European Quality Craftsmanship Made in America
September 8, 2014
CAD/CAM Zirconia Screw-Retained Bridges
A CAD/CAM zirconia screw-retained implant bridge negates many of the problems of the prosthetic alternatives. The fact that it is fabricated through a CAD/CAM protocol and not the lost-wax casting method helps to resolve any issues with casting distortion.The resulting framework equates to less stress on the implants and prosthetic parts. However, passive fit and precision are dependent on accurate impressions and verification of the master cast.
The high modulus of elasticity of zirconia allows for in¬creased implant stability and cross arch stabilization.31 The resistance to fracture of yttrium (YTZ) stabilized zirconia and its transformational toughness counters the chipping problems seen with acrylic or porcelain prosthetic options. When a prosthesis is fabricated with full-contour zirconia, chipping of the screw access hole or occlusal areas is almost nonexistent. The wear studies on opposing teeth show that polished YTZ-zirconia offers less wear than porcelain. Where space for both metal and porcelain or acrylic is necessary and significant for conventional hybrid designs, due to its monolithic nature, a CAD/CAM zirconia bridge requires far less prosthetic space. Depending on cantilever length, pontic length, and other factors, a monolithic zirconia bridge requires only 12 to 15 mm of prosthetic space.34 The success rate of implant supported screw-retained zirconia prostheses have been shown to be as high as 100% for a period of 5 years.