Cross-contamination potential with dental equipment

The consistent application of hydrogen peroxide controls biofilm growth and removes Vermamoeba vermiformis from multi-kingdom in-vitro dental unit water biofilms

The water systems inside a dental unit are known to be contaminated with a multi-kingdom biofilm encompassing bacteria, fungi, viruses and protozoa. Aerosolization of these micro-organisms can potentially create a health hazard for both dental staff and the patient. Very little is known on the efficacy of dental unit disinfection products against amoeba. In this study we have examined the effect of four different treatment regimens, with the hydrogen peroxide (H₂O₂) containing product Oxygenal, on an in-vitro multi-kingdom dental unit water system (DUWS) biofilm. The treatment efficacy was assessed in time using heterotrophic plate counts, the bacterial 16S rDNA, fungal 18S rDNA gene load and the number of genomic units for Legionella spp. the amoeba Vermamoeba vermiformis. The results indicated that a daily treatment of the DUWS with a low dose H₂O₂ (0.02% for 5 h), combined with a weekly shock dose (0.25% H₂O₂, 30 min) is necessary to reduce the heterotrophic plate count of a severely contaminated DUWS (>10⁶ CFU.mL^-1) to below 100 CFU.mL^-1. A daily treatment with a low dose hydrogen peroxide alone, is sufficient for the statistically significant reduction of the total amount of bacterial 16S rDNA gene, Legionella spp. and Vermamoeba vermiformis load (p < 0.005). Also shown is that even though hydrogen peroxide does not kill the trophozoite nor the cysts of V. vermiformis, it does however result in the detachment of the trophozoite form of this amoeba from the DUWS biofilm and hereby ultimately removing the amoeba from the system.

High-Speed Dental Instruments: An Investigation of Protein-Contaminated Dental Handpieces with the Bicinchoninic Acid Assay in Dental Offices in Styria, Austria

Due to permanent contact with bodily secretions such as blood and saliva, the dental workplace poses a high risk of infection for patients as well as for personnel. High-speed dental instruments are still considered one of the major hygienic risks, as the high-speed rotation of the attachments leads to the retraction of infectious material from patients' oral cavities. The aim of this study was to investigate the extent to which dental handpieces are contaminated after use. Spray-water samples were taken from different handpieces used in seven dental offices and protein concentrations were measured photometrically. In the first part of the study, samples were collected from each handpiece before and after the treatment of the patients. Additionally, the changes in protein concentration after consecutive treatments in which the same high-speed dental instrument was used were investigated. The results demonstrated measurable protein concentrations in 91.2% of a total of 398 samples, and 96.4% of the spray-water samples taken after treatment showed a discrepancy from the initial measured protein concentration. In 68.4% an increase in protein concentration was observed, whereas in 27.9% a decrease was measured. In conclusion, the internal contamination of high-speed dental instruments frequently occurs in daily usage and consequently may lead to the transmission of infectious agents by flushing the contaminated water out of the spray water tubes. Moreover, it must be pointed out that internal cleansing of handpieces is insufficient and that a final mechanical disinfection is indispensable.

Development of a customized mask retainer for improving the fit performance of surgical masks

This study introduces a customized mask retainer to improve the fit performance of surgical masks using various advanced digital techniques. The participant's 3D face scans with and without a surgical mask were taken by using a smartphone. The mask retainer was designed using the 3D face scan data based on the facial anthropometric landmarks. The fitting was inspected and adjusted using the masked face scan data. The retainer was fabricated using a 3D printer. The effectiveness of the retainer on the augmentation of the fit of the surgical mask was tested according to the Chinese Standard (GB 19083-2010). A questionnaire was used to assess the effect of wearing surgical masks with and without retainers and N95 respirators on subjective perception of discomfort. The effectiveness test of the retainer on the augmentation of the fit performance showed a better than 25-fold increase in the overall fit factor, meeting the fit requirement for KN95 respirators in China. The subjective perception of discomfort of wearing N95 was significantly greater than surgical mask with and without retainers. The fit factor results indicated that by using the retainer, the overall fit factors and that of each exercise significantly increased compared to that of the group with the surgical mask alone. And compared with N95, the surgical mask with the retainer significant improved comfort. The surgical mask with the retainer can provide an alternative of personal protective equipment for healthcare workers.

Evaluation of Effective Chloramine-T Concentration to Be Incorporated in Dental Stone for Antimicrobial Activity

Objective The objective of this study was to determine the antimicrobial activity of type III gypsum at three different chloramine-T concentrations and to ascertain the most effective concentration to be added for optimum inhibitory activity against Candida albicans. Method Ten discs of type III gypsum were fabricated for each group. Standard type III gypsum without any disinfectant was used for the control group. For the experimental group, an admixture of chloramine-T and standard dental stone was employed in varying w/w concentrations (0.1%, 0.25%, and 0.5%). Discs were placed in a petri dish containing Sabouraud dextrose agar lawned with Candida albicans culture and incubated for 24 hours. The zone of inhibition created around the discs was measured and evaluated. Result The mean zone of inhibition (mean ± standard deviation) in the control group was 0 mm; 0.70±1.05 mm in group 1 (0.1% w/w concentration), 2.70 ± 2.35 mm in group 2 (0.25% w/w concentration), and 20.80 ± 1.68 mm in group 3 (0.5% w/w concentration). A one-way ANOVA test showed that there was a significant difference in the inhibition zone created around all groups (p < 0.05), with the discs of group 3 yielding the most positive results. Conclusion The addition of 0.5% chloramine-T to type III gypsum showed the most promising result, out of the concentrations tested, as a self-disinfecting dental stone and could be used for further investigations.

Factors Affecting Compliance of Infection Control Measures among Dental Radiographers

OBJECTIVES

To assess the level of dental radiographers' compliance with infection control measures and to evaluate the factors affecting their compliance.

METHODS

The study included 175 dental radiographers. Compliance with infection control was evaluated with a self-administered questionnaire consisting of 33 questions related to vaccination, hand hygiene (HH), personal protective equipment (PPE), disinfection and sterilization, and use of surface barriers. Pearson's chi-square test was used to compare compliance between subgroups of radiographers.

RESULTS

64.6% of participants were females, and 62.9% was younger than 30 years. 13.0% of the sample population had >10 years of experience and 28.0% take radiographs for >20 patients/day. 66.9% of participants wash their hands before/after taking radiographs. 26.3% of participants had vaccination against hepatitis B, tetanus, and tuberculosis. 12.6% fully use PPE, 10.9% perform complete disinfection and sterilization, and 16.0% apply all kinds of surfaces barriers. Vaccination was significantly affected by age, gender, and practice type. HH was affected by years of experience and number of patients radiographed per day. PPE was influenced by number of hours worked per week and patients radiographed daily. Disinfection and sterilization was affected by practice type and years of experience. The use of surface barriers was affected by age, practice type, and number of patients radiographed/day.

CONCLUSIONS

The current study indicated poor compliance with infection control practices among dental radiographers. We recommend continuing educational programs and training courses to increase dental radiographers' awareness of local and international infection control guidelines and to enhance their implementation of these guidelines.

Topographic aspects of airborne contamination caused by the use of dental handpieces in the operative environment

BACKGROUND

The use of dental handpieces produces aerosols containing microbial agents, bacteria, and viruses representing a high-risk situation for airborne cross infections. The aim of this study was to map and quantify the biological contamination of a dental operatory environment using a biological tracer.

METHODS

Streptococcus mutans suspension was infused into the mouth of a manikin, and an operator performed standardized dental procedures using an air turbine, a contra-angle handpiece, or an ultrasonic scaler. The presence of the tracer was measured at 90 sites on the dental unit and the surrounding surfaces of the operatory environment.

RESULTS

All tested instruments spread the tracer over the entire dental unit and the surrounding environment, including the walls and ceiling. The pattern and degree of contamination were related to the distance from the infection source. The maximum distance of tracer detection was 360 centimeters for air turbine, 300 cm for contra-angle handpiece, and 240 cm for ultrasonic scaler. No surface of the operative environment was free from the tracer after the use of the air turbine.

CONCLUSIONS

Attention should be paid to minimize or avoid the use of rotary and ultrasonic instruments when concerns for the airborne spreading of pandemic disease agents are present.

PRACTICAL IMPLICATIONS

This study supports the recommendations of dental associations to avoid treatments generating aerosols, especially during pandemic periods. Guidelines for the management of dental procedures involving aerosols, as well as methods for the modification of aerosols aimed to inactivate the infective agent, are urgently needed.

Cross-transmission in the Dental Office: Does This Make You Ill?

PURPOSE OF REVIEW

Recently, numerous scientific publications were published which shed new light on the possible risks of infection for dental healthcare workers and their patients. This review aimed to provide the latest insights in the relative risks of transmission of (pathogenic) micro-organisms in the dental office.

RECENT FINDINGS

Of all different routes of micro-organism transmission during or immediately after dental treatment (via direct contact/via blood-blood contact/via dental unit water and aerosols), evidence of transmission is available. However, the recent results put the risks in perspective; infections related to the dental office are most likely when infection control measures are not followed meticulously.

SUMMARY

The risk for transmission of pathogens in a dental office resulting in an infectious disease is still unknown; it seems to be limited in developed countries but it cannot be considered negligible. Therefore, maintaining high standards of infection preventive measures is of high importance for dental healthcare workers to avoid infectious diseases due to cross-contamination.

Detection and Quantification of Dental Unit Water Line Contamination by Oral Streptococci

Objective.

(1) To investigate the prevalence of oral streptococci (OS) and biological indicators of water contamination by oral fluids in water from dental unit water lines (DUWs) by detection and quantification and of saprophytes indigenous to the oral cavity. (2) To test whether measurement of the total cultivable mesophilic flora (TCF), the parameter commonly used to monitor water quality in DUWs, is an effective predictor for OS contamination.

Design.

Survey of 21 dental units equipped with antiretraction devices. Water samples were collected from air-water syringes, cup fillers, tap water, and before and during the working day.

Setting.

Units were from 7 public dental offices selected for convenience from among those in proximity of the microbiological laboratory.

Methods.

For detection of OS, samples were plated on an enriched medium, to revitalize the organisms. Colonies were subcultured on a selective medium and biochemically identified (lower detection limit, 1 cfu/mL). For measurement of the TCF, samples were plated on a nutrient-poor medium. Cultures with colony counts greater than 200 cfu/mL were considered to be TCF positive. The sensitivity and specificity of TCF positivity in predicting OS detection was calculated.

Results.

Prevalence rates for OS contamination and for TCF positivity were, respectively, 34.4% (11 of 32 samples) and 25.0% (8 of 32 samples) for syringes, 27.8% (10 of 36 samples) and 8.3% (3 of 36 samples) for cup fillers, and 0.0% (0 of 7 samples) for tap water. OS contamination levels ranged from 1 to 6 cfu/mL. No statistically significant differences were found between samples obtained before and during the working day. TCF positivity did not predict OS contamination effectively, because of low sensitivity.

Conclusions.

Given the absence of OS in tap water, the reported prevalence of OS contamination suggests that oral fluids are aspirated during dental therapy with relatively high frequency and that DUWs can potentially expose successive patients to bloodborne cross-infections.

Evaluation of bacterial contamination of dental unit waterlines and use of a newly designed measurement device to assess retraction of a dental chair unit

INTRODUCTION

Dental unit waterline (DUWL) output water is delivered through instruments of a dental chair unit (DCU) to irrigate and cool teeth. However, these waterlines can be heavily contaminated with bacteria.

AIM

The purpose of the present study was to assess retraction and investigate the contamination level and prevalence of bacteria in DUWL output water.

METHODS

Fifty-eight DCUs were randomly selected from 30 hospitals in 10 districts of Tianjin, one of the four special municipalities of China. A unique sampling connector was used in place of the dental handpiece to collect water samples. Evaluation of retraction was accomplished using a retraction measurement device designed in accordance with the International Standard ISO 7494-2:2015(E).

RESULTS

A total of 263 water samples were collected, and the highest concentration of bacteria [1.8 × 10(6) colony-forming units (CFU)/mL] was found in the handpiece group. Thirty (51.72%) water samples in the handpiece group and 21 (36.21%) in the air/water syringe groups were cultured, yielding colony counts of > 500 CFU/mL. Potential infectious agents, such as Bacillus cereus, Kocuria kristinae and Pseudomonas fluorescens, were isolated from the water samples. Thirty (51.72%) DCUs failed the retraction evaluation. There was a significant, positive correlation (P < 0.05) between the concentration of bacteria in the water sample and the retracted volume.

CONCLUSION

It is of paramount importance to increase compliance with the standards for controlling DUWL contamination. Routine microbial monitoring and evaluation of retraction are necessary to provide high-quality water for use in dental treatment.

Impact of vaginal-rectal ultrasound examinations with covered and low-level disinfected transducers on infectious transmissions in france

BACKGROUND

The risk of cross-infection from shared ultrasound probes in endorectal and vaginal ultrasonography due to low-level disinfection (LLD) is difficult to estimate because potential infections are also sexually transmitted diseases, and route of contamination is often difficult to establish. In France, the widely used standard for prevention of infections is through the use of probe covers and LLD of the ultrasound transducer by disinfectant wipes. We performed an in silico simulation based on a systematic review to estimate the number of patients infected after endorectal or vaginal ultrasonography examination using LLD for probes.

STUDY DESIGN

We performed a stochastic Monte Carlo computer simulation to produce hypothetical cohorts for a population of 4 million annual ultrasound examinations performed in France, and we estimated the number of infected patients for human immunodeficiency virus (HIV), herpes simplex virus, hepatitis B virus, hepatitis C virus, human papilloma virus, cytomegalovirus, and Chlamydia trachomatis. Modeling parameters were estimated by meta-analysis when possible.

RESULTS

The probability of infection from a contaminated probe ranged from 1% to 6%, depending on the pathogen. For cases of HIV infection, this would result in approximately 60 infected patients per year. For other common viral infections, the number of new cases ranged from 1,600 to 15,000 per year that could be attributable directly to ultrasound and LLD procedures.

CONCLUSIONS

Our simulation results showed that, despite cumulative use of probe cover and LLD, there were still some cases of de novo infection that may be attributable to ultrasound procedures. These cases are preventable by reviewing the currently used LLD and/or upgrading LLD to high-level disinfection, as recommended by the US Centers for Disease Control and Prevention.

Microbial contamination of used dental handpieces

Microbial contamination of used, unprocessed internal components of dental handpieces (HPs) was assessed. HPs were dismantled aseptically, immersed in phosphate-buffered saline, ultrasonicated, and cultured. A median of 200 CFU per turbine (n = 40), 400 CFU per spray channel (n = 40), and 1000 CFU per item of surgical gear (n = 20) was detected. Isolates included oral streptococci, Pseudomonas spp, and Staphylococcus aureus. Recovery of S aureus confirms the need for appropriate HP cleaning and sterilization after each patient to prevent cross-infection.

Efficacy of air/water syringe tip sterilization

BACKGROUND

Dental procedures involve contact between instruments and the patient's tissues, blood or saliva. This study evaluated the efficacy of the standardized sterilization of non-disposable air/water syringe tips and corrosion and contaminant build-up in these tips.

METHODS

The bacterial contamination of single-use and multiple-use non-disposable air/water syringe tips after routine use and sterilization was compared to that of single-use disposable tips by microbial culturing on PCA and blood agar plates. The effect of flushing the syringe tips prior to sterilization was also measured. The amount of corrosion in single-use and multiple-use non-disposable syringes was measured by SEM and EDS analyses.

RESULTS

Non-disposable syringe tips had significantly (p < 0.05) greater bacterial contamination than single-use disposable tips. There were no statistically different levels of contamination between flushed and non-flushed non-disposable syringes or between single-use and multiple-use non-disposable syringes. SEM and EDS analyses showed greater evidence of corrosion and contaminant build-up in multiple-use syringes compared to single-use non-disposable syringes.

CONCLUSIONS

Sterilization of non-disposable air/water syringes is not completely effective and rinsing, or the number of uses, does not affect the effectiveness of sterilization. There may be a lower risk of cross-infection from the use of disposable air/water syringe tips, instead of non-disposable ones.

Dental handpiece contamination: a proteomics and surface analysis approach

Dental handpieces (DHPs) become biofouled internally with patient derived material that is difficult to access for removal and inactivation. This study undertook a quantitative and qualitative investigation of protein contamination of internal components from three different types of DHP: the turbine, slow speed contra-angle and surgical. Eluates from the high speed turbine, low speed spray channels and surgical gear were assayed for protein using an orthophthaldehyde assay. Eluates concentrated by Amicon ultrafiltration were also analysed by SDS-PAGE, mass spectroscopy, Western blotting and ELISA. The surfaces of handpiece components were also investigated by SEM, EFSCAN and EDAX microscopy. Surgical gears contained highest levels of protein (403 μg), followed by low speed spray channels (17.7 μg) and the high speed turbine (<5 μg). Mass spectroscopy of surgical gears demonstrated mostly serum derived proteins. Decontamination of the DHPs using an automated washer disinfector and handpiece irrigator showed a significant reduction in residual protein levels.

Detection of oral streptococci in dental unit water lines after therapy with air turbine handpiece: biological fluid retraction more frequent than expected

AIM

Oral streptococci detected in water from dental unit water lines (DUWLs) are a surrogate marker of patients' biological fluid retraction during therapy. We investigated oral streptococci detection rate in DUWLs in a representative sample of private offices in real-life conditions.

MATERIALS & METHODS

Samples of nondisinfected water (100 ml) were collected from the DUWL designated for the air turbine handpiece in 81 dental units, immediately after dental treatment of patients with extensive air turbine handpiece use. Water was filtered and plated on a selective medium for oral streptococci and, morphologically, typical colonies of oral streptococci were counted. The lowest detection limit was 0.01 CFU/ml.

RESULTS

The oral streptococci detection rate was 72% (95% CI: 62-81%), with a mean level of 0.7 CFU/ml. Oral streptococci detection was not affected by handpiece age or dental treatment type, but was associated with dental unit age.

CONCLUSION

Biological fluid retraction into DUWLs during patient treatment and, possibly, the risk for patient-to-patient blood- or air-borne pathogen transmission are more frequent than expected.

Hepatitis B virus transmissions associated with a portable dental clinic, West Virginia, 2009

BACKGROUND

Although hepatitis B virus (HBV) transmission in dental settings is rare, in 2009 a cluster of acute HBV infections was reported among attendees of a two-day portable dental clinic in West Virginia.

METHODS

The authors conducted a retrospective investigation by using treatment records and volunteer logs, interviews of patients and volunteers with acute HBV infection as well as of other clinic volunteers, and molecular sequencing of the virus from those acutely infected.

RESULTS

The clinic was held under the auspices of a charitable organization in a gymnasium staffed by 750 volunteers, including dental care providers who treated 1,137 adults. Five acute HBV infections-involving three patients and two volunteers-were identified by the local and state health departments. Of four viral isolates available for testing, all were genotype D. Three case patients underwent extractions; one received restorations and one a dental prophylaxis. None shared a treatment provider with any of the others. One case volunteer worked in maintenance; the other directed patients from triage to the treatment waiting area. Case patients reported no behavioral risk factors for HBV infection. The investigation revealed numerous infection control breaches.

CONCLUSIONS

Transmission of HBV to three patients and two volunteers is likely to have occurred at a portable dental clinic. Specific breaches in infection control could not be linked to these HBV transmissions.

PRACTICAL IMPLICATIONS

All dental settings should adhere to recommended infection control practices, including oversight; training in prevention of bloodborne pathogens transmission; receipt of HBV vaccination for staff who may come into contact with blood or body fluids; use of appropriate personal protective equipment, sterilization and disinfection procedures; and use of measures, such as high-volume suction, to minimize the spread of blood.

Current biomedical waste management practices and cross-infection control procedures of dentists in India

OBJECTIVES

To investigate the knowledge, attitudes and behaviour of dentists working in dental clinics and dental hospitals regarding biomedical waste management and cross-infection control.

METHODS

A national survey was conducted. Self-administered questionnaires were sent to 800 dentists across India.

RESULTS

A total of 494 dentists responded, giving a response rate of 61.8%. Of these, 228 of 323 (70.6%) general dentists reported using boiling water as a sterilising medium and 339 (68.6%) dentists reported disposing of hazardous waste such as syringes, blades and ampoules in dustbins and emptying these into municipal corporation bins.

CONCLUSIONS

Dentists should undergo continuing education programmes on biomedical waste management and infection control guidelines. Greater cooperation between dental clinics and hospitals and pollution control boards is needed to ensure the proper handling and disposal of biomedical waste.

Update on infectious risks associated with dental unit waterlines

Modern dental chair units consist of a network of interconnected narrow-bore plastic tubes called dental unit waterlines (DUWLs). The water delivered by these DUWLs acts as both a coolant for a range of instruments and an irrigant during dental treatments. The quality of water is of considerable importance because both patients and dental team are regularly exposed to water and aerosols generated by dental equipment. Studies have demonstrated that DUWLs provide a favourable environment for microbial proliferation and biofilm formation, and that water is consequently often contaminated with high densities of various microorganisms (bacteria, fungi, protozoa, viruses). The presence of high levels of microbial contamination may be a health problem for dentists and patients, especially those who are immunocompromised. The current status of knowledge on microbial contamination of DUWLs is presented, with an emphasis on the infectious risk associated with DUWLs and on the various approaches for disinfecting and protecting DUWLs.

Evaluation of residual protein on unprocessed and decontaminated dental extraction forceps

Research into protein contamination of surgical instruments has received increasing attention and has focused on a quantitative analysis, without subsequent identification of these proteins. This study aimed to validate methods for the isolation and identification of instrument protein contamination using extraction forceps as a model. The working ends of used, unclean and decontaminated forceps were boiled in 1% (v/v) SDS and samples precipitated using StrataClean™ resin and Amicon® filtration. Proteins were visualised using SDS-PAGE and identified by mass spectrometry and Western blot. A total of 17 proteins were identified from used, unclean forceps, including blood and bacterial proteins and 2 protein bands from decontaminated forceps samples which could not be accurately identified. The methods described, when used in conjunction with quantitative and surface analysis of instruments, can aid development of cleaning processes by identifying contaminants on used devices that have been removed following cleaning.

Microbial contamination of musical wind instruments

Retrospective and prospective studies were used to assess the numbers, types and persistence of microbes that contaminate wind instruments. All previously played instruments (n = 20) harbored viable bacteria as well as mold and/or yeast. Reedinstruments consistently carried higher microbial loads than did flutes or trumpets. Instruments played within the previous three days bore typical mouth flora, while bacteria recovered after 72 h following play consisted of normal environmental flora. Prospective studies tested survival of potentially pathogenic bacteria (Staphylococcus, Streptococcus, Moraxella, Escherichia coli and attenuated Mycobacterium tuberculosis) when applied to reeds or following simulated 'play' of a clarinet. All species survived for a maximum of 24-48 h on reeds, except Mycobacterium, which persisted through 13 days. In simulated play experiments, test bacteria could persist for up to five days. These findings support the establishment of guidelines for decontamination of wind instruments and for sharing or transfer of these instruments among players.

An investigation of the disposal of dental clinical waste in Ibadan City, south-west Nigeria

This study investigated the disposal of dental clinical waste in and from dental surgeries in Ibadan, south-west Nigeria and followed the waste trail to the rubbish tips. A questionnaire was sent to 130 dentists in dental practices in Ibadan city. Rubbish collectors and scavengers were interviewed to see if they encountered clinical dental waste. The response rate of dentists was 93%. A total of 68.6% of the dentists sampled stated that there were no special disposal facilities for the different kinds of waste materials generated in their clinics: 52.9% disposed of sharp items into the waste bins; and 77.7% said there was no special treatment/disposal of needles and other items used on patients with infectious diseases. Most practices burned their wastes in the hospital area and 73.6% said they were not aware of any rules or body to regulate dental waste disposal in Nigeria. Rubbish collectors and scavengers knew what dental rubbish looked like and tried to avoid it. The survey clearly demonstrates a failure by dentists to dispose of waste appropriately and also provides evidence that scavengers encounter the waste. There is need for the government to provide recommendations, reinforced by legislation and education, to the dental profession concerning the waste materials that they generate.

Health Technical Memorandum 01-05 - a view from north of the border

A large scale observational survey of instrument decontamination processes in general dental A practice has demonstrated gaps between required guidance, standards, legislation and current practice. Guidance, to help dental practices close the gap and replace previous infection prevention guidelines, has been published in England and Wales in the form of Health Technical Memorandum 01-05. This review provides an overview of its rationale, evidence base and comparison with other existing guidance in the United Kingdom.

Development of a validated process for manual preparation of dental transmission instruments

The goal of the study was to develop a validated manual preparation process that conforms to the requirements of validation guidelines. Twelve dental transmission devices from various manufacturers (turbines, handpieces, and contra-angle handpieces) were artificially contaminated with bovine hemoglobin for the test. Ten microliters (corresponding to 800 μg) of bovine hemoglobin solution (concentration 80 mg/ml) was pipetted into the spray water and spray air channels. The manual preparation was conducted by blowing air through the spray channels of the transmission instruments through an attachment to a treatment unit (model 1060T, KaVo, Biberach, Germany) for 5 s. The spray channels were cleaned with WL-Clean (Alpro, Georgen, Germany) as directed by the manufacturer. The spray channels were disinfected with WL-Cid (Alpro) and the spray channels were blow-dried with WL-Dry (Alpro) at the end of the exposure time as directed by the manufacturer. To determine the protein content (protein residue analysis) in the channels of the transmission instruments, 2 ml of an alkaline SDS solution (1%; pH 11) was flushed through the channels. For the quantitative protein residue analysis, the Biuret method was used as described in DIN EN 15883-1:2006. After the application of this method, all results of the protein residue analysis were within the acceptance criteria of the validation guideline. The newly developed manual preparation process is therefore confirmed as suitable from a hygienic viewpoint for preparation of transmission instruments in the dental practice.

A survey of cross-infection control procedures: knowledge and attitudes of Turkish dentists

Objectives:

The objective of this study was to investigate the knowledge, attitudes and behavior of Turkish dentists in Samsun City regarding cross-infection control.

Material and methods:

A questionnaire was designed to obtain information about procedures used for the prevention of cross-infection in dental practices and determine the attitudes and perceptions of respondent dental practitioners to their procedures. The study population included all dentists in the city of Samsun, Turkey, in April 2005 (n=184). The questionnaire collected data on sociodemographic characteristics, knowledge and practice of infection control procedures, sterilization, wearing of gloves, mask, use of rubber dam, method of storing instruments and disposal methods of contaminated material, etc. Questionnaire data was entered into a computer and analyzed by SPSS statistical software.

Results:

From the 184 dentists to whom the questionnaires were submitted, 135 participated in the study (overall response rate of 73.36%). As much as 74.10% dentists expressed concern about the risk of cross-infection from patients to themselves and their dental assistants. Forty-three percent of the participants were able to define "cross-infection" correctly. The greatest majority of the respondents (95.60%) stated that all patients have to be considered as infectious and universal precautions must apply to all of them. The overall responses to the questionnaire showed that the dentists had moderate knowledge of infection control procedures.

Conclusions:

Improved compliance with recommended infection control procedures is required for all dentists evaluated in the present survey. Continuing education programs and short-time courses about cross-infection and infection control procedures are suitable to improve the knowledge of dentists.

Fast sterility assessment by germinable-endospore biodosimetry

The increased demand for sterile products has created the need for rapid technologies capable of validating the hygiene of industrial production processes. Bacillus endospores are in standard use as biological indicators for evaluating the effectiveness of sterilization processes. Currently, culture-based methods, requiring more than 2 days before results become available, are employed to verify endospore inactivation. We describe a rapid, microscopy-based endospore viability assay (microEVA) capable of enumerating germinable endospores in less than 15 min. MicroEVA employs time-gated luminescence microscopy to enumerate single germinable endospores via terbium-dipicolinate (Tb-DPA) luminescence, which is triggered under UV excitation as 10(8) DPA molecules are released during germination on agarose containing Tb(3+) and a germinant (e.g., L-alanine). Inactivation of endospore populations to sterility was monitored with microEVA as a function of thermal and UV dosage. A comparison of culturing results yielded nearly identical decimal reduction values, thus validating microEVA as a rapid biodosimetry method for monitoring sterilization processes. The simple Tb-DPA chemical test for germinability is envisioned to enable fully automated instrumentation for in-line monitoring of hygiene in industrial production processes.

The in vivo contamination of air-driven low-speed handpieces with prophylaxis angles

BACKGROUND

The authors conducted an in vivo study to determine if low-speed handpiece motors can become contaminated with oral flora when used with prophylaxis angles.

METHODS

This crossover study involved 20 subjects, two types of handpieces and three prophylaxis angles. The authors used each handpiece/prophylaxis angle system to polish teeth. They then collected samples, spiral-plated the specimens and incubated them at 37 degrees C anaerobically and aerobically (with 5 percent carbon dioxide). After incubation, the authors examined the plates for the presence of bacterial colonies.

RESULTS

At least 75 percent of the handpiece/prophylaxis angle systems used on the 20 subjects had bacterial contamination for at least one cultured area. Of the 420 specimens, 258 (61.4 percent) produced bacterial growth. Contamination varied from zero to 6,300 colony-forming units per milliliter.

CONCLUSIONS

These data suggest that the internal surfaces of low-speed handpieces can become microbially contaminated during use with prophylaxis angles.

CLINICAL IMPLICATIONS

Unless low-speed handpieces are sterilized properly after each use, they pose a risk for crossinfection.

Occupational hazards in orthodontics: A review of risks and associated pathology

The purpose of this article was to review the occupational hazards related to the practice of orthodontics. A systematic approach was used to include all risks involved in an orthodontic practice. The classification of hazards was based on major sources of risks by system or tissue and by orthodontic office area (dental chair, laboratory, sterilization area, x-ray developing area). Potentially hazardous factors relate to the general practice setting; to specific materials and tools that expose the operator to vision and hearing risks; to chemical substances with known allergenic, toxic, or irritating actions; to increased microbial counts and silica particles of the aerosols produced during debonding; to ergonomic considerations that might have an impact on the provider's muscoleskeletal system; and to psychological stress with proven undesirable sequelae. The identification and elimination of these risk factors should be incorporated into a standard practice management program as an integral part of orthodontic education. Professional organizations can also assist in informing practitioners of potential hazards and methods to deal with them.

The presence of Pseudomonas aeruginosa in the dental unit waterline systems of teaching clinics

OBJECTIVE

The objective of this study was to evaluate the extent of Pseudomonas aeruginosa contamination of Dental Unit Water (DUW) at a Dental Teaching Center in Jordan.

METHODS

Water samples were collected from 30 dental units, 10 from each of three teaching clinics, namely conservative dentistry, periodontology, and prosthodontics. Samples were collected from the outlet of the air/water syringe, high-speed handpiece and water cup filler, at the beginning of the working day (before use), after 2 min flushing, and at midday.

RESULTS

P. aeruginosa was detected in 86.7% (26/30) of the dental units at the beginning of the working day, and in 73.3% (22/30) after 2 min of flushing and at midday. Conservative dentistry units had the highest counts, followed by periodontology and prosthodontics (P<0.05). Overall, the highest counts (log10 count CFU ml-1) were at the beginning of the working day (1.38+/-1.05), and the lowest counts after flushing for 2 min (1.10+/-1.03), and higher numbers were seen again at midday (1.15+/-1.04) (P<0.05).

CONCLUSIONS

86.7% of the dental units were contaminated with P. aeruginosa, the conservative dentistry units had the highest amount of contamination. Flushing the DUW for 2 min significantly reduced the counts of P. aeruginosa.

Risk of hepatitis B virus transmission via dental handpieces and evaluation of an anti-suction device for prevention of transmission

We evaluated the risk of hepatitis B virus (HBV) transmission via dental handpieces and the effects of an anti-suction device in preventing HBV contamination. The results of our study show that under certain conditions, HBV transmission can occur when an anti-suction device is used during dental procedures. We conclude that such devices may decrease contamination, but do not eliminate it.

Hygiene und Infektionsprävention in Zahnarztpraxen

Recommendations for prevention of infection in dentistry have been published in many countries and in Germany as well. In a pilot project in collaboration with the Public Health Service of the City of Frankfurt and the chamber of dentists in Hesse, compliance with these recommendations was studied in dental practices in Frankfurt/M in 2005. After being informed about the recommendations, more than 50% of the 560 Frankfurt dentists agreed to participate in this project, and 127 of these practitioners were visited by experts of the dentist chamber. Hygienic standards in the practices were examined using a checklist. A proper hygiene schedule was observed in 84% of the practices. Facilities for hand hygiene such as dispensers for soap, disinfectant and towels were available in 98, 93 and 92% of the practices, and personal protective equipment such as gloves, masks, eye wear and gowns was found in 98, 100, 98 and 88% of the practices, respectively. Reprocessing of dental instruments was done either manually (52%), manually in combination with ultrasonic cleaning (48%) or by using special reprocessing machines (32%). Steam sterilization was used in all practices; in some practices gravity displacement sterilizers were used (14%), whereas in most of the practices (61%) a high-speed prevacuum sterilizer was available -- especially in dental surgeon practices (77%). Monitoring and documentation of the sterilization process was done automatically (33%) or by hand (55%). In 80% of the practices, pressure, temperature, time and person responsible were documented. Documents of routine maintenance and regular biological testing of the sterilizers could be shown in 93 and 84% of the practices. The Frankfurt pilot project based on information and advice in combination with control has proven to be successful in the majority of practices enrolled. Encouraged by this experience, the chamber of dentists wants to implement this project all over the state of Hesse. The intention is to inform and to visit all 4,500 dental practices in agreement with the local public health services, which in turn could reduce their own control visits in dental practices. Thus, hygiene control visits of the public health services could focus on other practices such as ambulatory surgery or endoscopy.

Basic infection control procedures in dental practice in Khartoum-Sudan

OBJECTIVES

To survey the infection control procedures used by dental practitioners in Khartoum, Sudan.

METHODS

Questionnaires were distributed to150 randomly sampled dentists practising in Khartoum state. Each questionnaire comprised 17 questions about basic infection control procedures.

RESULTS

A 100% response rate to the questionnaire showed that 92% of dentists routinely wore gloves when treating patients, 50% face masks, 61% a gown and 14.7% protective eye wear. Furthermore 52% of the practitioners had been immunised against Hepatitis B. The majority of practitioners (72%) used dry heat as their method of instrument sterilisation, 22% used an autoclave, 2% used boiling water and the remainder used chemical sterilisation. Safe disposal of clinical waste was undertaken by only 23% of dentists although 47% of practitioners stored sharp items in closed containers. All respondents used disposable dental needles, but only a few used other disposable items. There was a significant difference in the implementation of cross infection control procedures between salaried and private dental practitioners, especially with regard to handpiece sterilisation, use of disposables, the wearing of face masks and the availability of additional sets of instruments.

CONCLUSION

There is a clear need to improve the existing situation particularly with regard to immunisation of dentists against Hepatitis B, the safe disposal of clinical waste and instrument sterilisation in Khartoum.

Problems with the decontamination of dental handpieces and other intra-oral dental equipment in hospitals

Dental departments within district general hospitals contain items of equipment that require decontamination between patients. Some of these items are complex and expensive, and in busy clinics, may be required in large numbers if a sterile services department (SSD) were to be used. This may result in local manual cleaning of these instruments and sterilization in non-vacuum downward displacement autoclaves within dental departments, despite some items having narrow lumens, deep recesses and cavities, which will not adequately sterilize these instruments. Infection control teams should be aware of these difficulties particularly when arranging satisfactory infection control and decontamination procedures in hospital dental departments.

Efficacy of anti-retraction devices in preventing bacterial contamination of dental unit water lines

OBJECTIVE

In this study we examine the efficacy of anti-retraction devices in preventing microbial contamination of dental unit water lines (DUWLs).

METHODS

The study was performed on 54 randomly selected DUs in use at private and public institutions for over six months. The selected DUs were all currently commercially available. To evaluate the efficiency of anti-retraction devices, two different methods were employed, mechanical and microbiological. The ADA/ANSI specification #47 (corresponding to a water retraction of less than 40.3 microl) was used for the evaluation of the retraction determined using the mechanical method; the presence/absence of test microorganisms in DUWLs upstream the turbine after the test was used for evaluating the microbiological assay.

RESULTS

Both evaluation methods indicated correct amounts of retraction and prevention of DUWL contamination occurred in only two cases (3.7%). Correct retraction was noted in six other dental units (DUs), but their DUWLs became contaminated during testing. Six other produced the opposite results-improper retraction, yet no contamination. The remaining 40 DUs (74.0%) failed both evaluations.

CONCLUSION

The results showed that the overwhelming majority of the anti-retraction devices did not prevent retraction when the turbine stopped running, leading to a contamination of the water lines, and to a consequent possible cross-contamination of the patients.

The virucidal spectrum of a high concentration alcohol mixture

The virucidal spectrum of a high concentration alcohol mixture (80% ethanol and 5% isopropanol) was determined for a broad series of lipid-enveloped (LE) and non-lipid-enveloped (NLE) viruses covering all relevant blood-borne viruses. LE viruses were represented by human immunodeficiency virus (HIV), bovine viral diarrhoea virus (BVDV), a specific model virus for hepatitis C virus (HCV), pseudorabies virus (PRV), and vaccinia virus. For the NLE viruses hepatitis A virus, canine parvovirus (a model for human parvovirus B19), and reovirus type 3 (Reo-3) were used. PRV, vaccinia, and Reo-3 served as general model viruses. The alcohol mixture was spiked with 5% (v/v) virus, mixed and tested for residual virus after 5 min treatment. Complete clearance (reduction by a factor of >10(6)) was observed for LE viruses, whereas incomplete to insignificant clearance (ranging from no reduction up to a maximum factor of 10(4)) was found for NLE viruses. In a second series of spiking experiments using the LE viruses BVDV, HIV, and PRV, complete clearance (reduction by a factor of >10(6)) was found after 20 s treatment. These data strongly suggest that treatment with a high concentration alcohol mixture has a high virucidal potential in particular for the blood-borne LE-viruses HIV, hepatitis B virus, and HCV. Such mixtures are well suited for rapid and frequent disinfection in dental practice being non-hazardous and non-toxic.

Effect of steam sterilization inside the turbine chambers of dental turbines

OBJECTIVE

It has been demonstrated that contamination of the insides of high-speed dental turbines occurs and that bacteria as well as viruses may remain infectious when expelled from such turbines during subsequent use. Consequently, it has been widely recommended that a high-speed turbine be sterilized after each patient. The purpose of this study was to evaluate the effect of steam autoclaving on a high-speed dental turbine with a contaminated turbine chamber.

STUDY DESIGN

Streptococcus salivarius and endospores of Bacillus stearothermophilus were used as test organisms to determine the effectiveness of 4 different small non-vacuum autoclaves and one vacuum autoclave.

RESULTS

The study demonstrated different efficiencies among the small non-vacuum autoclaves, the best showing close to a 6 log reduction of the test organisms inside the turbine chamber. When cleaning and lubrication of the high-speed dental turbine was carried out before autoclaving, this level of reduction was observed for all the examined non-vacuum autoclaves.

CONCLUSIONS

It is concluded that cleaning before sterilization is essential for safe use of high-speed dental turbines and that small non-vacuum autoclaves should be carefully evaluated before being used for the reprocessing of hollow instruments such as high-speed turbines.

Contamination of the turbine air chamber: a risk of cross infection

In the present work, we evaluated (a) the influx of contaminating fluid into the air chamber when a high-speed turbine stops rotating, (b) the significance of a series of variables (type of handpiece and dental unit, shape of the bur, number of stops set on the turbine) which condition it, and (c) the time required to expel the contaminating fluid from the turbine head. Results showed that contamination takes place every time the turbine stops rotating with the bur in contact with an external fluid. The main variable affecting the influx of contaminating fluid into the air chamber of the turbine head was represented by the shape of the bur (F=54.9; p<0.01). Another significant variable was the type of handpiece and dental unit (F=7.3; p<0.01). The number of stops set on the turbine was irrelevant (F=0.03; p=n.s.). The expulsion of the contaminant from the turbine head showed 2 different exponential rates: a very rapid-elimination phase within 30 s and a slow-elimination phase between 60 and 300 s. In order to remove over 99% of the contaminant from the air chamber, a turbine had to run for more than 4-7 min depending on the type of the handpiece. In conclusion, data from the present study suggest that a significant cross-infection potential exists with high-speed handpieces whenever they are only externally scrubbed and disinfected so the internal cleaning and sterilization between patients is mandatory. The practice of flushing by running the turbines between patients should be discouraged.

Microbial contamination of dental unit waterlines: the scientific argument

The quality of dental unit water is of considerable importance since patients and dental staff are regularly exposed to water and aerosols generated from the dental unit. The unique feature of dental chair water lines is the capacity for rapid development of a biofilm on the dental water supply lines combined with the generation of potentially contaminated aerosols. The biofilm, which is derived from bacteria in the incoming water and is intrinsically resistant to most biocides, then becomes the primary reservoir for continued contamination of the system. Dental water may become heavily contaminated with opportunistic respiratory pathogens such as Legionella and Mycobacterium spp. The significance of such exposure to patients and the dental team is discussed. There is at the present time, no evidence of a widespread public health problem from exposure to dental unit water. Nevertheless, the goal of infection control is to minimise the risk from exposure to potential pathogens and to create a safe working environment in which to treat patients. This paper evaluates the range of currently available infection control methods and prevention strategies which are designed to reduce the impact of the biofilm on dental water contamination, and are suitable for use in general practice. Bacterial load in dental unit water can be kept at or below recommended guidelines for drinking water (less than 200 colony forming units/ml) using a combination of readily available measures and strict adherence to maintenance protocols. Sterile water should be employed for all surgical treatments.

Improved compliance with recommended infection control practices in the dental office between 1994 and 1995

OBJECTIVE

To investigate changes in Ontario dentists' infection control practices between 1994 and 1995.

METHODS

Data from responses of 4003 dentists to a 1994 survey and responses of 987 dentists to a 1995 survey were compared by using descriptive statistics from all respondents and McNemar's test for paired data from those participating in both surveys.

RESULTS

Response rates were 70% (1994) and 62% (1995). There were improvements in reports of routine use of gloves (92% to 94%); masks (73% to 79%); and protective eyewear (83% to 84%); vaccination for hepatitis B virus (HBV) or naturally acquired immunity of dentists (93% to 94%); HBV vaccination of clinical staff (64% to 77%); heat sterilization of handpieces (83% to 95%); and no extra precautions for patients with HIV (13% to 48%). Pairwise comparison of data for 788 dentists participating in both surveys showed statistically significant increases in reports of all practices except use of protective eyewear. The 1995 follow-up data also indicated low compliance with handwashing (74% before treating each patient; 62% after removing gloves); flushing water lines after treating each patient (54%); and using postexposure protocol for needlesticks and cuts (36%).

CONCLUSIONS

Dentists' reports of compliance with recommended infection control practices and universal precautions against HBV and HIV infection increased between 1994 and 1995, but most dentists apparently have not adopted universal precautions. More education is needed to promote universal precautions, HBV vaccination for clinical staff, handwashing, and postexposure protocol.

An investigation of the effect of repeated autoclaving on the speed of some dental turbines in general dental practice

OBJECTIVE

To determine if five types of turbine handpieces could withstand autoclaving in dental practice.

METHOD

Five makes of handpieces were used sequentially by four NHS dental practices in the UK. The practitioners oiled and autoclaved the handpieces after every patient use according to the manufacturer's instructions. The number of times the turbine was used and for what procedure was noted. The turbine use was discontinued when the practitioner perceived a significant fall in handpiece performance and the output speed measured.

RESULTS

Only one handpiece withstood one year of use in practice with a 1.8% drop in output speed. The other four handpieces had drops in output speeds of 23.5-63.6%.

CONCLUSIONS

The results of this survey confirm that some handpieces do not withstand autoclaving. It is also suggested that the tests used in this investigation represent a good assessment of whether a handpiece can withstand autoclaving. It would be useful if data comparable to that described in this paper were available for all handpieces.

A comparison of infection control practices of different groups of oral specialists and general dental practitioners

OBJECTIVE

The purpose of this study was to compare the infection control practices of general dentists and dental specialty groups.

METHODS

A survey was mailed to 5997 dentists in 1994; the response rate was 70%. The data were analyzed with multiple logistic regression (reference group: general dentists).

RESULTS

When sociodemographic influences were taken into consideration, significant predictors of routine infection control practices included all of the following characteristics (odds ratios are in parentheses): 1. Gloves: being younger than 40 years of age (4.5) and being female (5.9). 2. Using gloves and changing gloves after each patient: being younger than 40 years of age (4.0), being female (3.0), being an oral surgeon (3.6), and being an orthodontist (0.2). 3. Using gloves, masks, and protective eyewear: being younger than 40 years of age (2.5), being female (2.3), and being an orthodontist, oral physician, or oral pathologist (0.2). 4. Hepatitis B vaccination for the practitioner: being younger than 40 years of age (5.1). 5. Hepatitis B vaccination for all clinical staff members: being younger than 40 years of age (1.2), being an oral surgeon (1.7), and being an orthodontist (0.6). 6. Heat sterilization of handpieces: being younger than 40 years of age (1.5), being an oral surgeon (5.4), and being an orthodontist (0.2). 7. Taking no additional precautions for patients with HIV: being younger than 40 years of age (1.7), being a periodontist (2.6), being a pedodontist (2.3), and being an oral physician/oral pathologist (4.3).

CONCLUSION

Improved compliance with recommended infection control procedures is required for all groups and is particularly necessary for orthodontists.

Evaluation of a new device for sterilizing dental high-speed handpieces

Dental high-speed turbines and handpieces can take up and expel microorganisms during operation and thus need regular sterilization. This study established a method for validating devices used to sterilize high-speed turbines and handpieces. The air and water channels and turbine chambers were contaminated with suspensions of Streptococcus salivarius or endospores of Bacillus stearothermophilus. The effect of flushing and/or autoclaving performed by a new device combining both procedures was evaluated by counting the number of viable bacteria recovered from these devices. Further, the effect on clinically used handpieces was evaluated. In an initial experiment, the device partially reduced S. salivarius, and the endospores survived. In a second experiment, a 5 to 6 log reduction of S. salivarius in air and water channels was obtained. No growth was observed in clinically used high-speed handpieces, and both S. salivarius and endospores were eliminated from the turbine chambers. Thus, the method of validation proved capable of discriminating between different levels of bacterial reduction.

Infection control and contaminated waste disposal practices in Southern Sydney Area Health Service Dental Clinics

The sterilization and contaminated waste disposal practices in all 14 dental clinics operated by the Southern Sydney Area Health Service were surveyed. All of the clinics used autoclaves for sterilization. All hand instruments, handpieces and triplex syringes were autoclaved between patients. Chemical disinfection solutions were used in 12 of the 14 dental clinics, mainly for surface decontamination. Five dental clinics had separate storage areas for contaminated waste which compiled with contaminated waste separation and disposal guidelines. The practice of recapping needles with fingers and some inadequate washing facilities are areas that require particular attention.