In vitro fracture resistance of teeth with dentin-bonded ceramic crowns and core build-ups

Purpose: To assess the fracture strength of dentin-bonded crowns placed on cores of amalgam, resin composite and viscous glass-ionomer. Methods: 40 sound maxillary premolar teeth were selected. These were mounted in acrylic resin in stainless steel molds. The palatal cusp of each tooth was removed in a standardized manner to simulate a core build-up preparation. Teeth were randomly divided into four groups, and each group was allocated a core material. For Group A, the core was pin-retained amalgam, for Group B the core was bonded amalgam, for Group C the core material was resin composite and for Group D the core material was high-viscosity glass-ionomer material. Cores were then constructed to the original tooth dimensions. A standardized crown preparation was made, impressions taken and an all-ceramic crown constructed in feldspathic porcelain. The crowns were luted in position using a dentin-bonding agent/dual cure resin-composite cement and the completed specimens subjected to compressive loading in a Universal Testing machine at 1 mm/minute. Results: The mean forces to produce fracture of the crowns were 1.58 kN (+/-0.41), 1.35 kN (+/-0.44), 1.25 kN (+/-0.24), and 1.12 kN (+/-0.25) respectively for groups A, B, C and D. Statistical analysis by ANOVA indicated that the pinned amalgam group performed significantly better than the glass-ionomer group (P > 0.05).