The current discussion about the importance of intracanal dressings and the effect of vehicles on calcium hydroxide pastes is justified by controversy concerning the achievement of complete disinfection after preparation of infected root canals and the real antimicrobial effect of these vehicles. The aim of this study is to investigate the role of vehicles in the antimicrobial effect of calcium hydroxide pastes. Well-conducted research about the characteristics of calcium hydroxide, such as antimicrobial potential, physico-chemical aspects and histocompatibility, gives credibility to the choice of this medication in several clinical situations. Different vehicles have been added to calcium hydroxide in an attempt to enhance its properties. Scientific reasoning indicates the use of hydrosoluble vehicles (distilled water, saline) associated with calcium hydroxide because of their chemical characteristics of dissociation, diffusibility and filling capability which are decisive for the biological behavior, i.e., antimicrobial qualities and induction of tissue repair.