journal club on disinfection of oral impressions

1. Journal Club
Clinical Evaluation of the Efficacy of
Removing Microorganisms to Disinfect
Patient-Derived Dental Impressions
Egusa et al, Int J Prosthodont 2008; 21:531-538
Presented by: Dr. Rohan Bhoil

2. Purpose
• Clinically evaluate the disinfection efficacy of
commercially available agents in removing
oral pathogens from patient-derived
impressions.

3. Background
• Disinfection of dental impressions is
indispensable for control of cross-
contamination; however there is limited
information on the efficacy of disinfection
under clinical conditions.

4. Materials and Methods
• Impressions from 54 adult patients with mean
age 53.6 years divided into groups and were
disinfected or left un-disinfected.
• Inclusion criteria -
– No complete denture on either jaw
– More than 10 teeth present in maxilla
– Age over 20 years
– Had not received oral hygiene / tooth brushing
instructions

5. Materials and Methods
• Alginate impression material (Aroma Fine, GC
Corporation), rubber bowl, spatulas,
polyethylene containers and boxing wax were
sterilized with ethylene oxide.
• Impressions trays were sterilized by
autoclaving.

6. Impressions
• Alginate impression –maxillary arch– patient
• Alginate impression –maxillary arch–typodont
• Separated impressions were left undisinfected
(controls) or underwent a disinfection
treatment

7. Disinfection agents
• 2% glutaraldehyde (GA)
• 1% sodium hypochlorite (SH)
• 0.25% benzalkonium chloride (BC)
• 1ppm ozonated water (OW)
• Hygojet / MD520 system (HJ)
• Combined use of 0.25% BC with either 2% GA or
1% SH

8. Disinfection treatments

9. Impression Culture
• The two halves of impression were placed in a
sterile polyethylene container with two
compartments.
• Brain Heart Infusion agar medium was poured
onto surface side of impression
• 1 hr cooling at 40 C, the agar was aseptically
separated from impression and incubated at 370 C
aerobically for 48 hrs.

10. • Photographs of impression culture surface
were taken and existence of colonies was
determined by visual observation.
• Colony area on impression surface was
analyzed by Poplmaging software version
3.61.
• The percentage reduction of colony area
following disinfection was
calculated and steel-dwass
comparison test used to assess
the difference.

11. Microbial Isolation
• Colonies on surface of BHI impression culture
for the samples were collected by sterile
cotton swab.
• They were suspended in 1ml of sterile
phosphate-buffered saline.
• The suspension was plated on 5 selective agar
medium plates.

12. Selective Agar Medium Plates
• Mitis-salivarius agar, Candida GE agar, Mannitol
salt agar, OPAII Staphylococcus agar, and P
aeruginosa selective agar medium.(Becton
Dickinson)
• To detect presence of Streptococcus mutans,
Candida, Staphylococci, MRSA, and P aeruginosa
respectively.
• 48 hrs of incubation under aerobic conditions at
370 C, existence of positive colonies for each
selective medium was determined visually
according to the manufacturer’s instructions.

13. Results
• A large number of colonies were seen on the
samples of alginate impressions
• They varied in colour, size and form
• Mainly over areas of hard palate and dental arch
• No live colonies were seen
on impression cultures of
negative controls from sterilized
typodonts.

15. Microbial Colonies on Non-
Disinfected Impressions

16. Reduction in Colony Growth Area

17. Disinfection of Oral Pathogens on
Dental Impressions

18. Disinfection and Sterilization

21. Running Water
• Was the recommended practice until 1991
• Helps remove certain amount of saliva, blood and
debris.
• Cannot effectively remove
oral pathogens and may spread
a significant number of
remaining bacteria over surface
of impression material
• Inadequate method without
use of a disinfectant.

22. 1 ppm Ozonated Water
• Acts against bacteria, fungi and viruses.
• Insufficient disinfection, following 10 min of
immersion in 1ppm ozonated water.
• Can be used as a soaking solution for medical
instruments if used properly.
• Can be mutagenic if used for
a long period and in high
concentrations.

23. 1% Sodium Hypochlorite
• An intermediate level disinfectant
• May not destroy spores but is active against
tubercle bacilli, HIV & HBV.
• Immersion for 10 min in 1% solution, disinfects
the impression but does not sterilize it.
• Potentially existing opportunistic
pathogens like MRSA may transfer
to healthy personnel

24. 2% Glutaraldehyde
• A high-level disinfectant
• Inactivates spores and microbial forms including
HIV & HBV
• Exposure to 2% conc at room temperature results
in disinfection after 10 min, but sterilizes only
after 10 hours.
• Disinfection is only partially
successful against streptococci
and staphylococci.

25. Hygojet / MD520 System
• Active ingredients of this solution are 0.5%
glutaraldehyde, 0.25% ammonium chloride, special
surfactants and complexing agents.
• Uses a disinfectant spray procedure in a closed
chamber.
• Impression sprayed with solution for 10 seconds,
stored for 10 min in closed chamber and rinsed for 10
seconds with water in Hygojet chamber.
• Highest disinfection efficacy
• Does not significantly influence
quality of surface of gypsum.
• Recommended for clinical & lab use

26. Hygojet system

27. 0.25% Benzalkonium Chloride
• A quaternary ammonium compound
• A low-level disinfectant, unacceptable for disinfection
of contaminated impressions as it cannot inactivate
spores, HIV & HBV.
• However study found it effective in removing examined
oral pathogens as the Hygojet system.
• Active ingredient is a surface Active agent: alkyl
dimethyl benzyl ammonium chloride
• Surfactant action may also help
clear saliva, blood and debris.
• Recommended to add 0.25% of this
agent to general disinfection
solutions like 2% GA or 1% SH

28. Combined Use of Agents

29. Conclusion
• Contaminants like Candida, MRSA, P aeruginosa are
present on impressions even after general
disinfection procedures like immersion for 10 min in
2% glutaraldehyde or 1% sodium hypochlorite.
• From viewpoint of microbiologic effectiveness and
dimensional accuracy, Hygojet/MD520 system can
be recommended for clinical or laboratory use;
alternatively, the use of surfactants like 0.25%
benzalkonium chloride together with high or
intermediate level disinfectants like 2%
glutaraldehyde or 1% sodium hypochlorite.

30. Critique
• Study does not evaluate efficacy of
disinfection procedures against
viruses or cross-infection with HIV
& HBV.
• It does not focus upon the changes
associated with the use of
disinfectant solutions on the
dimensional accuracy of
impression materials or surface
characteristics of gypsum
products.
• Does not dwell upon prevalence of
cross infection from impression
related procedures.
• No statistical evaluation of findings

31. Cross References
Effect of disinfectant agents on dimensional stability of
elastomeric impression materials
Adabo et al (J Prosthet Dent 1999;81:621-4.)
They compared the effect of disinfectant agents on
dimensional stability of elastomeric impression
materials. Impressions were immersed in 5.25% sodium
hypochlorite solution for 10 minutes, immersion in 2%
glutaraldehyde solution for 30 minutes, and no
immersion (control).
They found that the elastomeric materials had different
reproduction capacities, and the disinfecting treatments
did not differ from the control.

32. Disinfection procedures: Their efficacy and effect on
dimensional accuracy and surface quality of an
irreversible hydrocolloid impression material
Rentzia et al -- Journal Of Dentistry 39 ( 2011 ) 133 – 140
They investigated the antibacterial efficacy and effect of 0.55%
orthophthalaldehyde (Cidex OPA1) and 0.5% sodium
hypochlorite (NaOCl) on the dimensional accuracy of gypsum
casts retrieved from an irreversible hydrocolloid impression
material.
They found that the dimensional accuracy of the gypsum casts
was not significantly affected by the disinfection protocols and
Immersion of irreversible hydrocolloid impressions in Cidex
OPA1 for 30 s was proved to be the most effective disinfection
procedure.

33. A Survey of Disinfection of Irreversible Hydrocolloid
and Silicone Impressions in European Union Dental
Schools: Epidemiologic Study
Bolla et al -- Int J Prosthodont 2004;17:165–171
This study demonstrated that there are no universally
recognized impression disinfection procedures, which
could be explained by the lack of dental literature that
provides precise guidance about how specific
impression materials should best be disinfected to
balance the goals of safety and accuracy.

34. The Persistence of Microorganisms on
Impression Materials Following Disinfection
Jennings et al, Int J Prosthodont 1991; 4:382-387
They found that disinfection procedures were
more effective and there was less persistence of
microorganisms in relation to poly vinyl siloxane
and polysulfide impression materials as compared
to the irreversible hydrocolloids.

35. Disinfection of Irreversible Hydrocolloid Impressions:
A Comparative Study
McNeil et al, Int J Prosthodont 1992; 5:563-567
They evaluated the efficacy of disinfection
systems on irreversible hydrocolloid impressions
contaminated with Streptococcus sanguis or poliovirus
and found that the impression materials could act as a
vehicle for the transfer of both bacteria and viruses.
Further, the viruses were shown to be present in the
body of the impression and under certain conditions
could evade decontamination.

36. Antimicrobial Effects From Incorporation of
Disinfectants Into Gypsum Casts
Mansfield et al, Int J Prosthodont 1996;4:180-185.
They spatulated type IV dental stone with disinfectant
solutions, before pouring them into intentionally
contaminated impressions and found that
incorporation of sodium hypochlorite, glutaraldehyde,
and iodophor into gypsum casts reduced the viable
bacteria to a level equal to the negative controls at 24
hours

37. The influence of different disinfectants
on primary impression materials
Bock et al, Quintessence Int 2008;39:264.e93–98
Different impression disinfection methods have
only a marginal influence on dimensional
stability and surface quality of dental casts. To
achieve a higher precision, the use of an addition
silicone can be recommended.

38. High- level microwave disinfection of dental
gypsum casts
Berg et al, Int J Prosthodont 2005; 18:520-525
They found that microwave oven irradiation can
disinfect gypsum casts in compliance with
current disinfection requirements, and this
method was more effective than gypsum casts
poured from chemically disinfected
impressions.

39. Ultrasonically nebulised electrolysed oxidising water:
a promising new infection control programme for
impressions, metals and gypsum casts used in dental
hospitals
Wu et al, Journal of Hospital Infection; Vol 68, Issue 4, April
2008, Pages 348–354
They found that the disinfection efficacy and
dimensional changes in resulting gypsum casts, fared
better with exposure to UNEOW for 30-45 min; as
compared with immersion in 1% Sodium hypochlorite
for 10 min or immersion in electrolysed oxidising
water for 10 min.

40. Thank you