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PubMed1993

A prospective randomized trial comparing manual and automated endoscope disinfection methods.

OBJECTIVE: To compare the efficacy of endoscope disinfection using automated and manual systems. DESIGN: Prospective randomized trial. SETTING: A 1,000-bed tertiary care referral center. METHODS: All endoscopes underwent a three-stage decontamination process including brushing and cleaning with water and detergent, manual or automated disinfection with 2% glutaraldehyde, and 70% alcohol rinse with forced air drying. Cultures were obtained from endoscopes from both groups before and after alcohol rinse and then after overnight storage. RESULTS: Cultures from 8/30 (27%) automated and 11/30 (37%) manually disinfected (P = 0.58) endoscopes grew gram-negative bacteria and/or nontuberculous mycobacteria before the alcohol rinse. After alcohol rinse, 3 (10%) of 30 automated and 8 (27%) of 30 manually disinfected endoscopes remained contaminated (P = 0.28). Manually disinfected endoscopes were contaminated more frequently with coliform bacteria, whereas endoscopes undergoing automated disinfection were more frequently contaminated with nontuberculous mycobacteria, but the differences were not statistically significant. After alcohol rinse and forced air drying, there was no difference in contamination rates between freshly disinfected endoscopes and those stored overnight (7/30 (23%) versus 4/30 (13%), P = 0.50). Colonoscopes and duodenoscopes were contaminated more often than gastroscopes (P = 0.00001). CONCLUSION: The persistent endoscope contamination after manual and automated disinfection indicates the importance of developing more reliable and effective disinfection methods.

Automation↗
PubMed2002

Evaluation of chemical disinfectants for the elimination of Salmonella biofilms from poultry transport containers.

Containers used in transporting live poultry between production and processing units are a primary source of contamination for processed poultry products. Because disinfection of transport containers (TC) has been difficult to accomplish, it is probable that the choice of appropriate disinfectant and its application are partially or wholly responsible for the failure to adequately eliminate pathogens from TC. Therefore, 13 commercial disinfectants were selected and evaluated for their capacities to destroy Salmonella. The disinfectants were applied in various concentrations on prescribed areas (10 cm diameter circle) of galvanized steel surfaces (representative of TC material) that were artificially contaminated with Salmonella (10(8) cfu/mL) with a mixture of organic material. Likewise, coupons (1.9 cm2) made of the same metallic surfaces and covered with biofilms of Salmonella spp. were tested in the same manner for each disinfectant. Two of the disinfectants completely eliminated Salmonella on the artificially contaminated and biofilm-covered surfaces. These compounds produced logarithmic reductions in Salmonella populations as high as 7.18 within 2 min. One of the two effective disinfectants contained sodium hypochlorite and was effective at a concentration of 0.05% (vol/vol). The other disinfectant was an alkaline peroxide compound and was effective at a concentration of 1% (wt/vol). Evaluation of these two disinfectants under simulated conditions suggested that application under the prescribed regimen could result in effective elimination of Salmonella from TC within a limited period.

Animals↗
PubMedDate not supplied

Effect of disinfectants on the hardness and roughness of reline acrylic resins.

PURPOSE: Potential effects on hardness and roughness of a necessary and effective disinfecting regimen (1% sodium hypocholorite and 4% chlorhexidine) were investigated for two hard chairside reline resins versus a heat-polymerizing denture base acrylic resin. MATERIALS AND METHODS: Two standard hard chairside reliners (Kooliner and Duraliner II), one heat-treated chairside reliner (Duraliner II +10 minutes in water at 55 degrees C), and one standard denture base material (Lucitone 550) were exposed to two disinfecting solutions (1% sodium hypochlorite; 4% chlorhexidine gluconate), and tested for two surface properties [Vickers hardness number (VHN, kg/mm(2)); Roughness (Ra, microm)] for different times and conditions (1 hour after production, after 48 hours at 37 +/- 2 degrees C in water, after two disinfection cycles, after 7 days in disinfection solutions, after 7 days in water only). For each experimental condition, eight specimens were made from each material. Data were analyzed by analysis of variance followed by Tukey's test, and Student's t-test (p= 0.05). RESULTS: For Kooliner (from 6.2 +/- 0.3 to 6.5 +/- 0.5 VHN) and Lucitone 550 (from 16.5 +/- 0.4 to 18.4 +/- 1.7 VHN), no significant changes in hardness were observed either after the disinfection or after 7 days of immersion, regardless of the disinfectant solution used. For Duraliner II (from 4.0 +/- 0.1 to 4.2 +/- 0.1 VHN), with and without heat treatment, a small but significant increase in hardness was observed for the specimens immersed in the disinfectant solutions for 7 days (from 4.3 +/- 0.2 to 4.8 +/- 0.5 VHN). All materials showed no significant change in roughness (Kooliner: from 0.13 +/- 0.05 to 0.48 +/- 0.24 microm; Duraliner II, with and without heat treatment: from 0.15 +/- 0.04 to 0.29 +/- 0.07 microm; Lucitone 550: from 0.44 +/- 0.19 to 0.49 +/- 0.15 microm) after disinfection and after storage in water for 7 days. CONCLUSIONS: The disinfectant solutions, 1% sodium hypochlorite and 4% chlorhexidine gluconate, caused no apparent damage on hardness and roughness of the materials evaluated.

Acrylic Resins↗
PubMed1998

Efficacy of various disinfectants in killing a resistant strain of Pseudomonas aeruginosa by comparing zones of inhibition: implications for endoscopic equipment reprocessing.

OBJECTIVE: Previous studies have shown that high-level disinfection of GI endoscopes may not be reliably achieved using glutaraldehyde at room temperature. In our laboratory, we have isolated a strain of Pseudomonas aeruginosa that is resistant to disinfection with glutaraldehyde. We compared the bactericidal activity of various disinfectants against this organism. METHODS: One hundred microliters of an overnight culture of this organism was spread onto blood agar plates. Twenty microliters of a disinfectant was placed on a sterile 7-mm filter paper, placed on the blood agar plate, and incubated overnight at 37 degrees C to determine the zone of inhibition for each disinfectant tested. Disinfectants included Cidex, Dispatch, Virahol, OMNI II, Lysol, IodoFive, Lysol I.C. Spray, and Chlorox. The zone of inhibition (i.e., clearing) roughly correlates with the bactericidal strength of the disinfectant. RESULTS: Compared with the glutaraldehyde-containing solution Cidex, the alcohol-containing disinfectants Lysol I.C. Spray and Virahol had the largest mean zones of inhibition (11.33 vs 20.60 and 20.55 mm; p = 0.0001). The hypochlorite compounds Chlorox (1:10 dilution) and Dispatch had mean zones of inhibition similar to that of Cidex (11.08 and 11.25 mm vs 11.33 mm; p = not significant). The phenolic compounds OMNI II and Lysol had mean zones of inhibition smaller than that of Cidex (10.50 and 10.35 mm vs 11.33 mm; p < 0.006), and the phosphoric acid and iodine-containing IodoFive had the smallest mean zone of inhibition (9.70 vs 11.33 mm; p = 0.0001). CONCLUSIONS: The alcohol-containing disinfectants had the largest zones of inhibition against resistant P. aeruginosa. These compounds may be more effective than glutaraldehyde for endoscopic equipment reprocessing.

2-Propanol↗
PubMed2003

South African survey on disinfection techniques for the flexible nasopharyngoscope.

This random survey was to determine the flexible nasopharyngoscope disinfection practice employed by South African otolaryngologists and to establish whether a breach in the disinfection process exists. The study also aimed to identify organisms most likely to be transmitted via endoscopy and to propose a protocol for the disinfection of the flexible nasopharyngoscope. A questionnaire regarding disinfection techniques used for the flexible nasopharyngoscope was sent to 90 otolaryngologists in South Africa. All provinces were equally represented in the survey. Forty-five otolaryngologists out of a total of 90 participated in the study. Many of the otolaryngologists had no access to a flexible nasopharyngoscope and were therefore not included in the study. Fewer than 50 per cent of the 45 surgeons washed the instrument with soap/detergent and water after use. Only 42 per cent of surgeons used a FDA-approved disinfectant, 52 per cent of which immersed the scope for a shorter period than the recommended contact time. Of the 58 per cent using non-FDA-approved products, 33 per cent used only a 70 per cent Isopropyl alcohol wipe, without immersion of the scope in disinfectant solution. The remaining 25 per cent used non-FDA-approved disinfectants either by wiping or limited immersion of the scope. Of the 45 surgeons, 49 per cent used a different method of disinfection for high-risk patients. Strict guidelines have been proposed for the disinfection of this semi-critical device by the Association of Professionals for Infection Control (APIC) and the Centers for Disease Control (CDC). These guidelines are currently not being followed by many South African otolaryngologists. There is therefore a real risk of transmitting infectious diseases, especially tuberculosis, via endoscopy.

Cross Infection↗
PubMed1976

Evaluation of chlorine compounds for surface disinfection by laboratory and in-use testing.

The disinfecting properties of chloramine and compounds containing chlorinated trisodium phosphate and potassium bromide or sodium dichlorisocyanurate and detergents were studied by laboratory and in-use tests and compared with a phenolic disinfectant containing detergents. In a modified Kelsey test all the preparations were effective in the recommended dilutions in clean conditions. The effectiveness of the chlorine-bromine disinfectant substantially decreased in the presence of organic material. The in-use testing was performed in infectious disease and intensive care wards. Chloramine was so disliked that the in-use test could not be carried out. In the infectious disease ward the total bacterial colony counts of the floors (disinfected once a day) were twice as high as those of the intensive care ward (disinfected 3 times a day) during the use of the phenolic and chlorine-bromine disinfectants. The frequent cleaning routine seemed thus to have an effect on the microbial contamination of the floors. The same difference was found in the contamination of the other non-vertical surfaces although they were disinfected only once a day in both wards. In both wards the total bacterial colony counts of all non-vertical surfaces were lower during the use of halogen compounds than during the use of the phenolic disinfectant. The staff, however, complained of the irritation of the skin and the mucous membranes when using chlorine disinfectants.

Chloramines↗
PubMed1999

[The efficacy of repeated disinfection of disposable gloves during usage].

The efficacy of disinfecting medical gloves with isopropanol 60% (v/v) while they are worn was assessed for 4 different brands of latex gloves (Biogel Diagnistic (A), Safeskin Satin Plus (B), Safeskin LPE (C) and Baxter Non-Sterile Latex Exam Gloves (D)) and one latex-free nitrile glove (100% Nitrile N-Dex (E)). Even in the presence of coagulated blood disinfection of the gloves was more efficient than disinfection of the bare hand. The efficacy of the disinfection of glove C, D and E decreased if 10 disinfections were carried out successively. An increase of perforations detected with the water inflation test according to EN 455-1 was found for brand E. As gloves of brand C and D became tacky after 10 disinfections, they were inappropriate for manual work. As a result, disinfection with isopropanol 60% (v/v) can be recommended for gloves of brand A and B only. Disinfection of these gloves is admissible e.g. after indirect patient contact, taking blood samples or laboratory work if no visible contamination or perforation has occurred. However, after contact with patients suffering from an infectious disease or carrying multiresistant organisms the gloves have to be changed. The same holds true if the gloves might be contaminated with naked viruses (e.g. Poliomyelitis virus), since virucidal alcoholic hand disinfectants require high concentration thus leading to materials incompatibility.

2-Propanol↗
PubMed1992

Surface disinfection of saliva-contaminated dental X-ray film packets.

A study was undertaken to determine the most effective method for the surface disinfection of saliva-contaminated dental X-ray film packets. Size 2 Kodak Poly-Soft film packets were placed in the oral cavities of patients and "sham" irradiated. After removal from the oral cavity, some of these packets were left untreated before being placed in transfer vials containing transport medium. Other packets were handled in one of three different ways before being placed in the transfer vials: 1) wiped with a piece of sterile tissue paper to remove visible saliva; 2) wiped once with a sterile piece of gauze soaked with disinfectant and then immediately wiped dry with a piece of tissue paper ("one-wipe" surface-disinfection technique); or, 3) wiped twice with a sterile piece of gauze soaked with disinfectant and allowed to air dry ("two-wipe" surface-disinfection technique). The transport medium was serially diluted and microbiological processing completed to obtain bacterial counts corresponding to the levels of bacterial contamination of the film packet surfaces. The two-wipe surface-disinfection method effectively eliminated bacterial contamination of the film packets, with all of the disinfectants tested being equally effective. The one-wipe technique, using disinfectant, appeared to be slightly less effective. Mere physical removal of the saliva from the film packet, without the use of disinfectant, was the least effective method.

Bacteria, Aerobic↗
PubMed2005

Effects of disinfectants on resilient denture-lining materials contaminated with Staphylococcus aureus, Streptococcus sobrinus, and Candida albicans.

OBJECTIVES: Resilient denture-lining materials are more susceptible to microbial adhesion than are denture base acrylic resin. As denture hygiene is essential to maintain the serviceability of the denture, disinfectant solutions have been suggested as a method for effectively cleaning resilient liners. The aim of this study was to determine the effectiveness of four different disinfectant solutions on four different resilient lining materials contaminated with Staphylococcus aureus, Streptococcus sobrinus, and Candida albicans. METHOD AND MATERIALS: Three microorganisms (Sta aureus, Str sobrinus, and C albicans), four resilient lining materials (Tempo, Immediate, Flexacryl soft, Ufi Gel P), and four disinfectant solutions (5.25% sodium hypochlorite, 2% sodium hypochlorite, 5% Deconex, and 3.5% Savlex solutions) were investigated. The four resilient lining materials were contaminated with each of the microorganisms, then the disinfection tests were applied to detect the efficacy of disinfectant solutions on resilient denture base materials in an in vitro test. The specimens (n = 5, total = 240) were soaked for 5 minutes in each solution to disinfect the microorganisms. The control specimens (one of each material; n = 5, total = 60) were soaked in distilled water for 5 minutes. As a result, a reduction in microorganism counts was determined. The Kruskal-Wallis and one-way analysis of variance tests were used to analyze for significant differences among test groups at the level of significance. RESULTS: For all microorganisms, soaking in 5.25% sodium hypochlorite reduced the number of viable adherent microorganisms significantly compared to soaking in 2% sodium hypochlorite, which led to greater reduction than soaking either 5% Deconex or 3.5% Savlex. The use of 5.25% sodium hypochlorite in all groups is statistically significant. CONCLUSION: Disinfection of four different resilient denture-lining materials with 5.25% sodium hypochlorite solution was the most effective immersion technique. To achieve an efficient disinfection, the immersion time of the other disinfectant solutions could be increased.

Analysis of Variance↗
PubMed1984

Microbiological evaluation of soft contact lens disinfecting solutions.

Several chemical disinfecting solutions for soft contact lenses were evaluated according to the tests suggested by FDA in the May 1983 revision of the Microbiological Guidelines. It was experimentally determined that cleaning and rinsing lenses remove 3.5 to 3.9 logs of microorganisms. Furthermore, it was determined that only 3% hydrogen peroxide had a rapid enough disinfection rate to meet the safety factor requirement within four hours as suggested in the "D-value test.' when contaminated lenses were cleaned, rinsed, and disinfected with commercially available solutions, all failed to disinfect the lenses within the minimum time specified on the label. These results were used to recommend significant changes in the Microbiological Guidelines. These changes include (1) limiting the rechallenge requirement during preservative effectiveness testing to only disinfecting solutions, (2) using the death rate kinetic profile of any approved chemical disinfecting solution as a basis for comparison of a new chemical disinfecting solution, and (3) using the results of the multi-item test for any approved chemical disinfecting solution as a basis for comparison of a new, proposed chemical disinfecting solution.

Contact Lenses, Hydrophilic↗
PubMed1993

[Experimental study of the antibacterial activity of cloth impregnated with a disinfectant solution].

Disinfecting cloths were commercialized for several years. The solutions of disinfectant used are generally active in vitro in the conditions required by the french standards published by AFNOR, but it is also necessary to know the effectiveness of disinfecting cloths in conditions of use. We describe in this paper a method for this determination. Four bacterial stains recommended in the french standards were used: Staphylococcus aureus ATCC 9144, Enterococcus hirae ATCC 10541, Pseudomonas aeruginosa CIP A 22 and Escherichia coli ATCC 10536. The bacteria were layed on a test watch-glass and the disinfecting cloth was applied on it following the conditions recommended by the manufacturer. 15 minutes after using the disinfecting cloth, the bacteria on the watch-glass and those which were recovered on the disinfecting cloth during application were collected in a neutralising agent suitable for the disinfecting solution used and the surviving bacteria were counted. A similar test was performed using cloth impregnated with sterile distilled water. We studied the activity of unweaved cloths impregnated with a mixture of quaternary ammonium compounds (0.5%) and peroxides (0.1%). The results show that the method allows us to estimate the proper activity of the disinfectant used. In this study, a much higher decontamination of the watch-glass was observed with impregnated cloths than with cloths containing distilled water only. The mean reduction of the number of bacteria layed on the watch-glass was 5.95 log10 in 15 minutes in the first case and only 2.4 log10 in the second case. In addition, the disinfectant leads to the destruction of the bacteria recovered on the cloth during application.

Bedding and Linens↗
PubMed2005

Are surgical scrubbing and pre-operative disinfection of the skin in orthopaedic surgery reliable?

This study attempts to establish the actual effectiveness of pre-surgical disinfection of the patient and surgeon's hands. We evaluated bacterial density and composition on the skin of 15 patients undergoing knee arthroscopy and the left hand of two surgeons after standard disinfection with povidone-iodine. Three samples were taken after the first 6-min scrub in the first surgical operation from the periungual space of the 1 degrees finger, from the interdigital space between the 2 degrees and 3 degrees fingers and from the transverse palmar crest of the left hand of two surgeons for seven consecutive surgical sessions, for a total of 42 samples, and two samples from the pre-patellar skin and from the popliteal skin of 15 patients undergoing knee arthroscopy, for a total of 30 samples. Pre-surgical handwashing and disinfection procedures were identical in each case. Pre-surgical disinfection of the patient's skin with povidone-iodine was shown to be completely effective, with 100% of samples negative. Samples taken from the interdigital space and the palmar crest (100% of samples negative) demonstrated the efficacy of disinfection of the surgeon's hands with povidone-iodine, while the periungual space was contaminated in 50% of the samples. The bacterial strains isolated belong to the staphylococcus genus in 100% of the cases, with pathogenic strains in 29.6% of the cases. Standard pre-surgical disinfection of skin in areas easily accessible to the disinfectant is sufficient in itself to guarantee thorough sanitization. Standard scrubbing of the surgeon's hands is insufficient in eliminating bacterial contamination, including pathogenic germs, in the periungual space, where it is probably difficult for the disinfectant to come into contact with the skin.

Anti-Infective Agents, Local↗
PubMed1993

A direct viable count method for the enumeration of attached bacteria and assessment of biofilm disinfection.

This report describes the adaptation of an in situ direct viable count (in situ DVC) method in biofilm disinfection studies. The results obtained with this technique were compared to two other enumeration methods, the plate count (PC) and conventional direct viable count (c-DVC). An environmental isolate (Klebsiella pneumoniae Kp1) was used to form biofilms on stainless steel coupons in a stirred batch reactor. The in situ DVC method was applied to directly assess the viability of bacteria in biofilms without disturbing the integrity of the interfacial community. As additional advantages, the results were observed after 4 h instead of the 24 h incubation time required for colony formation and total cell numbers that remained on the substratum were enumerated. Chlorine and monochloramine were used to determine the susceptibilities of attached and planktonic bacteria to disinfection treatment using this novel analytical approach. The planktonic cells in the reactor showed no significant change in susceptibility to disinfectants during the period of biofilm formation. In addition, the attached cells did not reveal any more resistance to disinfection than planktonic cells. The disinfection studies of young biofilms indicated that 0.25 mg/l free chlorine (at pH 7.2) and 1 mg/l monochloramine (at pH 9.0) have comparable disinfection efficiencies at 25 degrees C. Although being a weaker disinfectant, monochloramine was more effective in removing attached bacteria from the substratum than free chlorine. The in situ DVC method always showed at least one log higher viable cell densities than the PC method, suggesting that the in situ DVC method is more efficient in the enumeration of biofilm bacteria. The results also indicated that the in situ DVC method can provide more accurate information regarding the cell numbers and viability of bacteria within biofilms following disinfection.

Amines↗
PubMed2004

Viruses adsorbed on musculoskeletal allografts are inactivated by terminal ethylene oxide disinfection.

In 1987 it was anticipated that unsterilized tissues would transmit virus diseases such as hepatitis and HIV-1 from infected donors so a freeze-drying process for musculoskeletal tissue was developed to include terminal ethylene oxide (EO) exposure for 14 h. We found no studies of EO efficacy when viruses were associated with human allografts so we studied the antiviral effect of terminal EO disinfection using all but the final freeze-drying phase of this clinical processing protocol (CPP). Specifically we looked at EO inactivation of HIV-1, a human hepatitis B surrogate and test viruses known to be highly resistant to disinfecting agents, including irradiation. Freeze-drying, ordinarily required after EO disinfection and part of the CPP, was not done. Suspensions of HIV-1, Bovine viral diarrhea, Reovirus type 3, Duck hepatitis B, Poliomyelitis and Canine parvovirus were adsorbed on glass, demineralized bone powder, and preprocessed strips of femoral cortex, iliac wedges, cancellous blocks and patellar bone-tendon-bone preparations and subjected to EO disinfection. Test viruses were inactivated at the end of 7 h of EO disinfection, providing a safety factor in the CPP of at least 100%. Because allografts can transmit viruses, terminal EO disinfection should provide safer musculoskeletal allografts than non-disinfected tissues or those irradiated with a standard irradiation dose. New spontaneously appearing viruses would probably be inactivated with this terminal EO disinfection but they and viral bioweapons will require individual validation to assure viral inactivation.

Animals↗
PubMed2005

Inactivation of enteric microorganisms with chemical disinfectants, UV irradiation and combined chemical/UV treatments.

The relative disinfection efficiencies of peracetic acid (PAA), hydrogen peroxide (H2O2) and sodium hypochlorite (NaOCl) against Escherichia coli, Enterococcus faecalis, Salmonella enteritidis and coliphage MS2 virus were studied in laboratory-scale experiments. This study also evaluated the efficiency of combined PAA/ultraviolet irradiation (UV) and H2O2/UV treatments to determine if the microbial inactivation was synergistic. Microbial cultures were added into a synthetic wastewater-like test medium and treated by chemical disinfectants with a 10 min contact time, UV irradiation or the combination of chemical and UV treatments. A peracetic acid dose of 3 mg/l resulted in approximately 2-3 log enteric bacterial reductions, whereas 7-15 mg/l PAA was needed to achieve 1-1.5 log coliphage MS2 reductions. Doses of 3-150 mg/l hydrogen peroxide achieved below 0.2 log microbial reductions. Sodium hypochlorite treatments caused 0.3-1 log microbial reductions at an 18 mg/l chlorine dose, while 2.6 log reductions of E. faecalis were achieved at a 12 mg/l chlorine dose. The results indicate that PAA could represent a good alternative to chlorine compounds in disinfection procedures, especially in wastewaters containing easily oxidizable organic matter. Hydrogen peroxide is not an efficient disinfectant against enteric microorganisms in wastewaters. The combined PAA/UV disinfection showed increased disinfection efficiency and synergistic benefits with all the enteric bacteria tested but lower synergies for the coliphage MS2. This suggests that this method could improve the efficiency and reliability of disinfection in wastewater treatment plants. The combined H2O2/UV disinfection only slightly influenced the microbial reductions compared to UV treatments and showed some antagonism and no synergies.

Disinfectants↗
PubMed2007

Effect of immersion disinfection with Perform-ID on alginate, an alginate alternative, an addition-cured silicone and resultant type III gypsum casts.

OBJECTIVE: This study investigated the effect of a commonly used immersion disinfectant upon three different impression materials and any subsequent effects on the abrasion resistance, hardness and surface detail reproduction of gypsum casts. DESIGN: A laboratory study. MATERIALS AND METHODS: Under standardised conditions a total of 120 impressions were made of a ruled test block using irreversible hydrocolloid (Alginoplast), an 'alginate alternative' addition-cure silicone (Position Penta) and a conventional addition-cure silicone (President). The impressions were examined for surface detail reproduction prior to and after disinfection with Perform-ID. The type III casts were evaluated for surface detail reproduction, surface hardness and abrasion resistance. RESULTS: (1) None of the disinfected alginate specimens could reproduce the 50 microm line. (2) Casts produced from the disinfected alginate were significantly less hard than from disinfected Position Penta and President (P <0.001). (3) Disinfection significantly affected the abrasion resistance of casts made from Position Penta (P = 0.029). (4) Disinfection did not significantly affect President or its subsequent casts (P >0.05). CONCLUSION: If disinfecting with Perform-ID, the impression should be made with a conventional addition-cured silicone if good surface detail reproduction of the impression material and a hard and abrasion resistant type III gypsum cast are required.

Alginates↗
PubMed2005

Bond strength of disinfected metal and ceramic brackets: an in vitro study.

The aim of this in vitro investigation was to test whether disinfecting with Chlorhexamed fluid had an influence on the shear bond strength of metal and ceramic orthodontic brackets. Metal and ceramic brackets were fixed by the composite adhesives Transbond XT (light curing) and Concise (chemical curing) to 224 bovine permanent mandibular incisors. Bovine teeth were divided into eight groups of 28 each as group 1: metal bracket/Transbond XT, group 2: disinfected metal bracket/Transbond XT, group 3: metal bracket/Concise, group 4: disinfected metal bracket/Concise, group 5: ceramic bracket/Transbond XT, group 6: disinfected ceramic bracket/Transbond XT, group 7: ceramic bracket/Concise, and group 8: disinfected ceramic bracket/Concise. Adhesive bonding was done according to the manufacturers' instructions. As shown by group comparison (Kruskal-Wallis test, univariate analysis of variance, P < .001), the disinfection of metal brackets had no statistically relevant influence on shear bond strength (P = .454). However, disinfecting ceramic brackets with either adhesive led to a significant reduction in shear bond strength compared with the untreated ceramic bracket group (P < .001). The Fisher's exact test of the Adhesive Remnant Index (ARI) scores showed a significant difference within the metal group bonded with different adhesives (P = .0003). The ARI scores 1 and 2 were not reached by the ceramic bracket groups. The disinfection of the ceramic brackets is a suitable procedure for clinical use because the measured shear bond strength values were higher than 6-8 MPa required in orthodontics.

Analysis of Variance↗
PubMed2003

Formation of natural biofilms during chlorine dioxide and u.v. disinfection in a public drinking water distribution system.

AIMS: The influence of two disinfection techniques on natural biofilm development during drinking water treatment and subsequent distribution is compared with regard to the supply of a high-quality drinking water. METHODS AND RESULTS: The growth of biofilms was studied using the biofilm device technique in a real public technical drinking water asset. Different pipe materials which are commonly used in drinking water facilities (hardened polyethylene, polyvinyl chloride, steel and copper) were used as substrates for biofilm formation. Apart from young biofilms, several months old biofilms were compared in terms of material dependence, biomass and physiological state. Vital staining of biofilms with 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and the DNA-specific 4',6-diamidino-2-phenylindole (DAPI) staining resulted in a significant difference in physiological behaviour of biofilm populations depending on the disinfection technique. Compared with chlorine dioxide disinfection (0.12-0.16 mg l-1), the respiratory activities of the micro-organisms were increased on all materials during u.v. disinfection (u.v.254; 400 J m-2). The biofilm biocoenosis was analysed by in situ hybridization with labelled oligonucleotides specific for some subclasses of Proteobacteria. Using PCR and additional hybridization techniques, the biofilms were also tested for the presence of Legionella spp., atypical mycobacteria and enterococci. The results of the molecular-biological experiments in combination with cultivation tests showed that enterococci were able to pass the u.v. disinfection barrier and persist in biofilms of the distribution system, but not after chlorine dioxide disinfection. CONCLUSIONS: The results indicated that bacteria are able to regenerate and proliferate more effectively after u.v. irradiation at the waterworks, and chlorine dioxide disinfection appears to be more applicative to maintain a biological stable drinking water. SIGNIFICANCE AND IMPACT OF THE STUDY: As far as the application of u.v. disinfection is used for conditioning of critical water sources for drinking water, the efficiency of u.v. irradiation in natural systems should reach a high standard to avoid adverse impacts on human health.

Biofilms↗