The aim of this in vitro study was to assess intratubular calcium penetration induced by two root canal restoration materials, one calcium oxide based, and the other calcium hydroxide based. Pig teeth were restored with no preliminary root canal preparation. The filling materials were left in place for 8, 15, or 21 days. The samples were then examined using various microanalytical techniques and, in parallel, by backscattered electron image (BEI) scanning electron microscopy. The Ca/P ratios obtained by microanalysis were higher for samples restored with calcium oxide. In addition, the distances over which the ratios increased were also greater than those obtained using calcium hydroxide. BEI photographs confirm these results and show corresponding retrodiffusion fringes.