Diffusion of carbon-14-labeled formocresol and glutaraldehyde in tooth structures

14C-Formocresol and 14C-glutaraldehyde were placed in the root canals of freshly extracted human teeth. The outward diffusion of labeled aldehydes was then measured and autoradiograms of cross-sections taken. No diffusion of glutaraldehyde was detectable within 72 hours, whereas there was a rapidly increasing outflow of formocresol during the same period. In a separate group normal root canal treatment was completed until 2 mm. short of the roentgenologic apex with glutaraldehyde as an irrigant. The walls of the root canals of some of the specimens were examined with electron microscopy and the outflow of 14C-formocresol which was later placed in some specimens was counted. The use of glutaraldehyde as an irrigant resulted in closure of the apical third of the root canal as indicated by the absence of 14C-formocresol diffusion.