Residual Eugenol From Zinc Oxide-Eugenol Compounds

¹ Loyola University School of Dentistry, Chicago College of Dental Surgery, Dental Materials Department, Chicago, Illinois

The free eugenol in ZOE compounds has been studied in reference to the effect of consistency and time. When zinc oxide was added to the solution of methyl alcohol and eugenol, not all of the eugenol could be extracted. The amount of eugenol that could be extracted from a freshly-mixed, dry ZOE sample was approximately the same as when the eugenol was in solution. After hardening, the amount of free eugenol was about 5 percent and remained constant. Apparently, an equilibrium condition was reached at the time of hardening. Agitation of the ZOE mixture during the extraction of eugenol affected the rate of reaction. The greater the amount of agitation, the less free eugenol was present. The effect of zinc-salt accelerators and water increased the amount of free eugenol extracted immediately after hardening. Eventually, the amount of free engenol decreased to approximately the same amount found when the accelerators were not present.

Since free eugenol is always present even in small amounts, changes in the tooth structure and tissue can be expected when ZOE cement is used.