When the goal is sterility assurance,
there are no short cuts and the process must be started with a clear vision of
direction and destination; the plan for success is to begin with the end in
mind (Figure 1). Covey’s simple
quote from his book, The 7 Habits of
Highly Effective People should be a guiding principle for sterilization.
Every step that happens--from instrument cleaning, packaging, sterilization,
monitoring, storage, and delivery--must be in alignment for quality assurance.
Sterilization describes a process that destroys or eliminates all
forms of microbial life and is carried out in healthcare facilities by physical
or chemical methods. Steam under pressure, dry heat, ethylene oxide (EtO) gas,
hydrogen peroxide gas plasma, and liquid chemicals are the principal sterilizing
agents used in healthcare facilities.1
The predominate sterilization method
used in dentistry is the time-honored technique of steam sterilization. Advantages
of steam sterilization include its non-toxic approach, rapid cycle time, and
that it is highly efficacious, cost effective, easily monitored, and with
According to CDC Guidelines, monitoring
of sterilization procedures should include a combination of process parameters,
specifically mechanical, chemical, and biological. Combined, these parameters
evaluate both the sterilizing conditions and the procedure’s effectiveness.2
The first monitoring tool is mechanical,
which includes assessing cycle time, temperature, and pressure by observing the
gauge, digital displays, or printout on the sterilizer and noting these
parameters for each load. Correct end point response does not ensure
sterilization, but incorrect readings can be the first indication of a gross
Chemical indicators (CIs) provide
information about certain conditions within the package, but do not provide
sterility assurance of the load. The internal and external CIs use reactive ink
that changes color to assess one or more of the physical parameters (i.e., time,
temperature, saturated steam) to which the instruments were exposed during the
cycle. Single-parameter indicators provide information on only one parameter,
while multiparameter indicators measure two to three parameters and provide a
more complete evaluation of the sterilization conditions. While these chemical
indicators do not necessarily prove sterility, they allow an early warning
system for processing errors and they can help identify procedural errors. Every
package should be examined by the clinician opening it, and an assessment
should be made as to the acceptability of the end point response of the CI; any
package indicator that fails to display the correct change and intensity of
color should not be used and must be reprocessed.
Biological indicators (BIs) commonly
use highly resistant spores (i.e., spore test) to challenge the sterilization
process. Since they are more resistant and are usually present in greater
numbers than are the common microbial contaminants found on instruments,
destruction of these organisms will indicate destruction of other potential
pathogens. While all three types of monitoring are important to the quality
assurance process, biological monitoring is considered the gold standard for
The most commonly used forms of BIs in dentistry are spore strips and
self-contained spore vials. Spore strips are small pieces of filter paper
impregnated with nonpathogenic bacterial spores (e.g., Geobacillusstearothermophilus and Bacillus atrophaeus) encased in a protective glassine envelope. After
processing, the spore test envelope is sent to a laboratory where the paper
strip is aseptically transferred to a test tube containing sterile culture
media and then incubated. Self-contained vials have a glass ampule of sterile
media, which is encased in a plastic vial with a spore strip inside. After
sterilization, the vial is crushed--allowing the media to come into contact
with the spore strip and then incubated. With either the strips or vials after
incubation, if the pH indicator in the growth media changes the color from
purple to yellow, this is an indication of a positive culture (i.e., spore
growth) and meaning a failed test. It is recommended that a control be conducted
with every BI test.
Three options are available for monitoring sterility assurance in the
dental office: mail-in sterilization monitoring services to a third-party
testing laboratory (i.e., private companies or dental schools), in-office
24-hour monitoring systems, and a newly released in-office 10-hour monitoring
system. While some offices prefer use of a professional lab for testing
verification (i.e., gram staining) and third-party documentation of results,
others appreciate the convenience in-office processing provides, with a direct
turnaround time and without the challenge of mailing and waiting for results.
It should be noted that in-office monitoring systems can only be used with
steam (autoclave) sterilizers; mail-in monitoring services can provide results
for steam, dry heat, chemical vapor, and EtO.
(Continued from page 1 )
The CDC guidelines state: Correct functioning of sterilization cycles should be verified for each
sterilizer by the periodic (at least weekly) use of BIs. Consideration should
be given for more frequent testing if the sterilizer is used multiple times
each day or with use of a variation of sterilization cycles. Users
should follow the manufacturer's directions concerning the appropriate
placement of the BIs in the sterilizer; the preferred area for the BI placement
is in the least-effective zone of the sterilizer--often near the door or the
middle of the load near the drain.
In addition to conducting routine biological monitoring,
equipment users should perform biological monitoring for the following
a new type of packaging material or tray is used;
training new sterilization personnel;
a sterilizer process failure is indicated by a failed (positive) BI+;
a sterilizer has been repaired;
any change in the sterilizer loading procedures;
initial use of a new sterilizer;
relocation of an existing sterilizer; and
electrical/power source failure.
Importance of Compliance
In several studies, dental
practices have demonstrated variability in sterilization compliance. For
example, 68% of respondents believed they were sterilizing their instruments
but did not use appropriate chemical sterilants or exposure times, and 49% of
respondents did not challenge autoclaves with biological indicator.3
Other investigators using BIs have found a high proportion (15% to 65%) of
positive spore tests after assessing the efficacy of sterilizers used in dental
offices.4 In one study of Minnesota dental offices, operator error--rather
than mechanical malfunction--caused 87% of sterilization failures.5
Common factors in the improper use of sterilizers include chamber overload, low
temperature setting, inadequate exposure time, failure to preheat the
sterilizer, and interruption of the cycle.
On December 8, 2011, the
Supreme Judicial Court of Massachusetts affirmed the final decision and order
of the Board of Registration in Dentistry, suspending the license of a dentist
who failed to conduct and record weekly spore testing. The dentist’s failure
constituted dental malpractice. The
entire summary of Chadwick vs. Board of Registration in Dentistry case #SJC-10831
is available on the Internet.
In March, a health center
contacted the families of eight school children who were treated in a mobile
clinic with potential exposure to blood-borne pathogens due to use of improperly
sterilized instruments. Some of the instrument packages used during treatment
displayed failed chemical indicators that would have identified either a procedural or processing sterilization error.
An accurately detailed and consistent
documentation establishes accountability for sterilization. The information to
be included with each sterilization cycle includes:
identification (serial) number;
and temperature of the sterilization cycle (if not provided by a machine
printout) (Figure 2);
of the general contents of the load;
results of biological monitoring (pass or fail);
and preventive maintenance procedures; and
notes citing conditions outside of normal procedures, i.e. different operators
or load content.
Clinicians should refer to state or
local regulation guidelines for the length of time such documentation should be
Effective sterilization is critical to
safety and optimal patient care. Proper functioning of the sterilization
process should be routinely monitored and documented using mechanical,
chemical, and biological methods.
Manager & Director of Education, Crosstex International, Englewood, CO.
- Rutala WA, Weber, DJ et al. Guideline for disinfection and sterilization in healthcare facilities, 2008; Available at: http://www.cdc.gov/hicpac/pdf/guidelines/Disinfection_Nov_2008.pdf. Accessed March 1, 2012.
- KohnWG, Collins AS, Cleveland JL, et al. Guidelines for infection
control in dental healthcare settings – 2003. MMWR Recomm Rep. 2003. Available
at http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5217a1.htm. Accessed March 1,
- Gurevich I, Dubin R, Cunha
BA. Dental instrument and device
sterilization and disinfection practices. J Hosp Infect 1996;32:295-304.
- Smith A, Dickson M, Aitken J, Bagg J. Contaminated dental
instruments. J Hosp Infect 2002;51:233-235.
- Hastreiter RJ, Molinari JA,
Falken MC, et al. Effectiveness of dental
office instrument sterilization procedures. J Am Dent Assoc 1991;122:51-56.
- Wahlberg, D. Access says 8 children givendental care with
improperly sterilized instruments. Wisconsin State J 2012; March.Available at: http://host.madison.com/wsj/news/local/health_med_fit/access. Accessed March, 2012.