Estudo in vitro da adaptação de retentores intra-radiculares fundidos, modelados com diferentes resinas acrílicas autopolimerizáveis

Abstract

Endodontically treated teeth are often mutilated by caries and access requirements. The remaining structure requires special treatment to prevent further destruction. When a large portion of the clinical crown has been lost, it is often impossible to achieve sufficient anchorage of a restoration in the remaining dentin. In s uch situations, a root-canal-retained restoration is required. Only the root portion can offer the needed retention for a functional and esthetic artificial crown. Different approaches can be taken to the fabrication of cast posts and cores. In this study, direct method was chosen to fashion it, by auto polymerizing acrylic resin. We used six standard metal patterns that simulate an anterior tooth prepared to receive cast post and core. Burnout plastic patterns were fitted into the root canal and, using a fine sable hair brush, the polymer was introduced to fill the canal. After polymerization of the post, additional auto-polymerizing acrylic resin was added to form the core portion. This process can be repeated and correct if necessary. The acrylic resin patterns were then invested and casting was performed using nickelchromium alloy. The cast was removed from investment. Cleaning was performed exclusively to remove the small positive nodules on the metal post and sandblast surface. The aim of this research was to compare the marginal fit of 54 cast posts constructed with three auto-polymerizing acrylic resins: 18 of DuraLay (Reliance Dental MFG Co., USA); 18 of Pattern Resin (GC Products, Japan); 18 of Cop Clas (Artigos Odontológicos Clássico Ltda., Brasil). The posts and cores were seated over the six standard metal patterns. Marginal discrepancies were observed in scanning electron microscope (SEM). The measurements were registered and statistically analyzed. The results obtained showed that: (1) The cast post and core obtained from DuraLay (42,31 µm ± 9,54 µm) had significant best fit than the cast post and core obtained from the others acrylic resins, Pattern Resin (73,25 µm ± 32,86 µm) and Cop Clas (95,32 µm ± 45,02 µm) respectively; (2) No significant statistic difference occur (p=0,273) in the average marginal gap between the cast posts and cores obtained from Pattern Resin and Cop Class (22,07 µm ± 13,13 µm). Key-works: Cast post and core-Marginal fit; Auto polymerizing acrylic resinacrylic resin patterns; denture prosthesis.