- Email: [email protected]
Improved compliance with recommended infection control practices in the dental office between 1994 and 1995
Improved compliance with recommended infection control practices in the dental office between 1994 and 1995 Gillian M. McCarthy, BDS, MSc John K. MacDonald, MA London, Ontario, Canada
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. (AJIC Am J Infect Control 1998;26:24-28)
During the past decade, recommendations for infection control for dentistry have been revised to minimize the risk of cross-infection related to hepatitis B virus (HBV), hepatitis C virus (HCV), and HIV.1-3 These measures include the use of basic barrier techniques (i.e., use of gloves, masks, and eye protection), heat sterilization of dental handpieces, and HBV vaccination. Infected perFrom the Faculty of Medicine and Dentistry, School of Dentistry and Department of Epidemiology and Biostatistics, University of Western Ontario. Supported by grants from the Ontario Ministry of Health (04739) and the National Health Research and Development Program, Health Canada (6606-5463-AIDS). G. M. McCarthy is a Career Scientist of the Ontario Ministry of Health, Health Research Personnel Development Program. Reprint requests: G. M. McCarthy, BDS, MSc, Division of Oral Biology, Faculty of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada N6A 5C1. Copyright © 1998 by the Association for Professionals in Infection Control and Epidemiology, Inc. 0196-6553/98 $5.00 + 0
24
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sons are frequently unaware that they are infected, cannot be identified by a medical history, or are unwilling to reveal their status for fear of disclosure or rejection for dental treatment. Thus professional organizations now recommend the use of universal precautions, so that all patients are treated as potential carriers of infection. There are reports of increasing compliance with recommended infection control over time,4-7 but there are few data from Canada. In a preliminary investigation, we showed that there were significant time changes in the infection control practices of dentists.8 In this study we expanded our research to investigate changes in infection control practices among Ontario dentists between 1994 and 1995. The study was designed to measure changes in the proportions of dentists who reported the use of • Basic barrier techniques, including use of gloves, mask, and protective eyewear • HBV vaccination of dentists and clinical staff
AJIC
McCarthy and MacDonald 25
Volume 26, Number 1
Table 1. Reported infection control practices of dentists who responded to 1994 survey and dentists who responded to 1995 survey Procedure
Use gloves
Use mask
Use eye protection
HBV vaccination of dentist HBV vaccination of all clinical staff Heat sterilize handpieces Use extra precautions for patients with HIV
Category
% in 1994 (n = 4003)
Always Sometimes Never Always Sometimes Never Always Sometimes Never Yes Acquired immunity Yes Yes Yes
91.8 7.8 0.4 73.3 22.1 4.5 82.5 13.9 3.6 92.0 0.6 63.9 83.4 87.0
• Heat sterilization of handpieces • Additional infection control precautions for patients with HIV/AIDS METHODS
The study population in 1994 included the 5997 dentists listed by the Royal College of Dental Surgeons of Ontario. The 1995 data were obtained from a random sample of 1655 dentists in Ontario who participated in a national survey of Canadian dentists. The questionnaires included items on demographics, attendance at continuing education courses on HIV, attitudes toward HIV-infected patients, and knowledge and practices of infection control. The reliability of each item was measured by using a test–retest procedure, and all items had an unweighted kappa statistic of 0.45 to 1.00. A kappa statistic greater than 0.4 is considered to indicate reliability.9 The administration of the 1994 census had been described previously.10 In 1995, questionnaires with identification numbers were mailed to a random sample of dentists in Ontario. The same follow-up procedures were used in the 1994 and 1995 surveys based on Dillman’s Total Design Method11: a reminder postcard and two additional mailings of the questionnaire to nonresponders. The 1994 questionnaire had 40 items; the 1995 questionnaire had 70 items. The additional questions on the 1995 questionnaire included a more comprehensive range of items on infection control. Data from responses to the infection control items in both surveys were used for the analysis of paired data. To facilitate comparison, we used the same identification numbers for dentists who participated in both surveys. Names and identification numbers
% in 1995 (n = 987)
93.8 6.2 0.0 78.6 16.9 4.5 83.8 11.0 5.2 90.9 3.1 77.1 95.2 52.3
were kept strictly confidential and were accessed only by the study secretary. The completed questionnaires were delivered to a research assistant in another location. This research assistant was the only person with access to the completed questionnaires and was responsible for data entry, validation, and tracking of nonrespondents. The list of identification numbers for nonrespondents was sent to the secretary, to facilitate additional mailings for follow-up. The cover letters and the survey instructions described methods of protecting anonymity of response. Separate analyses of the data from the 1994 and the 1995 surveys were performed. Descriptive statistics were obtained with the Statistical Package for the Social Sciences (SPSS.PC+). Because data from the 1994 and 1995 surveys were not independent, a paired-data analysis (McNemar’s test) was used for responses of the 788 dentists who participated in both surveys. This analysis identified statistically significant differences in responses for 1994 and 1995. We used Fleiss’ statistical methods for rates and proportions12 to calculate (1) the differences in proportions of dentists reporting compliance with recommended infection control practices in 1994 and in 1995 and (2) the confidence intervals for these differences. Investigations of bias due to nonresponse were performed for the data from 1994 and from 1995.10, 13 RESULTS
The response rates for 1994 and 1995 were 70.3% and 62.3%, respectively, with adjustment for nondelivery of the questionnaire. An assessment of bias due to nonresponse revealed no bias for infection control items in the 1994 data.10 We
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26 McCarthy and MacDonald
February 1998
Table 2. Comparison of paired data from responses of 788 dentists who participated in both 1994 and 1995 surveys Variable
Always use gloves Always use mask Use eye protection HBV vaccination of dentist or acquired immunity HBV vaccination of all clinical staff Heat sterilize handpieces Never use extra precautions for patients with HIV
% in 1994
91.6 72.5 96.8 92.6 65.0 83.7 13.7
% in 1995
93.5 77.5 95.9 94.4 76.8 95.7 47.7
Difference between percentages*
95% confidence interval*
1.9 5.0 -0.9 1.8 11.8 12.0 34.0
0.1–3.2 3.1–7.0 -2.7–0.8 0.2–3.2 3.3–11.8 9.5–14.3 28.3–36.3
p Value (McNemar test)
0.0311 0.0000 0.3487 0.0259 0.0005 0.0000 0.0000
*Calculated according to Fleiss’ statistical methods for rates and proportions.12
found minimal evidence of nonresponse bias for heat sterilization of handpieces in the 1995 data.13 The infection control practices of the study populations in 1994 and 1995 are shown in Table 1. The proportion of dentists who reported use of basic barrier techniques and heat sterilization of handpieces was higher in the 1995 survey than in the 1994 survey. The proportion of reports of HBV vaccination for clinical staff was higher in 1995 than in 1994. Proportionally fewer respondents in 1995 reported using extra precautions with patients who had HIV/AIDS. Table 2 shows the results of a comparison of paired data on responses from the 788 dentists who participated in both the 1994 and 1995 surveys. Statistical significance was demonstrated for increases in the proportion of dentists who reported use of gloves (p < 0.05) or masks (p < 0.00001); HBV vaccination or naturally acquired immunity of the dentist (p < 0.05); HBV vaccination of staff (p < 0.001); heat sterilization of handpieces (p < 0.00001); and never taking extra precautions for patients with HIV/AIDS (p < 0.00001). Compared with respondents in 1994, dentists in 1995 were significantly more likely to report continuing education related to HIV/AIDS (p < 0.00001). DISCUSSION
The full results of the national study of dentists are reported elsewhere (manuscript submitted). Our results confirm other reports of increasing compliance with recommended infection control practices over time.4-8, 14 The paired-data comparison showed significant increases between 1994 and 1995 in use of gloves and masks; HBV vaccination or naturally acquired immunity of the dentist; HBV vaccination of staff; heat sterilization of handpieces; and not taking extra precautions with patients who had HIV/AIDS. The sample size for this analysis was large enough for detection of sig-
nificant differences of small magnitude (e.g., changes of approximately 2% for use of gloves and HBV vaccination or naturally acquired immunity of the dentist). In contrast, improvements greater than 10% were noted for HBV vaccination of all clinical staff and heat sterilization of handpieces. The greatest improvement was in the proportion of respondents who never used additional infection control precautions for patients with HIV. The recommendation to use universal precautions is based on the need to treat patients as if they are infected with HBV or HIV; additional precautions for infected patients are therefore unnecessary. Although the proportion of respondents who reported never using additional precautions increased 34% between 1994 and 1995, the majority of respondents in 1995 still reported the use of extra infection control procedures for patients with HIV/AIDS. Most respondents in this study also reported concerns about providing care for patients with HIV. These concerns included staff fears about patients with HIV/AIDS (65.4%), loss of patients from the practice (67.0%), and personal safety (61.9%). It is possible that some dentists take unnecessary precautions to alleviate staff fears and concerns for personal safety. However, dentists who take extra infection control precautions when treating HIV-infected patients or who refuse to provide care for patients with HIV may face charges of discrimination from human rights organizations in Canada15, 16 or charges of violating the Americans with Disabilities Act in the United States.17 Recent publicity in professional journals and in the media about such discrimination cases may partially explain increased compliance with the use of recommended infection control and universal precautions by Ontario dentists. Changes in infection control practices may also be attributable to an increased emphasis on education. Mandatory continuing education for dentists
AJIC Volume 26, Number 1
in Ontario was introduced by the Royal College of Dental Surgeons of Ontario in 1993. In 1995 the proportion of Ontario dentists who reported attending continuing education in the previous 2 years was 79.6% for infection control courses, 56.5% for courses on hepatitis viruses, and 68.8% for courses on HIV/AIDS. If routine infection control procedures in the dental office are not adequate to protect against HBV and HIV, the potential for cross-infection exists. It is difficult to identify many patients who have infections because of lack of awareness or unwillingness to reveal their infectious status. Many patients are unaware of their HIV infectivity, because of the long incubation period before signs or symptoms are diagnosed and the window period before antibodies can be detected. In addition, some patients who have high risk of acquiring HIV avoid HIV testing, and others are not tested because they are unaware of their risk. There is also evidence that patients with HIV do not disclose their infection for fear of discrimination, rejection for dental treatment, or breach of confidentiality. In our previous study of patients infected with HIV, 18% of respondents who attended private dental offices did not disclose their seropositivity.18 Similarly many patients with HBV are unaware of their infection or escape detection.19 The Canadian Dental Association20 and the American Dental Association1 have stated that it is unethical for dentists to refuse care to patients with HBV or HIV on the basis of their infectious status and that these patients may be treated safely in the dental office if recommended infection control practices are followed. The increased trend toward heat sterilization of handpieces confirmed our preliminary observations8 and reports from other researchers.5, 14 In preliminary studies, we showed an increase in heat sterilization of handpieces from 68% in 1992 to 85% in 1994.8 In a 1989 random sample survey, 14% of dentists surveyed in Quebec reported heat sterilization of high-speed handpieces.21 Our results from the 1995 national survey indicated that the percentage of dentists in Quebec reporting heat sterilization of handpieces had risen to 71%. In a recent study of infection control practices of specialists in British Columbia, two thirds of the respondents reported heat sterilization of handpieces.22 The increased use of this procedure, which was reported in more recent investigations, including this study, may reflect a response to reports about the potential for transmission of microbes by means of dental handpieces.23-25
McCarthy and MacDonald 27
Hepatitis C virus, for which there is no vaccine, is now becoming a major concern in the health care environment. Previously, cross infection with HBV caused much concern in the health care setting; however, the frequency of occupational transmission of HBV to health care workers has been reduced as a result of vaccination. Unvaccinated health care workers and patients are still vulnerable. The risk of transmission is approximately 25% if the carrier is HBeAg positive. HBV vaccines are effective in more than 95% of cases and also confer protection against hepatitis D virus.26 There have been reports of increased HBV vaccination of dentists.4, 5, 7, 8 In this study, we noted an increase in reports by dentists who had either HBV vaccination or naturally acquired immunity to HBV as a result of previous exposure. Although the proportion of Ontario dentists who reported HBV vaccination of clinical staff increased from 65.0% to 76.8% between 1994 and 1995 (Table 2), approximately one quarter of respondents in 1995 still reported that all clinical assistants had not been vaccinated against HBV and were therefore vulnerable to infection with HBV and hepatitis D. There is a need for more education of dentists and clinical staff to promote HBV vaccination. The questionnaire used in 1995 included a more comprehensive range of items on infection control procedures, and it was not possible to investigate changes in reports of these items between 1994 and 1995. As a result of increasing concern about waterborne microorganisms,1,27,28 we included items on the reduction of potential for transmission of microbes via waterlines. Of the respondents in Ontario who participated in the national survey in 1995, 53.8% reported that they always flushed water lines after treating each patient. The 1995 data also indicated low compliance with other recommended infection control practices including handwashing. Only 74.4% of respondents reported that they always washed their hands before they treated each patient, and 61.9% reported that they always washed their hands after removing gloves. In addition, only 36.0% reported that they had a postexposure protocol for needlesticks and cuts. Recent evidence demonstrates that zidovudine (AZT) reduces the risk of HIV seroconversion resulting from occupational exposure by approximately 80%. Consequently, recommendations for prophylaxis after exposure to HIV have been changed. It is now recommended that persons who have significant exposure to HIV receive prophylaxis with AZT or another antiretroviral
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28 McCarthy and MacDonald
agent, alone or in combination with other antiretroviral drugs, within 2 hours.29 Although dentist reports of compliance with recommended infection control practices and universal precautions increased between 1994 and 1995, it appears that the majority of dentists have not adopted universal precautions. Considerable improvements were noted in HBV vaccination of all clinical staff and heat sterilization of handpieces, but the proportion of respondents who reported these practices was still too low. More education is needed to promote the treatment of all patients as if they are infected with bloodborne pathogens. Particular emphasis is required to improve compliance with HBV vaccination for clinical staff, handwashing, and use of postexposure protocol in the dental office. References 1. American Dental Association. Infection control recommendations for the dental office and the dental laboratory. J Am Dent Assoc 1996;127:672-80. 2. Canadian Dental Association. Recommendations for infection control procedures. Communique, May 1992;10. 3. Centers for Disease Control. Recommended infection-control practices for dentistry, 1993. MMWR 1993;41:1-12. 4. DiAngelis AJ, Martens LV, Little JW, Hastreiter RJ. Infection control practices of Minnesota dentists: changes during one year. J Am Dent Assoc 1989;118:299-303. 5. Verrusio AC, Neidle EA, Nash KD, Silverman S Jr, Horowitz AM, Wagner KS. The dentist and infectious diseases: a national survey of attitudes and behavior. J Am Dent Assoc 1989;118:553-62. 6. Nash KD. How infection control procedures are affecting dental practice today. J Am Dent Assoc 1992;123:67-73. 7. Gibson GB, Mathias RG, Epstein JB. Compliance to recommended infection control procedures: changes over six years among British Columbia dentists. J Can Dent Assoc 1995;61:526-32. 8. McCarthy GM, Koval JJ. Changes in dentist’s infection control practices, knowledge and attitudes concerning HIV over a two year period. Oral Surg Oral Med Oral Pathol 1996;81:297-302. 9. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159-74. 10. McCarthy GM, Koval JJ, MacDonald JK. Non-response bias in a survey of Ontario dentists’ infection control and attitudes concerning HIV. J Public Health Dent 1997; 57:59-62. 11. Dillman DA. Implementing mail surveys. In: Mail and telephone surveys. The total design method. Toronto: Wiley; 1978. p. 160-200.
February 1998
12. Fleiss JC. Statistical methods for rates and proportions. 2nd ed. New York: John Wiley & Sons; 1981. 13. McCarthy GM, MacDonald JK. Non-response bias in a national study of dentists’ infection control practices and attitudes related to HIV. Community Dent Oral Epidemiol 1997;25:119-25. 14. Bentley EM, Sarll DW. Improvements in cross-infection control in general dental practice. Br Dent J 1995;179:19-21. 15. Canadian Dental Association. Ottawa dentist faces charges of discrimination. Communique, July-Aug 1995. 16. Crawford PR. AIDS and discrimination: the Windsor case. J Can Dent Assoc 1995;61:25-7. 17. American Dental Association. ADA takes action on two HIV fronts. ADA News Releases, June 1996. 18. McCarthy GM, Haji FS, Mackie IDF. HIV-infected patients and dental care: nondisclosure of HIV status and rejection for treatment. Oral Surg Oral Med Oral Pathol 1995;80:655-9. 19. Brooks GF, Butel JS, Ornston LN. Hepatitis viruses. In: Jawetz, Melnick and Adelberg’s medical microbiology. 19th ed. Norwalk (CT): Appleton & Lange; 1995. p. 451-68. 20. Canadian Dental Association. Statement on the ethical and legal considerations of treating patients with infectious diseases. J Can Dent Assoc 1988;54:385. 21. Soto JC, Levi M, Allard R, Franko E. Survey on attitudes, beliefs and knowledge related to AIDS among dental professionals in Quebec. In: Adjukovic D, editor. Oral AIDS: manifestations, safety measures, and questions of transmissibility. New York: Elsevier; 1990. p. 181-91. 22. Epstein JB, Mathias RG, Bridger DV. Survey of knowledge of infectious disease and infection control practices of dental specialists. J Can Dent Assoc 1995;61:35-7, 40-4. 23. Lewis DL, Boe RK. Infection risks associated with current procedures for using high speed dental hand pieces. J Clin Microbiol 1992;30:401-6. 24. Lewis DL, Arens M, Appleton SS, Nakashima K, Ryu J, Boe RK, et al. Cross-contamination potential with dental equipment. Lancet 1992;340:1252-4. 25. Epstein JB, Rea G, Sibau L, Sherlock CH. Assessing viral retention and elimination in rotary dental instruments. J Am Dent Assoc 1995;126:87-92. 26. Porter S, Scully C, Samaranayake L. Viral hepatitis: current concepts for dental practice. Oral Surg Oral Med Oral Pathol 1994;78:682-95. 27. Molinari JA. Waterborne microorganisms: questions about health-care problems and solutions. Compendium Continuing Educ 1995;16:130,132. 28. Challacombe SJ, Fernandes LL. Detecting Legionella pneumophila in water systems: a comparison of various dental units. J Am Dent Assoc 1995;126:603-8. 29. Centers for Disease Control and Prevention. Update: provisional public health service recommendations for chemoprophylaxis after occupational exposure to HIV. MMWR 1996;45:468-72.
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. (AJIC Am J Infect Control 1998;26:24-28)
During the past decade, recommendations for infection control for dentistry have been revised to minimize the risk of cross-infection related to hepatitis B virus (HBV), hepatitis C virus (HCV), and HIV.1-3 These measures include the use of basic barrier techniques (i.e., use of gloves, masks, and eye protection), heat sterilization of dental handpieces, and HBV vaccination. Infected perFrom the Faculty of Medicine and Dentistry, School of Dentistry and Department of Epidemiology and Biostatistics, University of Western Ontario. Supported by grants from the Ontario Ministry of Health (04739) and the National Health Research and Development Program, Health Canada (6606-5463-AIDS). G. M. McCarthy is a Career Scientist of the Ontario Ministry of Health, Health Research Personnel Development Program. Reprint requests: G. M. McCarthy, BDS, MSc, Division of Oral Biology, Faculty of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada N6A 5C1. Copyright © 1998 by the Association for Professionals in Infection Control and Epidemiology, Inc. 0196-6553/98 $5.00 + 0
24
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sons are frequently unaware that they are infected, cannot be identified by a medical history, or are unwilling to reveal their status for fear of disclosure or rejection for dental treatment. Thus professional organizations now recommend the use of universal precautions, so that all patients are treated as potential carriers of infection. There are reports of increasing compliance with recommended infection control over time,4-7 but there are few data from Canada. In a preliminary investigation, we showed that there were significant time changes in the infection control practices of dentists.8 In this study we expanded our research to investigate changes in infection control practices among Ontario dentists between 1994 and 1995. The study was designed to measure changes in the proportions of dentists who reported the use of • Basic barrier techniques, including use of gloves, mask, and protective eyewear • HBV vaccination of dentists and clinical staff
AJIC
McCarthy and MacDonald 25
Volume 26, Number 1
Table 1. Reported infection control practices of dentists who responded to 1994 survey and dentists who responded to 1995 survey Procedure
Use gloves
Use mask
Use eye protection
HBV vaccination of dentist HBV vaccination of all clinical staff Heat sterilize handpieces Use extra precautions for patients with HIV
Category
% in 1994 (n = 4003)
Always Sometimes Never Always Sometimes Never Always Sometimes Never Yes Acquired immunity Yes Yes Yes
91.8 7.8 0.4 73.3 22.1 4.5 82.5 13.9 3.6 92.0 0.6 63.9 83.4 87.0
• Heat sterilization of handpieces • Additional infection control precautions for patients with HIV/AIDS METHODS
The study population in 1994 included the 5997 dentists listed by the Royal College of Dental Surgeons of Ontario. The 1995 data were obtained from a random sample of 1655 dentists in Ontario who participated in a national survey of Canadian dentists. The questionnaires included items on demographics, attendance at continuing education courses on HIV, attitudes toward HIV-infected patients, and knowledge and practices of infection control. The reliability of each item was measured by using a test–retest procedure, and all items had an unweighted kappa statistic of 0.45 to 1.00. A kappa statistic greater than 0.4 is considered to indicate reliability.9 The administration of the 1994 census had been described previously.10 In 1995, questionnaires with identification numbers were mailed to a random sample of dentists in Ontario. The same follow-up procedures were used in the 1994 and 1995 surveys based on Dillman’s Total Design Method11: a reminder postcard and two additional mailings of the questionnaire to nonresponders. The 1994 questionnaire had 40 items; the 1995 questionnaire had 70 items. The additional questions on the 1995 questionnaire included a more comprehensive range of items on infection control. Data from responses to the infection control items in both surveys were used for the analysis of paired data. To facilitate comparison, we used the same identification numbers for dentists who participated in both surveys. Names and identification numbers
% in 1995 (n = 987)
93.8 6.2 0.0 78.6 16.9 4.5 83.8 11.0 5.2 90.9 3.1 77.1 95.2 52.3
were kept strictly confidential and were accessed only by the study secretary. The completed questionnaires were delivered to a research assistant in another location. This research assistant was the only person with access to the completed questionnaires and was responsible for data entry, validation, and tracking of nonrespondents. The list of identification numbers for nonrespondents was sent to the secretary, to facilitate additional mailings for follow-up. The cover letters and the survey instructions described methods of protecting anonymity of response. Separate analyses of the data from the 1994 and the 1995 surveys were performed. Descriptive statistics were obtained with the Statistical Package for the Social Sciences (SPSS.PC+). Because data from the 1994 and 1995 surveys were not independent, a paired-data analysis (McNemar’s test) was used for responses of the 788 dentists who participated in both surveys. This analysis identified statistically significant differences in responses for 1994 and 1995. We used Fleiss’ statistical methods for rates and proportions12 to calculate (1) the differences in proportions of dentists reporting compliance with recommended infection control practices in 1994 and in 1995 and (2) the confidence intervals for these differences. Investigations of bias due to nonresponse were performed for the data from 1994 and from 1995.10, 13 RESULTS
The response rates for 1994 and 1995 were 70.3% and 62.3%, respectively, with adjustment for nondelivery of the questionnaire. An assessment of bias due to nonresponse revealed no bias for infection control items in the 1994 data.10 We
AJIC
26 McCarthy and MacDonald
February 1998
Table 2. Comparison of paired data from responses of 788 dentists who participated in both 1994 and 1995 surveys Variable
Always use gloves Always use mask Use eye protection HBV vaccination of dentist or acquired immunity HBV vaccination of all clinical staff Heat sterilize handpieces Never use extra precautions for patients with HIV
% in 1994
91.6 72.5 96.8 92.6 65.0 83.7 13.7
% in 1995
93.5 77.5 95.9 94.4 76.8 95.7 47.7
Difference between percentages*
95% confidence interval*
1.9 5.0 -0.9 1.8 11.8 12.0 34.0
0.1–3.2 3.1–7.0 -2.7–0.8 0.2–3.2 3.3–11.8 9.5–14.3 28.3–36.3
p Value (McNemar test)
0.0311 0.0000 0.3487 0.0259 0.0005 0.0000 0.0000
*Calculated according to Fleiss’ statistical methods for rates and proportions.12
found minimal evidence of nonresponse bias for heat sterilization of handpieces in the 1995 data.13 The infection control practices of the study populations in 1994 and 1995 are shown in Table 1. The proportion of dentists who reported use of basic barrier techniques and heat sterilization of handpieces was higher in the 1995 survey than in the 1994 survey. The proportion of reports of HBV vaccination for clinical staff was higher in 1995 than in 1994. Proportionally fewer respondents in 1995 reported using extra precautions with patients who had HIV/AIDS. Table 2 shows the results of a comparison of paired data on responses from the 788 dentists who participated in both the 1994 and 1995 surveys. Statistical significance was demonstrated for increases in the proportion of dentists who reported use of gloves (p < 0.05) or masks (p < 0.00001); HBV vaccination or naturally acquired immunity of the dentist (p < 0.05); HBV vaccination of staff (p < 0.001); heat sterilization of handpieces (p < 0.00001); and never taking extra precautions for patients with HIV/AIDS (p < 0.00001). Compared with respondents in 1994, dentists in 1995 were significantly more likely to report continuing education related to HIV/AIDS (p < 0.00001). DISCUSSION
The full results of the national study of dentists are reported elsewhere (manuscript submitted). Our results confirm other reports of increasing compliance with recommended infection control practices over time.4-8, 14 The paired-data comparison showed significant increases between 1994 and 1995 in use of gloves and masks; HBV vaccination or naturally acquired immunity of the dentist; HBV vaccination of staff; heat sterilization of handpieces; and not taking extra precautions with patients who had HIV/AIDS. The sample size for this analysis was large enough for detection of sig-
nificant differences of small magnitude (e.g., changes of approximately 2% for use of gloves and HBV vaccination or naturally acquired immunity of the dentist). In contrast, improvements greater than 10% were noted for HBV vaccination of all clinical staff and heat sterilization of handpieces. The greatest improvement was in the proportion of respondents who never used additional infection control precautions for patients with HIV. The recommendation to use universal precautions is based on the need to treat patients as if they are infected with HBV or HIV; additional precautions for infected patients are therefore unnecessary. Although the proportion of respondents who reported never using additional precautions increased 34% between 1994 and 1995, the majority of respondents in 1995 still reported the use of extra infection control procedures for patients with HIV/AIDS. Most respondents in this study also reported concerns about providing care for patients with HIV. These concerns included staff fears about patients with HIV/AIDS (65.4%), loss of patients from the practice (67.0%), and personal safety (61.9%). It is possible that some dentists take unnecessary precautions to alleviate staff fears and concerns for personal safety. However, dentists who take extra infection control precautions when treating HIV-infected patients or who refuse to provide care for patients with HIV may face charges of discrimination from human rights organizations in Canada15, 16 or charges of violating the Americans with Disabilities Act in the United States.17 Recent publicity in professional journals and in the media about such discrimination cases may partially explain increased compliance with the use of recommended infection control and universal precautions by Ontario dentists. Changes in infection control practices may also be attributable to an increased emphasis on education. Mandatory continuing education for dentists
AJIC Volume 26, Number 1
in Ontario was introduced by the Royal College of Dental Surgeons of Ontario in 1993. In 1995 the proportion of Ontario dentists who reported attending continuing education in the previous 2 years was 79.6% for infection control courses, 56.5% for courses on hepatitis viruses, and 68.8% for courses on HIV/AIDS. If routine infection control procedures in the dental office are not adequate to protect against HBV and HIV, the potential for cross-infection exists. It is difficult to identify many patients who have infections because of lack of awareness or unwillingness to reveal their infectious status. Many patients are unaware of their HIV infectivity, because of the long incubation period before signs or symptoms are diagnosed and the window period before antibodies can be detected. In addition, some patients who have high risk of acquiring HIV avoid HIV testing, and others are not tested because they are unaware of their risk. There is also evidence that patients with HIV do not disclose their infection for fear of discrimination, rejection for dental treatment, or breach of confidentiality. In our previous study of patients infected with HIV, 18% of respondents who attended private dental offices did not disclose their seropositivity.18 Similarly many patients with HBV are unaware of their infection or escape detection.19 The Canadian Dental Association20 and the American Dental Association1 have stated that it is unethical for dentists to refuse care to patients with HBV or HIV on the basis of their infectious status and that these patients may be treated safely in the dental office if recommended infection control practices are followed. The increased trend toward heat sterilization of handpieces confirmed our preliminary observations8 and reports from other researchers.5, 14 In preliminary studies, we showed an increase in heat sterilization of handpieces from 68% in 1992 to 85% in 1994.8 In a 1989 random sample survey, 14% of dentists surveyed in Quebec reported heat sterilization of high-speed handpieces.21 Our results from the 1995 national survey indicated that the percentage of dentists in Quebec reporting heat sterilization of handpieces had risen to 71%. In a recent study of infection control practices of specialists in British Columbia, two thirds of the respondents reported heat sterilization of handpieces.22 The increased use of this procedure, which was reported in more recent investigations, including this study, may reflect a response to reports about the potential for transmission of microbes by means of dental handpieces.23-25
McCarthy and MacDonald 27
Hepatitis C virus, for which there is no vaccine, is now becoming a major concern in the health care environment. Previously, cross infection with HBV caused much concern in the health care setting; however, the frequency of occupational transmission of HBV to health care workers has been reduced as a result of vaccination. Unvaccinated health care workers and patients are still vulnerable. The risk of transmission is approximately 25% if the carrier is HBeAg positive. HBV vaccines are effective in more than 95% of cases and also confer protection against hepatitis D virus.26 There have been reports of increased HBV vaccination of dentists.4, 5, 7, 8 In this study, we noted an increase in reports by dentists who had either HBV vaccination or naturally acquired immunity to HBV as a result of previous exposure. Although the proportion of Ontario dentists who reported HBV vaccination of clinical staff increased from 65.0% to 76.8% between 1994 and 1995 (Table 2), approximately one quarter of respondents in 1995 still reported that all clinical assistants had not been vaccinated against HBV and were therefore vulnerable to infection with HBV and hepatitis D. There is a need for more education of dentists and clinical staff to promote HBV vaccination. The questionnaire used in 1995 included a more comprehensive range of items on infection control procedures, and it was not possible to investigate changes in reports of these items between 1994 and 1995. As a result of increasing concern about waterborne microorganisms,1,27,28 we included items on the reduction of potential for transmission of microbes via waterlines. Of the respondents in Ontario who participated in the national survey in 1995, 53.8% reported that they always flushed water lines after treating each patient. The 1995 data also indicated low compliance with other recommended infection control practices including handwashing. Only 74.4% of respondents reported that they always washed their hands before they treated each patient, and 61.9% reported that they always washed their hands after removing gloves. In addition, only 36.0% reported that they had a postexposure protocol for needlesticks and cuts. Recent evidence demonstrates that zidovudine (AZT) reduces the risk of HIV seroconversion resulting from occupational exposure by approximately 80%. Consequently, recommendations for prophylaxis after exposure to HIV have been changed. It is now recommended that persons who have significant exposure to HIV receive prophylaxis with AZT or another antiretroviral
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agent, alone or in combination with other antiretroviral drugs, within 2 hours.29 Although dentist reports of compliance with recommended infection control practices and universal precautions increased between 1994 and 1995, it appears that the majority of dentists have not adopted universal precautions. Considerable improvements were noted in HBV vaccination of all clinical staff and heat sterilization of handpieces, but the proportion of respondents who reported these practices was still too low. More education is needed to promote the treatment of all patients as if they are infected with bloodborne pathogens. Particular emphasis is required to improve compliance with HBV vaccination for clinical staff, handwashing, and use of postexposure protocol in the dental office. References 1. American Dental Association. Infection control recommendations for the dental office and the dental laboratory. J Am Dent Assoc 1996;127:672-80. 2. Canadian Dental Association. Recommendations for infection control procedures. Communique, May 1992;10. 3. Centers for Disease Control. Recommended infection-control practices for dentistry, 1993. MMWR 1993;41:1-12. 4. DiAngelis AJ, Martens LV, Little JW, Hastreiter RJ. Infection control practices of Minnesota dentists: changes during one year. J Am Dent Assoc 1989;118:299-303. 5. Verrusio AC, Neidle EA, Nash KD, Silverman S Jr, Horowitz AM, Wagner KS. The dentist and infectious diseases: a national survey of attitudes and behavior. J Am Dent Assoc 1989;118:553-62. 6. Nash KD. How infection control procedures are affecting dental practice today. J Am Dent Assoc 1992;123:67-73. 7. Gibson GB, Mathias RG, Epstein JB. Compliance to recommended infection control procedures: changes over six years among British Columbia dentists. J Can Dent Assoc 1995;61:526-32. 8. McCarthy GM, Koval JJ. Changes in dentist’s infection control practices, knowledge and attitudes concerning HIV over a two year period. Oral Surg Oral Med Oral Pathol 1996;81:297-302. 9. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159-74. 10. McCarthy GM, Koval JJ, MacDonald JK. Non-response bias in a survey of Ontario dentists’ infection control and attitudes concerning HIV. J Public Health Dent 1997; 57:59-62. 11. Dillman DA. Implementing mail surveys. In: Mail and telephone surveys. The total design method. Toronto: Wiley; 1978. p. 160-200.
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12. Fleiss JC. Statistical methods for rates and proportions. 2nd ed. New York: John Wiley & Sons; 1981. 13. McCarthy GM, MacDonald JK. Non-response bias in a national study of dentists’ infection control practices and attitudes related to HIV. Community Dent Oral Epidemiol 1997;25:119-25. 14. Bentley EM, Sarll DW. Improvements in cross-infection control in general dental practice. Br Dent J 1995;179:19-21. 15. Canadian Dental Association. Ottawa dentist faces charges of discrimination. Communique, July-Aug 1995. 16. Crawford PR. AIDS and discrimination: the Windsor case. J Can Dent Assoc 1995;61:25-7. 17. American Dental Association. ADA takes action on two HIV fronts. ADA News Releases, June 1996. 18. McCarthy GM, Haji FS, Mackie IDF. HIV-infected patients and dental care: nondisclosure of HIV status and rejection for treatment. Oral Surg Oral Med Oral Pathol 1995;80:655-9. 19. Brooks GF, Butel JS, Ornston LN. Hepatitis viruses. In: Jawetz, Melnick and Adelberg’s medical microbiology. 19th ed. Norwalk (CT): Appleton & Lange; 1995. p. 451-68. 20. Canadian Dental Association. Statement on the ethical and legal considerations of treating patients with infectious diseases. J Can Dent Assoc 1988;54:385. 21. Soto JC, Levi M, Allard R, Franko E. Survey on attitudes, beliefs and knowledge related to AIDS among dental professionals in Quebec. In: Adjukovic D, editor. Oral AIDS: manifestations, safety measures, and questions of transmissibility. New York: Elsevier; 1990. p. 181-91. 22. Epstein JB, Mathias RG, Bridger DV. Survey of knowledge of infectious disease and infection control practices of dental specialists. J Can Dent Assoc 1995;61:35-7, 40-4. 23. Lewis DL, Boe RK. Infection risks associated with current procedures for using high speed dental hand pieces. J Clin Microbiol 1992;30:401-6. 24. Lewis DL, Arens M, Appleton SS, Nakashima K, Ryu J, Boe RK, et al. Cross-contamination potential with dental equipment. Lancet 1992;340:1252-4. 25. Epstein JB, Rea G, Sibau L, Sherlock CH. Assessing viral retention and elimination in rotary dental instruments. J Am Dent Assoc 1995;126:87-92. 26. Porter S, Scully C, Samaranayake L. Viral hepatitis: current concepts for dental practice. Oral Surg Oral Med Oral Pathol 1994;78:682-95. 27. Molinari JA. Waterborne microorganisms: questions about health-care problems and solutions. Compendium Continuing Educ 1995;16:130,132. 28. Challacombe SJ, Fernandes LL. Detecting Legionella pneumophila in water systems: a comparison of various dental units. J Am Dent Assoc 1995;126:603-8. 29. Centers for Disease Control and Prevention. Update: provisional public health service recommendations for chemoprophylaxis after occupational exposure to HIV. MMWR 1996;45:468-72.