[Factors involved in microbial colonization of acrylic resins].

Unlabelled: The objective of this study was to evaluate the effect of polishing technique and the polymerisation type on the microbial colonization of acrylic resins.

Material And Methods: The studied resins were: Castapress/Vertex, Prothyl Hot/Zermack, Duracryl Plus/Spofa Dental, Vertex-Soft/Vertex, Superacryl Plus/Spofa Dental. Ten specimens, two for every resin, presenting dimensions of 50/25/2 cm were done. One sample of each resin was polished with extrahard tungsten carbide burs, the other sample being polished with extrahard extrafine and diamond burs. The final polishing was done using a conventional method: pumice, water and lathe bristle brush for 90 seconds, 1500 rpm and soft leather polishing wheel for 90 seconds, 3000 rpm. One sample of Duracryl Plus was glazed after polishing with Glaze/Bosworth. Vertex Soft specimens were not polished because it is a resilient material. The samples were immersed in human saliva for 24 hours and after that were colored with May Grunwald Giemsa (MGG). The total germs number (TGN) was determined by Buiuc method.

Results: The lowest value of the microbial colonization was related to the heat-curing resins treated by conventional polishing combined with glazing techniques.

Conclusions: The results noticed that the type of acrylic resin (autopolymerizing and heat-cured) and the polishing techniques have a significant influence on the microbial colonization. Specimens of self curing resin had a higher porosity than heat curing resin after the same surface treatment, generating a higher TGN.