Directly MPCVD diamond-coated Si 3N 4 disks for dental applications

Abstract

Embedded diamond grains in a metal matrix, generally Ni, constitutes a very common material for abrasive machining, namely, in dentistry. Its replacement with CVD diamond in high added-value technological areas is desirable, since metal contamination from the binder matrix can thus be eliminated, and the tool life can be extended. This was already reported in dental burs but has never been attempted in abrasive disks. In this work, silicon nitride (Si 3N 4) substrates were sintered, disk shaped (Ø16 mm ×0.35 mm), laser patterned and diamond coated by microwave plasma CVD (MPCVD). For a performance comparison with an electroplated diamond commercial disk in the grinding of two materials used in dentistry (Opaque Dentine 900 ceramic and Luna metal alloy), CVD diamond-coated disks having distinct surface roughness were prepared. Laser patterning was successful for increasing the Si 3N 4 surface roughness, but this feature was less important for the grinding efficiency than the CVD diamond grain size and shape. A CVD diamond disk removed 1.7 times more material in the ceramic grinding than the commercial one, which evidenced wear by extensive grain pullout in the grinding of the metal alloy.