[Effect of the convergence angle of the ground tooth and the force of cast crown fastening using various types of cement].

The authors measured the effect of the convergence angle of the ground tooth on the fastening of cast crowns. The study was carried out on phantom models of teeth made of stainless steel with abutement convergence angles from 1 to 10 degrees. The force of the connection was measured using the Instron testing device. The avulsing force acted along the long axis of the abutement. Additionally the fixing force of phosphate, polycarboxylate and ionomer-glass was compared. A fall of the force of crown fastening was observed with increasing value of the convergence angle of the abutement, especially for phosphorus and ionomer-glass cement. The crowns fastened with polycarboxylate cement showed a threefold smaller fall of the fastening force with increasing value of the convergence angle of the abutement.