The effect of tooth preparation height and diameter on the resistance of complete crowns to fatigue loading.

This study investigated the relationship between tooth preparation height and diameter and the resistance of cemented crowns to dynamic loading. Crown and abutment analogs were cemented using zinc oxide-eugenol, zinc phosphate, glass-ionomer, and resin composite luting agents. Abutment height varied from 1 to 7 mm in increments of 1 mm. Diameters of 3, 4, 5, 6, 7, and 8 mm were tested. A testing apparatus designed to apply dynamic stresses was used. The cemented crowns were loaded until the cement bond failed or the components reached 1 million stress cycles. The staircase technique was applied for data analysis. The results showed that: (1) the relationship between abutment height (or diameter) and resistance to dynamic lateral loading is approximately linear; and (2) crowns luted using resin composite cement were more resistant than those placed using glass-ionomer cement, which in turn were more resistant than crowns cemented with zinc phosphate or zinc oxide-eugenol cements.