The rate of development of strength in base forming materials for dental amalgam.

Eleven base forming materials used under amalgam restorations were examined for the rate of development of their compressive and tensile strengths. Materials from three categories were compared. Under in vitro conditions of testing, it was found that, immediately after a state of clinical set had been reached, the quick-setting zinc oxide-eugenol materials possessed strengths significantly greater than the calcium hydroxide cements but significantly weaker than the zinc phosphate cements. Calcium hydroxide cements possessed the lowest compressive strength to tensile strength ratio and modified zinc oxide-eugenol materials the highest.