الفهرس 
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Abstract
Dental impressions can transmit serious diseases to dental staff, because they are in
contact with saliva and blood from the patients and they can transfer microorganisms to the
stone casts. Some of these microorganisms survive by a very long time, even when they
are outside the mouth fluids, which is a potential health risk. In this way, all impression
must be disinfected before being sent to prosthetic laboratories or by the time they arrive
there, avoiding the spread of cross-infection.
Disinfection protocols have been recommended to prevent technicians from exposure
to infectious diseases such as hepatitis B, hepatitis C, tuberculosis, herpes, and AIDS.
Additionally, communication between prosthodontists and their dental laboratories
concerning particular disinfection practices could eradicate a potential problem.
The present study was conducted to assess the current practices of cross infection
control measures of dental impressions in governmental dental laboratories and
prosthodontic clinics.
A descriptive study design was used which included self-administered checklists on
50 impressions about infection control measures taken by dental technicians and dentists
from 7 different dental clinics and 6 laboratories in Alexandria.
Based on the results of the present study, there was a verbal communication between
dental clinics and dental laboratories about dental impression disinfection.
Despite that the majority of prosthodontists participating in the study routinely rinse
the preliminary/ final impressions prior to sending them to the dental laboratory, there were
a percent of prosthodontists who did not rinse the impression.
The vast majority(84%) of dental impressions in the present study were disinfected
and only a small percent dental impressions did not undergo any disinfection process
which indicate increased awareness regarding the importance of dental impression
disinfection among prothodontists and also dental technicians.
All dental impressions were disinfected chemically by sodium hypochlorite but with
different concentrations (1:10), (1:50) and (1:1). Nearly all disinfection processes took
more than 10 minutes which indicate that there was no correlation between disinfectant
concentration and contact time. Sodium hypochlorite (1:1) dilution is very high and not
recommended to use. The majority of disinfection processes in the present study were in
the form of immersion method.
Procedure of impression disinfection should ideally be taken care of at the dental
clinic level soon after the dental impression is made. In the present study 48% of dental
impressions were disinfected in the dental laboratory, (36%) of them were disinfected in
the dental clinic, while the rest (16%) of dental impressions did not undergo any
disinfection process.
Impressions should be suitably packaged when being sent to the laboratory. In the
present study only 34.0% of total impressions were delivered packed to the dental
laboratory.
Summary and Conclusion
51
Three of six dental laboratories included in this study have a special designated
receiving/disinfection area separate from other work areas .while the other half do not
which indicate lack of proper guidelines on receiving dental impressions. For the dental
laboratories that carried out disinfection despite not having special disinfection areas,
disinfection was performed in the dental plaster area. This is considered an eminent risk
because it can result in cross-infection between newly received impressions and the
disinfected ones.
As regard to personal protective equipment adherence during disinfection process in
dental clinic and dental laboratory, dental impressions disinfection processes have been
carried out with 100% adherence to both gloves and protective clothing. Protective goggles
were not used at all which necessitate clarification of the importance of using protective
goggles for protection of eyes from any contaminated splashes.
Hand hygiene is regarded as one of the most important element of infection control
activities. In the present study, the majority of prothodontists perform hand hygiene only
after impression taking while a small percent perform hand hygiene before and after
procedure.
Also all 100% impression trays have been cleaned and sterilized after their use which
is the ideal practice for dental impression trays decontamination. According to the Centers
for Disease Control and Prevention (CDC) heat-tolerant items used in the mouth should be
heat-sterilized before being used on another patient.
Disinfectants must be used to decontaminate non-sterilable apparatus like plastic
mixing spatula, rubber bowl. Concerning mixing spatula, in the present study more than
half 56% of them have been cleaned and sterilized, 34% were cleaned and disinfected. As
regard the mixing rubber bowl the majority 82% have been cleaned and disinfected and the
rest 18% were only cleaned.
Concerning the awareness on infection control amongst prosthodontists and dental
technicians nearly all of them received theoretical lectures about infection control
measures, but non received any practical demonstrations.