Formalin Penetration of Extracted Teeth

¹ Departments of Operative Dentistry and Biochemistry, University of Oregon Dental School, Portland, Oregon

An investigation of penetration of dental tissues by radioactive neutral 10 per cent formalin has been completed. Contact autoradiographs of tooth sections obtained from freshly extracted human teeth were studied to determine the extent and degree of fixative penetration with increasing times of immersion in the fixing solution.

It was found that the early penetration of the dental pulps of whole, intact teeth and of teeth whose roots had been shortened by cutting proceeded primarily, if not entirely, via the apical openings of the pulp canals. Teeth whose pulp chambers were significantly longer than 11 mm. required several hours of exposure to the formalin before penetration of the pulp chambers appeared to be complete.

All observable portions of pulpal tissues of teeth "shaved" prior to fixation were rapidly and completely penetrated by the formalin solution.

Penetration of dental pulp, cementum, dentin, and enamel seemed related in a direct manner to the time of immersion in the fixing solution. Dental pulp, cementum, and dentin acquired relatively high concentrations of labeled formalin following a few hours of immersion in the fixing solution, but intact enamel contained only minute amounts of the radioactive formalin even after 8 days of immersion in the formalin solution.

Formalin penetration of gross defects of enamel and dentin was rapid and extensive, often reaching deeply into the underlying portions of the dentin and dental pulp.