This investigation measured the diffusion of Ca2+ through dentin by using Ca(OH)2 associated with various vehicles. After mechanical preparation and removal of smear layer, 41 human premolar teeth were stored individually in flasks containing 800 ml of ultra-pure deionized water for 2855 h. The Ca2+ concentration was measured by atomic absorption spectrophotometry as a function of time. These measurements were divided into two phases: dissolution, to check the loss of Ca2+ from the tooth structure itself, for which all canals were kept empty and open in the absence of medication for 1168 h, and diffusion, in which the specimens were divided into 10 groups (3 control groups: group 1 = water control, group 2 = sealing control, and group 3 = open canal dissolution control; 7 experimental groups in which the whose canals were filled with Ca(OH)2 paste associated with the following vehicles: group 4 = saline; group 5 = polyethylene glycol (Calen); group 6 = glycerin and camphorated parachlorophenol group 7 = camphorated paramonochlorophenol; group 8 = glycerin; group 9 = glycerin and tricresol formaldehyde (TCF); and group 10 = anesthetic solution. This phase lasted 1687 h. A total of 1058 measurements of Ca2+ were made. Regression analysis was used for statistical evaluation. We concluded that diffusion occurred differently for each group: the medications used in the root canals interacted with the dentinal structure or among themselves; the medication coated the dentinal tubule, facilitating the diffusion of Ca2+ into the external part of the root.