Use of removable appliances in the treatment of orthodontic patients may lead to traumatic injury. Pathologic changes could occur by using improper equipment. For this reason we have planned to compare different types of acrylic bases. Two groups containing 15 patients each were included in the study and than microbiologically studied. We advise the use of pressure during polimerisation prepeaning removable appliances.

Keywords: Acrylic bases, microbiologic study