Combining periodic and continuous sodium hypochlorite treatment to control biofilms in dental unit water systems.

BACKGROUND: This study evaluated the efficacy of combined intermittent and continuous treatment with diluted sodium hypochlorite, or NaClO, to improve dental unit water quality in a clinical setting. METHODS: In this prospective study, 10 dental units were fitted with separate water reservoir systems. Dental units were maintained with weekly rinses with 1:10 NaClO. Treatment water consisted of 750 milliliters of tap water and one drop of undiluted commercial bleach. Bacterial contamination in the effluent coolant water was assayed via microbiologic culture on a weekly basis. At the end of the study, scanning electron microscopy of the inner surfaces of the dental unit waterlines corroborated the results. RESULTS: All 10 dental units consistently delivered water with less than 10 colony-forming units per milliliter, or CFU/mL, with a mean bacterial contamination of less than 1 CFU/mL. Baseline scanning electron microscopy demonstrated biofilm formation. Scanning electron microscopy at the end of the study demonstrated the lack of features consistent with biofilm formation. Although tri-halomethanes were detected in output water, all samples were below Environmental Protection Agency limits for drinking water. CONCLUSIONS: Weekly treatment with 5.25 percent NaClO diluted 1:10, and concomitant use of chlorinated treatment water (3 parts per million chlorine) consistently attained the proposed American Dental Association goal of fewer than 200 CFU/mL in the unfiltered output. The effects of continuous treatment on dentin and enamel bond strength may require further evaluation. CLINICAL IMPLICATIONS: The success of this protocol suggests that optimal attainment of dental water quality goals may require a combination of approaches.

Comparison of methods to enumerate bacteria in dental unit water lines.

Millipore HPC samplers are simple, self-contained test devices that can be used by personnel in dental offices who do not have microbiologic training to easily and economically monitor dental unit water quality without laboratory support. This study evaluated the correlation of HPC samplers to R2A agar for enumerating planktonic bacteria in dental unit treatment water. Eight different dental units were sampled. Five replicates were performed for each media at each dilution. The Pearson correlation coefficient between the R2A agar and HPC sampler is 0.89. These data suggest HPC samplers correlate with conventional laboratory-based R2A culture techniques for determining dental unit water line contamination.

Validation of an in-office dental unit water monitoring technique.

The authors conducted a study to determine the sensitivity, specificity and accuracy of HPC Samplers (Millipore Corp.) as compared with that of R2A agar and HPC agar when used to monitor dental unit water, or DUW, quality. Results were either a pass (200 colony-forming units per milliliter, or CFU/mL, or less) or a fail (greater than 200 CFU/mL). Of the 408 tests conducted, the results of the HPC Sampler agreed with R2A agar 377 times, for an accuracy rate of 92.6 percent. The authors recommend that clinicians consider using HPC Samplers, as they are a user-friendly, economical means of monitoring compliance of DUW quality.

Pulp response to the combined effects of cavity preparation and periodontal ligament injection.

Thirteen random-source dogs provided 54 experimental and 50 control teeth. Controls received either a periodontal ligament (PDL) injection only, or no injection, with deep cavities prepared and restored. Experimental teeth received both a PDL injection and the deep cavity preparation and were then restored with an IRM base and acid-etched composite. Teeth were surgically removed for observation periods of one and 18 weeks and prepared for histologic evaluation. Results indicated that, in this model system, there was little additive effect to the pulpal reaction due to the PDL injection. Controls that were prepared had essentially the same pulpal response as did the experimental teeth (PDL injection/preparation). In both experimental and control pulps, the effects were primarily related to the depth of the cavity preparation.