The effect of frequent clinical use of dental unit waterlines on contamination.

Three dental units with self-contained water systems in an outpatient teaching dental clinic were treated with a proprietary chlorine dioxide waterline cleaner. Three similar units were used as controls. After four weeks, test and control units were crossed over. Water samples were taken from each line on each unit and from the sink faucets at six time periods; and the frequency of use of each line was recorded. Statistical analysis showed that increased frequency of use of waterlines did not affect lines that were chemically treated, but was associated with less contamination of untreated lines.

Tuberculosis: infection control/exposure control issues for oral healthcare workers.

AIM: The aim is to present the essential elements of an infection control/exposure control plan for the oral healthcare setting with emphasis on tuberculosis (TB). METHODS AND MATERIALS: A comprehensive review of the literature was conducted with special emphasis on TB infection-control issues in the oral healthcare setting. RESULTS: Currently available knowledge related to TB infection-control issues is supported by data derived from well-conducted trials or extensive controlled observations. In the absence of supportive data the information is supported with the best-informed, most authoritative opinion available. CONCLUSION: Essential elements of an effective TB infection-control plan include a three-level hierarchy of administrative, environmental, and respiratory-protection controls. CLINICAL SIGNIFICANCE: Standard precautions provide the fabric for strategies to prevent or reduce the risk of exposure to bloodborne pathogens and other potentially infectious material. However, standard precautions are inadequate to prevent the spread of organisms through droplet nuclei 1-5 micron in diameter and additional measures are necessary to prevent the spread of Mycobacterium tuberculosis. Oral healthcare settings have been identified as outpatient settings in which patients with suspected or confirmed infectious TB disease are expected to be encountered. Therefore, oral healthcare settings must have a written TB infection-control program.

Measuring the validity of two in-office water test kits.

BACKGROUND: The authors conducted a study to determine the validity of two commercially available in-office water test kits compared with a spread plate technique using the gold standard dehydrated culture medium R2A agar for monitoring the quality of dental treatment water. METHODS: Over a 12-week period, one author monitored nine dental units in a dental school that each were equipped with an independent water reservoir. The author collected 351 split samples, cultured them using three test methods, counted bacterial colonies manually and assessed validity using two cutoff values: < or = 200 colony-forming units per milliliter (CFU/mL) (an American Dental Association goal) and < or = 500 CFU/mL (a Centers for Disease Control and Prevention [CDC] recommendation and a U.S. Environmental Protection Agency [EPA] mandate). RESULTS: Of the 351 split samples processed, the in-office test kits' accuracy ranged from 25 to 69 percent, according to the ADA and CDC/EPA recommendations, compared with the R2A agar. CONCLUSIONS: Overall, the in-office test kits underestimated bacteria levels, producing inaccurate measurements of bacterial levels compared with the R2A agar. CLINICAL IMPLICATIONS: The data suggest that use of the two in-office test kits could result in a lack of compliance, owing to underestimating bacterial contamination with recognized recommendations for dental unit waterline quality.

Isolation of an unusual fungus in treated dental unit waterlines.

BACKGROUND: Numerous organisms have been identified in dental unit waterlines, or DUWLs. Decontamination of DUWLs focuses on maintaining heterotrophic, mesophilic bacteria below 200 colony-forming units per milliliter as recommended by the ADA. METHODS: The authors conducted a study to test the efficacy of a continuous-use, stabilized chlorine dioxide proprietary compound to decrease the number of bacteria in DUWLs. The authors used three dental units with self-contained water systems to test the product and three similar units as controls. They aseptically collected water samples weekly according to recommended methods, plated the samples on R2A agar and incubated them for seven days. RESULTS: The authors isolated heterotrophic, mesophilic bacteria from treatment and control units for eight weeks. In the ninth week, the predominant isolates from one of the treatment units changed in appearance to small, dark, shiny colonies that the authors tentatively identified as fungal. The authors then isolated similar colonies from the source tap water and ultrasonic and handpiece lines. They added three additional dental units from the same clinic in the sixth week of the study and isolated similar fungal colonies from them after five weeks of treatment. The authors performed DNA sequencing with an automated sequencer and identified the organism Exophiala mesophila. CONCLUSIONS: The authors did not observe fungal isolates in the control units, which suggests that continuous waterline treatment may cause proliferation of a fungus present in small amounts in source water. CLINICAL IMPLICATIONS. The findings of this study indicate the need to monitor water quality regularly when treating waterlines with continuous-use chemical cleaners.

Reduction of bacterial levels in dental unit waterlines.

OBJECTIVES: To test the efficacy of an intermittent use, dental unit waterline cleaner, containing 0.12% chlorhexidine, in a proprietary formulation, to reduce bacterial levels in three functioning dental units with independent water reservoir systems. METHOD AND MATERIALS: Baseline water samples were first taken from six units. Two ounces of the undiluted test product was run through lines, left overnight, and flushed out the next morning. This was repeated for 6 nights initially, and once a week thereafter for 12 weeks. Three control dental units did not have chemicals added. Weekly samples were collected in bottles containing sodium thiosulphate on the afternoon before overnight treatment, plated on R2A agar, and incubated at room temperature for 7 days. RESULTS: Mean colony-forming units per millimeter (CFU/mL) in treatment units declined from 23,389 (+/- 20,085) at baseline, to 6 (+/- 10) in week 4, to 5 (+/- 2) in week 12. Statistical analysis showed a significant difference between treatment and control units. CONCLUSION: Intermittent treatment of dental unit waterlines with 0.12% chlorhexidine gluconate (CHX), in a proprietary formulation, resulted in significantly reduced bacterial counts to levels that were consistently below the American Dental Association's goal of 200 CFU/mL for 8 weeks.

The efficacy of a continuous-use stabilized chlorine dioxide dental unit waterline cleaner and the evaluation of two water sampling methods.

Many commercial dental unit waterline cleaners are available. Results regarding the efficacy of these products vary and sampling methods and laboratory procedures can affect results. This study was conducted to test the efficacy of a continuous-use stabilized chlorine dioxide product and determine if two different sampling methods produced the same results. There was a statistically significant difference between the treated units and the control units (p < 0.05) but the two sampling methods revealed no statistically significant difference (p > 0.5). Treated units showed a decline in the mean number of colony forming units per milliliter (CFU/mL) over the study period but the level was not consistently low enough to meet the ADA-recommended levels of 200 CFU/mL. The findings of this study indicate that it is not necessary to replace a continuous use product with fresh, untreated water when testing water quality.

A survey of infection control teaching in U.S. dental schools.

This study was conducted to determine the content of infection control (IC) curricula, the extent of IC monitoring and compliance, and the number of bloodborne pathogen (BBP) exposures/year in U.S. dental schools. A questionnaire was emailed to persons responsible for predoctoral IC programs. The response rate was 60 percent. Most schools did not have an independent course and used classroom lectures and clinic demonstrations to teach IC. Schools with an IC committee were more likely to use online learning (p<0.05), utilize multiple teaching methods (p<0.05), issue written warnings for IC violations (p<0.0001), and use multiple disciplinary actions (p<0.005) than schools without an IC committee. Schools with an IC coordinator were less likely to issue grade reductions for IC violations than schools with no IC coordinator (p<0.05). Thirty-eight percent reported ≥ 16 BBP exposures/year, and 18 percent reported <5. There was significant correlation between BBP exposure incidents and large class size (p<0.005). Respondents were satisfied with their IC curriculum and perceived that dental students had a high level of IC compliance and satisfaction, along with staff IC promotion and compliance. The findings suggest that schools without an IC committee should consider its benefits. Further investigation of schools with high numbers of BBP exposures is recommended.