Surface Strain on Crown and Luting Cement Fractures

This study investigated fractures of the cement layer between a crown and a die. Model crowns were luted on dies with zinc phosphate cement and various magnitudes of load were applied. Surface strain on the crown was measured using strain gauges. Seal was evaluated using dye penetration and tensile tests. Results showed that cement frac ture affected surface strain behavior on the crown and was detected using the surface strain measurement. The dye penetration test and the tensile test could not be used to detect the cement fracture. It is suggested that the three-dimensional realtive positioning between the crown and the die affected the development of the cement fracture.