Journal ClubClinical 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

Purpose

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

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.

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

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.

Impressions• Alginate impression –maxillary arch– patient• Alginate impression –maxillary arch–typodont• Separated impressions were left undisinfected

(controls) or underwent a disinfection treatment

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

Disinfection treatments

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.

• 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.

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.

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.

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.

Microbial Colonies on Non-Disinfected Impressions

Reduction in Colony Growth Area

Disinfection of Oral Pathogens on Dental Impressions

Disinfection and Sterilization

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.

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.

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

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.

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

Hygojet system

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

Combined Use of Agents

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.

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

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.

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.

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.

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.

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.

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

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.

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.

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.

Thank you