.74, AUC 0.806). The whole lesion ADC_mean value had best diagnostic performance in differentiating PA from SGM (P = 0.007; best detected cut-off 1.16 × 10^?3 mm²/s, AUC 0.948). In conclusion, histogram analysis of ADC maps may offer added value in the differentiation of parotid tumours.