Noncompliance with infection control, or IC—specifically, inadequate surface disinfection and failure to use or change barriers between patients—will result in increasing numbers of microorganisms on surfaces. Compliance, on the other hand, can result in low microbial counts. Thus, the level of bacterial contamination on surfaces is an indication of compliance with certain IC and universal precautions, or UP, protocols. One of few objective methods for assessing compliance with IC and, specifically, proper disinfection or use of barriers on surfaces is microbiological monitoring. Changes in the level of surface contamination over time may reflect trends in compliance.

The results of a number of surveys reported in the literature reveal that the number of dental professionals reporting compliance with IC measures over time has increased.^4–6 The expected outcome of this would be reduced levels of bacterial contamination in the dental operatory. In the 1998 study, we assessed changes in surface contamination in a teaching clinic over two decades during which time the clinic underwent a major renovation and redesign and many changes occurred in IC protocols and enforcement.

In 1976, the authors reported the results of a pioneer study of bacterial contamination among surfaces in operatories in a dental clinic at the University of Maryland Dental School that had more than 200 dental chairs.⁷ The results revealed large numbers of bacteria recovered from an assortment of operatory surfaces, including the light handles and chair control switches. Clinic jacket cuffs also were included in the survey and were found to be heavily contaminated. At the time of the study, many of the current policies and recommendations for surface IC either had not been adopted or were not stringently followed. Handpieces and burs were not autoclavable and typically were wiped with alcohol-soaked gauze. Chair position was changed by using a panel of finger-operated control switches on the side of the chair. Surface disinfection between patients or at intervals during the day was not typical. Isopropyl alcohol was used for surface disinfection. Anecdotal evidence suggested that the situation was similar among private practitioners. The clinic design consisted of stationary countertops on both sides of the dental chair that extended the length (approximately 7 feet) of the operatory.

In 1990, the clinic underwent a total renovation and was refurbished with state-of-the-art design and technology. To reduce the risks of bacterial cross-contamination and cross-infection, we paid particular attention to IC issues. We incorporated many new features:

– we reduced the number of surface areas in the operatories;

– we replaced stationary countertops with mobile units for placing instruments and other materials used during patient treatment;

– we constructed a new staffed central sterilization facility;

– we replaced nonautoclavable handpieces with autoclavable handpieces;

– we replaced sink handles and chair control switches with foot pedal controls;

– we contracted with a laundry service to provide clean clinic jackets for practitioners (as opposed to the previous practice, in which people owned and were responsible for laundering their own jackets);

– we made wearing gloves, masks and eye protection, as well as using light handle covers and draping countertops on which contaminated instruments would be placed a part of the routine procedure for treating patients.

We increased the awareness of IC guidelines among student practitioners and faculty, and everyone was required to take a course on blood-borne pathogens. We also increased enforcement of IC and UP protocols; these practices were not the norm when the 1976 surface contamination study was conducted.

Although many advances have been made since the 1976 study to promote IC, decrease the potential for contamination of surfaces and reduce the risk of disease transmission, the effect of these advances on surface contamination has not been evaluated. In this study, we examined the collective impact of these new technologies and designs and the increased emphasis on compliance with IC on reducing surface bacterial contamination. We tested the following hypotheses:

– Average bacterial counts from 11 surfaces will be higher at the end of the day than those obtained at the beginning of the day in both the 1976 and 1998 studies. There will be a significant difference, however, between morning and afternoon bacterial counts in the 1976 study (reflecting inadequate compliance with surface IC between patients during the clinic day) and no significant difference between morning and evening counts in the 1998 study (reflecting improved compliance).

– Improvements in IC procedures and clinic design will yield significantly lower bacterial counts from the 11 surfaces in the 1998 study than in the 1976 study.

	MATERIALS AND METHODS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
To the extent possible, we performed the experimental protocol in the same manner as in the 1976 study. In some cases, however, surfaces from which samples had been obtained previously either had been eliminated or their designs were considerably modified, thus making obtaining samples impossible. Examples of design modifications include chair control switches that were replaced by foot control pedals and instruments such as the handpieces, burs and air-water syringe tips, which were autoclavable and sterilized by staff at the central facility, not by the students, as was done in the 1976 study.

Sample collection. We randomly selected 30 dental operatories at the clinic—the approximate number included in the 1976 study. We obtained samples from similar surfaces in each operatory, including the walls to the right and left of the chair, floor, headrest cover, sink (side and bottom), instrument tray and clinic jacket cuffs (left and right). The redesigned light handle did not have the flat surface area needed for the sampling method. Instead, we removed and obtained samples from the plastic cover on the light handle, which was where hand contact occurred.

As in the 1976 study, we did not forewarn the dental students about sampling. We conducted the sampling twice a day, in the morning before the first patient was seen and at the end of the day after the last patient was seen. We used Replicate Organism Detection and Counting, or RODAC, plates (Becton, Dickinson, Baltimore) containing blood agar as the primary method for sampling surfaces. These plates were designed specifically to obtain samples from flat, smooth surfaces. For sampling, we removed the lids from the RODAC plates and touched the raised agar surface to the operatory surface for about 10 seconds. We replaced the lids and transported the plates to the laboratory within 30 minutes and incubated the samples at 37 C for one week. We then calculated the number of bacterial colony-forming units per RODAC plate.

Statistical analysis. For the statistical analysis, we compared the raw data from the 1976 study with the raw data from the 1998 investigation. We compared and analyzed the bacterial counts from the same type of surfaces as in the 1976 study and the 1998 study for significant differences using the matched pairs t tests and independent t tests. We set total probability bounds at P .05 to compensate for the fact that the same data were used twice, for morning and afternoon comparisons and for 1976 and 1998 comparisons. When P values for the 1976 study indicated significant results with type 1 error being extremely small (results that could have occurred by chance less than five times in 1,000), we considered these results to be significant even if the second time we used the data, the results were not significant.

	RESULTS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
When we compared the mean counts from the morning samples with those from the afternoon samples, we found the bacterial count numbers at the end of the day to be higher than those obtained at the beginning of the day in both studies (Figure 1). The only significant difference we found was between the morning and afternoon counts in 1976.

View larger version (24K): [in this window] [in a new window]   Figure 1. Comparison of the average morning bacterial counts with those from the afternoon in the 1976 (t = –3.589, P .05, significant) and 1998 (t = – 0.832, P .05, not significant) studies.

View larger version (32K): [in this window] [in a new window]   Figure 2. Comparison of morning and afternoon bacterial counts each of 11 surfaces in the 1976 study. Areas with significant differences were light handle (t = –2.269, P .05), right jacket cuff (t = –2.666, P .05), left jacket cuff (t = –2.509, P .05), floor (t = –3.142, P .01) and sink side t = –2.432, P .05.

View larger version (30K): [in this window] [in a new window]   Figure 3. Comparison of morning and afternoon bacterial counts from each of 11 surfaces in the 1998 study; all differences were not significant.

View larger version (28K): [in this window] [in a new window]   Figure 4. Areas with significant differences (P .05) between 1998 and 1976 were light handle (afternoon: t = 4.589, P .05; morning: t = 3.641, P .05), headrest (afternoon: t = 2.908, P .05; morning: t = 2.931, P .05), floor (afternoon: t = 2.388, P .005; morning: t = 3.572, P .05), right jacket cuff (morning: t = 1.312, P .002) and left jacket cuff (afternoon: t = 4.811, P .005; morning: t = 3.197, P .005). No significant differences were found between afternoon right jacket cuff counts. PM: Afternoon. AM: Morning.

	DISCUSSION

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

Another objective method for gauging compliance with some aspects of IC is assessing the level of surface contamination. Surface contamination may be influenced by a number of IC factors, including disinfection, type of disinfectant used, use of barriers to cover surfaces such as the light handle, use of high-vacuum suction during use of high-speed instruments, and placement of contaminated instruments and other materials. Surface contamination and disinfection in dentistry have received considerable attention as IC issues. As a result, the necessity for disinfecting surfaces was emphasized to clinicians, and recommendations on controlling surface contamination in the clinic in this study were developed by the dental school’s infection control committee.

Few studies,^2,7,9 however, have been conducted to assess compliance in a direct, objective manner, and none have analyzed changes in the levels of surface contamination over time to validate that new IC practices are effective. A unique opportunity to make such a validation was presented to us through an opportunity to repeat a 1976 study that monitored bacterial surface contamination in a dental clinic. We repeated the study in 1998 at the same site but after the clinic had undergone a complete renovation that included an IC-sensitive design and implementation of recommended IC protocols. We expected 1998 bacterial counts to be lower than those in 1976 because of the better clinic design, the increase in student practitioners’ education and awareness about disinfection and other IC protocols and greater enforcement of IC practices. This hypothesis was substantiated, as the level of bacterial contamination was significantly decreased on most surfaces in 1998. This validates that improved IC practices and education and a sensitive clinic design can result in a safer environment for delivery of dental care.

The areas we found to be most contaminated typically were the same in the two studies; however, the bacterial counts from surfaces in the 1998 study were reduced in all cases except for those from the floor, which increased significantly. The reasons for this may be linked to reductions in the frequency of floor cleanings and maintenance that occurred in the early 1990s as a cost-saving move.

In the 1976 study, clinic jacket cuffs were one of the most contaminated surfaces. The reduced bacterial counts in the 1998 study for clinic jackets can be attributed to the change to a professional laundering service that makes a clean jacket available to practitioners on a daily basis or whenever soiling with body fluids occurs. From informal interviews with student clinicians in the 1976 study, it is apparent that clinic jackets were not changed on a standard schedule.

The use of plastic covers on light handles and headrests also has contributed to the dramatic reduction in surface contamination.

More evidence for the improvement of IC practices is suggested by comparing the results of the morning vs. afternoon counts in the two studies. Although the bacterial counts typically increased in both studies between the morning and afternoon samples, the counts in the 1976 study were significantly greater in the afternoon than the morning. In the 1998 study, the difference was not significant, suggesting that there was more effective surface disinfection between patients. Although much improved over those from the 1976 study, the bacterial counts from the 1998 study indicate that there is a continuing need to improve surface disinfection.

The only other recent study reported in the literature that assessed levels of surface contamination in dentistry was done in a clinic in which many IC and UP practices were lacking altogether or deficient, as was the clinician’s knowledge of disinfection procedures, recommendations and practices.⁹ The results from that study are more comparable to the counts observed in the 1976 study and much higher than those in the 1998 study. This also suggests that proper IC practices were the basis for the reduction in counts observed in the 1998 study. The results of the 1998 study are consistent with the survey studies that report a trend of increasing compliance with IC and UP.^5,6,8,10 A 1998 survey of Maryland dentists reported high rates of compliance with most IC practices, though there remains room for improvement.⁶

Although some IC issues can be resolved through equipment and clinic designs—such as replacing sink handles with foot pedal controls and reducing available counter space where microbes could be deposited—compliance with IC practices such as proper disinfection of surfaces between patients remains most important. It cannot be assumed that having the technology translates into compliance. For example, it was reported in 1993 that 83 percent of dentists used autoclavable handpieces but only 62 percent sterilized them.⁴

Although not recommended as a routine in small offices, the periodic use of microbial monitoring in large clinics as described in the 1976 and 1998 studies may be useful in determining relative compliance with disinfection protocols. It also may be helpful in maintaining a high level of consciousness for surface disinfection and IC in general.¹¹ In the case of high bacterial counts, it should be presumed that pathogenic organisms including hepatitis B, C or Mycobacterium tuberculosis could be present and that they represent an increased risk of causing disease transmission in the dental environment. Steps should be taken to implement proper IC procedures immediately. The results of the 1976 and 1998 studies have revealed that attention to operatory and equipment design and the institution of sound IC practices can reduce surface bacterial contamination. These findings are consistent with increased compliance with certain IC measures reported by Hazelkorn and colleagues.¹⁰

	CONCLUSIONS

TOP ABSTRACT MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
A reduction in bacterial surface contamination over a 22-year period was evident in a teaching dental clinic, after renovations and changes in the clinic design to make it more compatible with recommended IC guidelines were made and asepsis guidelines were adhered to more strictly. Changes that likely contributed to this improvement include stronger policies relating to IC issues in general, a switch from personal to institutional laundering of clinic jackets and making clinic jackets available and use of an approved surface disinfectant. Other factors that also may have contributed include a seemingly greater awareness among student practitioners about IC procedures, greater enforcement of policies and procedures by faculty, greater institutional control over instrument sterilization and the use of more items that can be disposed of directly instead of being placed on a surface.