Influência de diferentes tipos de retentores intrarradiculares de fibra de vidro na resistência de união de um cimento resinoso autoadesivo à dentina radicular bovina

Abstract

This study evaluated the bond strength of different fiberglass post types to root dentin in cases of severely damaged endodontically treated teeth. A pilot study was carried out and sample size was calculated from the results. Around 340 bovine teeth were obtained in a certified slaughterhouse. Teeth were cleaned and sectioned at dentinenamel’s junction. After selection criteria were met, teeth were selected, the roots were endodontically treated and root canals were prepared with Largo burs #2, 3 and 4. After the treatment with Largo bur #4, the specific bur from EXACTO fiberglass post kit was used. The working length was 11 mm and 4 mm gutta-percha remnant were left to seal the apical region. The #4137 diamond bur (ø 2,5 mm) was used on the roots’ most coronal 3,5 mm region to simulate extensive loss of tooth structure. The prepared roots (n=33) received different types of fiberglass posts, which were fixed with self-adhesive resin cement (RelyXÔ U200, 3M ESPE), and were randomly divided into 3 groups: 1) conventional glass fiber posts; 2) relined glass fiber posts; 3) glass fiber posts milled on CAD/CAM units. After posts fixing procedure, each root (n=30) was sectioned in different root thirds (coronal, medium and apical), originating 2 specimens/third in a total 6 specimens/root, that were submitted to push-out bond strength test. Other additional root from each experimental group (n=3) was prepared and analyzed using Scanning Electron Microscopy to describe the marginal adaptation to radicular dentin, presence of voids and thickness of the resin cement film, in each root third (coronal, medial and apical. To perform statistical analysis, alpha was preset at 0.05 and 80% power test. The values of bond strength and root third was analyzed using One-way ANOVA and Tukey post-hoc test. The relined fiberglass post group presented better performance than the other two groups at the coronal level (8,92 MPa) (p=0,010). Additionally, the relined fiber post group was also the only group which bond strength values were influenced by root third, and the apical third reported the worst results (4,51MPa) (p=0,037). Therefore, it was concluded that the type of fiberglass post and the root third affected the bond strength to root dentin.