INFECTION
STERILIZATION
CONTROL
AND DISINFECTION: W H A T E V E R Y D E N T IS T N E E D S T O
K N O W
C H R IS H. M IL L E R , PH .D .
ABSTRACT
T h is p a p e r r e v ie w s i n f e c t io n c o n t r o l p r o c e d u r e s w it h t h e r e la t e d r e g u la t io n s a n d r e c o m m e n d a t io n s . P r o c e d u r e s fo r p r o c e s s i n g c o n t a m in a t e d i n s t r u m e n t s in c lu d e p r e s o a k in g , c le a n in g , p a c k a g in g , s t e r iliz a t io n , s p o r e -te s tin g a n d h a n d p i e c e a s e p s is . S u r f a c e a s e p s is t e c h n iq u e s in c lu d e s u r f a c e c o v e r in g , s u r f a c e p r e c le a n i n g a n d s u r f a c e d i s in f e c t i o n .
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ince sterilization and disinfection are pivotal steps in in stru m en t processing and surface asepsis, we m ust have a clear understanding of the m eaning of these term s. Sterilization is a process intended to kill all m icroorganism s and is the highest level of microbial kill th a t can be achieved. A process cannot be called a sterilization process unless it has been shown to be capable of killing high num bers of bacterial spores, the most difficult of m icroorganism s to kill. Office sterilization procedures involve the proper use of steam , dry heat, chemical vapor and gas sterilizers. The effectiveness of these procedures can be routinely verified during office use by spore testing. Using a glutaraldehyde solution a t 2.0 percent or 3.2 percent concentration w ith a contact tim e of 10 hours a t about room tem p eratu re also is capable of killing bacterial spores (that is, capable of achieving sterilization). B ut sterilization by this method cannot be routinely verified during office use. Disinfection is a less lethal process th a n sterilization and is intended to kill disease-producing m icroorganism s, b u t not bacterial spores. Office disinfection procedures involve using a liquid chemical a t room tem perature to kill m icroorganism s on subm erged in stru m en ts or operatory surfaces. If th e chemical used is not sporicidal, it is called a disinfectant (for example, iodophors, synthetic phenolics, phenols, alcohol/phenolics, sodium hypochlorite, low-concentration glutaraldehyde) and can be expected to achieve only disinfection. If the chemical is sporicidal, it is called a ste rila n t (for example, 2.0 percent or 3.2 percent concentrations of glutaraldehydes) and m ay be expected to achieve sterilization, b u t only after a 10-hour contact tim e on precleaned item s. U nfortunately, the level of microbial killing achieved by use of liquid chemical disinfectants or sterilants in the office cannot be routinely verified as can be done with h eat sterilizers through spore-testing.
INFECTION
IN S T R U M E N T P R O C E S S IN G : R E C O M M E N D A T IO N S A N D R E G U L A T IO N S
Processing contam inated in stru m en ts for reuse on subsequent p atients is a key p a rt in patient-protection
aspects of the office infection control program . The Centers for Disease Control and the A m erican D ental Association recommend th a t surgical and other instrum ents th a t norm ally penetrate soft tissue
CONTROL
or bone m ust be sterilized after each use and th a t other in stru m ents, burs and handpieces th a t come into contact w ith oral tissue should be sterilized after each u se .'2 The division of Occupational Safety and H ealth
TABLE 1
COMPARISON OF HEAT STERILIZATION METHODS M ETHO D
Steam autoclave
STANDARD S T E R IL IZ IN G C O N D IT IO N S *
20 min a t 250 F (15 psi)
20 m in a t 270 F U n satu rated chemical vapor (20-40 psi)
Dry heat Dry h e a t oven 60-120 m in at 320 F
Rapid h e a t tran sfer
12 m in a t 375 F (for wrapped items) 6 min a t 375 F (for unw rapped item s)
SPORET E S T IN G
A D V A N T A G ES
P R E C A U T IO N S
Time efficient Good penetration Sterilize waterbased liquid
Do not use closed containers May dam age plastic and rubber item s N on-stainless steel m etal item s corrode Use of hard w ater m ay leave deposits
Bacillus stearothermop h ilu s strips, vials or am pules
Do not use closed containers Time efficient No corrosion May dam age plastic and Item s dry quickly rubber item s M ust use special solution after cycle Predry instrum ents or dip in special solution Provide adequate ventilation C annot sterilize liquids
Bacillus stearothermophilus strips
No corrosion C an use closed containers Large capacity per cost Item s are dry after cycle No corrosion Short cycle Item s are dry after cycle
Longer sterilization tim e Cannot sterilize liquids May damage plastic and rubber item s Do not open door before end of cycle Predry instrum ents C annot sterilize liquids May damage plastic and rubber item s Do not open door before end of cycle Small capacity per cost Predry instrum ents U nw rapped item s quickly contam inated after cycle
Bacillus subtilis strips
Bacillus subtilis strip s
* T hese conditions do not include w arm -up tim e and they m ay vary depending upon the n atu re and volume of the load. S terilizing conditions in your office sterilizer should be defined by results of routine spore-testing. A dapted w ith perm ission from M iller CH: Take the safe approach to prevent disease transm ission. RDH 1989; 9(5):35.
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CONTROL
A dm inistration in the U.S. D epartm ent of Labor barely m entions in stru m e n t processing and sterilization in th eir final rules because th is prim arily relates to p atien t protection. OSHA is charged w ith pro tecting the workers of America, not patients. On th e other hand, OSHA h as requirem ents for protecting h ealth care workers during the handling and proces sing of contam inated, reusable in stru m en ts.3 The approach to sterilize all reusable in stru m en ts contam inated w ith blood or saliva (“U niversal Sterilization”4) ra th e r th a n to sterilize some and disinfect others is the safest approach to preventing disease spread to p a tie n ts from instrum ents. This is being recognized more and more as evidenced by law s in Ohio and Indiana requiring sterilization, ra th e r th a n ju s t disinfection of all reusable dental instrum ents, and is being considered in other states.5'7 PROCEDURES
The objective of in stru m en t processing is to prevent the spread of disease agents from one p atien t to the next via contam inated instrum ents. Several steps m u st be per formed correctly to assure effective microbial kill w ith m inim al in stru m e n t dam age and protection to the staff perform ing the procedures. ™ Presoaking. Soaking contam inated in stru m en ts in a mild detergent or in an in stru m en t disinfectant or ste rila n t until there is tim e for thorough processing will prevent drying of blood and saliva and facili tate cleaning. Do not presoak for more th a n a few hours, as the longer in stru m en ts rem ain 48
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TABLE 2
CAUSES OF STERILIZATION FAILURE ™ Im proper loading of sterilizer cham ber - overloading - no separation betw een packs or trays ™ Im proper packaging - wrong packaging m aterial for m ethod of sterilization - more th a n two layers of wrap - closed container not penetrated by steam or chemical vapor ™ Im proper tim ing - incorrect use of the sterilizer - tim ing for sterilization sta rte d before sterilizing tem perature is reached - dry h e a t sterilizer door opened to add more item s w ithout sta rtin g steriliza tion tim e over - sterilizer tim er m alfunction ™ Im proper tem perature - incorrect use of the sterilizer - sterilizer m alfunction ™ Im proper cleaning of item s to be sterilized
wet, the greater the chances for corrosion of non-stainless item s. If ultrasonic cleaning will be used, a good way to m anage the presoaking is to place the instrum ents in the ultrasonic cleaning basket and place the basket in a pan of th e presoak solution. Using th e basket prevents direct handling of the
instrum ents through the pre soak, cleaning and rinsing steps. W ear heavy utility gloves when handling contam inated instrum ents and m ixing chemi cal solutions. W ear protective eyewear, a m ask and protective clothing to prevent contam i nation from splashing of the solutions. ■■ Cleaning. Two approaches to instru m en t cleaning are handscrubbing and ultrasonic cleaning. H and-scrubbing is directly contrary to one of the dogmas of infection control— reduce direct contact with contam inated surfaces as m uch as possible. Hand-scrubbing increases such contact and adds the danger of handling sharp and pointed objects. If an item m ust be m anually scrubbed, w ear heavy utility gloves, a m ask and protective eyewear and clothing. S p atter or aerosols generated during hand-scrubbing m ust be minimized. Scrub in an area away from sterilized in stru m ents while th e instrum ents are submerged. Scrubbed instrum ents should be rinsed and dried before being wrapped or packaged. D rying is especially im portant for items th a t will be sterilized in an u n sa tu ra te d chemical vapor or in a dry heat sterilizer. U ltrasonic cleaning is effec tive and reduces the chances for instrum ent-puncture injuries th a t m ay occur w ith handscrubbing. Reasonably priced cleaners are available in a variety of sizes from several m anufacturers. E ach cleaner should be supplied w ith a m etal cleaning basket, a lid th a t should be used a t all tim es during operation and clear instructions for use and care. D isinfectants should not be
INFECTION
used in place of a detergent solution unless they are designed for this use. D eter gents containing an antim icro bial agent are available. The m anufacturer’s directions m ust be followed for best results. For ultrasonic cleaning, subm erge the rinsed in stru m ents in the cleaning solution using a basket, which keeps the in stru m en ts off the bottom of the tank. Place the lid on the cleaner, and operate the u n it for six to 10 m inutes or until debris disappears. If plastic/resin type of in stru m ent cassettes are used directly in the ultrasonic cleaner, in crease th e cleaning tim e as directed by the m anufacturer (for example, to 15 m inutes).8 This increased cleaning tim e isn ’t lost tim e as other work can be done during the process. U ltrasonic cleaners are excellent for cleaning b ut can not be considered sterilizers. Thus, th e “cleaned” instrum ents are still contam inated, and the cleaning solution m ay be contam inated w ith live micro organism s. Change the solution a t least once a day, using gloves, m asks and protective eyewear and clothing. At the end of th e day, disinfect, rinse and dry the cleaner chamber. ■■ Corrosion control and lubri cation. Cleaned instrum ents to be processed through a dry heat, chemical vapor or ethylene oxide gas sterilizer or through a liquid chemical ste rila n t or are to be packaged in a paper w rap should first be dried to reduce chances for corrosion, or to prevent dilution of th e liquid chemical agent or ru p tu re of paper wrap. A ru st inhibitor (dip or spray) m ay be applied to non-stainless items to be processed through the
steam autoclave. Hinged in stru m ents also m ay be lubricated a t this tim e if necessary. ™ Packaging. Instrum ents should be prepackaged before processing through a sterilizer so they will be protected from contam ination after steriliz ation. Use only w rapping m aterial
CONTROL
designed for th e particular m ethod of sterilization used in your office. Some paper/plastic w raps or polyfilm bags or tubing m ay be appropriate for steam b u t m ay m elt in the dry heat sterilizer. O ther wraps appropriate for dry heat sterilization m ay prevent penetration by steam or
TABLE 3
USE OF GLUTARALDEHYDE Use gloves, m asks and protective eyew ear and clothing when preparing, using and discarding chemical to protect skin, mucous m em branes and eyes from contact. Follow the m anufacturer’s label directions. Prepare/activate properly. Date activated solutions for shelf-life. Label used containers/pans w ith th e word “glutaraldehyde” and the brand nam e and w ith the date for use-life. Preclean and dry all item s to be processed. Completely subm erge all items in the solution and cover the container/pan. Keep subm erged for proper contact tim e (e.g., 10 hours for sterilization). Use a m onitor (for example, “dip stick”) to te st glutaraldehyde concentration during use. Discard and replace w ith fresh solution when indicated. Thoroughly rinse processed item s w ith w ater. Use sterile w ater if the item may penetrate tissue during use. Handle the processed item aseptically and prevent contam ination from hands, aerosols and d u st before placem ent a t chairside (for example, use sterile forceps to handle items; use bags or covers). G lutaraldehyde sterilants are indicated for im m ersion use only and are not recommended for use as a surface disinfectant to “wipe down” operatory surfaces.
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INFECTION
CONTROL
ÏO ÏT E S T IN G of office sterilizers WHEN
W HY
Once per week
To routinely verify proper use and functioning
W henever a new type of packaging m aterial or tray is used
To assure th a t the agent is getting inside to the surface of the instrum ents
D uring and after training of new sterilization staff
To verify proper use of the sterilizer
D uring initial use of a new sterilizer
To m ake sure th a t unfam iliar operating instructions are being followed
At least the first cycle after a sterilizer has been repaired
To m ake sure th a t the sterilizer is functioning properly
After any change in sterilizer loading procedure
To m ake sure th a t each item has access to the sterilizing agent
W ith every im plantable device and hold device until results of te s t are known
E xtra precaution for sterilization of item s to be im planted into tissues
chemical vapor. Avoid using th in paper bags, as they allow sharp in stru m ents to protrude, possibly causing injury during handling. “See-through” m aterial such as polyfilm /paper pouches and nylon tubing allow ready iden tification of package contents. W rapping m aterial, bags and pouches should be either self sealing, heat-sealed or double folded and sealed with appropriate tape. M etal clips or staples should not be used. The popularity of instru m en t 50
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cassettes is increasing as these contain the in stru m en ts through the ultrasonic cleaning, rinsing and sterilizing proce dures and serve as th e in stru m ent tray a t chairside. These cassettes are perforated to facilitate ultrasonic cleaning and entrance of sterilizing agents. Therefore, they m ust be wrapped w ith sterilization paper or bagged before steril ization to prevent post-sterilization contam ination. Non-perforated, closed containers of m etal or glass or
alum inum foil m ust not be used in steam , chemical vapor or ethylene oxide gas sterilizers. They will prevent the sterilizing agents from actually reaching the in stru m en ts inside. Processing unw rapped or unpackaged instrum ents through a sterilizer and then sorting and distributing them on tray s is least satisfactory. U nw rapped instrum ents have a zero shelf-life and can become contam inated w ith blood or saliva from hands, surfaces or aerosols during sorting and distribution if not handled in an aseptic m anner. Even if the instrum ents are to be used im m ediately a fter sterilization, they m ust be handled aseptically and protected from contam ination during the “trip ” from the sterilizer to chairside. " Sterilization. C haracteristics of the common m ethods of h eat sterilization used in dental offices are described in Table 1. Although stan d ard sterilizing tim es and tem peratures are given in the table, these do not include sterilizer “w arm -up” tim e. These will vary from one model to another depending on the n a tu re and volume of the item s being sterilized and how they are arranged w ithin the chamber. Follow the m anu facturer’s directions and define the proper sterilizing tim e by results of routine spore-testing. Sterilization failure occurs when the sterilizing agent does not contact th e surface of the instrum ents for a sufficient time. Causes for such failure are usually procedural in nature ra th e r th a n a m alfunc tion of the sterilizer, although the la tte r does occur. Table 2 lists the causes of sterilization failure, which in m ost instances can be detected only by spore-
INFECTION
testing. If an item is destroyed in h e a t sterilizers, it m ay be sterilized in an ethylene oxide gas sterilizer, followed by appropriate aeration or im m ersion in a liquid ste rila n t (for example, a glutaraldehyde product a t 2.0 percent or 3.2 percent concentration for 10 hours of contact tim e) and th e n thoroughly rinsed w ith w ater. C haracteristics of various glutaraldehydes have been reported recently.9 Tips for th eir use are given in Table 3. ™ Sterilization monitoring. Routine spore-testing (biological m onitoring) of th e office sterilizer helps assure the quality of p atien t care (Table 4).10 Sterilization failure from im proper use or m alfunction of the sterilizer increases the chances for spread of disease agents from patient to p atien t via the processed instrum ents. Routine spore-testing can detect these failures and alert the office to check and correct pack aging procedures and sterilizer loading, operating and functioning—m aking sporetestin g a very im portant form of risk m anagem ent. The C enters for Disease Control, the Am erican D ental Association, the Association for A dvancem ent of Medical Instru m en tatio n and the Office Sterilization and Asepsis Proce dures Research Foundation recom mend weekly spore-test ing of dental office steril izers.1,21112 Indiana and Ohio law s m andate spore-testing of dental office sterilizers. O ther states will soon follow.4'8 H ospitals m ust spore-test th eir sterilizers a t least weekly, but preferably daily. Proper spore-testing in the dental office involves placing
CONTROL
TABLE 5
*■ Check u nit for w ater retraction m onthly, and add or replace antiretraction valves when indicated. ■■ Flush the lines in high-speed handpieces and air/w ater syringes by operating for 30 seconds a t the beginning of th e day and for 15 seconds after each patient. ■■ Follow the handpiece m anufacturer’s directions for proper m aintenance, cleaning, sterilization, disinfection and compatibility with chemical agents. am Clean the external portion w ith a detergent or detergentdisinfectant and rinse w ith w ater. ■“ Lubricate high-speed handpieces w hen indicated by the m anufacturer and spray out excess lubricant. Depending upon the handpiece, some m ust be lubricated before, after, or before and after sterilization or not a t all. *■ Avoid spraying aerosols into the environm ent when operating the handpiece during processing/lubrication (for example, spray into a vacuum line). ■■ Package for sterilization in steam or u n sa tu ra te d chemical vapor following the m anufacturer’s directions. ■■ If disinfecting a handpiece th a t cannot be h eat sterilized, spray or sa tu ra te w ith the disinfectant recommended by the m anufacturer. Use a t least a 10-minute contact tim e (see disinfectant label) and thoroughly rinse w ith w ater and dry. Protect from contam ination before placem ent a t chairside.
the appropriate type of biological indicator (spore test) inside a norm al in strum ent pack, bag or tray. It is processed through the usual cycle in the sterilizer. The conditions of the cycle (for example, tim e, tem p erature, pressure) are recorded. The biological indicator m ust then be cultured under proper conditions to allow growth of any rem aining live spores. If growth is detected, then sterili zation failure occurred. A control biological indi-
cator—not processed through the sterilizer—m ust alw ays be analyzed a t the same tim e as the te s t biological indicator. The control m ust show grow th of the spores to validate the test. Routine spore-testing can be conveniently accomplished by subscribing to a m ail-in sterilization m onitoring service available commercially and through some dental schools.13 W hen performed properly, spore-testing through th e m ail provides reliable verification of JADA, Vol. 123, March 1992
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TABLE 6
12366648
: ASEPSIS
■■ Surfaces th a t are difficult to disinfect (such as chair buttons, control buttons on the air/w ater syringe, switches on th e unit, light handles, hoses, handpiece and air/w ater syringe holders) should be covered w ith plastic wrap, alum inum foil, or other m aterial impervious to w ater. Replace w ith fresh covers after each patient. It takes less tim e to replace a cover th a n to disinfect the uncovered surface. ■“ Disposable item s should be discarded after a single use ra th e r th a n cleaned and disinfected for reuse. *■ Disinfecting electrical switches on the chair or u nit may dam age or cause a short in the switch. Cover them! ■■ Preclean the surface prior to disinfection. ™ Choose an EPA -registered, ADA-accepted surface disinfectant, and use this agent for both the cleaning step and the disinfecting step for uncovered surfaces. U sing a waterbased agent w ith both cleaning and disinfecting properties provides some protection during the cleaning step, helps sanitize any debris splattered by the cleaning procedure, and helps keep the num ber of different products th a t need to be ordered to a m inim um . “ Follow the m anufacturer’s directions on the disinfectant product label. " W ater, ra th e r th a n alcohol, m ust be used w ith those agents requiring dilution before use. “ Use u tility gloves, a m ask, and protective eyewear and clothing during surface cleaning and disinfection to reduce chances of direct contam ination of the skin, mucous m em branes or eyes. Adapted w ith perm ission from M iller CH. Disinfection of surfaces and equipm ent. D ental Asepsis Review 1988; 9/12:2.
sterilization.14 M ost of these services can te st steam , dry heat, u n sa tu ra te d chemical vapor and ethylene oxide gas sterilizers. They provide the proper type of biological indi cator, instructions, re tu rn mail envelopes, im m ediate telephone 52
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notification of sterilization failures and a w ritten report for each test. Some also include infection control new sletters, certificate of participation and specific advice on how to pin point and correct sterilization failures.
The cost of such services ranges from about $8 to $20 per test. As an alternative for steam sterilizers, special spore vials and an appropriate 56 C incubator can be purchased and the vials processed, cultured and analyzed and the results recorded by properly trained office staff. Chemical indicators are strips, tapes and m arkings on bags and pouches th a t change color or physical form after exposure to the sterilizing agent (for example, h eat, steam , chemical vapor). W hen used on the inside and outside of packs, bags or trays, they im m ediately indicate th a t the item s have been processed through the sterilizer and have been exposed to heat, steam or chemical vapor. Since chemical indicators do not analyze for microbial kill, they should be used in conjunction with, but never as a replacem ent for spore-testing, which provides the m ain g u arantee of sterilization. ■■ Handpiece asepsis. The out side surfaces of all handpieces become contam inated during use. In addition, the inside lines of high-speed handpieces may become contam inated when patient fluids re tra c t back through the air-w ater opening at the head of th e handpiece when the handpiece is turned off after use.15 If th e handpiece is not properly processed, the retracted fluids m ay enter the m outh of the next patient. D ental units m anufactured after the middle 1980s have anti-retraction valves already installed. O lder u n its should be retrofitted w ith these valves by cutting the handpiece and the air-w ater syringe w ater lines in the control box and inserting
INFECTION
FACTS ABO UT A
Q v the end of 1993, as m any as 480,000 Am ericans will have full-blown AIDS, and as m any as 340,000 will have died from the disease. W hat follows are some facts on AIDS and the hum an immunodeficiency virus, current to Dec. 31, 1991, unless otherwise noted: ■■ One million U.S. residents are HIV-infected. ■■ AIDS h as been diagnosed in 206,392 Am ericans. — As of Sept. 30, 1991, 7,250 U.S. h ealth care w orkers had AIDS. *■ Of th a t num ber, 209 were dentists or dental-office staff members. ■■ A total of 133,232 Americans have died as a resu lt of AIDS. ■ S ource: F e d e ra l C e n te rs for D is e a s e C o n tro l
these “one-way” valves. Since these valves m ay fail periodi cally, retraction m ust be routinely checked and the valves replaced when necessary. R etraction is checked by observing the tip of th e w a te r line opening a t the handpiece connection when the w ater is turned on and then off. If a drop of w ater “hangs” on the tip, retraction is not occurring. If
the w ater is draw n back into the line, retraction is occurring. Cleaning and wiping the handpiece w ith a surface disin fectant m ay decontam inate the exterior but will not decontam inate the interior portion of high-speed handpieces th a t m ay have become contam inated because of no anti-retraction valves or valves th a t have failed. D ata showing th a t the in tern al portions of the high speed handpiece can indeed be effectively steam sterilized have been reported.16 The Am erican D ental Association and the Centers for Disease Control currently state th a t handpieces should be h e a t sterilized, if possible.1,2Also, some states are developing laws to m andate h eat sterilization of all h an d pieces.7An approach to h a n d piece asepsis is described in Table 5. S U R F A C E A S E P S IS
Blood or saliva on environ m ental surfaces (for example, operatory, laboratory, steril izing area) m ay serve as a source of contam ination for patients, office staff or item s th a t may contact those surfaces. Surface asepsis is a collection of procedures th a t prevent or remove contam ination from surfaces (Table 6). ■■ Surface covers. One approach to surface asepsis is preventing th e initial contam ination of the surface. Surfaces and equip m ent (particularly those th a t are difficult to clean) are covered w ith plastic w rap or bags, alum inum foil or plasticbacked paper before patient care or before the item is used. After patient care or after a covered item has been used, remove and discard the cover
CONTROL
w ithout touching th e under lying surface and replace w ith a fresh cover for reuse. It is not necessary to clean and disinfect a properly covered surface betw een patien ts unless the cover failed or the surface was accidentally contam inated during cover removal. Replacing surface covers also is less tim econsuming th a n are proper surface cleaning and disin fecting. Although local laws m ay dictate disposal of such covers, generally they are not considered as regulated medical waste unless dripping w et or caked w ith blood or saliva. ■■ Surface precleaning. If surface covers are not used, contam inated surfaces m ust be precleaned before being disinfected as indicated by the Centers for Disease Control,1by OSHA’s final bloodborne patho gens stan d ard 3 and by the label directions on surface disinfect an t products. Precleaning reduces the bioburden on the surface and facilitates subse quent disinfection. It is m ost convenient to use a w ater-based cleaning agent th a t has both cleaning and disin fecting properties. This provides some protection during cleaning and reduces the spread of con tam ination to Dr. Miller is profes sor and chairman, adjacent Department of Oral surfaces Microbiology, during the Indiana University School of Dentistry, process. It also 1121 W. Michigan reduces the St., Indianapolis, 46202. Dr. Miller is num ber of chairman of the products Office Sterilization needed in the and Asepsis Proced ures Research offices. Gloves Foundation. Address and protective reprint requests to Dr. Miller. eyewear also JADA, Vol. 123, March 1992
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should be worn during handling of the cleaner and during the cleaning itself. The cleaner should be sprayed onto the surface and the surface vigorously wiped w ith paper towels or scrubbed w ith a b rush and rinsed over the sink. This precleaning step m u st not be slighted, as it can determ ine th e success of the disinfecting step to follow. *■ Surface disinfection. The precleaned surface is now ready for disinfection. There are several ADA-accepted surface disinfectants representing different chemical categories (chlorines, iodophors, combi nation synthetic phenolics, phenolics and alcoholphenolics). C haracteristics of several brands have been recently described.9 Diluted iodophors, synthetic phenolics and chlorines have both clean ing and disinfecting properties for use in the precleaning step and th e disinfecting step.17After precleaning, spray on the disin fectant and leave moist for the prescribed contact tim e on the disinfectant label (10 m inutes). ■■ Disposable items. Disposable item s m anufactured for use on a single p atien t should indeed be discarded after a single use ra th e r th a n cleaned and disin fected for reuse. Such item s include disposable air/w ater syringe tips, prophy angles, high-volume evacuator tips, saliva ejector tips, prophy cups
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and brushes. These item s were not designed to be cleaned and reprocessed since m ost consist of plastic th a t scratches easily and can harbor debris and microorganism s. They also may adsorb disinfecting chemicals or be m echanically weakened by the processing. If such item s are processed for reuse, then the u ser assum es all responsibility for safety and effectiveness. C O N C L U S IO N
Sterilizing all reusable in stru m ents contam inated w ith blood or saliva ra th e r than sterilizing some and disinfecting others is the safest approach to prevent ing disease spread among patients. Procedures and techniques conforming to the late st regulations are described in detail for the dental practitioner. ■ 1. C e n te rs fo r D is e a s e C o n tro l. R eco m m en d ed in fectio n -co n tro l p ra c tic e s fo r d e n tis try . M M W R 1986; 35:237-42. 2. ADA C o u n cils on D e n ta l M a te ria ls, In s tr u m e n ts a n d E q u ip m e n t; D e n ta l P ra ctice ; a n d D e n ta l T h e ra p e u tic s . In fe c tio n c o n tro l rec o m m e n d a tio n s fo r th e d e n ta l office a n d d e n ta l lab o ra to ry . JA D A 1988; 116:241-8. 3. D e p a r tm e n t o f L ab o r, O c c u p a tio n a l S a fety a n d H e a lth A d m in is tra tio n . 29 C F R P a r t 1910.1030, o c c u p atio n al e x p o su re to b loodborne p a th o g e n s; fin al ru le . F e d R eg 1991; 56:64004-182. 4. M ille r CH . S te riliz a tio n : d isc ip lin e d m icro b ial co n tro l. D e n t C lin N o rth A m 1991; 35:339-55. 5. O h io S ta te D e n ta l B o a rd o f E x a m in e rs. In fe c tio n co n tro l ru le s. C o lu m b u s, Ohio: N o v e m b e r 1, 1987. 6. I n d ia n a S ta te B o ard o f H e a lth , D e n ta l H e a lth
D iv isio n . I n d ia n a P u b lic L aw 123-1988 d e n ta l on -site c o m p lian c e rev ie w ch e ck list. In d ia n a p o lis , In d ia n a : F e b r u a r y 1, 1990. 7. W a sh in g to n S ta te D e p a rtm e n t o f H e a lth , D e n ta l D isc ip lin a ry B o ard . In fectio n co n tro l ru le s-p ro p o se d . O ly m p ia , W a sh in g to n : D ecem b er 3, 1991. 8. M ille r C H , H a rd w ic k LM . U ltra s o n ic c le a n in g of d e n ta l in s tr u m e n ts in c a ss e tte s . G en D e n t 1988; 36:31-6. 9. C o tto n e JA , M o lin ari JA . S ta te -o f-th e -a rt in fe c tio n control in d e n tis try . JA D A 1991; 123:33-40. 10. M ille r C H , P a le n ik C J. S te riliz a tio n , d isin fec tio n a n d a s e p s is in d e n tis try . In D isinfection, S te riliz a tio n a n d P re se rv a tio n (SS Block, ed). P h ila d e lp h ia : L ea & F e b ig er; 1991:676-94. 11. A sso ciatio n for th e A d v a n c e m e n t o f M edical I n s tr u m e n ta tio n , S te riliz a tio n S ta n d a r d s C o m m itte e , A m b u lato ry -C are a n d O ffice-B ased S te a m S te riliz a tio n W o rk in g G ro u p . S te a m s te riliz a tio n a n d s te r ility a s s u r a n c e in office-based, a m b u la to ry -ca re , m ed ic a l a n d d e n ta l fac ilitie s— d r a f t o f reco m m en d ed p rac tic e . A rlin g to n , V irg in ia: N o v e m b e r 1, 1991. 12. O ffice S te riliz a tio n a n d A se p sis P ro c ed u re s R e s e a rc h F o u n d a tio n . In fectio n co n tro l g u id elin es. D e n v e r: 1991. 13. ADA. Biological in d ic a to rs for v erify in g s te riliz a tio n . JA D A 1988; 117:653-4. 14. M ille r C H , S h e ld ra k e MA. T h e a b ility of b iological in d ic a to rs to d e te c t ste riliz a tio n failu re (A b s tra c t 1919). J D e n t R es (S p ecial Issu e ) 1990; 69:348. 15. A D A C ouncil on D e n ta l M a te ria ls, I n s tr u m e n ts a n d E q u ip m e n t. D e n ta l u n its a n d w a te r re tra c tio n . JA D A 1988; 116:417-20. 16. M ille r C H , S h e ld ra k e MA. S te riliz in g th e i n te r n a l lin e s o f h ig h sp e ed d e n ta l h a n d p ie c e s (A b stra c t, Society for In fectio n C o n tro l in D e n tistry ). T ra n s m is s io n s 1992;8. 17. M o lin a ri JA , G leaso n M J, C o tto n e J A , e t al. C le a n in g a n d d isin fe c ta n t p ro p e rtie s o f d e n ta l su rfa c e d isin fe c ta n ts . JA D A 1988; 117:179-82.
STERILIZATION
CONTROL
AND DISINFECTION: W H A T E V E R Y D E N T IS T N E E D S T O
K N O W
C H R IS H. M IL L E R , PH .D .
ABSTRACT
T h is p a p e r r e v ie w s i n f e c t io n c o n t r o l p r o c e d u r e s w it h t h e r e la t e d r e g u la t io n s a n d r e c o m m e n d a t io n s . P r o c e d u r e s fo r p r o c e s s i n g c o n t a m in a t e d i n s t r u m e n t s in c lu d e p r e s o a k in g , c le a n in g , p a c k a g in g , s t e r iliz a t io n , s p o r e -te s tin g a n d h a n d p i e c e a s e p s is . S u r f a c e a s e p s is t e c h n iq u e s in c lu d e s u r f a c e c o v e r in g , s u r f a c e p r e c le a n i n g a n d s u r f a c e d i s in f e c t i o n .
46 JADA, Vol. 123, March 1992
ince sterilization and disinfection are pivotal steps in in stru m en t processing and surface asepsis, we m ust have a clear understanding of the m eaning of these term s. Sterilization is a process intended to kill all m icroorganism s and is the highest level of microbial kill th a t can be achieved. A process cannot be called a sterilization process unless it has been shown to be capable of killing high num bers of bacterial spores, the most difficult of m icroorganism s to kill. Office sterilization procedures involve the proper use of steam , dry heat, chemical vapor and gas sterilizers. The effectiveness of these procedures can be routinely verified during office use by spore testing. Using a glutaraldehyde solution a t 2.0 percent or 3.2 percent concentration w ith a contact tim e of 10 hours a t about room tem p eratu re also is capable of killing bacterial spores (that is, capable of achieving sterilization). B ut sterilization by this method cannot be routinely verified during office use. Disinfection is a less lethal process th a n sterilization and is intended to kill disease-producing m icroorganism s, b u t not bacterial spores. Office disinfection procedures involve using a liquid chemical a t room tem perature to kill m icroorganism s on subm erged in stru m en ts or operatory surfaces. If th e chemical used is not sporicidal, it is called a disinfectant (for example, iodophors, synthetic phenolics, phenols, alcohol/phenolics, sodium hypochlorite, low-concentration glutaraldehyde) and can be expected to achieve only disinfection. If the chemical is sporicidal, it is called a ste rila n t (for example, 2.0 percent or 3.2 percent concentrations of glutaraldehydes) and m ay be expected to achieve sterilization, b u t only after a 10-hour contact tim e on precleaned item s. U nfortunately, the level of microbial killing achieved by use of liquid chemical disinfectants or sterilants in the office cannot be routinely verified as can be done with h eat sterilizers through spore-testing.
INFECTION
IN S T R U M E N T P R O C E S S IN G : R E C O M M E N D A T IO N S A N D R E G U L A T IO N S
Processing contam inated in stru m en ts for reuse on subsequent p atients is a key p a rt in patient-protection
aspects of the office infection control program . The Centers for Disease Control and the A m erican D ental Association recommend th a t surgical and other instrum ents th a t norm ally penetrate soft tissue
CONTROL
or bone m ust be sterilized after each use and th a t other in stru m ents, burs and handpieces th a t come into contact w ith oral tissue should be sterilized after each u se .'2 The division of Occupational Safety and H ealth
TABLE 1
COMPARISON OF HEAT STERILIZATION METHODS M ETHO D
Steam autoclave
STANDARD S T E R IL IZ IN G C O N D IT IO N S *
20 min a t 250 F (15 psi)
20 m in a t 270 F U n satu rated chemical vapor (20-40 psi)
Dry heat Dry h e a t oven 60-120 m in at 320 F
Rapid h e a t tran sfer
12 m in a t 375 F (for wrapped items) 6 min a t 375 F (for unw rapped item s)
SPORET E S T IN G
A D V A N T A G ES
P R E C A U T IO N S
Time efficient Good penetration Sterilize waterbased liquid
Do not use closed containers May dam age plastic and rubber item s N on-stainless steel m etal item s corrode Use of hard w ater m ay leave deposits
Bacillus stearothermop h ilu s strips, vials or am pules
Do not use closed containers Time efficient No corrosion May dam age plastic and Item s dry quickly rubber item s M ust use special solution after cycle Predry instrum ents or dip in special solution Provide adequate ventilation C annot sterilize liquids
Bacillus stearothermophilus strips
No corrosion C an use closed containers Large capacity per cost Item s are dry after cycle No corrosion Short cycle Item s are dry after cycle
Longer sterilization tim e Cannot sterilize liquids May damage plastic and rubber item s Do not open door before end of cycle Predry instrum ents C annot sterilize liquids May damage plastic and rubber item s Do not open door before end of cycle Small capacity per cost Predry instrum ents U nw rapped item s quickly contam inated after cycle
Bacillus subtilis strips
Bacillus subtilis strip s
* T hese conditions do not include w arm -up tim e and they m ay vary depending upon the n atu re and volume of the load. S terilizing conditions in your office sterilizer should be defined by results of routine spore-testing. A dapted w ith perm ission from M iller CH: Take the safe approach to prevent disease transm ission. RDH 1989; 9(5):35.
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A dm inistration in the U.S. D epartm ent of Labor barely m entions in stru m e n t processing and sterilization in th eir final rules because th is prim arily relates to p atien t protection. OSHA is charged w ith pro tecting the workers of America, not patients. On th e other hand, OSHA h as requirem ents for protecting h ealth care workers during the handling and proces sing of contam inated, reusable in stru m en ts.3 The approach to sterilize all reusable in stru m en ts contam inated w ith blood or saliva (“U niversal Sterilization”4) ra th e r th a n to sterilize some and disinfect others is the safest approach to preventing disease spread to p a tie n ts from instrum ents. This is being recognized more and more as evidenced by law s in Ohio and Indiana requiring sterilization, ra th e r th a n ju s t disinfection of all reusable dental instrum ents, and is being considered in other states.5'7 PROCEDURES
The objective of in stru m en t processing is to prevent the spread of disease agents from one p atien t to the next via contam inated instrum ents. Several steps m u st be per formed correctly to assure effective microbial kill w ith m inim al in stru m e n t dam age and protection to the staff perform ing the procedures. ™ Presoaking. Soaking contam inated in stru m en ts in a mild detergent or in an in stru m en t disinfectant or ste rila n t until there is tim e for thorough processing will prevent drying of blood and saliva and facili tate cleaning. Do not presoak for more th a n a few hours, as the longer in stru m en ts rem ain 48
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TABLE 2
CAUSES OF STERILIZATION FAILURE ™ Im proper loading of sterilizer cham ber - overloading - no separation betw een packs or trays ™ Im proper packaging - wrong packaging m aterial for m ethod of sterilization - more th a n two layers of wrap - closed container not penetrated by steam or chemical vapor ™ Im proper tim ing - incorrect use of the sterilizer - tim ing for sterilization sta rte d before sterilizing tem perature is reached - dry h e a t sterilizer door opened to add more item s w ithout sta rtin g steriliza tion tim e over - sterilizer tim er m alfunction ™ Im proper tem perature - incorrect use of the sterilizer - sterilizer m alfunction ™ Im proper cleaning of item s to be sterilized
wet, the greater the chances for corrosion of non-stainless item s. If ultrasonic cleaning will be used, a good way to m anage the presoaking is to place the instrum ents in the ultrasonic cleaning basket and place the basket in a pan of th e presoak solution. Using th e basket prevents direct handling of the
instrum ents through the pre soak, cleaning and rinsing steps. W ear heavy utility gloves when handling contam inated instrum ents and m ixing chemi cal solutions. W ear protective eyewear, a m ask and protective clothing to prevent contam i nation from splashing of the solutions. ■■ Cleaning. Two approaches to instru m en t cleaning are handscrubbing and ultrasonic cleaning. H and-scrubbing is directly contrary to one of the dogmas of infection control— reduce direct contact with contam inated surfaces as m uch as possible. Hand-scrubbing increases such contact and adds the danger of handling sharp and pointed objects. If an item m ust be m anually scrubbed, w ear heavy utility gloves, a m ask and protective eyewear and clothing. S p atter or aerosols generated during hand-scrubbing m ust be minimized. Scrub in an area away from sterilized in stru m ents while th e instrum ents are submerged. Scrubbed instrum ents should be rinsed and dried before being wrapped or packaged. D rying is especially im portant for items th a t will be sterilized in an u n sa tu ra te d chemical vapor or in a dry heat sterilizer. U ltrasonic cleaning is effec tive and reduces the chances for instrum ent-puncture injuries th a t m ay occur w ith handscrubbing. Reasonably priced cleaners are available in a variety of sizes from several m anufacturers. E ach cleaner should be supplied w ith a m etal cleaning basket, a lid th a t should be used a t all tim es during operation and clear instructions for use and care. D isinfectants should not be
INFECTION
used in place of a detergent solution unless they are designed for this use. D eter gents containing an antim icro bial agent are available. The m anufacturer’s directions m ust be followed for best results. For ultrasonic cleaning, subm erge the rinsed in stru m ents in the cleaning solution using a basket, which keeps the in stru m en ts off the bottom of the tank. Place the lid on the cleaner, and operate the u n it for six to 10 m inutes or until debris disappears. If plastic/resin type of in stru m ent cassettes are used directly in the ultrasonic cleaner, in crease th e cleaning tim e as directed by the m anufacturer (for example, to 15 m inutes).8 This increased cleaning tim e isn ’t lost tim e as other work can be done during the process. U ltrasonic cleaners are excellent for cleaning b ut can not be considered sterilizers. Thus, th e “cleaned” instrum ents are still contam inated, and the cleaning solution m ay be contam inated w ith live micro organism s. Change the solution a t least once a day, using gloves, m asks and protective eyewear and clothing. At the end of th e day, disinfect, rinse and dry the cleaner chamber. ■■ Corrosion control and lubri cation. Cleaned instrum ents to be processed through a dry heat, chemical vapor or ethylene oxide gas sterilizer or through a liquid chemical ste rila n t or are to be packaged in a paper w rap should first be dried to reduce chances for corrosion, or to prevent dilution of th e liquid chemical agent or ru p tu re of paper wrap. A ru st inhibitor (dip or spray) m ay be applied to non-stainless items to be processed through the
steam autoclave. Hinged in stru m ents also m ay be lubricated a t this tim e if necessary. ™ Packaging. Instrum ents should be prepackaged before processing through a sterilizer so they will be protected from contam ination after steriliz ation. Use only w rapping m aterial
CONTROL
designed for th e particular m ethod of sterilization used in your office. Some paper/plastic w raps or polyfilm bags or tubing m ay be appropriate for steam b u t m ay m elt in the dry heat sterilizer. O ther wraps appropriate for dry heat sterilization m ay prevent penetration by steam or
TABLE 3
USE OF GLUTARALDEHYDE Use gloves, m asks and protective eyew ear and clothing when preparing, using and discarding chemical to protect skin, mucous m em branes and eyes from contact. Follow the m anufacturer’s label directions. Prepare/activate properly. Date activated solutions for shelf-life. Label used containers/pans w ith th e word “glutaraldehyde” and the brand nam e and w ith the date for use-life. Preclean and dry all item s to be processed. Completely subm erge all items in the solution and cover the container/pan. Keep subm erged for proper contact tim e (e.g., 10 hours for sterilization). Use a m onitor (for example, “dip stick”) to te st glutaraldehyde concentration during use. Discard and replace w ith fresh solution when indicated. Thoroughly rinse processed item s w ith w ater. Use sterile w ater if the item may penetrate tissue during use. Handle the processed item aseptically and prevent contam ination from hands, aerosols and d u st before placem ent a t chairside (for example, use sterile forceps to handle items; use bags or covers). G lutaraldehyde sterilants are indicated for im m ersion use only and are not recommended for use as a surface disinfectant to “wipe down” operatory surfaces.
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INFECTION
CONTROL
ÏO ÏT E S T IN G of office sterilizers WHEN
W HY
Once per week
To routinely verify proper use and functioning
W henever a new type of packaging m aterial or tray is used
To assure th a t the agent is getting inside to the surface of the instrum ents
D uring and after training of new sterilization staff
To verify proper use of the sterilizer
D uring initial use of a new sterilizer
To m ake sure th a t unfam iliar operating instructions are being followed
At least the first cycle after a sterilizer has been repaired
To m ake sure th a t the sterilizer is functioning properly
After any change in sterilizer loading procedure
To m ake sure th a t each item has access to the sterilizing agent
W ith every im plantable device and hold device until results of te s t are known
E xtra precaution for sterilization of item s to be im planted into tissues
chemical vapor. Avoid using th in paper bags, as they allow sharp in stru m ents to protrude, possibly causing injury during handling. “See-through” m aterial such as polyfilm /paper pouches and nylon tubing allow ready iden tification of package contents. W rapping m aterial, bags and pouches should be either self sealing, heat-sealed or double folded and sealed with appropriate tape. M etal clips or staples should not be used. The popularity of instru m en t 50
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cassettes is increasing as these contain the in stru m en ts through the ultrasonic cleaning, rinsing and sterilizing proce dures and serve as th e in stru m ent tray a t chairside. These cassettes are perforated to facilitate ultrasonic cleaning and entrance of sterilizing agents. Therefore, they m ust be wrapped w ith sterilization paper or bagged before steril ization to prevent post-sterilization contam ination. Non-perforated, closed containers of m etal or glass or
alum inum foil m ust not be used in steam , chemical vapor or ethylene oxide gas sterilizers. They will prevent the sterilizing agents from actually reaching the in stru m en ts inside. Processing unw rapped or unpackaged instrum ents through a sterilizer and then sorting and distributing them on tray s is least satisfactory. U nw rapped instrum ents have a zero shelf-life and can become contam inated w ith blood or saliva from hands, surfaces or aerosols during sorting and distribution if not handled in an aseptic m anner. Even if the instrum ents are to be used im m ediately a fter sterilization, they m ust be handled aseptically and protected from contam ination during the “trip ” from the sterilizer to chairside. " Sterilization. C haracteristics of the common m ethods of h eat sterilization used in dental offices are described in Table 1. Although stan d ard sterilizing tim es and tem peratures are given in the table, these do not include sterilizer “w arm -up” tim e. These will vary from one model to another depending on the n a tu re and volume of the item s being sterilized and how they are arranged w ithin the chamber. Follow the m anu facturer’s directions and define the proper sterilizing tim e by results of routine spore-testing. Sterilization failure occurs when the sterilizing agent does not contact th e surface of the instrum ents for a sufficient time. Causes for such failure are usually procedural in nature ra th e r th a n a m alfunc tion of the sterilizer, although the la tte r does occur. Table 2 lists the causes of sterilization failure, which in m ost instances can be detected only by spore-
INFECTION
testing. If an item is destroyed in h e a t sterilizers, it m ay be sterilized in an ethylene oxide gas sterilizer, followed by appropriate aeration or im m ersion in a liquid ste rila n t (for example, a glutaraldehyde product a t 2.0 percent or 3.2 percent concentration for 10 hours of contact tim e) and th e n thoroughly rinsed w ith w ater. C haracteristics of various glutaraldehydes have been reported recently.9 Tips for th eir use are given in Table 3. ™ Sterilization monitoring. Routine spore-testing (biological m onitoring) of th e office sterilizer helps assure the quality of p atien t care (Table 4).10 Sterilization failure from im proper use or m alfunction of the sterilizer increases the chances for spread of disease agents from patient to p atien t via the processed instrum ents. Routine spore-testing can detect these failures and alert the office to check and correct pack aging procedures and sterilizer loading, operating and functioning—m aking sporetestin g a very im portant form of risk m anagem ent. The C enters for Disease Control, the Am erican D ental Association, the Association for A dvancem ent of Medical Instru m en tatio n and the Office Sterilization and Asepsis Proce dures Research Foundation recom mend weekly spore-test ing of dental office steril izers.1,21112 Indiana and Ohio law s m andate spore-testing of dental office sterilizers. O ther states will soon follow.4'8 H ospitals m ust spore-test th eir sterilizers a t least weekly, but preferably daily. Proper spore-testing in the dental office involves placing
CONTROL
TABLE 5
*■ Check u nit for w ater retraction m onthly, and add or replace antiretraction valves when indicated. ■■ Flush the lines in high-speed handpieces and air/w ater syringes by operating for 30 seconds a t the beginning of th e day and for 15 seconds after each patient. ■■ Follow the handpiece m anufacturer’s directions for proper m aintenance, cleaning, sterilization, disinfection and compatibility with chemical agents. am Clean the external portion w ith a detergent or detergentdisinfectant and rinse w ith w ater. ■“ Lubricate high-speed handpieces w hen indicated by the m anufacturer and spray out excess lubricant. Depending upon the handpiece, some m ust be lubricated before, after, or before and after sterilization or not a t all. *■ Avoid spraying aerosols into the environm ent when operating the handpiece during processing/lubrication (for example, spray into a vacuum line). ■■ Package for sterilization in steam or u n sa tu ra te d chemical vapor following the m anufacturer’s directions. ■■ If disinfecting a handpiece th a t cannot be h eat sterilized, spray or sa tu ra te w ith the disinfectant recommended by the m anufacturer. Use a t least a 10-minute contact tim e (see disinfectant label) and thoroughly rinse w ith w ater and dry. Protect from contam ination before placem ent a t chairside.
the appropriate type of biological indicator (spore test) inside a norm al in strum ent pack, bag or tray. It is processed through the usual cycle in the sterilizer. The conditions of the cycle (for example, tim e, tem p erature, pressure) are recorded. The biological indicator m ust then be cultured under proper conditions to allow growth of any rem aining live spores. If growth is detected, then sterili zation failure occurred. A control biological indi-
cator—not processed through the sterilizer—m ust alw ays be analyzed a t the same tim e as the te s t biological indicator. The control m ust show grow th of the spores to validate the test. Routine spore-testing can be conveniently accomplished by subscribing to a m ail-in sterilization m onitoring service available commercially and through some dental schools.13 W hen performed properly, spore-testing through th e m ail provides reliable verification of JADA, Vol. 123, March 1992
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INFECTION
CONTROL
TABLE 6
12366648
: ASEPSIS
■■ Surfaces th a t are difficult to disinfect (such as chair buttons, control buttons on the air/w ater syringe, switches on th e unit, light handles, hoses, handpiece and air/w ater syringe holders) should be covered w ith plastic wrap, alum inum foil, or other m aterial impervious to w ater. Replace w ith fresh covers after each patient. It takes less tim e to replace a cover th a n to disinfect the uncovered surface. ■“ Disposable item s should be discarded after a single use ra th e r th a n cleaned and disinfected for reuse. *■ Disinfecting electrical switches on the chair or u nit may dam age or cause a short in the switch. Cover them! ■■ Preclean the surface prior to disinfection. ™ Choose an EPA -registered, ADA-accepted surface disinfectant, and use this agent for both the cleaning step and the disinfecting step for uncovered surfaces. U sing a waterbased agent w ith both cleaning and disinfecting properties provides some protection during the cleaning step, helps sanitize any debris splattered by the cleaning procedure, and helps keep the num ber of different products th a t need to be ordered to a m inim um . “ Follow the m anufacturer’s directions on the disinfectant product label. " W ater, ra th e r th a n alcohol, m ust be used w ith those agents requiring dilution before use. “ Use u tility gloves, a m ask, and protective eyewear and clothing during surface cleaning and disinfection to reduce chances of direct contam ination of the skin, mucous m em branes or eyes. Adapted w ith perm ission from M iller CH. Disinfection of surfaces and equipm ent. D ental Asepsis Review 1988; 9/12:2.
sterilization.14 M ost of these services can te st steam , dry heat, u n sa tu ra te d chemical vapor and ethylene oxide gas sterilizers. They provide the proper type of biological indi cator, instructions, re tu rn mail envelopes, im m ediate telephone 52
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notification of sterilization failures and a w ritten report for each test. Some also include infection control new sletters, certificate of participation and specific advice on how to pin point and correct sterilization failures.
The cost of such services ranges from about $8 to $20 per test. As an alternative for steam sterilizers, special spore vials and an appropriate 56 C incubator can be purchased and the vials processed, cultured and analyzed and the results recorded by properly trained office staff. Chemical indicators are strips, tapes and m arkings on bags and pouches th a t change color or physical form after exposure to the sterilizing agent (for example, h eat, steam , chemical vapor). W hen used on the inside and outside of packs, bags or trays, they im m ediately indicate th a t the item s have been processed through the sterilizer and have been exposed to heat, steam or chemical vapor. Since chemical indicators do not analyze for microbial kill, they should be used in conjunction with, but never as a replacem ent for spore-testing, which provides the m ain g u arantee of sterilization. ■■ Handpiece asepsis. The out side surfaces of all handpieces become contam inated during use. In addition, the inside lines of high-speed handpieces may become contam inated when patient fluids re tra c t back through the air-w ater opening at the head of th e handpiece when the handpiece is turned off after use.15 If th e handpiece is not properly processed, the retracted fluids m ay enter the m outh of the next patient. D ental units m anufactured after the middle 1980s have anti-retraction valves already installed. O lder u n its should be retrofitted w ith these valves by cutting the handpiece and the air-w ater syringe w ater lines in the control box and inserting
INFECTION
FACTS ABO UT A
Q v the end of 1993, as m any as 480,000 Am ericans will have full-blown AIDS, and as m any as 340,000 will have died from the disease. W hat follows are some facts on AIDS and the hum an immunodeficiency virus, current to Dec. 31, 1991, unless otherwise noted: ■■ One million U.S. residents are HIV-infected. ■■ AIDS h as been diagnosed in 206,392 Am ericans. — As of Sept. 30, 1991, 7,250 U.S. h ealth care w orkers had AIDS. *■ Of th a t num ber, 209 were dentists or dental-office staff members. ■■ A total of 133,232 Americans have died as a resu lt of AIDS. ■ S ource: F e d e ra l C e n te rs for D is e a s e C o n tro l
these “one-way” valves. Since these valves m ay fail periodi cally, retraction m ust be routinely checked and the valves replaced when necessary. R etraction is checked by observing the tip of th e w a te r line opening a t the handpiece connection when the w ater is turned on and then off. If a drop of w ater “hangs” on the tip, retraction is not occurring. If
the w ater is draw n back into the line, retraction is occurring. Cleaning and wiping the handpiece w ith a surface disin fectant m ay decontam inate the exterior but will not decontam inate the interior portion of high-speed handpieces th a t m ay have become contam inated because of no anti-retraction valves or valves th a t have failed. D ata showing th a t the in tern al portions of the high speed handpiece can indeed be effectively steam sterilized have been reported.16 The Am erican D ental Association and the Centers for Disease Control currently state th a t handpieces should be h e a t sterilized, if possible.1,2Also, some states are developing laws to m andate h eat sterilization of all h an d pieces.7An approach to h a n d piece asepsis is described in Table 5. S U R F A C E A S E P S IS
Blood or saliva on environ m ental surfaces (for example, operatory, laboratory, steril izing area) m ay serve as a source of contam ination for patients, office staff or item s th a t may contact those surfaces. Surface asepsis is a collection of procedures th a t prevent or remove contam ination from surfaces (Table 6). ■■ Surface covers. One approach to surface asepsis is preventing th e initial contam ination of the surface. Surfaces and equip m ent (particularly those th a t are difficult to clean) are covered w ith plastic w rap or bags, alum inum foil or plasticbacked paper before patient care or before the item is used. After patient care or after a covered item has been used, remove and discard the cover
CONTROL
w ithout touching th e under lying surface and replace w ith a fresh cover for reuse. It is not necessary to clean and disinfect a properly covered surface betw een patien ts unless the cover failed or the surface was accidentally contam inated during cover removal. Replacing surface covers also is less tim econsuming th a n are proper surface cleaning and disin fecting. Although local laws m ay dictate disposal of such covers, generally they are not considered as regulated medical waste unless dripping w et or caked w ith blood or saliva. ■■ Surface precleaning. If surface covers are not used, contam inated surfaces m ust be precleaned before being disinfected as indicated by the Centers for Disease Control,1by OSHA’s final bloodborne patho gens stan d ard 3 and by the label directions on surface disinfect an t products. Precleaning reduces the bioburden on the surface and facilitates subse quent disinfection. It is m ost convenient to use a w ater-based cleaning agent th a t has both cleaning and disin fecting properties. This provides some protection during cleaning and reduces the spread of con tam ination to Dr. Miller is profes sor and chairman, adjacent Department of Oral surfaces Microbiology, during the Indiana University School of Dentistry, process. It also 1121 W. Michigan reduces the St., Indianapolis, 46202. Dr. Miller is num ber of chairman of the products Office Sterilization needed in the and Asepsis Proced ures Research offices. Gloves Foundation. Address and protective reprint requests to Dr. Miller. eyewear also JADA, Vol. 123, March 1992
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CONTROL
should be worn during handling of the cleaner and during the cleaning itself. The cleaner should be sprayed onto the surface and the surface vigorously wiped w ith paper towels or scrubbed w ith a b rush and rinsed over the sink. This precleaning step m u st not be slighted, as it can determ ine th e success of the disinfecting step to follow. *■ Surface disinfection. The precleaned surface is now ready for disinfection. There are several ADA-accepted surface disinfectants representing different chemical categories (chlorines, iodophors, combi nation synthetic phenolics, phenolics and alcoholphenolics). C haracteristics of several brands have been recently described.9 Diluted iodophors, synthetic phenolics and chlorines have both clean ing and disinfecting properties for use in the precleaning step and th e disinfecting step.17After precleaning, spray on the disin fectant and leave moist for the prescribed contact tim e on the disinfectant label (10 m inutes). ■■ Disposable items. Disposable item s m anufactured for use on a single p atien t should indeed be discarded after a single use ra th e r th a n cleaned and disin fected for reuse. Such item s include disposable air/w ater syringe tips, prophy angles, high-volume evacuator tips, saliva ejector tips, prophy cups
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and brushes. These item s were not designed to be cleaned and reprocessed since m ost consist of plastic th a t scratches easily and can harbor debris and microorganism s. They also may adsorb disinfecting chemicals or be m echanically weakened by the processing. If such item s are processed for reuse, then the u ser assum es all responsibility for safety and effectiveness. C O N C L U S IO N
Sterilizing all reusable in stru m ents contam inated w ith blood or saliva ra th e r than sterilizing some and disinfecting others is the safest approach to prevent ing disease spread among patients. Procedures and techniques conforming to the late st regulations are described in detail for the dental practitioner. ■ 1. C e n te rs fo r D is e a s e C o n tro l. R eco m m en d ed in fectio n -co n tro l p ra c tic e s fo r d e n tis try . M M W R 1986; 35:237-42. 2. ADA C o u n cils on D e n ta l M a te ria ls, In s tr u m e n ts a n d E q u ip m e n t; D e n ta l P ra ctice ; a n d D e n ta l T h e ra p e u tic s . In fe c tio n c o n tro l rec o m m e n d a tio n s fo r th e d e n ta l office a n d d e n ta l lab o ra to ry . JA D A 1988; 116:241-8. 3. D e p a r tm e n t o f L ab o r, O c c u p a tio n a l S a fety a n d H e a lth A d m in is tra tio n . 29 C F R P a r t 1910.1030, o c c u p atio n al e x p o su re to b loodborne p a th o g e n s; fin al ru le . F e d R eg 1991; 56:64004-182. 4. M ille r CH . S te riliz a tio n : d isc ip lin e d m icro b ial co n tro l. D e n t C lin N o rth A m 1991; 35:339-55. 5. O h io S ta te D e n ta l B o a rd o f E x a m in e rs. In fe c tio n co n tro l ru le s. C o lu m b u s, Ohio: N o v e m b e r 1, 1987. 6. I n d ia n a S ta te B o ard o f H e a lth , D e n ta l H e a lth
D iv isio n . I n d ia n a P u b lic L aw 123-1988 d e n ta l on -site c o m p lian c e rev ie w ch e ck list. In d ia n a p o lis , In d ia n a : F e b r u a r y 1, 1990. 7. W a sh in g to n S ta te D e p a rtm e n t o f H e a lth , D e n ta l D isc ip lin a ry B o ard . In fectio n co n tro l ru le s-p ro p o se d . O ly m p ia , W a sh in g to n : D ecem b er 3, 1991. 8. M ille r C H , H a rd w ic k LM . U ltra s o n ic c le a n in g of d e n ta l in s tr u m e n ts in c a ss e tte s . G en D e n t 1988; 36:31-6. 9. C o tto n e JA , M o lin ari JA . S ta te -o f-th e -a rt in fe c tio n control in d e n tis try . JA D A 1991; 123:33-40. 10. M ille r C H , P a le n ik C J. S te riliz a tio n , d isin fec tio n a n d a s e p s is in d e n tis try . In D isinfection, S te riliz a tio n a n d P re se rv a tio n (SS Block, ed). P h ila d e lp h ia : L ea & F e b ig er; 1991:676-94. 11. A sso ciatio n for th e A d v a n c e m e n t o f M edical I n s tr u m e n ta tio n , S te riliz a tio n S ta n d a r d s C o m m itte e , A m b u lato ry -C are a n d O ffice-B ased S te a m S te riliz a tio n W o rk in g G ro u p . S te a m s te riliz a tio n a n d s te r ility a s s u r a n c e in office-based, a m b u la to ry -ca re , m ed ic a l a n d d e n ta l fac ilitie s— d r a f t o f reco m m en d ed p rac tic e . A rlin g to n , V irg in ia: N o v e m b e r 1, 1991. 12. O ffice S te riliz a tio n a n d A se p sis P ro c ed u re s R e s e a rc h F o u n d a tio n . In fectio n co n tro l g u id elin es. D e n v e r: 1991. 13. ADA. Biological in d ic a to rs for v erify in g s te riliz a tio n . JA D A 1988; 117:653-4. 14. M ille r C H , S h e ld ra k e MA. T h e a b ility of b iological in d ic a to rs to d e te c t ste riliz a tio n failu re (A b s tra c t 1919). J D e n t R es (S p ecial Issu e ) 1990; 69:348. 15. A D A C ouncil on D e n ta l M a te ria ls, I n s tr u m e n ts a n d E q u ip m e n t. D e n ta l u n its a n d w a te r re tra c tio n . JA D A 1988; 116:417-20. 16. M ille r C H , S h e ld ra k e MA. S te riliz in g th e i n te r n a l lin e s o f h ig h sp e ed d e n ta l h a n d p ie c e s (A b stra c t, Society for In fectio n C o n tro l in D e n tistry ). T ra n s m is s io n s 1992;8. 17. M o lin a ri JA , G leaso n M J, C o tto n e J A , e t al. C le a n in g a n d d isin fe c ta n t p ro p e rtie s o f d e n ta l su rfa c e d isin fe c ta n ts . JA D A 1988; 117:179-82.
