Influence of tooth surface roughness and type of cement on retention of complete cast crowns

Abstract

Statement of Problem. Bond strength of luting cements to dentin is a critical consideration for success of cast restorations. Purpose of Study. This study determined the relationship between surface characteristics of teeth prepared for complete cast crowns and retention of respective cemented restorations. Material and Methods. Ninety artificial crowns were cast for standardized complete crown tooth preparations accomplished with the use of a milling machine on extracted human teeth. Diamond, tungsten carbide finishing, and cross-cut carbide burs of similar shape were used. The crowns in each group were randomly subdivided into three subgroups of 10 for the three luting cements selected for this study: zinc phosphate cement (Fleck's), glass ionomer cement (Ketac-Cem), and adhesive resin cement (Panavia-EX). Retention was evaluated by measuring the tensile load required to dislodge the artificial crowns from tooth preparations with an Instron testing machine. Results. Analysis of forces with parametric analysis of variance and Tukey's Studentized Range (HSD) disclosed a statistically significant difference for both luting cement and finishing burs ( p < 0.001). A statistically significant interaction effect ( p < 0.001) was also found. The greatest retention value (372.9 N) was for tooth preparations refined with carbide burs and cemented with Panavia-EX cement. However, the least retention value (201.6 N) was for tooth preparations completed with finishing burs and luted with zinc phosphate cement. Conclusions. Significant differences were found among all three cements for finishing burs. However, there was a difference only between Panavia-EX cement and the other two cements for tungsten carbide burs. For diamond rotary instruments, zinc phosphate cement was significantly different from glass ionomer and Panavia-EX cements.(J Prosthet Dent 1997;77:116-21.)