Microwave Sintering of Glass Ceramics.

Abstract

Glass ceramics’ mechanical properties, esthetics and biocompatibility show an important improvement compared to traditional dental ceramics. Materials such as lithium disilicate ceramics are increasingly popular in dentistry today, due to their improved mechanical performance and natural appearance, an improvement from previous systems based on zirconia. Previous research showed dental ceramics can be sintered with Microwave Hybrid Sintering (MHS), in a reduced time consuming process that may improve the mechanical properties of the material. The objective of this dissertation is to investigate if glass ceramics such as lithium disilicate can be sintered and improved with MHS.

Materials and methods: Samples of lithium disilicate glass ceramics were sintered using MHS and conventional sintering, as described by Kashi et al. (2006), Pendola et al. (2013). The produced samples were tested (density, hardness, flexural strength) and analyzed (X-rays diffraction, SEM) to compare the mechanical properties and microstructure of the material with samples sintered using Conventional Sintering.

Results: MHS process sintered the ceramic materials in shorter times when compared to conventional sintering. The mechanical properties of lithium disilicate glass ceramics appear to be improved using MHS. Hardness is increased in samples sintered using MHS (652 HV + 23, P<0.0001) when compared with conventional sintering (567 HV + 14) and flexural strength is also improved for MHS process (454 MPa + 51 vs 304 MPa + 75, P<0.0001). X-Ray Diffraction shows an increase of the crystalline phase in samples sintered with MHS, which may explain the improvement of the mechanical properties. SSALT shows a higher reliability for MHS ceramics when compared to Conventional Furnace Sintering processed ceramics.

Conclusion: MHS can be a good alternative for sintering dental ceramics, including the most recent dental glass ceramics, by offering a firing process with reduced processing times and therefore lower energy consumption. MHS also produces an improvement on the mechanical properties of the material.