마이크로파 소결이 지르코니아 치아에 미치는 영향 분석

<관련 논문 >

1. Comparison of Microwave and Conventionally Sintered Yttria-Doped Zirconia Ceramics

Colin J. Reidy¹, Thomas J. Fleming¹, Stuart Hampshire^1,*, Mark R. Towler²

Article first published online: 28 MAR 2011.DOI: 10.1111/j.1744-7402.2011.02608.x

© 2011 The American Ceramic Society. International Journal of Applied Ceramic Technology

It was found that microwave sintering improves physical and mechanical properties of Y₂O₃–ZrO₂ ceramics compared with conventional sintering. Compositions containing 2 mol% Y₂O₃ (이트리아를 2몰 첨가한 블록의 경우)exhibit the greatest improvement due to retention of tetragonal ZrO₂, with a 5% increase in relative density(상대 밀도 향상) compared with conventional sintering. Grain size analysis indicated that there was significant grain growth in microwave sintered (MWS) samples (353 nm) compared with their conventionally sintered (CS) counterparts (200 nm) which is thought to be related to enhanced diffusional effects during microwave sintering. Associated with this was a 22% increase in Young's modulus(탄성률 증가) to 220 GPa, a 77% increase in Vicker's Hardness(비커스 경도 향상) up to 11.5 GPa and a 165% increase in biaxial flexural strength (굴곡강도 증가)up to 800 MPa. Owing to the differences in physical and mechanical properties along with the altered phase assemblages produced, it is apparent that microwave heating provides an additional driving force during sintering which enhances diffusion processes.

2. Industrial-Scale Microwave Sintering: http://www.ceramicindustry.com/articles/91570-industrial-scale-microwave-sintering : By Kuruvilla (Karl) Cherian and Michael Kirksey, April 1, 2011

          Microwave Sintering Advantages

It is in this context that the microwave sintering of zirconia-based dental restorations assumes great practical significance. As mentioned earlier, microwave sintering could lead to finer microstructures(지르코니아 결정의 입자가 미세해짐) in ceramics. Such characteristics in microwave-sintered, zirconia-based dental restorations could not only improve the strength of the material(강도 향상) but, if the resulting grain size is comparable or less than the reported critical value of 0.42 microns, may also help reduce or eliminate the hydrothermal aging effect(따뜻한 구강내에서 코아가 노화되는 현상이 없음) . The fine microstructure may provide an additional aesthetic advantage in greater translucency of the finished restoration, which helps achieve a more natural appearance for the end user (patient).

Comparative analytical studies were undertaken of several different zirconia-based material samples sintered through conventional and microwave techniques. A 3Y-TZP composition (이트리아를 3몰 첨가한 블록의 경우)was used for a detailed scientific study ("Flexure Strength and Hydrothermal Degradation of Yttria-Stabilized Zirconia: Microwave vs. Conventional Sintering") by Arizona State University researchers Professor Pedro Peralta and Kirk Wheeler of the Department of Mechanical and Aerospace Engineering. (미국 아리조나 대학 연구 결과임) The resulting samples were tested according to standards established by the American Dental Association. Post-sintered flexure strengths were measured and correlated with the sintering method and resulting microstructure.

 It was estimated that this corresponded to about 10 years of simulated testing in the mouth, after which microwave-sintered zirconia does not deteriorate significantly and is nearly 50% stronger than traditionally sintered zirconia.(10년간 구강내에서 사용해도 특별히 노화되는 현상이 없으며 전기로로 소결한 것보다 거의 50% 더 강함)