Disinfection procedures: efficacy and effect on an irreversible hydrocolloid impression material
Objectives: This study investigated the antibacterial efficacy and effect of 0.55% ortho-phthalaldehyde (Cidex® OPA) and 0.5% sodium hypochlorite on the dimensional accuracy, surface quality, and detail reproduction of gypsum casts retrieved from an irreversible hydrocolloid impression material (Hydrogum). Methods: A simulated clinical cast and technique was developed to compare the dimensional and surface quality changes of the test gypsum casts with controls. Dimensional accuracy measurements were completed between fixed points using a travelling microscope under low angle illumination at a magnification of X3. Surface quality changes of smooth and rough areas were evaluated by means of contact profilometry. Detail reproduction was evaluated in accordance with the ADA Specification No 18 for alginate impression material. The efficacy of the disinfection procedures against Pseudomonas aeruginosa, was evaluated by counting the number of cfu/mL recovered after disinfection of alginate discs inoculated with a culture of 1x107 cfu/mL bacterial density. Results: The dimensional accuracy of the gypsum casts was not affected by the disinfection protocols. Neither solution nor time had an effect on the surface roughness of the smooth area on the cast, while immersion for 60 seconds in ortho-phthalaldehyde or 300 seconds in 0.5% sodium hypochlorite increased the roughness of the rough area. Detail reproduction on the gypsum casts was affected by the disinfection protocols. Complete elimination of Pseudomonas aeruginosa colonies was obtained after 30 and 120 seconds immersion in ortho-phthalaldehyde and 0.5% sodium hypochlorite respectively. Conclusion: Immersion of hydrocolloid impressions in ortho-phthalaldehyde for 30 seconds was proved to be the most effective disinfection procedure.