Aerobic bacterial contamination in dental materials

Microbiological appraisal of three different brands of commercially available irreversible hydrocolloid impression materials: an in vitro study

AIM

To evaluate factory-sealed containers of three different commercially available irreversible hydrocolloid impression materials for their microbial contamination and the type of microorganisms present.

MATERIALS AND METHODS

Thirty-six measured samples were taken of each brand and placed on chocolate agar plates or in thioglycolate broth tubes and were incubated along with appropriate parallel controls. After incubation, colonies were enumerated and identified using standard microbiological methods.

RESULTS

The three brands contained viable microorganisms in 90% of the samples. Samples from the top, middle and bottom layers had approximately equal contamination frequencies. The concentration of organism varied from 25 to 74 CFUs per gram of contaminated sample.

CONCLUSION AND CLINICAL SIGNIFICANCE

The samples contained viable microorganism which may be potentially dangerous to immunocompromised patients.

Bacterial, fungal and yeast contamination in six brands of irreversible hydrocolloid impression materials

This study assessed the level of contamination of six commercially available irreversible hydrocolloids (two containing chlorhexidine) and identified the contamination present in the materials. Petri dishes containing selective and enriched culture media were inoculated with alginate powder (0.06 g), in triplicate. After incubation (37 degrees C/7 days), the colony-forming units (CFU) were counted and Gram stained. Biochemical identification of the different morphotypes was also performed. The contamination levels for the materials were: Jeltrate--389 CFU/g; Jeltrate Plus--516 CFU/g; Jeltrate Chromatic--135 CFU/g; Hydrogum--1,455 CFU/g; Kromopan--840 CFU/g; and Greengel--59 CFU/g. Gram staining revealed the presence of Gram-positive bacillus and Gram-positive cocci. The bacteria Staphylococcus epidermidis, Bacillus subtilis, Bacillus sp., Bacillus coagulans, Bacillus licheniformis, Bacillus cereus, Micrococcus luteus, and Nocardia sp.; the filamentous fungi Aspergillus niger, Aspergillus flavus, Rhizopus sp., Neurospora sp.; and the yeast Candida sp. were isolated. The contamination detected in the impression materials points out the need for adopting measures to improve the microbiological quality of these materials. The use of contaminated materials in the oral cavity goes against the basic principles for controlling cross-contamination and may represent a risk for debilitated or immunocompromised patients.

Intraoral vesicles occurring after alginate impressions

In 47 of 227 dental students intraoral vesicles developed after multiple alginate impressions. The lesions were generally solitary and clear, and appeared within 24 to 48 hours after the impression. They were most frequently located inside the vermilion border of the lips and resolved spontaneously in 2 to 5 days. The purpose of this study was to determine the cause of these reactions. Histopathologically one lesion was suggestive of a contact allergy. Cutaneous patch tests, which proved negative, were performed on 14 students to determine whether an allergy to the alginate flavoring existed. The surface of three lesions were cultured and the organisms identified. Contamination studies were carried out on seven unopened containers of the alginate powder and resulted in the isolation of some organisms similar to the mucosal cultures; however, no relationship can be proved. These findings indicate that the cause of the vesicles remains unknown, and further studies are necessary to establish the cause.

Microbial contamination in two antimicrobial and four control brands of alginate impression material

Previous investigations have revealed commercial alginate impression material to be contaminated with viable microorganisms. Some manufacturers are now producing alginate materials that contain antimicrobial agents. The purpose of this study was to test and compare two antimicrobial and four control brands without antimicrobial agents of commercial dental alginate impression material for the presence of viable microorganisms. Forty-eight or 96 measured samples of each brand were taken from previously unopened containers using a sterile technique. The samples were placed on chocolate agar plates and in thioglycolate broth tubes and were incubated along with appropriate parallel controls. After incubation, colonies were enumerated, gram-stained, and identified using standard microbiologic methods. The two antimicrobial brands contained viable organisms in 12.5% of the samples incubated on agar media and also contained such organisms from 0% to 16.7% of the samples incubated in thioglycolate media. The four control brands contained viable organisms in from 29.2% to 100% of the samples incubated on agar media and also contained these organisms in from 25% to 79.2% of the samples incubated in thioglycolate media. There was a statistically significant difference (p less than 0.05) in contamination frequencies among some brands. Contamination frequencies of the top and middle portions of the containers did not differ significantly. The concentration of organisms in contaminated samples was 2.8 colony-formed units (CFUs) per gram for the antimicrobial alginates, and from 9 to 161.1 CFUs per gram for the control brands.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial contamination in irreversible hydrocolloid impression material and gingival retraction cord

This study tested two dental materials in factory-sealed containers for the presence of bacteria that may be a source of infection. Twenty samples of two dental materials found to have contamination in a pilot study were taken from unopened containers using a sterile technique. The samples were inoculated onto chocolate agar plates and into thioglycolate broths with appropriate controls. Plates were examined, colonies were enumerated, Gram stained, and identified. The resulting contamination frequencies were compared for statistical significance using Fisher's exact test. Organisms were isolated from 10% of the negative inoculation control agar plates, while none of the control broths showed contamination. The alginate (irreversible hydrocolloid) showed contamination in 50% of the plates and in 65% of the broths (p less than 0.05). The retraction cord had a small sample size and yielded organisms on 5% of the sample plates and in 20% of the thioglycolate broths (p greater than 0.05).

Microbial contamination in four brands of irreversible hydrocolloid impression materials

A previous investigation showed unopened irreversible hydrocolloid impression material to be contaminated with viable microorganisms. This study tested and compared four brands of commercial irreversible hydrocolloid impression material in factory-sealed containers for the presence of viable microorganisms. Twenty-four measured samples of each brand were taken from previously unopened containers using a sterile technique. The samples were placed on chocolate agar plates or in thioglycolate broth tubes and were incubated along with appropriate parallel controls. After incubation, colonies were enumerated, stained with Gram's stain and identified using standard microbiologic methods. The four brands contained viable organisms in 50% to 100% of the samples incubated of agar media, and in 12% to 67% of the samples incubated in thioglycolate media. Samples from the top and middle portions of the containers had approximately equal contamination frequencies. The concentration of organisms varied from 12 to 82 colony-formed units per gram of contaminated sample. Most organisms isolated were common environmental contaminants. These samples contained viable microorganisms which, during routine use, may present a hazard to immunocompromised patients.