Infection Control Procedures in Commercial
Dental Laboratories in Jordan
Ziad Nawaf Al-Dwairi, B.D.S., Ph.D.
Abstract: The risk of cross-infection in dental clinics and laboratories has attracted the attention of practitioners for the past few
years, yet several medical centers have discarded compliance with infection control guidelines, resulting in a non-safe environ-
ment for research and medical care. In Jordan, there is lack of known standard infection control programs that are conducted by
the Jordanian Dental Technology Association and routinely practiced in commercial dental laboratories. The aim of this study was
to examine the knowledge and practices in infection control among dental technicians working in commercial dental laboratories
in Jordan. Data were collected from the dental technicians by a mailed questionnaire developed by the author. The questionnaire
asked respondents to provide demographic data about age and gender and to answer questions about their knowledge and practice
of infection control measures: use of gloves, use of protective eyeglasses and face shields, hepatitis B virus (HBV) vaccination,
laboratory work disinfection when sent to or received from dental offices. and regularly changing pot water or pumice slurry.
Of the total respondents, 135 were males (67.5 percent) and sixty-five were females (32.5 percent) with a mean age of twenty-
seven years. The results showed that 24 percent of laboratory technicians wore gloves when receiving dental impressions, while
16 percent continued to wear them while working. Eyeglasses and protective face shields were regularly worn by 35 percent
(70/200) and 40 percent (80/200) of technicians, respectively. Fourteen (14 percent) had received an HBV vaccination, and 17
percent inquired if any disinfection measures were taken in the clinic. Eighty-six percent of the technicians reported that pumice
slurry and curing bath water were rarely changed. Only five dental technicians (two males and three females) were considered to
be fully compliant with the inventory of infection control measures, a compliance rate of 2.5 percent with no significant differ-
ence between males and females (p>0.05). In conclusion, there is lack of compliance with infection control procedures of dental
technicians working in commercial laboratories in Jordan.
Dr. Al-Dwairi is Assistant Professor, Department of Restorative Dentistry, Jordan University of Science and Technology. Direct
correspondence and requests for reprints to Dr. Ziad Nawaf Al-Dwairi, Department of Restorative Dentistry, Jordan University of
Science and Technology, P.O. Box 3030, Irbid-Jordan; firstname.lastname@example.org.
Key words: infection, dental, technician, laboratory, Jordan
Submitted for publication 1/24/06; accepted 6/7/07
here is growing concern about the issue of studies have found pumice in commercial laborato-
cross-infection in dental clinics and labora- ries that was contaminated by potentially pathogenic
tories, especially after several studies found microorganisms, such as gram-negative bacilli of
that transmission of infection to dental laboratory the genus Acinetobacter, as well as Micrococcus,
technicians is mainly by contaminated impressions Pseudomonas, Moraxella, and Alcaligenes.6-8 These
or by improper handling of clinical items after arrival bacteria, which are not part of normal oral flora, can
at the dental laboratory. Three studies published in cause serious diseases if passed to patients whose
1990, 1996, and 2002 reported that more than 60 dentures are polished with contaminated material
percent of prostheses delivered to dental clinics and to the technician by exposure to contaminated
from laboratories were contaminated with patho- aerosol. Williams et al.9 reported an increase in cases
genic microorganisms originating in the oral cavity of pneumonia in individuals exposed to lathe aero-
of patients.1-3 In prosthetic laboratories, lathes and sol. Another study reported ten cases of infection by
pumice used for polishing and finishing of prosthe- Mycoplasma pneumoniae involving persons working
ses have been described as the greatest sources of in dental prosthetic laboratories; the investigators
contamination.4 suspected that these infections were derived from
Potential pathogenic microbiologic cross- manipulation of prostheses contaminated by these
contamination from various sources by way of the microorganisms.10
dental laboratory has been documented, and guide- Dental prostheses should be disinfected before
lines to reduce it have been published.5 A previous they are sent to the laboratory and upon return to the
study reported that nine out of ten sterile complete dental clinic. However, despite rigorous control of
dentures that were fractured and sent to different sterilization and disinfection of instruments in dental
dental laboratories for repair were contaminated clinics, prosthetic appliances do not always receive
with potentially pathogenic microorganisms.6 Several adequate infection control.11
September 2007 ■ Journal of Dental Education 1223
Other studies demonstrated the presence of second investigated compliance with infection con-
bacteria on impressions, although at a low level. trol programs in private dental clinics in Jordan.13
One study showed that 12 percent of impressions Therefore, the present investigation aimed to
taken from known tuberculosis patients harbored examine the knowledge and practices in infection
mycobacterium tuberculosis, and seventy-seven out control among dental technicians working in com-
of 107 alginate impressions yielded growth of bacte- mercial dental laboratories in Jordan.
ria after they were transported in sealed plastic bags
to prevent any contamination, while no growth was
recorded in the remaining thirty samples.3 Another Materials and Methods
study showed that 67 percent of the impressions sent
to a dental laboratory had been contaminated with Data were collected from dental technicians by
bacteria such as Enterobacter cloacae, Escherichia a mailed questionnaire developed by the author. The
Coli, and Klebsiella oxytoca.8 These findings indicate questionnaire was pilot-tested by distributing it to
that infection control programs should be developed twenty dental technicians who work in a university-
and completed by dental technicians before handling based hospital. Responses from the pilot test were
any clinical items that arrive from dental clinics. analyzed to assess the clarity and relevance of the
In Jordan, there are no strict national guide- questions, and modifications were made. After receiv-
lines imposed by the Dental Technology Association ing feedback from pilot test participants, I sent each
regarding handling of impressions and prostheses of 200 dental technicians a personalized letter that
between dental laboratories and clinics, and there are explained the goal of the study and a self-addressed,
no previous articles on this topic in journals published stamped return envelope along with the question-
in Jordan. Of two reports published recently, the first naire. Follow-up consisted of reminder postcards
was in the American Journal of Infection Control and and two additional mailings of the questionnaire to
the second was in the Journal of Dental Education. nonrespondents. The study was conducted between
The first report addressed infection control knowl- August and November 2005.
edge and practices among dentists and dental nurses The questionnaire asked respondents to provide
at a Jordanian university teaching center,12 and the demographic data about their age and gender and
to answer questions about their knowledge
and practice of infection control measures.
Table 1. List of questions about infection control procedures in Respondents were asked if they used each
dental laboratories of the following infection control prac-
1. Wear gloves when receiving clinical items from dental clinics?
tices: gloves, protective eyeglasses and face
Regularly Occasionally No shields, hepatitis B virus (HBV) vaccination,
laboratory work disinfection when sent to or
2. Wear protective eyeglasses during laboratory work?
Regularly Occasionally No received from dental offices, and regularly
changing pot water or pumice slurry. Finally,
3. Wear protective face shields during laboratory work? technicians were asked if infection control
Regularly Occasionally No
procedures imposed a financial burden on
4. Vaccinated against HBV? them. Dental technicians were considered
compliant if they adhered to the complete
5. Ensure that clinical items had been disinfected in the clinic before list of infection control procedures included
you receive them? in the questionnaire. This list is shown in
Regularly Occasionally No
6. Disinfect clinical items if not disinfected in clinic? The returned questionnaires were
Regularly Occasionally No
reviewed for completeness. An SPSS statis-
7. Disinfect laboratory work before sending to clinic? tical package was used to analyze the data.
Regularly Occasionally No A binary outcome variable was generated to
8. Change pumice slurry and water of pressure pot? indicate compliance with infection control
Regularly Occasionally No procedures, and compliance was presented as
9. Infection control measures pose a financial burden?
percentages. P value was used to assess the
Yes No association of gender with compliance, and
significance was set at the 0.05 level.
1224 Journal of Dental Education ■ Volume 71, Number 9
Results Table 2. Age and gender distribution of dental techni-
cians in commercial dental clinics in Jordan
All the 200 dental technicians included in this Characteristic Number Percentage
study completed the questionnaires, which represents
a 100 percent response rate. Of the total respondents, Age in years
135 were males (67.5 percent) and sixty-five were 25-35 85 42.5%
females (32.5 percent), with an overall mean age of 36-45 63 31.5%
46-55 30 15%
twenty-seven years (Table 2).
>55 22 11%
Twelve percent (24/200) of these dental techni-
cians reported that they wear gloves regularly when Gender
receiving clinical items from various dental clinics, Male 135 67.5%
but only six of the twenty-four (3 percent overall; Female 65 32.5%
6/200) continued to wear gloves during technical
work. Eyeglasses and protective face shields were
regularly worn by 35 percent (70/200) and 40 percent
(80/200) of technicians, respectively (Table 3). Ten
percent (20/200) of dental technicians had been vac- The dental profession in Jordan has been ex-
cinated against HBV Only 17 percent (34/200) asked
. pected to meet traditional standards of cross-infection
clinical staff if the materials they delivered from the control, but recent expression of concern by both the
clinic had received any form of disinfection. Six public and the profession over the transmissibility of
technicians (3 percent) reported that they regularly infectious diseases in the dental office has demanded
disinfected clinical items after arrival if they had not a formalized and extended teaching of cross-infection
been disinfected in the clinic. The majority of dental control in the dental curriculum. This is the first study
technicians (86 percent) reported that they did not conducted to assess the compliance of dental techni-
change the pumice slurry or water of the curing bath cians working in commercial laboratories in Jordan
regularly, and only 20 percent disinfected laboratory with infection control procedures. Infection control
work before sending it back to the clinic. The major- in commercial laboratories in Jordan was investigated
ity of technicians (80 percent; 160/200) agreed that because these facilities often lack hazard risk instruc-
implementing infection control procedures in their tions or occupational health policies that are more
laboratories required extra budget and imposed fi- commonly available in universities and hospitals.
nancial burdens on them. The response rate to the questionnaire in
Only five dental technicians (two males and this study (100 percent) was higher than previ-
three females) were considered to be fully compli- ous studies.14 This high rate is presumably due to
ant with the inventory of infection control measures the importance of the issue of infection in dental
listed in Table 1, a compliance rate of 2.5 percent laboratories and because technicians recognize that
with no significant difference between males and dental laboratories are as important as dental clinics
females (p>0.05). in following infection control programs to create a
Table 3. Adherence to infection control procedures among dental technicians in commercial dental laboratories
Infection Control Procedure Regularly Occasionally Never
N (%) N (%) N (%)
Wear gloves when receiving clinical items from clinics. 20 (10%) 14 (7%) 166 (83%)
Continue to wear gloves during work. 6 (3%) 194 (97%)
Wear protective eyeglasses during laboratory work. 70 (35%) 15 (7.5%) 115 (57.5%)
Wear protective face shields during laboratory work. 80 (40%) 19 (9.5%) 101 (50.5%)
Ensure previous disinfection of clinical items. 34 (17%) 29 (14.5%) 137 (68.5%)
Disinfect clinical items if not disinfected in clinic. 6 (3%) 29 (14.5%) 165 (82.5%)
Change pumice slurry and water of pressure pot. 5 (2.5%) 23 (11.5%) 172 (86%)
Disinfect laboratory work before sending to clinic. 40 (20%) 35 (17.5%) 125 (62.5%)
Pose financial burden. 160 (80%) 40 (20%)
September 2007 ■ Journal of Dental Education 1225
safe work environment. Many of the technicians who an HBV vaccination.14 Furthermore, in this study a
participated in this study wrote comments on the low percentage (17 percent) inquired about the dis-
questionnaire that reflected their interest in this is- infection status of materials they received from the
sue. Follow-up—which included reminder postcards clinics. This is a disappointing result because it is well
and two additional mailings of the questionnaire to established that contaminated impressions transfer
nonrespondents—might be another reason for the microorganisms to the casts and harbor them; this
high response rate transfer process will spread infection throughout the
Dental laboratory technicians are at risk of laboratory when the casts or dies are trimmed.7 As a
cross-contamination from the clinical items they result, dentists should always ensure that impressions
receive and handle from dental offices.15 The use of are adequately disinfected before sending them to the
protective measures is important. In this study, only laboratory. A recent study reported that 44 percent
12 percent of the technicians wore gloves when re- of the 400 U.S. dental laboratories knew if incoming
ceiving the impressions or any work delivered from impressions had been disinfected or not.4
the clinic. This is in contrast to a previous report in Impressions have been considered the main
which 90 percent of the technicians in the United source of infections in dental laboratories.3 It is easy
Kingdom wore gloves when handling dental work for impressions to be contaminated with microorgan-
received and opened in the laboratory.16 A recent isms that are present in a patient’s saliva and blood.
study reported that 39.5 percent of dental techni- Disinfection protocols have been recommended
cians in Nigeria never wear gloves while working to prevent technicians from exposure to infectious
in the laboratory.14 Dermatological reactions related diseases such as hepatitis B, hepatitis C, tubercu-
to glove use and difficulties in adjusting to the use losis, herpes, and AIDS.19 Furthermore, it has been
of gloves were the main reasons reported by dental demonstrated that the impression material can act as
technicians for not using gloves regularly. a vehicle for the transfer of both bacteria and viruses.
Other protective measures, such as aprons, McNeill et al. reported that the virus was present in
protective glasses, and lathes with efficient shields, the body of the impression and, under certain condi-
should be used while working; these methods of tions, may evade decontamination.20
protection will reduce the risk of cross-contamina- Contaminated invisible aerosol particles remain
tion.17 In the present investigation, 35 percent and 40 in the air for long periods of time when lathes have
percent of dental technicians reported that they used been used for the polishing of prostheses.2,4 In spite of
protective eyeglasses and face shields, respectively. the fact that it is not possible to eliminate all sources
This contrasts with a previous report in which 74 of contamination in the laboratory, a series of pre-
percent were found to wear protective eye spectacles ventive measures to decrease these levels should be
when trimming or polishing prostheses.16 adopted. The use of sterile pumice and rag wheels or
Occupational infection of the dental laboratory the association of disinfectants with pumice for pol-
technician with HBV has been reported.18 Only 10 ishing are viable alternatives to significantly reduce
percent of the technicians who participated in this cross-contamination in the laboratory.7,8,21,22
study had received an HBV vaccination; this is lower Pumice slurry is a major source of cross-infec-
than another study in which 24.4 percent had received tion in the dental laboratory: microorganisms can be
harbored there easily unless the slurry is changed
regularly or mixed with a disinfectant. A study by
Table 4. Compliance with infection control practices in
Kugel et al. published in 2000 concluded that non-
commercial dental laboratories
clinical laboratories are not immune from the presence
Factor Compliant Non-Compliant of potentially pathogenic microorganisms in pumice
N (%) N (%)
slurry.4 An earlier study by Witt and Hart2 published in
Age 1990 showed that all pumice samples mixed with tap
25-35 3 (3.6%) 82 (96.4%) water were heavily contaminated and aerobic Gram-
36-45 1 (1.6%) 62 (98.4%)
46-55 1 (3.4%) 29 (96.6%)
positive bacilli including B.Cereus, B. brevis, and B.
>55 0 22 (100%) licheniformis with members of the coli-aerogenes
group predominated. On the other hand, samples
Gender that were prepared with the disinfectant Virkon had
Male 2 (1.5%) 133 (98.5%)
Female 3 (4.6%) 62 (95.4%)
growth of less than 1.0 and were stable for four days.
A study by Verran et al. published in 1996 showed the
1226 Journal of Dental Education ■ Volume 71, Number 9
growth of a range of bacteria and yeasts from pumice 5. Centers for Disease Control and Prevention. 2003 CDC
and water bath.1 The most common were Staphylo- infection control recommendations for dental health-
care settings. Compend Contin Educ Dent 2004;25(1
coccus, Candida and other yeasts, Pseudomonas, and
Micrococcus. In the present study, only 14 percent of 6. Wakefield CW. Laboratory contamination of dental pros-
laboratory technicians changed pumice and water bath theses. J Prosthet Dent 1980;44:143-6.
regularly. Unfortunately, none of the technicians used 7. Agostinho AM, Miyoshi PR, Gnoatto N, Paranhos Hde F,
a disinfectant while working with pumice. Figueiredo LC, Salvador SL, et al. Cross contamination
in the dental laboratory through the polishing procedure
In conclusion, the results of this study confirm
of complete dentures. Braz Dent J 2004;15(2):138-43.
the lack of adequate infection control compliance by 8. Powell GL, Runnells RD, Saxon BA, Whisenant BK. The
dental technicians in commercial dental laboratories presence and identification of organisms transmitted to
in Jordan. Only five of 200 (2.5 percent) technicians dental laboratory. J Prosthet Dent 1990;64(2):235-6.
complied with all infection control procedures, a 9. Williams HN, Falkler WA Jr, Hasler JF, Libonati JP. The
percentage that is very disappointing and represents recovery and significance of nonoral opportunistic patho-
genic bacteria in dental laboratory pumice. J Prosthet Dent
the lowest compliance among published data from 1985;54:725-30.
several different nations.14 10. Sande MA, Gadot F, Wenzel RP. Point source epidemic
of Mycoplasma Pneumonia infection in a prosthodontic
laboratory. Am Rev Respir Dis 1975;112:213-7.
Recommendations 11. Council on Dental Therapeutics, Council on Prosthetic
Services and Dental Laboratory Relations. Guidelines for
The most important strategy to improve com- infection control in the dental office and the commercial
dental laboratory. J Am Dent Assoc 1985;110:969-72.
pliance is to provide formal and obligatory infection 12. Qudeimat MA, Farrah RY, Owais AI. Infection control
control courses and guidelines for dental technicians knowledge and practices among dentists and dental nurses
by the Jordanian Dental Technology Association. In at a Jordanian university teaching center. Am J Infect
addition, standard infection control manuals that Control 2006;34(4):218-22.
incorporate current recommendations should be 13. Al-Omari MA, Al-Dwairi ZN. Compliance with infection
control programs in private dental clinics in Jordan. J Dent
disseminated. As for dental technology students,
they should be educated about this important issue 14. Akeredolu PA, Sofola OO, Jokomba O. Assessment of
as a component of their curriculum. These instruc- knowledge and practice of cross infection control among
tions should be updated as required; there should be Nigerian dental technologists. Niger Postgrad Med J
individual counseling, post-exposure evaluation, and 2006;13(3):167-71.
follow-up to prevent any misunderstanding about the 15. Kimondollo PM. Developing a workable infection
control policy for the dental laboratory. J Prosthet Dent
procedures and to cover any exposure incidents that 1992;68(6):974-8.
could happen in the dental clinics and laboratory. 16. Jagger DC, Huggett R, Harrison A. Cross-infection in
Considering the limitations of this study, more dental laboratories. Br Dent J 1995;179:93-6.
research is needed to provide comprehensive data on 17. Henderson CW, Schwartz RS, Herbold ET, Mayhew RB.
compliance with all recommended infection control Evaluation of the barrier system: an infection control
system for the dental laboratory. J Prosthet Dent 1987;58:
programs by dental technicians. Inclusion of a greater 517-21.
observational element within the study design may 18. Miller CH, Palenik CJ. Infection control and management
help to reduce the socially desirable responses result- of hazardous materials for the dental team. 2nd ed. St.
ing from the questionnaire currently available.23 Louis: Mosby, 1998.
19. Garn RJ, Sellen PN. Health and safety in the laboratory.
Dent Tech 1992;45(1):103.
REFERENCES 20. McNeill MR, Coulter WA, Hussey DL. Disinfection of ir-
1. Verran J, Kossar S, McCord JF. Microbiological study reversible hydrocolloid impressions: a comparative study.
of selected risk areas in dental technology laboratories. J Int J Prosthodont 1992;5(6):563-7.
Dent 1996;24:77-80. 21. Verran J, Winder C, McCord JF, Maryan CJ. Pumice
2. Witt S, Hart P. Cross-infection hazards associated with slurry as a cross infection hazard in nonclinical (teach-
the use of pumice in dental laboratories. J Dent 1990;18: ing) dental technology laboratories. Int J Prosthodont
3. Sofou A, Larser T, Fiehn NE, Owell B. Contamination 22. Seals RR Jr, Funk JJ. Minimizing cross-contamination
level of alginate impressions arriving at a dental labora- from dental pumice. J Prosthet Dent 1992;67(3):425-6.
tory. Clin Oral Investig 2002;6:161-5. 23. Al-Rabeah A, Mohamed AGI. Infection control in the
4. Kugel G, Perry RD, Ferrar M, Lalicata P. Disinfection private dental sector in Riyadh. Ann Saudi Med 2002;
and communication practices: a survey of U.S. dental 22:1-2.
laboratories. J Am Dent Assoc 2000;131(6):786-92.
September 2007 ■ Journal of Dental Education 1227