E F F E C T IV E N E S S OF D ENTAL O F F IC E
R IC H A R D J. HAS TR E ITE R , D.D .S ., M .P .H .; J O H N A. M O L IN A R I, P H .D .; M Y R O N C. F A L K E N , M .S ., M .P .H ., PH .D .; M IL D R E D H. R O ESC H , R.D .H ., M .P .H .; M IC H A E L J. G LE A S O N , P H .D , D .D .S .; V IR G IN IA A. M E R C H A N T , M .S ., D .M .D .
ABSTRACT
To evaluate instrum ent sterilization procedures in M innesota, biological indi cators w ere used to m onitor 406 sterilizers in 381 dental offices. Findings suggest a general im provem ent in instrum ent perform ance over that o f a decade ago, but sterilization failure rates are still too high. Sterilizer operator errors are a major cause o f sterilization failures. B is are useful in m onitoring sterilization perform ance only when sterilization procedures are perform ed con sisten tly and com petently by well-trained sta ff using adequately m aintained equipm ent.
ince human immunodeficiency virus was determined to be the cause of AIDS in 1983, concerns have been raised about treating HIV-infected patients in traditional dental office settings.1'2These concerns increased when a dentist was reported to have apparently acquired HIV as a result of performing clinical procedures.3 More recently, attention has shifted to the possible transmission of HIV from a dentist with AIDS to patients during the performance of invasive dental procedures.4'6 Professional organizations, educational institutions and government agencies have attempted to place dental team members’ concerns about the treatment of HIV-infected patients in scientific perspective by providing information and educational opportunities. Dentists, hygienists and assistants need to treat all patients in a knowledgeable and safe manner.711 Promoting the use of appropriate infection control techniques when treating all patients is crucial to this effort. Many studies of the infection control knowledge, attitudes and clinical practices of dental office staff have been conducted.1241Most surveys have focused on barrier technique infection control measures with less attention paid to dental instrument sterilization. The Centers for Disease Control recommend that all dental instruments that can physically withstand it should be sterilized by methods (steam autoclave, chemical vapor sterilizer, dry heat oven, ethylene oxide sterilizer) for which effectiveness can be verified by the use of biological indicator spore testing devices. Although heat and steam sensitive chemical process indicators (tape or instrument bags that demonstrate color change) can be used with each instrument pack to assure instruments have been exposed to a sterilizer cycle, they do not JADA, Vol. 122, October 1991
51
verify that sterilization has occurred, and are no substitute for the use of biological indicators. Biological indicators provide the only real method of verifying the effectiveness of sterilization procedures. They consist of ampules or strips enclosed in glassine envelopes that contain a known quantity of Bacillus stearothermophilus and/or B. subtilis spores. Because these bacterial spores are more resistant to sterilization than viruses or vegetative bacteria, destruction of these spores infer that sterilization has occurred. The CDC recom mends that Bis be used weekly in most dental practices to verify the sterilization performance of each sterilizer.7 Studies have used Bis to investigate the effectiveness of dental office instrument steril ization procedures,4249but most have been limited. Some evaluated only small numbers of sterilizers or were conducted in a relatively small geographic area.4448 Other studies did not investi gate all types of sterilizers used in
dental practice.42’434749Two studies 4243used a monitoring methodology
form with an accompanying cover letter, signed by the Minnesota Department of Health’s dental director and the president of the Minnesota Dental Association. The cover letter asked dentists to indicate their willingness to participate in the study by returning a completed study participation form. The form contained: the dentist’s preprinted name, address and telephone number; space for entering the results of the microbiological culturing of up to three BI series; and questions regarding dental office instrument sterilization methods and use of Bis to monitor sterilization performance. Two weeks after the initial mailing a follow-up reminder postcard was sent to all nonrespondents. Study participation forms were returned by 55 percent (497/900) of sampled dentists. Each of these dentists was mailed the first BI test series which contained steriliza tion testing procedure instructions and an addressed return mailing envelope containing four Bis. Each BI consisted of a spore strip
(3M Attest Biological Monitoring System) that subsequently was found to be of questionable validity for chemical vapor sterilizers (personal communi cation, Richard Joos, 3M, Jan. 30, I99l).60'53 Two other studies were limited to investigating steriliz ation performance in only one type of dental specialty practice.4446 Further research was indicated to assess more fully the effectiveness of dental office instrument sterilization procedures. METHODS
This study evaluates the effective ness of dental instrument steriliza tion procedures in Minnesota dental offices. In the fall of 1989, a random sample of 900 dentists was selected from 2,808 dentists in active practice. The sample size was chosen to provide a sufficient response rate to test 400 dental office sterilizers. Each selected dentist was assigned an identification number and sent a study participation
TABLE 1
DISTRIBUTION OF TOTAL DENTAL OFFICE INSTRUMENT STERILIZATION FAILURES, 1979 AND 1989 90 1979* N
Failures C °/o)
1989-90+ N
Failures (°/o)
1989-90* N
Failures (°/o)
P Value
1st BI Series
86
(3 1 )
58
(1 6 ;)
74
(1 8 )
< 0 .0 0 1 §
2nd BI Series
7
(1 4 )
14
(2 4 )
18
(2 4 )
N .S .V
3rd BI Series
2
(2 9 )
2
(1 4 )
3
(1 8 )
N .S .
* Simonsen, et al. Tested only steam autoclaves and chemical vapor sterilizersCAbstract no. 1236) J Dent Res 1979;58A:400.
t
Includes data for only steam autoclaves and chemical vapor sterilizers tested in 1989-90.
$ Includes data for all sterilizers tested in 1989-90: steam autoclaves, cliemical vapor sterilizers, dry heat ovens and ethylene oxide sterilizers. § Z^O.OOl for comparison of 1979 data with either the data set from all sterilizers tested in 1989-90 or only steam autoclaves and chemical vapor sterilizers tested in 1989-90. ^ N.S. = Not significant.
52
JADA, Vol. 122, October 1991
enclosed in aglassine envelope containing both B. stearothermophilus and B. subtilis spores. (B. stearothermophilus is resistant to moist heat and is used to test steam autoclaves and chemical vapor sterilizers. B. subtilis is resistant to ethylene oxide and dry heat and is used to test ethylene oxide steril izers and dry heat ovens.) Since study Bis contained both B. stearo thermophilus and B. subtilis, they could be used to test steam autoclaves, chemical vapor steril izers, dry heat ovens and ethylene oxide sterilizers. Three of the four spore strips in each BI series served as test Bis that were each run through a different sterilizer cycle with a moderate to heavy load of dental instruments. Specific instructions were given to operate the sterilizer in a manner normally used by the office and to place each BI in the most difficult area of the chamber to sterilize, such as in the center of a load of bagged or wrapped instru ments. Dentists were requested to provide information about sterilizer operating conditions for each tested sterilizer cycle (for example, for steam autoclaves the temperature, pressure and time of the cycle). The fourth spore strip in a BI series served as a study control BI that was used to determine the effect of mail transit, handling and storage on the viability of BI spores. The control BI was not processed through a sterilizer cycle but was returned with the other three test Bis for culturing. Dentists were instructed to immediately return the three processed test and one control Bis in an addressed mailing envelope to the University of Detroit, School of Dentistry for culturing. On receipt, each BI was placed in sterile Amsco spordi culture medium and incubated for seven
days at 56 C for B. stearothermophilus (steam autoclaves and chemical vapor sterilizers) and for seven days at 37 C for B. subtilis (dry heat ovens and ethylene oxide sterilizers). Culturing determined if test Bis had been inactivated during the sterilizer cycles and if the control BI had been inactivated by mail transit, storing or handling procedures. Dentists whose three test Bis cultured negative (indicating adequate sterilization) and whose control BI cultured positive (indicating no lethal damage to spores as a result of mail transit, storage or handling) received a report by mail explaining the test results, and were not sent any additional Bis. If a control BI cultured negative (indicating lethal damage to spores as a result of mail transit, storage or handling), the dentist was sent another BI series of three test and one control Bis to perform the sterilizer testing procedure again. Dentists whose sterilizer produced one or more Bis that cultured positive (indicating inadequate sterilization) were called with the finding, counseled on methods of improving steriliza tion performance, and sent another BI test series of three test and one control Bis to perform the sterilizer testing procedure for a second time. If any of the three test Bis in the second BI series cultured positive or if the control BI cultured negative, the dentist was again called with the finding, counseled on improving steriliza tion performance, and sent a third BI series to perform the sterilizer testing procedure for the final time. Data were analyzed using standard descriptive statistical methods. Statistical significance
was determined by analysis and Fisher’s Exact test when appro priate. Except where indicated in the findings, statistical signif icance is at the P
R IC H A R D J. HAS TR E ITE R , D.D .S ., M .P .H .; J O H N A. M O L IN A R I, P H .D .; M Y R O N C. F A L K E N , M .S ., M .P .H ., PH .D .; M IL D R E D H. R O ESC H , R.D .H ., M .P .H .; M IC H A E L J. G LE A S O N , P H .D , D .D .S .; V IR G IN IA A. M E R C H A N T , M .S ., D .M .D .
ABSTRACT
To evaluate instrum ent sterilization procedures in M innesota, biological indi cators w ere used to m onitor 406 sterilizers in 381 dental offices. Findings suggest a general im provem ent in instrum ent perform ance over that o f a decade ago, but sterilization failure rates are still too high. Sterilizer operator errors are a major cause o f sterilization failures. B is are useful in m onitoring sterilization perform ance only when sterilization procedures are perform ed con sisten tly and com petently by well-trained sta ff using adequately m aintained equipm ent.
ince human immunodeficiency virus was determined to be the cause of AIDS in 1983, concerns have been raised about treating HIV-infected patients in traditional dental office settings.1'2These concerns increased when a dentist was reported to have apparently acquired HIV as a result of performing clinical procedures.3 More recently, attention has shifted to the possible transmission of HIV from a dentist with AIDS to patients during the performance of invasive dental procedures.4'6 Professional organizations, educational institutions and government agencies have attempted to place dental team members’ concerns about the treatment of HIV-infected patients in scientific perspective by providing information and educational opportunities. Dentists, hygienists and assistants need to treat all patients in a knowledgeable and safe manner.711 Promoting the use of appropriate infection control techniques when treating all patients is crucial to this effort. Many studies of the infection control knowledge, attitudes and clinical practices of dental office staff have been conducted.1241Most surveys have focused on barrier technique infection control measures with less attention paid to dental instrument sterilization. The Centers for Disease Control recommend that all dental instruments that can physically withstand it should be sterilized by methods (steam autoclave, chemical vapor sterilizer, dry heat oven, ethylene oxide sterilizer) for which effectiveness can be verified by the use of biological indicator spore testing devices. Although heat and steam sensitive chemical process indicators (tape or instrument bags that demonstrate color change) can be used with each instrument pack to assure instruments have been exposed to a sterilizer cycle, they do not JADA, Vol. 122, October 1991
51
verify that sterilization has occurred, and are no substitute for the use of biological indicators. Biological indicators provide the only real method of verifying the effectiveness of sterilization procedures. They consist of ampules or strips enclosed in glassine envelopes that contain a known quantity of Bacillus stearothermophilus and/or B. subtilis spores. Because these bacterial spores are more resistant to sterilization than viruses or vegetative bacteria, destruction of these spores infer that sterilization has occurred. The CDC recom mends that Bis be used weekly in most dental practices to verify the sterilization performance of each sterilizer.7 Studies have used Bis to investigate the effectiveness of dental office instrument steril ization procedures,4249but most have been limited. Some evaluated only small numbers of sterilizers or were conducted in a relatively small geographic area.4448 Other studies did not investi gate all types of sterilizers used in
dental practice.42’434749Two studies 4243used a monitoring methodology
form with an accompanying cover letter, signed by the Minnesota Department of Health’s dental director and the president of the Minnesota Dental Association. The cover letter asked dentists to indicate their willingness to participate in the study by returning a completed study participation form. The form contained: the dentist’s preprinted name, address and telephone number; space for entering the results of the microbiological culturing of up to three BI series; and questions regarding dental office instrument sterilization methods and use of Bis to monitor sterilization performance. Two weeks after the initial mailing a follow-up reminder postcard was sent to all nonrespondents. Study participation forms were returned by 55 percent (497/900) of sampled dentists. Each of these dentists was mailed the first BI test series which contained steriliza tion testing procedure instructions and an addressed return mailing envelope containing four Bis. Each BI consisted of a spore strip
(3M Attest Biological Monitoring System) that subsequently was found to be of questionable validity for chemical vapor sterilizers (personal communi cation, Richard Joos, 3M, Jan. 30, I99l).60'53 Two other studies were limited to investigating steriliz ation performance in only one type of dental specialty practice.4446 Further research was indicated to assess more fully the effectiveness of dental office instrument sterilization procedures. METHODS
This study evaluates the effective ness of dental instrument steriliza tion procedures in Minnesota dental offices. In the fall of 1989, a random sample of 900 dentists was selected from 2,808 dentists in active practice. The sample size was chosen to provide a sufficient response rate to test 400 dental office sterilizers. Each selected dentist was assigned an identification number and sent a study participation
TABLE 1
DISTRIBUTION OF TOTAL DENTAL OFFICE INSTRUMENT STERILIZATION FAILURES, 1979 AND 1989 90 1979* N
Failures C °/o)
1989-90+ N
Failures (°/o)
1989-90* N
Failures (°/o)
P Value
1st BI Series
86
(3 1 )
58
(1 6 ;)
74
(1 8 )
< 0 .0 0 1 §
2nd BI Series
7
(1 4 )
14
(2 4 )
18
(2 4 )
N .S .V
3rd BI Series
2
(2 9 )
2
(1 4 )
3
(1 8 )
N .S .
* Simonsen, et al. Tested only steam autoclaves and chemical vapor sterilizersCAbstract no. 1236) J Dent Res 1979;58A:400.
t
Includes data for only steam autoclaves and chemical vapor sterilizers tested in 1989-90.
$ Includes data for all sterilizers tested in 1989-90: steam autoclaves, cliemical vapor sterilizers, dry heat ovens and ethylene oxide sterilizers. § Z^O.OOl for comparison of 1979 data with either the data set from all sterilizers tested in 1989-90 or only steam autoclaves and chemical vapor sterilizers tested in 1989-90. ^ N.S. = Not significant.
52
JADA, Vol. 122, October 1991
enclosed in aglassine envelope containing both B. stearothermophilus and B. subtilis spores. (B. stearothermophilus is resistant to moist heat and is used to test steam autoclaves and chemical vapor sterilizers. B. subtilis is resistant to ethylene oxide and dry heat and is used to test ethylene oxide steril izers and dry heat ovens.) Since study Bis contained both B. stearo thermophilus and B. subtilis, they could be used to test steam autoclaves, chemical vapor steril izers, dry heat ovens and ethylene oxide sterilizers. Three of the four spore strips in each BI series served as test Bis that were each run through a different sterilizer cycle with a moderate to heavy load of dental instruments. Specific instructions were given to operate the sterilizer in a manner normally used by the office and to place each BI in the most difficult area of the chamber to sterilize, such as in the center of a load of bagged or wrapped instru ments. Dentists were requested to provide information about sterilizer operating conditions for each tested sterilizer cycle (for example, for steam autoclaves the temperature, pressure and time of the cycle). The fourth spore strip in a BI series served as a study control BI that was used to determine the effect of mail transit, handling and storage on the viability of BI spores. The control BI was not processed through a sterilizer cycle but was returned with the other three test Bis for culturing. Dentists were instructed to immediately return the three processed test and one control Bis in an addressed mailing envelope to the University of Detroit, School of Dentistry for culturing. On receipt, each BI was placed in sterile Amsco spordi culture medium and incubated for seven
days at 56 C for B. stearothermophilus (steam autoclaves and chemical vapor sterilizers) and for seven days at 37 C for B. subtilis (dry heat ovens and ethylene oxide sterilizers). Culturing determined if test Bis had been inactivated during the sterilizer cycles and if the control BI had been inactivated by mail transit, storing or handling procedures. Dentists whose three test Bis cultured negative (indicating adequate sterilization) and whose control BI cultured positive (indicating no lethal damage to spores as a result of mail transit, storage or handling) received a report by mail explaining the test results, and were not sent any additional Bis. If a control BI cultured negative (indicating lethal damage to spores as a result of mail transit, storage or handling), the dentist was sent another BI series of three test and one control Bis to perform the sterilizer testing procedure again. Dentists whose sterilizer produced one or more Bis that cultured positive (indicating inadequate sterilization) were called with the finding, counseled on methods of improving steriliza tion performance, and sent another BI test series of three test and one control Bis to perform the sterilizer testing procedure for a second time. If any of the three test Bis in the second BI series cultured positive or if the control BI cultured negative, the dentist was again called with the finding, counseled on improving steriliza tion performance, and sent a third BI series to perform the sterilizer testing procedure for the final time. Data were analyzed using standard descriptive statistical methods. Statistical significance
was determined by analysis and Fisher’s Exact test when appro priate. Except where indicated in the findings, statistical signif icance is at the P
