UCSF

Soaring gold prices have created an almost impossible void in the Dental Materials supply reserves for affordable patient posterior crowns. Fortunately, aerotech fiber-reinforced composite (FRC) materials in use for many diverse structural applications can be developed for dentistry to replace gold with computer-assisted design/computer-assisted manufacture (CAD/CAM) technology. Current dental ceramics or high-strength oxide ceramics like alumina and zirconia available for CAD/CAM have extremely poor fracture-toughness properties and can propagate microscopic cracks rapidly to sudden adverse brittle failure. As a highly promising alternative, exceptional FRC fracture toughness properties counteract brittle failure with high-strength fibers that act as major barriers to crack propagation. In addition, excellent rapid FRC CAD/CAM machining can offer one-patient appointments for single crowns. FRCs have high-strength fibers coupled into a polymer matrix with the ability to form strong covalent bonds with resin adhesives whereas ceramics do not bond well and oxide ceramics have non-reactive inert surfaces making resin bonding extremely difficult. Prominent adhesive free-radical covalent bonding by FRCs then provides a great opportunity to achieve a crown marginal reline directly on the patienťs clinical tooth for possible near zero-gap defect tolerances. To place crown gingival marginal defects in proper perspective, gaps between the tooth and crown expose luting cements that can wash out and provide space for microbial plaque growth. Bacterial toxins released from a crown-tooth interface can subsequently produce secondary decay, gingival inflammation and eventually under severe plaque environments breed periodontal disease with bone loss.