title: The influence of the cement layer on the strength of porcelain crowns subjected to frequent loading.
abstract: The aim of this investigation was to find out whether the support of cemented porcelain crowns was altered by repeated loading. The experiments were carried out  on porcelain caps cemented with zincphosphate cement to cores of dentine. One cap was made half the scale of the other. The proximal tensile stresses were determined from strains measured from attached strain gauges with a measuring bridge. The top of the caps were loaded at an angle of 60 degrees. The first measurement was made one hour after the cementation. A loading cycle of 6000 loadings was afterwards started. A second measurement was then made. The proximal tensile stresses were increased after the loading cycle. Only in the small model this increase was significant. This was probably because the cement layer was relatively thinner in the large model. The experiments suggested that repeated loading of porcelain crowns alter the support and then to increase the risk of fractures of the crowns. If the cement layer is thin, this risk is smaller.
mesh_terms: D003442:Crowns / Q000592:standards*; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D003765:Models, Dental; D015036:Zinc Phosphate Cement
chemical_list: D003776:Dental Porcelain; D015036:Zinc Phosphate Cement