disinfection of dental impressions

1. Disinfection Of Impressions
Presented By
Dr Mali Tejaswi
Department Of Prosthodontics, Crown And Bridge
& Implantology
P.G I year
Ragas Dental College And Hospital

2. CONTENTS:
Introduction
Definition
Types of disinfectants
Methods of disinfection
Disinfection procedures
Cross infection control
Dimensional stability
Clinical implications
Conclusion

3. Disinfection:
The destruction or removal of all
pathogenic organisms, or organisms
capable of giving rise to infection.

4. Introduction:
It is important that impressions are
disinfected prior to their being sent to the
laboratory for the manufacture of models
and/or prostheses to protect the laboratory
staff from the transmission of infection from
patients.

5. Various Disinfectants:
•Acidic and alkaline compounds
•Chlorine and derivatives
•Quaternary ammonium compounds
•Amphoteric compounds
•Phenolic compounds
•Peracetic acid and hydrogenperoxide
•Iodine compounds
•Ozone
•Aldehyde compounds
•Biguanides

6. Methods Of Disinfection Of Impressions
Mainly:
•Immersion method
•Spray method
Others:
•Ozonated water
•UV chamber
•Ultrasonic

7. The disinfection of impressions poses
particular problems as
-some materials are water based (dental
plaster and the hydrocolloids),
-some are subject to water uptake and/or
loss (hydrocolloids and poly-ethers)

8. Irreversible Hydrocolloid:
(Alginate)
According to Phillip’s (11th edition):
Recommended disinfectant:
Chlorine compounds or iodophors
Method:
Immersion
Short-term exposure time (<10 min for alginate)
Note:
Short-term glutaraldehyde has been shown to be acceptable;
but time is inadequate for disinfection.
-According to Richard Van Noort
Internal disinfection is another possibility for alginate.

9. Disinfection:
•Relatively rapid to prevent dimensional change.
•Used according to manufacturer’s instructions.
- An alternative disinfection method is by
immersion, but this should not exceed 10 min.

10. Use household bleach (1 to 10 dilution), iodophors, or
synthetic phenols.
After rinsing the impression thoroughly, disinfectant
sprayed on exposed surface.
Impression wrapped immediately in disinfectant-soaked
paper towel and placed in a sealed plastic bag.
After 10 min, impression is unwrapped, rinsed, and
shaken to remove excess water.
The impression is then poured.
Protocol recommended by “centre for disease
control” –

11. Reversible Hydrocolloid:
•Agar impression materials can be immersed in sodium
hypochlorite solutions, iodophor or glutaraldehyde with
phenolic buffer.
•It is important that the manufacturer's instructions are
carefully followed with regard to dilution and immersion
time.
•The immersion time should on no account exceed 30 min.
•Another potential hazard with agar is associated with the
danger of crosscontamination from the conditioning baths.

12. Impression Compound:
Recommended disinfectant:
Iodophors or chlorine compounds.
Method:
Immersion preffered.
Spraying can be used for bite registrations.
Note:
Phenolic spray can be used.

13. Disinfection:
Recommended disinfectant solution for compuond –
2% alkaline glutaraldehyde solution
Impression is immersed for required amount of time
Rinsed and poured immediately.
Acc To William O Brien-
•Dental impression compound can be disinfected by immersion
in sodium hypochlorite, iodophors, or phenolic glutaraldehydes.
•The manufacturer's recommendations for proper disinfection
should be followed.

14. Zinc Oxide Eugenol Impression Paste:
Recommended Disinfectant:
Iodophors or chlorine compounds.
Method:
Immersion
Note:
•Not compatible with chlorine compounds.
•Phenolic spray can be used.
Neither dimensional stability nor surface detail
sharpness of zinc oxide-eugenol impressions was
affected by 1-hour immersion in the disinfectants.
Dimensional stability and surface detail sharpness following treatment with
Disinfection solutions. Bergman, M.; O lsson, S.; Swed Dent J -1980; cited- 101

15. Disinfection:
Recommended disinfectant solution for ZOE impression paste
–
2% alkaline glutaraldehyde solution
Impression is immersed for required amount of time
Rinsed and poured immediately.

16. Polysulfide Silicone:
Recommended Disinfectant:
Glutaraldehyde
Chlorine compounds
Iodophors
Phenolics
Method:
Immersion
Note:
Disinfectants requiring more than 30-min exposure times are
not recommended.

17. Studies using a wide range of disinfectants and
periods of immersion varying from 10 to 30 minutes
indicate that no adverse effects are observed with
polysulphide impression materials and that spray
disinfectants are also acceptable.
A comparison of conventional and ultrasonic
cleaning of polysulfide impressions by Lorton et al.
(1978)., demonstrated that ultrasonic cleaning was
equally as efficient as conventional methods, and no
increase in accuracy was observed.

18. Polyether:
Recommended disinfectant:
Chlorine compounds or iodophors
Method:
Immersion
Short exposure time(<10 min)
Note:
ADA recommends any of the disinfectant classes;
However, short-term exposures are essential to avoid
distortion.

19. Polyether impression materials-
•Known to expand when exposed to moisture.
•Immersion in a variety of disinfectants causes excessive
swelling after 10 minutes. Dimensional changes become highly
significant after 4 hours immersion in 10% aqueous succinic
aldehyde, but are acceptable after 10 minutes immersion.
•Spray disinfectants are acceptable.
•Recommendation - use of spray disinfectant or immersion in
products with a short disinfection time <10 minutes), such as
chlorine compounds.

20. Condensation Silicones:
Although condensation-cured silicones are
chemically unaffected by prolonged immersion
in a wide variety of disinfectants, the limiting
factor with this impression material is its
inherent dimensional instability.
(Textbook of introduction to dental materials by Richard Van Noort)

21. Addition Silicones:
•Many studies have been undertaken of the effects of
disinfectants on the dimensional stability of addition-cured
silicones.
•They conclude that no adverse effects result from even an
extended exposure (up to 18 hours) of addition-cured
silicones to all varieties of disinfectants.
•Only drawback appears to be a reduced wettability of the
model material on the set impression for the hydrophilic
silicone impression materials.

22. High-level disinfectant solutions (Cavicide,
Cidex Plus, Coecide XL) that belong to
different chemical groups (glutaraldehyde and
chlorine phenols) at different concentrations
(2% and 3.5%) did not affect the accuracy
and dimensional stability of polyether and
polyvinyl siloxane impression materials after
immersion for 30 or 60 minutes.
(Effects of chemical disinfectant solutions on the stability and
accuracy of the dental impression complex- Maria de Pilar Rios et
al., JPD-1996)

23. The American Dental Association suggests:
Immersion for 30 minutes in a glutaraldehyde-
based disinfectant for Polysulphide and
Condensation- and Addition-cured silicone
impression materials.
Chlorine compound spray disinfectant for
irreversible Hydrocolloid and Polyether impression
materials.
However, it is important in each case that the manufacturer’s
recommendations are adhered to.
(Textbook of introduction to dental materials by Richard Van Noort)

24. Current recommendations in the UK would then suggest –
All impressions should be further disinfected by
immersing them in sodium hypochlorite solution at a
concentration of 10 000 parts per million available
chlorine for 10 minutes.
This immersion time is sufficient to inactivate most
oral micro-organisms (Including HIV and HBV),
whilst at the same time avoiding distortion of
impressions.

25. Cross Infection Control:
•The first stage in prevention of transmission from the
patient to the technician is to carefully rinse the
surface of the impression to remove gross
contamination with blood or saliva.
•Aerosol-based disinfection processes are not
satisfactory.
•Glutaraldehyde and sodium dichloroisocyanate
solutions have also been advocated.

26. Recently developed disinfectants such as sodium
peroxymonosulphate (which is active in a 2% solution
against bacteria, fungi and viruses) are likely to
overcome many of the handling and storage problems
of sodium hypochlorite.
This product is effective with a 10 minute immersion
period and can be used with the full range of dental
impression materials, with the exception of the
reversible hydrocolloids.

27. Disinfection of dental impressions via short-term
immersion in 0.5% or 1% sodium hypochlorite does
not significantly affect the dimensional accuracy of
the resultant casts. In addition, immersion in
glutaraldehydes, povidone-iodine diluted in water,
or halogenated phenol has no apparent effect on
the dimensional stability of rubber impression
materials.
Dimensional stability of dental impressions after immersion disinfection
S. Pamela Herrera, MS, DDS,Virginia A. Merchant, MS, DMD
JADA – 1986: Cited- 136

28. The Disinfectant Protocol Used In A Study Included;
A 60-second “pretreatment”
Immersed in the disinfectant solution and swirled for 60
seconds.
Rinsed, dried, and placed in the main disinfectant bath.
•In a clinical setting, this procedure will minimize the
number of microorganisms that enter the main disinfectant
bath and theoretically prolong the useful life of the
disinfectant.
(Effects of chemical disinfectant solutions on the stability and accuracy of the
dental impression complex- Maria de Pilar Rios et al., JPD-1996), cited- 90.

29. CLINICAL IMPLICATIONS
Disinfectant sprays are commonly used to treat
impressions, and certain dentists have been reluctant
to soak impressions because of fear of distortion.
Nevertheless, aerosol treatment of an impression
with a disinfectant may not be as effective in
destroying microorganisms as a 30- or 60-minute soak
in a high-level disinfectant.

30. Studies have shown that the disinfectant solutions used did
not affect the accuracy and dimensional stability of polyether
or polyvinyl siloxane impressions when measured up to 48
hours after immersion.
Dentists should be encouraged to disinfect impression
materials as a routine procedure for infection control
procedures.
(Effects of chemical disinfectant solutions on the stability and accuracy of the
dental impression complex- Maria de Pilar Rios et al., JPD-1996)

31. Conclusion:
• Disinfection of dental impressions must be undertaken
to prevent transmission of bloodborne viruses to
members of the dental team.
• The correct dilution of the disinfection agent should be
observed.
• The dentist should indicate clearly to the dental
technician that disinfection has been undertaken.
• Repeat disinfection of impressions by technicians risks
their dimensional stability.
Disinfection Of Dental Impressions – Compliance To Accepted Standards
N. Almortadi and R. G. Chadwick- BDJ 2010