Abstract : Calcium hydroxide is used to assist the formation of dentin in direct pulp capping and pupotomies. In recent years, it has come to replace phenol or formaldehyde in root canal treatment.

 Our purpose was to study the role of calcium hydroxide (UltraCal^TM XS^TM, Calcipex^® and home-made calcium hydroxide paste) in the sealing process of intra-canal dressings.

 The root canals of fifty extracted mandibular incisors were endodontically prepared and dressed with calcium hydroxide paste, then irrigated by ultrasonic files with water and guttapercha obturated (the sectional method). Obturated teeth were then immersed in the India ink, and the penetration distance of the dye measured from the apex of the root.

 Meanwhile, we scanned using a SEM (scanning electron microscope) the paste type medication used in root canal treatments after irrigation by ultrasonic files with water.

 The results were as follows :

 1. UltraCal XS dressings : the dye penetration distance was 0.41 mm. Calcipex : 0.25 mm. Home-made calcium hydroxide paste : 0.11 mm. Dressing without paste : 0.23 mm. However, no difference appeared when results were Dunn multi-comparison tested.

 2. UlraCal XS dressing : 30.2% non penetration of the distance from the apex of the root. Calcipex : 75.6%. Home-made calcium hydroxide paste : 84.6%. No medication : 50.0%. A two way analysis (test for the proportion) showed that both Calcipex and home-made paste offer apical sealing capability.

 3. Fisher’s exact probability test showed differences between UltraCal XS and Calcipex/UltraCal XS and home-made paste sealing capability. The other hand, it was not showed diffrences between non-paste and other calcium hydroxide pastes.

 4. Those differences can be explained by the different ratio of those medications’ components.