Immersion In Peroxide Research Articles

Investigating dynamics, etiology, pathology, and therapeutic interventions of Caligus clemensi and Vibrio alginolyticus co-infection in farmed marine fish

This study investigated a disease outbreak characterized by caligid copepod infestations and subsequent secondary bacterial infections in European seabass (Dicentrarchus labrax) and flathead grey mullet (Mugil cephalus) cultivated at a private facility in the Deeba Triangle region of Egypt. Moribund fish displayed brown spots on the skin, tongue, and gills, along with lethargy and excess mucus. The fish suffered severe infections, exhibiting external hemorrhages, ulcers, and ascites. The fish had pale, enlarged livers with hemorrhaging. Comprehensive parasitological, bacteriological, molecular, immunity and histopathological analyses were conducted to identify the etiological agents and pathological changes. Caligid copepod infestation was observed in wet mounts from the buccal and branchial cavities of all examined fish, and the caligids were identified as Caligus clemensi through COI gene sequencing and phylogenetic analysis. Vibrio alginolyticus was confirmed as a secondary bacterial infection through biochemical tests, recA gene sequencing, and phylogenetic analyses. Antibiotic susceptibility testing revealed resistance to β-lactams, aminoglycosides, and trimethoprim-sulfamethoxazole in V. alginolyticus isolates. Upregulation of the inflammatory marker IL-1β in gill and skin tissues indicated a robust cell-mediated immune response against the pathogens. Histopathological examination revealed severe tissue damage, hyperplasia, hemorrhage, and congestion in the gills, along with hepatocellular degeneration and steatosis in the liver, providing initial insights into this outbreak. A comprehensive therapeutic regimen was implemented, comprising prolonged hydrogen peroxide immersion baths, followed by the application of the nature-identical plant-based compound Lice-less and probiotic Sanolife Pro-W supplementation. This integrated approach effectively eliminated C. clemensi infestations, controlled secondary bacterial infections, and restored fish health, reducing morbidity and mortality rates to minimal levels.

Effects of Combinations of Hydrogen Peroxide and Vinegar in Different Ratios on the Surface Roughness of Heat-Cure Denture Base Acrylic Resin

Background: Complete dentures are at high risk of contamination, and their disinfection is imperative to prevent cross-contamination. Also, chemical disinfecting agents can effectively eliminate microorganisms. This study aimed to assess the effect of combinations of hydrogen peroxide (HP) and vinegar in different ratios on the surface roughness of heat-cure denture base acrylic resin. Methods: This in vitro, experimental study evaluated 40 heat-cure acrylic resin specimens that were flasked and heated at 70 ° C for 9 hours for heat polymerization. The acrylic specimens were cut into small cubic pieces measuring 20×20×3 mm using a cutting machine and polished with metallographic abrasive paper. The specimens were randomized into 4 groups of control (artificial saliva) and HP and vinegar in 1:1, 1:3, and 3:1 ratios (three experimental groups). Then, they were immersed in the respective solutions for 8 hours/day for one month. Their surface roughness (Ra) was measured before and after immersion by a profilometer. The data were analyzed using a one-way analysis of variance (α=0.05). Results: The immersion of acrylic specimens in HP+vinegar in 1:1 and 1:3 ratios did not cause a significant change in their surface roughness (P>0.05). However, the surface roughness significantly decreased after immersion in HP+vinegar in a 3:1 ratio (P=0.032). Despite the reduction in the surface roughness of specimens in the 3:1 group, the difference in surface roughness was not significant among the four groups after immersion (P>0.05). Conclusion: Combinations of HP and vinegar in different ratios appear to be suitable for cleaning removable dentures due to their insignificant effects on the surface roughness of acrylic resin.

Breaking Dormancy of Shallot (Allium ascolonicum L.) Bulb Using Hydrogen Peroxide

Shallot bulbs have a dormancy period, so they must be stored for 3-4 months. This condition inhibits the acceleration of planting, which has a short time, so efforts are needed to accelerate the dormancy period by using hydrogen peroxide. This research was carried out from June to July 2023 at the Screen House, Teaching Farm, Faculty of Agriculture, Hasanuddin University. The study was arranged in a randomized block design with a two-factor factorial design. The first factor is the variety of Mentes, Rubaru, Violetta 2 Agrihorti, Kramat 1, and Ambassador 3 Agrihorti. The second factor is hydrogen peroxide concentration with three levels, namely 0%, 10% and 20%. The results showed that breaking the dormancy of shallot bulbs using hydrogen peroxide at a concentration of 20% effectively triggered the process of bulb growth in the various shallot varieties tested, marked by an increase in the percentage of rooted and sprouted bulbs. The Rubaru and Mentes varieties had an excellent response to 20% hydrogen peroxide immersion, indicated by a shorter rooting and sprouting time, compared to other varieties and concentrations of hydrogen peroxide. Therefore, hydrogen peroxide with a concentration of 20% can be used to break dormancy in shallot bulbs. However, further studies are needed on growth and production in the field and the quality and safety of shallot bulbs. Keywords: Bulb, Dormancy, Hydrogen peroxide, Shallot.

Does microwave and hydrogen peroxide disinfection reduce Candida albicans biofilm on polymethyl methacrylate denture surfaces?

Statement of problemWhether the disinfection of polymethyl methacrylate (PMMA) dentures eliminates Candida albicans biofilm is unclear. PurposeThe purpose of this in vitro study was to determine the antimicrobial effect of immersion in hydrogen peroxide (H2O2) and subsequent application of microwaves on the formation of C albicans biofilm on the surface of polished and unpolished PMMA disks. Material and methodsPolished and unpolished PMMA disks (n=40) were mounted in a Center for Disease Control (CDC) biofilm reactor by adding yeast-dextrose-peptone (YPD) broth inoculated with C albicans in a cell suspension for 24 hours. After this period, the PMMA disks (n=8) were disinfected with 5 different solutions: saline solution, 1% sodium hypochlorite (NaOCl), H2O2, H2O2 microwaved at 650 W for 3 minutes (H2O2/μw), and distilled water microwaved at 650 W for 3 minutes (H2O/μw). On the polished and unpolished surface of each disk, arbitrary fluorescence units (AFU) were quantified with the live/dead bacterial viability kit (Invitrogen) by using confocal laser scanning microscopy (CLSM) to evaluate 10 different areas of each surface; these were counted as the colony-forming units (CFUs). The mean values were compared by using the Mann–Whitney U test (α=.05). ResultsPolished surfaces disinfected with H2O2/μw obtained the lowest viable cells (9.76 AFU) and nonviable cells (12.46 AFU) compared with H2O/μw and H2O2. In the unpolished surface the lowest mean values of viable cells (14.64 AFU) and nonviable cells (12.46 AFU) were obtained for the PMMA disks disinfected with H2O/μw compared with H2O2/μw and H2O2. Both polished and unpolished disks showed significant difference (P<.05) compared with the group of PMMA disks immersed in saline solution. No CFUs were detected in the polished or unpolished PMMA disks immersed in H2O2/μw or in NaOCl. ConclusionsH2O2 alone did not eliminate the formation of the biofilm of C albicans; however, in combination with the use of the microwave at 650 W for 3 minutes, the biofilm formation of C albicans on polished surfaces was reduced. The number of AFUs of viable-nonviable cells and CFUs depended on whether the surfaces are polished or unpolished.

EFFECT OF DENTURE CLEANSERS ON HARDNESS OF ACRYLIC SOFT LINER

Plasticizer is the content of the soft liner (with soft acrylic polymer (poly ethylmethacrylate)) or denture tissue conditioner material that maintains the soft said material. However, it will release as a result of the saliva or water solution being absorbed that could be effected on the acrylic soft liner physical properties such as a hardness. Selection of the denture cleanser is very important to minimize its impact, which is the traditional plant cinnamon (Cinnamomum burmani) can be used as an alternative of natural denture cleansure agents besides alkaline peroxide chemicals used frequently. The aim of this study was to determine the effect of different denture cleansers on hardness of acrylic soft liner. Method: Eighteen cylindrical acrylic soft liner samples (15mm x 10 mm (ASTM: D-2240 64T)) were divided into 3 groups : group I aquadest immersion, group II alkaline peroxide immersion and group III cinnamon immersion. The measurement of acrylic soft liner hardness was done using Shore A hardness D2240 after 7 days of immersion. The results were submitted to one-way ANOVA and post hoc Bonferroni. Results: The highest average of acrylic soft liner hardness was shown by alkaline peroxide immersion group followed by cinnamon immersion group and aquadest immersion group sequentially. There was a significant difference between all groups (p&lt;0.05). Conclusion: There was effect of different denture cleansers on hardness of acrylic soft liner. Keywords: soft liner, denture cleanser, cinnamon

Effect of Hydrogen Peroxide on Cyclic Fatigue Resistance of NiTi Endodontic Files

OBJECTIVE: To investigate the effect of nickel titanium rotary endodontic file immersion in hydrogen peroxide on cyclic fatigue resistance. METHODOLOGY: Twenty Six Protaper Universal (Dentsply Maillerfier) F1 files were randomly divided into two experimental groups. In Group I, Protaper universal variable taper F1 files were immersed in normal saline where as in Group II, the files were soaked in hydrogen peroxide (6% w/v) for 2 hours at 37°C. Cyclic fatigue of each file was checked by recording the number of rotations required to break a file in a 90°curve with a 5 mm radius. For statistical analysis of data, Two-way ANOVA was applied. A p value of &lt;0.05 was considered significant. RESULT: Out of Twenty Six, Six files fractured spontaneously after immersion in hydrogen peroxide. Twenty files were subjected to fracture resistance testing. Statistically significant difference in cyclic fatigue resistace between the two groups was found (p=0.002). The files soaked in Group II required less revolutions to fracture than the ones immersed Group I. CONCLUSION: The immersion of NiTi endodontic files in hydrogen peroxide significantly reduces cyclic fatigue resistance. Therefore, immersion of the NiTi endodontic files in hydrogen peroxide solution for removal of clogged debris should be discouraged. KEYWORDS: Cyclic fatigue, Endodontic instruments, Hydrogen peroxide, NiTi HOW TO CITE: Sarwar H, Naeem MM, Shabbir S, Riaz S, Afaq H, Shabbir J. Effect of hydrogen peroxide on cyclic fatigue resistance of NiTi endodontic files. J Pak Dent Assoc 2020;29(4):246-248.

Surface damage of dental implant systems and ions release after exposure to fluoride and hydrogen peroxide.

The aim of this study was to evaluate surface changes on dental implant systems and ions release after immersion in fluoride and hydrogen peroxide. Ten implant-abutment assemblies were embedded in acrylic resin and cross-sectioned along the implant vertical axis. Samples were wet ground and polished. Delimited areas of groups of samples were immersed in 1.23% sodium fluoride gel (F) or in 35% hydrogen peroxide (HP) for 16min. Gels (n=3) were collected from the implant surfaces and analyzed by inductively coupled plasma mass spectrometry (ICP-MS), to detect the concentration of metallic ions released from the implant systems. Selected areas of the abutment and implant (n=15) were analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). SEM images revealed surface topographic changes on implant-abutment joints after immersion in fluoride. Implants showed excessive oxidation within loss of material, while abutment surfaces revealed intergranular corrosion after immersion in fluoride. ICP-MS results revealed a high concentration of Ti, Al, V ions in fluoride after contact with the implant systems. Localized corrosion of implant systems could not be detected by SEM after immersion in hydrogen peroxide although the profilometry showed increase in roughness. ICP-MS showed the release of metallic ions in hydrogen peroxide medium after contact with dental implants. Therapeutical substances such as fluorides and hydrogen peroxide can promote the degradation of titanium-based dental implant and abutments leading to the release of toxic ions.

Denture disinfection by brushing and 6% hydrogen peroxide immersion on denture base resin after biofilm formation: An in vitro study

Background: Biofilm formation on acrylic dentures is often seen in denture wearers for which wide variety of denture cleansers are available. This study uses the commonly available 6% British Pharmacopoeia grade 20 volume hydrogen peroxide as denture cleanser. Aim: The aim of this study was to evaluate colonization and population dynamics of oral pathogenic microbial biofilm formation after assigning to one of the cleansing methods, manual brushing, or compound method (manual brushing with soft bristle wetted in distilled water and rinsed then immersion in 6% hydrogen peroxide solution) for the heat-cure acrylic denture base resin. Materials and Methods: Specimens of heat-cure acrylic resins discs were fabricated n = 120. Specimens n = 60 were placed in bacterial culture (Group I) and n = 60 were placed in fungal culture (Group II) until the formation of a biofilm which then was subjected to denture cleansing. They were then immersed in respective broth. The specimens were discarded, and Petri plate was incubated, and colony-forming units (CFUs) were counted. Values of microorganisms were grouped and analyzed according to the different hygiene methods by the Kruskal–Wallis test. Pairwise comparison was done by Mann–Whitney U-test. Results: The CFU in Group I and Group II after brushing was 60 CFU/ml and 50 CFU/ml, respectively. The CFU in Group I and Group II after subjecting to compound method was 1 CFU/ml. Conclusion: The compound method of this study was better when compared to only brushing method. Therefore, for the better maintenance of oral hygiene in denture wearers, the dentures need to be cleaned by manual brushing followed by immersion in hydrogen peroxide solution.

Facile Modulation of Electrical Properties on Al doped ZnO by Hydrogen Peroxide Immersion Process at Room Temperature

Facile Modulation of Electrical Properties on Al doped ZnO by Hydrogen Peroxide Immersion Process at Room Temperature

Pretreatment For Removal of Organic Material Is Not Necessary For X-Ray-Diffraction Determination of Mineralogy In Temperate Skeletal Carbonate

Abstract: Quantifying the effects of ocean acidification requires understanding the skeletal carbonate mineralogy in living marine organisms. X-ray diffractometry (XRD) is the simplest and most commonly used technique for determining this. Samples being analyzed by XRD are typically pretreated to remove organic material prior to grinding to a crystallite powder. This pretreatment was traditionally performed as organic material may obscure the mineral peaks on XRD traces. This study compared controls with no pretreatment with the most common pretreatment methods: roasting, immersion in chlorine bleach, and immersion in hydrogen peroxide. The latter two methods were performed at two strengths and two durations. We test the hypothesis that bleaching and/or roasting of skeletal carbonate to remove organic material does not affect the mineralogy of temperate skeletal carbonate at a scale detectable by XRD. This was done with biogenic skeletal carbonate from temperate marine environments around southern New Zealand. Specimens included 5 species of bivalve mollusks, 4 species of bryozoans, 2 species of barnacles, as well as 1 species each of serpulid worm, echinoid, gastropod mollusk, brachiopod, and coralline algae. Comparison to the untreated control showed that all pretreatments removed some organic matter and that the presence of organic matter in temperate skeletal carbonate does not affect the ability to qualitatively interpret mineralogy or semiquantitatively measure mineralogy using XRD. Given that pretreatment does not appear to be necessary and that some methods at least can cause unacceptable changes in mineralogy, we recommend that pretreatment for the removal of organic material be abandoned.

Cooperative Effects in Aligned and Opposed Multicomponent Charge Gradients Containing Strongly Acidic, Weakly Acidic, and Basic Functional Groups.

Bifunctionalized surface charge gradients in which the individual component gradients either align with or oppose each other have been prepared. The multicomponent gradients contain strongly acidic, weakly acidic, and basic functionalities that cooperatively interact to define surface wettability, nanoparticle binding, and surface charge. The two-step process for gradient formation begins by modifying a siloxane coated silicon wafer in a spatially dependent fashion first with an aminoalkoxysilane and then with a mercapto-functionalized alkoxysilane. Immersion in hydrogen peroxide leads to oxidation of the surface immobilized sulfhydryl groups and subsequent protonation of the surface immobilized amines. Very different surface chemistries were obtained from gradients that either align with or oppose each other. X-ray photoelectron spectroscopy (XPS) data show that the degree of amine group protonation depends on the local concentration of sulfonate groups, which form ion pairs with the resulting ammonium ions. Contact angle measurements show that these ion pairs greatly enhance the wettability of the gradient surface. Finally, studies of colloidal gold binding show that the presence of both amine and thiol moieties enhance colloid binding, which is also influenced by surface charge. Cooperativity is also revealed in the distribution of charges on uniform samples used as models of the gradient surfaces, as evaluated via zeta potential measurements. Most significantly, the net surface charge and how it changes with distance and solution pH strongly depend on whether the gradients in amine and thiol align or oppose each other. The aligned multicomponent gradients show the most interesting behavior in that there appears to be a point at pH ∼ 6.5 where surface charge remains constant with distance. Setting the pH above or below this transition point leads to changes in the direction of charge variation along the length of the substrate.

A new sample processing protocol for procuring seawater REE signatures in biogenic and abiogenic carbonates

Rare Earth Elements are important proxies for tracing the evolution and redox history of the Earth's hydrosphere. Many biogenic and abiogenic archives have been analyzed for their REE contents with qualified success, which may be due to depositional and post-depositional alteration effects. Review of the database reveals a lack of a rigorous sample processing protocol and probably the leading cause for the spurious REE results reported in the literature.We propose a ‘sample cleaning protocol’ that should satisfy the most stringent demands for procuring reliable and robust REEs from marine materials. Without cleaning, the results may represent REE compositions not only of the shell's structure but also of lattice-bound oxides, detritus, particulates and organic remnants. Thus, cleaning of material is a fundamental step that should be conducted with care and attention to detail prior to analyzing their REE contents. To achieve this goal, valves from recently dead Liothyrella neozelanica recovered from deep water of the South Pacific Ocean (north of New Zealand) were subjected to five different cleaning procedures. In Procedure-1 (P-1) valve fragments were only washed and rinsed with distilled water. In Procedure-2 (P-2) a set of fragments was immersed in 2.5% hydrogen peroxide (H2O2) for three continuous days and then water washed. In Procedure-3 (P-3) valve fragments were physically cleaned using a sharp stainless-steel blade and then water washed. In Procedure-4 (P-4) a set of fragments was physically cleaned then immersed briefly in 10% hydrochloric acid (HCl) until they were deemed clean, and then water washed. In Procedure-5 (P-5) the last set of fragments was processed using all cleaning protocols such as physical scraping, H2O2, HCl leaches and water washing.Detritus and nano-particulates adsorbed on the calcitic structure of brachiopod shells including the proteinaceous periostracum may lead to elevated ∑REE content, anomalous Ce/Ce* and elevated Mn, Fe and U concentrations as documented by the P-1 protocol results. Hydrogen peroxide immersion (P-2) eliminates primarily the organic tissue, which leads to an invariant Ce/Ce* anomaly. Physical cleaning (P-3) removes adsorptive nano-particulates and the periostracum, and leads to depleted ∑REE and lower Mn, Fe, and U concentrations with a slight Ce/Ce* anomaly. Physical cleaning followed by chemical cleaning (P-4 and P-5) removes adsorptive particulates, organic remnants, the periostracum and the primary layer. These last two procedures produce drastic reductions in ∑REE, Mn, Fe, and U concentrations and normal Ce/Ce* anomalies with typical seawater REE signatures in brachiopod calcite.Procedure P-4 was tested on Silurian, Pennsylvanian and Permian brachiopods and enclosing whole rock as well as conodonts and fish debris to assess the reliability of REE contents in Deep-Time fossils and carbonates. The brachiopod shells contain ∑REEs, Mn, Fe, and U concentrations and Ce/Ce* values comparable to their modern counterparts, while in the coeval micritic whole rock they are slightly to significantly enriched. Those with elevated Fe and Mn (by more than 300 and 100ppm, respectively) their Ce/Ce* values should be adjusted by −13% if they are to be considered in paleoredox investigations. In contrast, REE contents of conodonts give the typical ‘bell shape’ trend for the lanthanides indicative of post-depositional alteration coupled with extraneous Ce/Ce* anomaly values. Strict adherence to the proposed sample processing protocol is critical if we want reliable and robust ‘seawater’ REE signatures from brachiopods and whole rocks, and potentially other archives.

Condensation heat transfer enhancement by surface modification on a monolithic copper heat sink

In this study, the condensation heat transfer performance on a pure copper surface, as well as a superhydrophobic-modified copper surface were compared. Differing from other condensation heat transfer experimental designs, a monolithic copper heat sink was utilized in this study to prevent contact thermal resistance and/or thermal conduction limitation of the thermal paste applied between the modified condensation surface and heat sink plate. This approach has not yet been documented in the literature. The superhydrophobic copper heat sink surface was prepared using a hydrogen peroxide immersion and fluorosilane polymer (EGC-1720) spin-coating. Experimental results show that the condensation heat transfer performance on the superhydrophobic copper surface is superior to that of a pure copper surface. Additionally, durability tests of the pure and superhydrophobic coating copper surfaces in a harsh vapor environment are discussed in this study.

A systematic review and cost-effectiveness analysis of tonometer disinfection methods

ObjectiveThe Goldmann applanation tonometer presents the problem of being one of the most widely used pieces of equipment in the ophthalmic clinic and a known risk factor for the transmission of epidemic keratoconjunctivitis (EKC). The purpose of this review is to assess the effectiveness of 3 methods of disinfection: alcohol swabs, immersion in peroxide, and the use of disposable prisms. An economic evaluation is undertaken to assess the cost-effectiveness of the 3 alternatives. In doing so, we contribute an evidence-based overview of the issue at an opportune time, because several jurisdictions are developing protocols regarding tonometer tip disinfection. DesignSystematic review and cost-effectiveness analysis. MethodsA comprehensive literature review was undertaken with a librarian, comprising searches of 6 electronic databases and hand searches of the grey literature. A 3-level screening process was undertaken by 2 reviewers according to prespecified inclusion and exclusion criteria. Values from included papers were used to inform a cost-effectiveness analysis undertaken using a decision tree model implemented in TreeAge. The analysis was undertaken from the hospital perspective and included all equipment and labour costs. ResultsSynthesis of in vitro data indicates that all 3 methods are plausible methods of disinfection with a 64% reduction in log growth of EKC when peroxide is used compared with alcohol swabs. The incremental cost-effective ratios from the cost-effectiveness analysis were $12 000/case averted using peroxide and $61 000/case averted with Tonosafe as compared with alcohol. ConclusionsAssuming clinical infection rates match in vitro disinfection data, the cost of bleach is high and the cost of Tonosafe is unacceptably high to reduce 1 potential case of adenoviral keratoconjunctivitis.

Effect of hydrogen peroxide and/or Flavobacterium psychrophilum on the gills of rainbow trout, Oncorhynchus mykiss (Walbaum).

The immune response and morphological changes in the gills of rainbow trout fry after immersion in hydrogen peroxide (H2O2), Flavobacterium psychrophilum or combined exposure were examined. The gills were sampled 4, 48, 125 and 192 h after exposure, and the regulation of expression of the following genes was investigated using qPCR: IgT, IgM, CD8, CD4, MHC I, MHC II, IL-4/13A, TcR-β, IL-10, IL-1β, IL-17, SAA and FoxP3. Bacteria were not observed in haematoxylin-and-eosin-stained gill tissue, but the presence of F. psychrophilum 16S rRNA was detected using qPCR. The 16S rRNA levels were correlated with gene expression. Although pretreatment with H2O2 before immersion in F. psychrophilum did not significantly alter the amount of bacteria found in the gill, the immune response was influenced: exposure to F. psychrophilum resulted in a negative correlation with expression of IL-17c1, MHC I and MHC II, while pretreatment with H2O2 resulted in a positive correlation with IL-4/13A and IgM. Exposure to either H2O2 or F. psychrophilum influenced the regulation of gene expression and damaged tissue. Exposure to both combined altered the immune response to infection and postponed healing of gill tissue.

EQCM Analysis of Titanium Corrosion in Peroxide- or Fluoride-Containing Solutions

Although offering superior resistance to corrosion, titanium is unable to withstand discoloration with exposure to peroxide or fluoride. The mechanism of this discoloration, however, remains to be clarified. The purpose of this study was to investigate the mechanism underlying discoloration of titanium with immersion in peroxide- or fluoride-containing solutions based on electrochemical quartz crystal microbalance (EQCM) analysis. A 9-MHz titanium-deposited quartz crystal was used as for the electrodes. Four test solutions were prepared for immersion of the electrodes: 154 mM (0.9%) NaCl; 150 mM H2O2+154 mM NaCl (pH=4 by addition of lactic acid); 150 mM H2O2+154 mM NaCl (pH=8 by addition of sodium hydroxide solution); and 48 mM (0.2%) NaF+154 mM NaCl (pH=5.0 by addition of lactic acid). A WinEchem electrochemistry software-controlled quartz crystal analyzer (QCA922) and the Potentiostat/Galvanostat (Princeton Applied Research) on Windows XP were used to measure concurrently the resonance frequency and potential of the electrodes. The EQCM data differed among solutions. In the acidulated fluoride-containing solution, the electrode showed lower open circuit potential and a gradual increase in electrode frequency, indicating a loss of mass by titanium dissolution. In the peroxide-containing solution, although open circuit potential showed no marked difference, electrode frequency showed a gentle decrease in acidic solution, indicating a gain in mass by oxidation; but an increase in alkaline solution, indicating a loss of mass by dissolution. These results confirmed that exposure to acidulated fluoride- or alkaline peroxide-containing solutions causes dissolution-induced discoloration, while that to acidulated peroxide-containing solutions resulted in the formation of an oxide film together with discoloration.

Infiltration of Natural Caries Lesions with Experimental Resins Differing in Penetration Coefficients and Ethanol Addition

Resin infiltration of enamel caries lesions requires materials optimized for penetration into the capillary structures of the lesion body. With increasing penetration coefficients (PC) improved penetration and caries-inhibiting properties of low-viscosity resins (infiltrants) could be observed in artificial caries lesions. The aim of the present in vitro study was to compare the penetrativity of experimental resins varying in PC and ethanol addition into natural caries lesions using this technique. Extracted human molars and premolars showing proximal white spot lesions (International Caries Detection and Assessment System: code 2) were etched for 2 min using 15% hydrochloric acid gel. After drying, the lesions were stained with tetramethylrhodamine isothiocyanate and 1 of 4 experimental resins (PC63; PC185; PC204; PC391) was applied for 5 min. The materials consisted of bisphenol-A-glycidyl-methacrylate (B), tri-ethylene-glycol-dimethacrylate (T) and ethanol (E) in ratios (B:T:E) of PC63: 25:75:0; PC185: 20:60:20; PC204: 0:100:0; PC391: 0:80:20. Excess material was removed before light curing. The teeth were sectioned perpendicularly to the lesion surfaces and unbound dye was bleached by immersion in hydrogen peroxide. The remaining lesion pores were stained with fluorescein solution. Lesion and penetration depths were analyzed using confocal microscopy (n = 60). At deep lesion sites the percentage penetration of PC204 was significantly higher compared to PC63 and PC391 (p < 0.05; Mann-Whitney test) but only slightly higher than PC185 (p > 0.05). It can be concluded that materials with high PC (infiltrants) are capable of penetrating almost completely into enamel parts of natural caries lesions in vitro. A solvent-free resin mainly consisting of triethylene glycol dimethacrylate seems to be preferable.

Effect of surface treatments of fiber posts on bond strength to composite resin cores

The purpose of the present study was to compare the influence of post-surface treatment with silane, hydrogen peroxide, hydrofluoric acid or sandblasting and to investigate the effect of silane in combination of the other treatments on the microtensile bond strength between fiber posts and composite resins for core build-up. Thirty-two glass-fiber posts (FRC Postec Plus, Ivoclar Vivadent, Schaan, Liechtenstein) were divided into eight groups according to the different surface pretreatments performed: silane application (S); immersion in 28% hydrogen peroxide (HP); immersion in hydrogen peroxide followed by application of silane (HP-S); immersion in 4% hydrofluoric acid gel (HF); immersion in hydrofluoric acid gel followed by application of silane (HF-S); sandblasting with aluminum oxide particles (SB); sandblasting followed by application of silane (SB-S). In control group, no surface treatment was performed. The composite resin (Tetric Flow, Ivoclar Vivadent, Schaan, Liechtenstein) was applied onto the posts to produce the composite cylinder specimen. It was sectioned into sticks to measure the microtensile bond strength. The data was analyzed with one-way ANOVA and LSD test for post hoc comparison (p < 0.05). Post pretreatment with sandblasting enhanced the interfacial strength between the fiber posts and core materials. Moreover, sandblasting followed by application of silane appears to be the most effective method that can improve the clinical performance of glass fiber posts. [J Kor Acad Cons Dent 35(3):173-179, 2010]

Validation of two dual fluorescence techniques for confocal microscopic visualization of resin penetration into enamel caries lesions

Fluorescence confocal microscopy is a useful tool to analyze the infiltration of enamel caries lesions with low-viscosity resins (infiltrants) in vitro. The conventionally used staining technique, which comprises dye labeling of the resin, has been shown to be limited by chromatographic separation of the resin-dye-mixture during penetration. The aim of this study was to develop an improved dual staining technique and to compare validity and reproducibility of both methods. Human molars with proximal white spots were cut across the demineralizations. After varnishing the cut surfaces, paired lesion halves were infiltrated with an infiltrant using either one of two different staining techniques. For the conventional direct technique (A) the infiltrant was labeled with rhodamine isothiocyanate (RITC) prior to application. Using the new indirect technique (B) lesions were stained with RITC solution and subsequently infiltrated with pure infiltrant. After light curing, unbound dye was bleached by immersion in hydrogen peroxide. Remaining lesion pores were stained with sodium fluorescein solution. Penetration depths (PD) and lesion depths (LD) were evaluated by five examiners using confocal microscopy and compared with the results of scanning electron microscopic (SEM; PD) and microradiographic (TMR; LD) analysis. The indirect technique showed better correlation (intraclass coefficients) with SEM (0.990) and TMR (0.982) compared with the direct technique (SEM: 0.513; TMR: 0.702). Inter- and intrarater reliability was higher for technique B compared with technique A. The new indirect technique yields to more valid and reliable results to visualize infiltrant penetration into natural enamel caries lesions compared with the conventional method.

Study on related factors in airway bacterial culture and inner tubes disinfection methods among patients after trachenstomy

Objective To investigate the classification of major bacteria and pathogen strains before and after inner tubes disinfection within the trachea after the tracheotomy, and to compare the method of disinfection and the results. Methods 110 patients after tracheotomy were randomly selected, and tracheal tubes were sampled before the disinfection and were conducted a bacterial culture analysis. These tracheal tubes were disinfected by boiling for 20 minutes and 30 minutes, respectively. Then they were soaked in 75% ethanol, 2% glularaldehyde and 3% hydrogen peroxide for 20 minutes and 30 minutes, respectively. The disinfection effects were compared among the four disinfection methods and disinfectants, and the two groups of disinfection time. Results 62 cases before the disinfection were sampled to make a bacterial culture. 89 strains in 18 species were cultivated, and no bacteria in six cases. Pathogenic bacteria and conditioned pathogen accounted for 80 percent (P<0.05). For the four disinfection methods including boiling disinfection, 75% ethanol, 2% glutaraldehyde and 3% hydrogen peroxide immersion disinfection, after 20 minutes of disinfection and immersion disinfection, 75% ethanol immersion disinfection had statistical meanings with the positive rates of boiling disinfection, 3% H2O2 and 2% glutaraldehyde soaking disinfection, respectively (P<0.05) ; After 30 minutes of disinfection, all of the four disinfection methods had no statistical meaning. Conclusions Pathogenic bacteria cultivated before the disinfection of tracheal tubes are much more than the non-pathogenic bacteria. Boiling disinfection for 20 minutes, 3% hydrogen peroxide and 2% glutaraldehyde disinfectant soaking for 20 minutes, and 75% ethanol immersion disinfection for 30 minutes can achieve good disinfection results. From the aspects of high efficiency, safety and low cost, 3% hydrogen peroxide is the best choice. Key words: Tracheostomy; Bacterial culture; Inner tubes; Disinfection