Uses of inorganic hypochlorite (bleach) in health-care facilities

Hypochlorite has been used as a disinfectant for more than 100 years. It has many of the properties of an ideal disinfectant, including a broad antimicrobial activity, rapid bactericidal action, reasonable persistence in treated potable water, ease of use, solubility in water, relative stability, relative nontoxicity at use concentrations, no poisonous residuals, no color, no staining, and low cost. The active species is undissociated hypochlorous acid (HOCl). Hypochlorites are lethal to most microbes, although viruses and vegetative bacteria are more susceptible than endospore-forming bacteria, fungi, and protozoa. Activity is reduced by the presence of heavy metal ions, a biofilm, organic material, low temperature, low pH, or UV radiation. Clinical uses in health-care facilities include hyperchlorination of potable water to prevent Legionella colonization, chlorination of water distribution systems used in hemodialysis centers, cleaning of environmental surfaces, disinfection of laundry, local use to decontaminate blood spills, disinfection of equipment, decontamination of medical waste prior to disposal, and dental therapy. Despite the increasing availability of other disinfectants, hypochlorites continue to find wide use in hospitals.

Disinfection by calcium hydroxide pastes of dentinal tubules infected with two obligate and one facultative anaerobic bacteria

Bovine dentine cylinders were experimentally infected with Actinomyces israelii, Fusobacterium nucleatum, or Enterococcus faecalis. The latter is a facultative anaerobic bacteria and the others are obligate anaerobes commonly found in endodontic infections. The infected specimens were exposed to pastes of calcium hydroxide mixed with saline solution or camphorated paramonochlorophenol for periods of 1 h, 1 day, and 1 week. The viability of bacteria after these exposure times was evaluated by specimen incubation in culture medium to compare the effectiveness of the pastes in disinfecting dentinal tubules. The calcium hydroxide/camphorated paramonochlorophenol paste effectively killed bacteria in the tubules after a 1-h period of exposure, except for E. faecalis that required one day of exposure. In contrast, the calcium hydroxide/saline paste was ineffective against E. faecalis and F. nucleatum even after 1 week of exposure. The results showed that camphorated paramonochlorophenol increased the antibacterial effects of calcium hydroxide.

Accuracy of newly formulated fast-setting elastomeric impression materials

STATEMENT OF PROBLEM

Elastomeric impression materials have been reformulated to achieve a faster set. The accuracy of fast-setting elastomeric impression materials should be confirmed, particularly with respect to disinfection.

PURPOSE

The purpose of this study was to assess the accuracy of 2 types of fast-setting impression materials when disinfected with acid glutaraldehyde.

MATERIAL AND METHODS

Impressions of the mandibular arch of a modified dentoform master model were made, from which gypsum working casts and dies were formed. Measurements of the master model and working casts included anteroposterior (AP) and cross-arch (CA) dimensions. A stainless steel circular crown preparation incorporated within the master model was measured in buccolingual (BL), mesiodistal (MD), and occlusogingival (OG) dimensions and compared to measurements from recovered gypsum dies. The impression materials examined were a fast-set vinyl polysiloxane (VPS-FS, Aquasil Ultra Fast Set), a fast-set polyether (PE-FS, Impregum Penta Soft Quick Step), and a regular-setting polyether as a control (PE, Impregum Penta). Disinfection involved immersion in 3.5% acid glutaraldehyde (Banicide Advanced) for 20 minutes, and nondisinfected impressions served as a control. Linear measurements were made with a measuring microscope. Statistical analysis utilized a 2-way and single-factor analysis of variance with pair-wise comparison of mean values when appropriate. Hypothesis testing was conducted at alpha = .05

RESULTS

No differences were shown between the disinfected and nondisinfected conditions for all locations. However, there were statistical differences among the 3 materials for AP, CA, MD, and OG dimensions. AP and CA dimensions of all working casts were larger than the master model. Impressions produced oval-shaped working dies for all impression materials. PE and PE-FS working dies were larger in all dimensions compared to the stainless steel preparation, whereas VPS-FS-generated working dies were reduced in OG and MD dimensions. Differences detected were small and may not be of clinical significance.

CONCLUSIONS

Impression material accuracy was unaffected by immersion disinfection. The working casts and dies were similar for PE and PE-FS. VPS-FS generated gypsum dies that were smaller in 2 of the 3 dimensions measured and may require additional die relief. Overall accuracy was acceptable for all 3 impression materials.

Effective, safe, practical and affordable periodontal antimicrobial therapy: where are we going, and are we there yet?

Several important trends are noticeable in the management of periodontal disease. Searching for specific risk factors for periodontal disease permits therapy planning with the intention of doing less for low-risk patients and increasing the preventive and therapeutic modalities for high-risk patients. Also, significant progress in the area of chemotherapeutic development enables dentists to increase the number of periodontitis patients receiving nondisruptive antimicrobial therapy and decreases the need for surgical treatment. Use of anti-infective chemotherapeutic and antibiotic agents has become a specialized and increasingly effective means of preventing and treating destructive periodontal disease. Local care, including subgingival application of some type of antiseptics, is widely accepted. The use of systemic antibiotics is not routine and should be reserved for aggressive and refractory periodontal infections. In general, it is better to be thoroughly familiar with a limited number of drugs and treatment methods and use them properly than to try to master a plethora of antimicrobial therapies. Combating periodontal infections is best accomplished by combined mechanical and chemotherapeutic efforts of the dental professional and the patient. The trend during recent years has been to treat periodontal infections aggressively, employing short-course antimicrobial therapy using a battery of safe and affordable antimicrobial agents, each exhibiting high activity against various periodontal pathogens and administered in ways to concurrently affect pathogens residing in different oral ecological niches, followed by regular maintenance visits having a strong anti-infective emphasis. At the beginning of therapy, patients should be assigned self-help tasks having maximal antimicrobial effectiveness, with a focus on control of the subgingival periodontopathic microbiota. When patients see positive clinical results from their daily oral hygiene efforts, they are motivated to remain active participants in managing their periodontal condition. This article emphasizes anti-infective periodontal therapies that are effective and, when properly administered, are essentially nontoxic; are widely available around the world to dentists as well as to patients; and are acceptable to most patients in terms of methods of application, supporting oral hygiene efforts and financial costs. We believe that, with improved knowledge of the periodontopathic microbiota, with the availability of microbiological tests to identify periodontal pathogens and optimal therapy, with various safe and affordable yet effective antimicrobial agents and therapies and, eventually, with the development of one or more effective vaccines, the future looks very bright for patients at risk for or suffering from destructive periodontal disease.

A review of the science regarding dental unit waterlines

BACKGROUND

The National Institute of Dental and Craniofacial Research, or NIDCR; the American Dental Association, or ADA; and the Organization for Safety & Asepsis Procedures, or OSAP, sponsored a workshop on the topic of dental unit waterlines, or DUWLs, on Sept. 29, 2000, at the National Institutes of Health in Bethesda, Md. These organizations invited a group of experts from the ADA, NIDCR, OSAP, the U.S. Food and Drug Administration, the Centers for Disease Control and Prevention, the U.S. Department of Defense, academia and private industry to participate.

TYPES OF STUDIES REVIEWED

The sponsors asked the participants to critically review the scientific literature on the subject in an attempt to determine the evidence basis for management of DUWL contamination and potential health risks, if any, in dental procedures. The ultimate goal of the workshop was to determine if a research agenda in the area of DUWLs should be pursued and what questions such an agenda should involve.

RESULTS

The workshop yielded four questions that need to be addressed in future research: What is the safest and most effective agent(s)/device(s) for achieving microbial levels of no more than 200 colony-forming units per milliliter, or CFU/mL, in the effluent dental water? How should these products be evaluated and by whom? What are the adverse health effects, if any, of chronic exposure to dental bioaerosol or to the agents introduced into the dental unit to treat the waterlines for both dental staff members and patients? How could these health issues be evaluated?

CLINICAL IMPLICATIONS

Developing evidence-based parameters for the management of biofilm contamination that are efficacious and cost-effective will allow clinicians to meet in proposed ADA standard of no more than 200 CFU/mL of effluent water.

Disinfection and communication practices: a survey of U.S. dental laboratories

BACKGROUND

The need to disinfect impressions is crucial to prevent the transmission of infectious diseases. The authors report the results of a survey of U.S. dental laboratory directors. The survey was designed to determine how well dental laboratory personnel are communicating with dentists regarding the disinfection of impressions, and, in turn, what laboratory technicians are doing to protect themselves against microbial cross-contamination.

METHODS

Four hundred dental laboratory directors were selected in a blinded and random manner. To create a geographically representative sample, an equal number of laboratory directors from the East, Midwest and West were interviewed. A survey consisting of 16 open-ended questions was conducted by trained interviewers via 10- to 15-minute telephone interviews. All dental laboratory directors stated that they were thoroughly familiar with their laboratory's disinfection protocol.

RESULTS

The survey documented that the majority of impressions were made of polyvinyl (57 percent) or polyether (27 percent) materials. Only 44 percent of the respondents stated that they knew if the impressions they received had been disinfected. Twenty-three percent of the laboratory directors did not know the method of disinfection used, and 47 percent did not know the length of time involved. Forty-five percent of the respondents reported that they receive inadequate instruction in regard to disinfection techniques. No one class of impression materials was found to be more problematic than others by the laboratory directors.

CONCLUSIONS

The results indicate a significant and problematic lack of communication between these team members. The responses also suggested that laboratory-perceived problems with impressions were not linked to any particular type of material, but more to the disinfection technique used.

PRACTICE IMPLICATIONS

Lack of communication between dentists, staff members and dental laboratory personnel, along with poor training of laboratory personnel in disinfection techniques, may have a direct effect on the prosthetic results achieved in dental practices.

The dimensional stability of dental impression materials following immersion in disinfecting solutions

OBJECTIVES

This investigation examined the effect of several disinfectant systems upon the dimensional stability of a range of common dental impression materials. A new disinfection process based upon hypochlorous acid was one of those examined (Sterilox).

METHODS

Test specimens of commercially available impression materials from the following categories were investigated: alginates, addition-cured silicones, condensation-cured silicones and polyether. Three disinfection regimes were tested: sodium hypochlorite 5.25%, Perform ID and Sterilox. A custom-built automatic laser micrometer was used to measure the dimensions of sample discs of the test materials before disinfection, immediately after and then following 24h storage. Analysis of variance was employed to identify statistically significant differences within groups and across groups.

RESULTS

All the disinfection routines tested resulted in acceptable levels of dimensional stability within the category of normal use of each impression material. All the materials tested can be disinfected with 10% Sterilox without undergoing unacceptable levels of dimensional change.

SIGNIFICANCE

All the disinfection routines tested resulted in acceptable levels of dimensional stability within the category of normal use of each impression material.

Survey on attitudes toward HIV-infected individuals and infection control practices among dentists in Mexico City

BACKGROUND

The teaching of infection control is gradually being introduced at dental schools in Mexico. However, most practicing dentists have limited access to current infection control standards. Deficiencies of knowledge with regard to blood-borne pathogens such as HIV and hepatitis B virus may influence attitudes toward infected individuals and reduce compliance with infection control recommendations.

OBJECTIVE

The purpose of this study was to assess (1) attitudes toward HIV-infected patients and hepatitis B virus-infected patients and (2) infection control knowledge and practices among dental practitioners in Mexico City.

METHOD

A total of 196 dentists were interviewed by means of a questionnaire with Likert-type scales and open-ended questions (response rate, 86.1%).

RESULTS

Most respondents had no previous social or professional contact with HIV-positive individuals. Nine percent indicated that they had knowingly treated HIV-positive patients. Perceived professional and moral obligations to treat HIV-positive patients were high. Thirty-five percent of the respondents perceived the risk of HIV infection as "considerable" to "very strong." The risk of hepatitis B infection was considered significantly higher than the risk of HIV infection (P <.01); however, 78% of the respondents had not been immunized against hepatitis B. Reported use of personal protective equipment was high. Most respondents used dry heat sterilization. The principal disinfectants used were quaternary ammonium compounds, bleach, and glutaraldehyde. Fifty-four percent of the respondents acknowledged that clinical precautions reduced occupational risks.

CONCLUSIONS

This survey revealed contradictory attitudes toward HIV-positive individuals and limited understanding of infection control recommendations. Educational and regulatory efforts are needed to promote better adherence to current infection control standards.

An investigation of the efficacy of super–oxidised (Optident/Sterilox) water for the disinfection of dental unit water lines

AIMS

To determine the efficacy of super-oxidised water (Optident/Sterilox) in the decontamination of dental unit water lines.

METHODS

Dental units (10) were first purged with concentrated super-oxidised water. After purging, a 5% (v/v) super-oxidised water was used as a maintenance dose. Samples for microbiology were taken after 0,1,2,3,4,5,6,7 d, and each week for a further 13 weeks.

RESULTS

After purging, 5% (v/v) super-oxidised water was successful in reducing the microbial counts to zero, although in three of the units some bacteria were intermittently isolated in the first week of treatment.

CONCLUSIONS

Super-oxidised water was successful in the removal of bacteria from dental unit water supplies. Complete removal required the treatment with a purge phase of concentrated disinfectant and a maintenance phase of at least two weeks.

Corrosion Behavior of Dental Alloys in Various Types of Electrolyzed Water

The corrosion behavior of dental alloys was examined in electrolyzed strong acid water, weak acid water and neutral water using a 7-day immersion test. The precious metal alloys, gold alloy. Au-Ag-Pd alloy and silver alloy showed the greatest surface color change and dissolution of constituents in the strong acid water and the smallest in the neutral water. The release of Au from gold alloy was especially marked in the strong acid water. Co-Cr alloy showed greater corrosion and tarnish resistance in the strong acid water rather than in the weak acid water and the neutral water. X-ray microanalysis revealed that the corrosion products on the precious metal alloys were silver chloride crystals and the thin brown products on Co-Cr alloy were cobalt and chromium oxides. Ti was sound in all three types of electrolyzed water. The neutral water appeared the least corrosive to metals among the three types showing equivalent bactericidal activity.

A novel automated waterline cleaning system that facilitates effective and consistent control of microbial biofilm contamination of dental chair unit waterlines: A one-year study

Microbial contamination of dental chair unit (DCU) output water caused by biofilm growth in dental unit waterlines (DUWs) is a universal problem and a potentially significant source of cross-infection. The microbial quality of output water from a Planmeca Compact i DCU equipped with the novel Water Management System (WMS), an integrated and automated DUW cleaning system, was investigated over a 12-month period with the hydrogen peroxide- and silver ion-containing disinfectants Planosil and Planosil Forte. Four weeks after connection to the potable-water quality mains supply the density of aerobic heterotrophic bacteria, rose from the low levels consistently found in the supply water throughout this study (mean average 77 cfu/mL) to 15,400 cfu/mL. Disinfection of DUWs once weekly with Planosil for 10 weeks resulted in a dramatic reduction in bacterial density immediately following disinfection (mean average 26 cfu/mL). Bacterial density rose steadily between disinfections and by 7 days post-disinfection, water quality failed (mean average 384 cfu/mL) the American Dental Association DCU water quality standard of <or=200 cfu/mL. The DCU was then disinfected once weekly for 40 weeks with Planosil Forte. The average bacterial density immediately post-disinfection was 20 cfu/mL and 7 days post-disinfection was 113 cfu/mL. Electron microscopy showed that improved output water quality following disinfection with both disinfectants was associated with marked elimination of DUW biofilm, but deterioration of water quality following disinfection was associated with its regrowth. The most common bacterial species cultured from the mains water and the DCU output water were Microcococcus luteus and Sphingomonas spp., respectively, the latter of which are known opportunistic pathogens. The findings of this study show that the Planmeca Compact i DCU equipped with the easy to use and automated WMS, that requires minimal effort on the part of the operator, consistently provides output water that passes the ADA quality standard of <or=200 cfu/mL for up to 7 days following once-weekly disinfection with Planosil Forte.

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.

Structural effects of sodium hypochlorite solutions on gutta-percha cones: atomic force microscopy study

Atomic force microscope (AFM) is a well-established methodology for structural characterization of materials. The purpose of this study was to investigate the effects of sodium hypochlorite (NaOCl) solutions on gutta-percha cone structure using AFM. Three standardized gutta-percha cones were cut 3 mm from the tip, attached to a glass base and immersed in 0.5, 2.5, or 5.25% NaOCl solutions. After 1 and 5 min the samples were positioned in the atomic force microscope. The analyses were performed on twelve different points (n=12) located between 1 and 2 mm from the tip after each period of immersion in NaOCl. Gutta-percha cone without any NaOCl treatment were used as control. Root mean square (RMS) parameters for contact mode imaging and force modulation microscopy variations were measured. The differences between RMS values were tested by ANOVA with Fisher's protected LSD test for multiple comparisons (p<0.05). Aggressive deteriorative effects on gutta-percha cone elasticity were observed for 5.25% NaOCl at 1 min when compared to the control (p<0.05). In addition, 2.5% and 5.25% NaOCl solutions caused topographic changes after 5 min when compared to the control (p<0.05). Conversely, 0.5% NaOCl solution did not cause any alteration on topography or elasticity of gutta-percha cone structure when compared to the control (p<0.05). Thus, 0.5% NaOCl solution is a safe alternative for rapid decontamination of gutta-percha cones.

Attitudes toward HIV-infected individuals and infection control practices among a group of dentists in Mexico City--a 1999 update of the 1992 survey

BACKGROUND

The teaching of infection control (IC) was introduced at dental schools in Mexico during the 1990s. A 1992 survey indicated that some dentists had limited access to current IC standards. Deficient knowledge of bloodborne pathogens may influence dentists' attitudes about infected individuals and reduce compliance with IC recommendations.

OBJECTIVE

To update the 1992 appraisal of attitudes about persons infected with HIV or the hepatitis B virus (HBV) and IC knowledge and practices in a nonrepresentative sample of dentists in Mexico City.

METHOD

One hundred eighty dentists were interviewed in 1999 (response rate, 84.1%) with the same methods used in 1992.

RESULTS

Seventy-nine percent of respondents perceived the risk of HIV infection as "considerable" to "very strong." The risk of HBV infection was considered higher than that of HIV. Only 32% of respondents had not been immunized against HBV. Reported use of personal protective equipment remained high. Dry heat was the preferred method for sterilization in 1992, but by 1999 it had been displaced by steam under pressure. Reported preference for more effective disinfectants was also evident overall.

CONCLUSIONS

We found certain improvements in IC knowledge and practices between 1992 and 1999, and the results suggest targets for educational and regulatory efforts that are needed to promote better adherence to current IC standards.

Decontamination of dental unit water systems: a review of current recommendations

It is now recognised that water delivered to dental handpieces and air/water syringes via dental unit water systems may become significantly contaminated with micro-organisms which originate from the incoming water supply and, to a lesser extent, with oral micro-organisms. The purpose of this article is to review the literature relating to the risks associated with contamination of dental unit water systems and methods which may be used to minimise these risks.

Effect of disinfecting solutions on the mechanical properties of orthodontic elastomeric ligatures

OBJECTIVE

To assess the effect extended exposure to disinfectant solutions has on the tensile load at failure and glass transition temperature (T(g)) of orthodontic elastomeric ligatures.

MATERIALS AND METHODS

Elastomeric ligatures from three manufacturers: Rocky Mountain Orthodontics (RMO, Denver, Colo), American Orthodontics (AO, Sheboygan, Wis), and 3M Unitek (3M, Monrovia, Calif) were exposed to two disinfectant solutions, Vital Defense-D and Cidexplus, for up to 28 days. Unexposed ligatures were also tested. Tensile load at failure was determined by stretching the ligatures using a universal testing machine until they fractured. Glass transition temperature was determined using differential scanning calorimetry (DSC).

RESULTS

For tensile load at failure and glass transition temperature of the ligatures, significant differences were observed among the different manufacturers and exposure times. Type of disinfectant solution was a significant factor with T(g), but not with failure load. The 3M ligatures had the highest tensile load at failure and most positive T(g) followed by AO and RMO, respectively. Compared to unexposed ligatures, strength significantly decreased after one hour of disinfectant exposure. Glass transition temperature was also significantly affected with extended disinfectant exposure, but the different disinfectants changed T(g) in opposite directions.

CONCLUSION

Exposure of elastomeric ligatures to disinfectant solution for one hour or more decreases their strength.

Influence of a 3-step tooth disinfection procedure on dentin bond strength

STATEMENT OF PROBLEM

Clinicians have used disinfection materials to remove surface contaminants during cavity preparation. It has been postulated that disinfection materials may negatively affect shear bond strength of restorative materials. If so, large numbers of restorations may be predestined for early failure with the use of a disinfection protocol.

PURPOSE

The purpose of this study was to determine whether there is a difference in the bond strength between dentin and resin composite with a 3-step disinfection technique compared to a conventional bonding technique without the additional disinfection protocol.

MATERIAL AND METHODS

Sixty human molar teeth were sectioned parallel to the occlusal surface to expose mid-coronal dentin and mounted parallel to a bond shearing device on a universal testing machine and divided into 2 groups. In the 3-step disinfection group (n = 30), specimens were treated with chlorhexidine, Tubulicid red, and sodium hypochlorite before dentin bonding, following the manufacturer's instructions for All Bond 2. In the control group (n = 30), specimens were treated only with the bonding protocol of All Bond 2. To ensure a uniform bond surface area, core paste was syringed into a cylindrical mold (2.38-mm diameter and 2.00-mm height) that was in contact with the dentin bonding surface of each specimen and allowed to polymerize under constant force. All specimens were subjected to fracture by shear loading in a universal testing machine at a uniform crosshead speed of 0.05 mm per minute and expressed as MPa. Statistical analysis was performed using the Student t test (alpha = .05). The mode of failure was noted after a visual examination using a light microscope under x30 magnification. Failures were recorded as adhesive, cohesive or mixed, and statistical analysis was performed using a chi-square of homogeneity (alpha = .05).

RESULTS

A significantly higher shear bond strength was found for the 3-step disinfection group (mean shear bond strength, 25.3 +/- 4.6 MPa) compared to the control group (mean shear bond strength, 20.5 +/- 3.4 MPa) (P < .0001). Most failures were adhesive for the control group, but the fracture modes were evenly divided for the 3-step disinfection protocol group. A chi-square test of homogeneity showed a value of 12.3, df = 2, P = .0012.

CONCLUSIONS

The 3-step disinfection technique group showed a significantly stronger dentin shear bond strength compared to the conventional bonding technique without disinfection.

Effect of Storage Period of Alginate Impressions following Spray with Disinfectant Solutions on the Dimensional Accuracy and Deformation of Stone Models

This study investigated the effect of storage period on dimensional change and deformation of stone models to determine an acceptable period of alginate impression storage in a sealed bag after spraying with disinfectant solution. Two alginate impression products: Aroma Fine DFIII and Alginoplast EM, characterized by greater or smaller contraction in 100% relative humidity, were used. The impressions were sprayed with 1% sodium hypochlorite or 2% glutaraldehyde solution and then stored in sealed bags. The storage periods were 1 hour, 2 hours, 3 hours, and 4 hours. The sectional profiles of the stone models obtained from each impression were measured using a three-dimensional coordinate measuring system. The results indicated that the impression characterized by greater contraction in 100% relative humidity should not be stored for even 1 hour, and that storage for up to 3 hours of the impression characterized by smaller contraction was clinically acceptable.

Sterilization of elastic ligatures for intraoperative mandibulomaxillary immobilization

Sterilization can influence the mechanical properties of elastic ligatures used for mandibulomaxillary immobilization. The aim of this study was to compare different sterilization protocols (ethylene oxide, autoclave, irradiation, plasma sterilization, povidone-iodine for 24 hours and 70% isopropyl alcohol for 24 hours) of three elastomers (natural rubber, silicone rubber, and polyurethane). Three mechanical variables were assessed in a testing machine: breaking strength, tensile strength and tensile strength after a 24-hour load (material fatigue). Natural rubber was most susceptible to mechanical alteration by sterilization and lost 46% of its breaking strength and 43% of its tensile strength after autoclaving. Polyurethane was more resistant (multiple comparison, Tukey-Kramer), but polyurethane ligatures stuck together after autoclaving. The protocols for low-temperature sterilization, ethylene oxide, irradiation, and plasma were superior to autoclaving and the disinfecting solutions. These data suggest that polyurethane sterilized with ethylene oxide is the material of choice.

Evaluation of the effectiveness of decontamination of dental syringes

AIM

Steam autoclaving is the gold standard for decontaminating dental instruments, but worldwide disinfection is still widely employed. We have evaluated a range of procedures for their ability to inactivate duck hepatitis B virus contaminating dental syringes.

METHODS

Residual infectivity of virus suspensions following 2% glutaraldehyde treatment, ultrasonication or steam sterilisation at 121 degrees or 134 degrees was assayed by injecting day-old ducklings and examining their livers for viral DNA 2.5 weeks later. Dental syringes were contaminated with DHBV positive blood, then treated by the same methods. An anaesthetic cartridge containing water was loaded into the syringe and 400microl aliquots used to inject day-old ducklings. Used dental syringes were examined by Scanning Electron Microscopy.

RESULTS

Suspension test:- ultrasonic treatment failed to inactivate DHBV in suspension, but complete inactivation was achieved by 2% glutaraldehyde and autoclaving. Syringe test:- neither ultrasonic treatment nor glutaraldehyde inactivated DHBV. Autoclaving at 134 degrees (3 minutes) permitted transmission to 1/16 ducklings but steam sterilisation at 121 degrees (15 minutes) was effective. Electronmicroscopy demonstrated organic debris (biofilm) in the lumen of used syringes.

CONCLUSION

Short autoclaving cycles, albeit at raised temperatures, may fail to inactivate the virus because of poor steam penetration, inadequate heat transfer and the accumulation of protective biofilm.

Effect of chemical disinfectants and repair materials on the transverse strength of repaired heat-polymerized acrylic resin

PURPOSE

The purpose of this study was to evaluate both the effects of immersion in different chemical disinfectant solutions and the type of repair material on the transverse strength of repaired heat-polymerized acrylic resin.

MATERIALS AND METHODS

A total of 110 rectangular specimens (65 x 10 x 3 mm) of heat-polymerized acrylic resin (Triplex) were fabricated. After polymerization, the specimens were polished, then stored in distilled water at 37 degrees C for 1 week. The specimens were divided into 11 groups (n = 10) coded A to K. Specimens of Group A remained intact (control). The specimens of Groups C to F and Groups H to K were immersed in the following chemical disinfectant solutions (1%, 2.5%, and 5.25% sodium hypochlorite and 2% glutaraldehyde, respectively) for 10 minutes. The specimens of all groups except those of Group A were sectioned in the middle to create 10 mm gaps and repaired with the same resin (Groups B to F) and autopolymerizing acrylic resin (Groups G to K). The specimens of Groups C to F and Groups H to K were again immersed in the disinfectant solutions in the same sequence. The transverse strength (N/mm(2)) was tested for failure in a universal testing machine, at a crosshead speed of 5 mm/min. Two-way analysis of variance (ANOVA) was performed to evaluate the effects of both the disinfectant solutions and repair materials on the transverse strength of repaired specimens. All data were statistically analyzed using one-way analysis of variance followed by Tukey's test at 95% confidence level.

RESULTS

The repaired specimens treated with/without disinfectant solutions showed similar (p > 0.05) transverse strength values. No differences (p > 0.05) were detected among the repaired specimens either with heat-polymerized or autopolymerizing acrylic resins. The intact specimens showed transverse strength values (86.9 +/- 11.8) significantly higher (p < 0.05) than the values of the repaired specimens.

CONCLUSIONS

Among the repaired specimens, transverse strength was not affected after immersion in the disinfectants for the immersion period tested (10 min). The repair material, either heat-polymerized or autopolymerizing acrylic resin, had no effect on the transverse strength of the repaired acrylic resin specimens.

An investigation of the decontamination of Siqveland matrix bands

OBJECTIVES

This study investigated blood contamination of artificially and clinically contaminated Siqveland matrix bands and retainers. A modified version of the recognised Kastle-Meyer test for blood was used to compare the efficacy of enzymatic agents, a washer-disinfector and an instrument washer for pre-sterilisation cleaning of Siqveland matrix bands and retainers.

METHODS

Assembled Siqveland matrix bands were contaminated either artificially with horse blood or clinically during dental treatment. Contaminated assembled matrix bands and retainers were subjected to immersion in an enzymatic agent, automated processing in a washer-disinfector or instrument washer, or a combination of pre-soaking and automatic cleaning. Residual blood contamination from each band and retainer was measured and compared to the volume of blood recovered from an unprocessed control group of contaminated assembled matrix bands or retainers.

RESULTS

Residual blood was recovered from every clinically contaminated assembled Siqveland matrix band and retainer. The volume of blood recovered from assembled Siqveland matrix bands ranged from 0.13-7.1 microl and from retainers, following removal of the matrix band, from 0.001-1.523 microl. The most effective method of pre-sterilisation cleaning for artificially contaminated assembled matrix bands was processing in the washer-disinfector. Conversely, the most effective method for cleaning clinically contaminated assembled matrix bands and retainers was pre-soaking in an enzymatic agent followed by a heavy-duty cycle in an instrument washer.

CONCLUSIONS

It is not possible to clean assembled Siqveland matrix bands using any method currently available to dental practitioners. Matrix bands should be discarded after use on one patient. Once the band is removed, all detectable blood can be removed from the retainer by pre-soaking in an enzymatic detergent followed by processing in an instrument washer.

Endoscope disinfection using chlorine dioxide in an automated washer-disinfector

Although 2% glutaraldehyde is often the first-line agent for endoscopic disinfection, its adverse reactions are common among staff and it is less effective against certain mycobacteria and spore-bearing bacteria. Chlorine dioxide is a possible alternative and an automated washer-disinfector fitted with this agent is currently available. This study was conducted to evaluate the effectiveness of chlorine dioxide in endoscopic disinfection after upper gastrointestinal examination. In vitro microbicidal properties of chlorine dioxide solutions were examined at high (600 ppm) and low (30 ppm) concentrations against various microbes including Pseudomonas aeruginosa, Helicobacter pylori, Mycobacterium avium-intracellulare and Bacillus subtilis in the presence or absence of bovine serum albumin (BSA). Immediately following endoscopic procedures and after application to the automated reprocessor incorporating chlorine dioxide at 30 ppm for 5 min, endoscopic contamination with infectious agents, blood, H. pylori ureA gene DNA and HCV-RNA was assessed by cultivation, sensitive test tape, polymerase chain reaction (PCR) and reverse transcriptase-PCR analysis, respectively. Chlorine dioxide at 30 ppm has equivalent microbicidal activity against most microbes and faster antimicrobial effects on M. avium-intracellulare and B. subtilis compared with 2% glutaraldehyde, but contamination with BSA affected the microbicidal properties of chlorine dioxide. Endoscopic contamination with microbes, blood and bacterial DNA was eliminated after application of the automated reprocessor/chlorine dioxide system. Thus, chlorine dioxide is a potential alternative to glutaraldehyde. The use of automated reprocessors with compatibility to chlorine dioxide, coupled with thorough pre-cleaning, can offer effective, faster and less problematic endoscopic disinfection.

Rapid chairside sterilization of endodontic files using 6% sodium hypochlorite

INTRODUCTION

The purpose of this study was to assess the percentage of new endodontic files (taken directly from the manufacturers' packages) that were contaminated with viable microorganisms and to determine the amount of time new files needed to be immersed in 6% sodium hypochlorite to achieve sterility.

METHODS

Endodontic files from four manufacturers were placed either immediately in thioglycolate broth or immersed in 6% sodium hypochlorite for 1, 2, or 5 minutes before placement in the broth. The files were aerobically incubated for 72 hours and sterility determined by the absence of broth turbidity, as determined by a blinded examiner. The data were analyzed using the Cochran-Q test followed by the McNemar test for pair-wise comparisons. The level of statistical significance was set at alpha = 0.05.

RESULTS

When pooling all manufacturers' files, no significant differences were found between groups.

CONCLUSION

New files demonstrated a 6% contamination rate and none of the immersion times in NaOCl achieved file sterility.