Ultrafast sintering of dental zirconia: composition-processing-property relationships with high-throughput fail-fast screening

Project Summary/Abstract Conventional sintering (CS) protocols produce high quality zirconia restorations suitable for a wide range of indications. However, CS requires a firing cycle of 4 – 10 h, a bottleneck in digital dental workflow precluding zirconia from chairside applications. Current speed sintering (SS) protocols using fast heating (up to 6C/s) in an induction furnace can reduce sintering times to 0.3 – 0.5 h. However, because of inefficiency of convective heat transfer, leading to temperature inhomogeneity, SS produces microstructures with higher porosities, thus compromising zirconia translucency and strength. In addition, non-uniform densification raises concerns about chemical and dimensional stability, internal fit and marginal adaptation of restorations. As a result, SS is largely limited to the fabrication of single-unit crowns from 4 mol% yttria stabilized zirconia (4YSZ). Accordingly, the long-term goal is to drastically increase sintering speed (on the order of 60 s) while maximizing mechanical and optical properties of dental zirconia (exceeding those of the SS- and CS-YSZ) by implementing novel UFS technologies. The overall objectives of this proposal are to (1) establish composition and time-temperature- transformation (TTT) relationships to guide material selections for various industries and sectors, with special attention to the optimization of strength and translucency of YSZ for dental applications; and (2) demonstrate improved dimensional, long-term chemical and structural stabilities pertaining to the quality and longevity of UFS-YSZ restorations relative to SS and CS. The central hypothesis is that novel UFS methodology will dramatically increase time efficiency of digital workflow while optimizing zirconia properties and expanding the range of indications for single-visit treatments. This hypothesis follows directly from preliminary results and a state-of-the-art material science knowledge base. To test this hypothesis, we will pursue 3 specific aims: (1) To characterize the properties of yttria stabilized zirconia using ultrafast sintering technology in conjunction with high-throughput fail-fast screening; (2) To determine the resistance to low temperature degradation and fatigue fracture of ultrafast sintered zirconia relative to current speed and conventional sintering; and (3) To evaluate the dimensional stability, internal fit, and marginal adaptation of ultrafast sintered 3-unit fixed dental prostheses relative to current speed and conventional sintering. The approach is innovative because it departs completely from the current furnace-sintering concept by using Joule heating elements with more effective radiation and conduction heat transfer. The proposed research is significant because it addresses current challenges in poor material properties associated with SS and the long sintering time of CS. Such an approach will improve the efficiency and accuracy of restorative procedures to provide more treatment options and better patient experience, thus improving quality of life and reducing cost to the patient.