The Influence of Dentin and/or Metal Surface Treatment on Crown Retention in Teeth with an Increased Taper

Objective: The purpose of this study was to evaluate the retention of metal-based crowns cemented to teeth with an increased taper as influenced by dentin and/or metal surface treatments. Methods: For the study, 60 intact extracted molars were embedded into an acrylic mold up to 2 mm apical to the CEJ, perpendicular to the long axis of the tooth. The occlusal aspect of the tooth was removed maintaining a standard height of 5 mm. Axial walls were prepared to a 40º convergence angle using a specially crafted device. NI-Cr crowns were fabricated. Teeth were randomly divided into four groups: Group A – cemented with Zinc Phosphate Cement (Harvard) and the inner aspect of the crown was sandblasted by 50 µm aluminum oxide; Group B – cemented with Composite cement (Compolute Cement, ESPE) without any surface treatment; Group C – cemented with Compolute with dentin etching and bonding (EBS Multi, ESPE); and Group D – cemented with Compolute with dentin etching and bonding and metal conditioning using the Co-Jet System (ESPE). Teeth were aged by storing in water for 3 months and thermocycling (500 cycles) from 5ºC to 55ºC. A tensile test was performed using a universal loading machine and tensile stress was calculated by dividing the load at failure by the axial surface area. Results: Group D presented the highest mean failure stress (3.52 MPa±1.3), significantly higher than all other groups (p<0.005). Group C presented values of 2.26 MPa±0.9, significantly higher than groups A and B (p<0.003). Group A exhibited values of 1.22 MPa±0.4, which was not significantly different from Group B (0.85 MPa±0.4). Conclusion: It is recommended to cement crowns with compromised retention using composite cement with dentin bonding, as well as tribochemical metal treatments.