Please cite this article as: Rentzia A, Coleman DC, O'Donnell MJ, Dowling AH, O'Sullivan M, Disinfection procedures: their efficacy and effect on dimensional accuracy and surface quality of an irreversible hydrocolloid impression material, Journal of Dentistry (2010Dentistry ( ), doi:10.1016Dentistry ( /j.jdent.2010 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 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 on the cast were evaluated by means of optical profilometry. The efficacy of the disinfection procedures againstPseudomonas aeruginosa was evaluated by determining the number of colony forming units (cfu) recovered after disinfection of alginate discs inoculated with 1x10 6 cfu for defined intervals. Results:The dimensional accuracy of the gypsum casts was not significantly affected by the disinfection protocols. Neither disinfectant solution nor immersion time had an effect on the surface roughness of the "smooth" area on the cast, however, a significant increase in surface roughness was observed with increasing immersion time for the "rough" surface. Complete elimination of viable Pseudomonas aeruginosa cells from alginate discs was obtained after 30 and 120 s immersion in Cidex OPA ® and NaOCl, respectively. Conclusions:Immersion of irreversible hydrocolloid impressions in Cidex OPA ® for 30 s was proved to be the most effective disinfection procedure.