Material-dependent clasp design of partial dentures – differences between Ultaire® AKP and partial denture alloys

In the world of dentistry it is not uncommon for manufacturing processes and materials to be advanced further or to be superceded by new techniques and materials if they offer added value. The latest addition to the Ceramill System is the high-performance polymer Ultaire®AKP, which allows partial dentures to be milled directly instead of being produced by the casting process. This saves time, energy and manual reworking. Since the material properties of Ultaire® AKP differ significantly from those of con ventional partial denture alloys, a different design is necessary, particularly for the clasps. To achieve the desired pull-off force of a CoCr clasp, this is designed to be as long and thin as possible and may only engage into an undercut by a maximum of 1/3 below the prosthetic equator. This clasp design results in CoCr clasps extending far into the visible range and their metallic sheen strongly impairs the patient’s esthetic appearance. Due to its greater elasticity, it is sufficient to construct short clasp lengths with higher shoulders with Ultaire® AKP to achieve identical pull-off forces. Due to the shortened lengths, undercuts closer to the shoulder can be used to hold the prosthesis securely in place and these are therefore less visible.