Microwave Sintering of Esthetic Dental Materials.

Abstract

Dental materials are routinely used to restore broken, lost or carious (i.e., diseased) tooth structure. Among the esthetic materials that are available, dental ceramics (e.g., zirconia) are popular choices for crown and bridge fabrication. Traditional techniques for sintering/processing dental ceramics include the use of conventional electric heating ovens. The entire sintering process (from a green state to a fully sintered state) for a zirconia dental ceramic takes about 12 to 14 hours to complete. However, alternate techniques including the use of microwave energy has been shown to be beneficial for processing ceramics. A research microwave (operating frequency of 2.45 GHz and maximum power input of 2 kW) was utilized to sinter zirconia (3 mol% yttria-stabilized zirconia) dental materials. Various configurations (i.e., strips, pellets and actual tooth copings) of the zirconia materials were sintered in the microwave furnace. The least time required to sinter the zirconia materials was studied. The sintered materials were characterized for their microstructural and mechanical properties. This included the study of grain size distribution and porosity, three-dimensional shrinkage, hardness, fracture toughness and flexural strength. The results of our study showed that microwave sintering provides an effective alternative to conventional sintering techniques. Furthermore, the overall mechanical and microstructural properties of the microwave sintered zirconia materials were within prescribed guidelines (i.e., ISO standards for dental ceramic materials) for dental applications.