|Effect of Multistep Processing Technique on the Formation of Micro-defects and Residual Stresses in Zirconia Dental Restorations|
|Zhao Jing1,2; Zhang Ke2; Liu Yihong3; Shen Zhijian2|
|关键词||Reliability Dental Ceramics Grinding Tetragonal-to-monoclinic Transformation Cad/cam Slow Crack Growth|
|刊名||JOURNAL OF PROSTHODONTICS-IMPLANT ESTHETIC AND RECONSTRUCTIVE DENTISTRY|
|WOS标题词||Science & Technology|
|类目[WOS]||Dentistry, Oral Surgery & Medicine|
|研究领域[WOS]||Dentistry, Oral Surgery & Medicine|
|关键词[WOS]||Y-TZP ; TETRAGONAL ZIRCONIA ; FLEXURAL STRENGTH ; COMPOSITES ; FRACTURE ; RELIABILITY ; FRAMEWORKS ; CERAMICS ; ORIGINS ; ZRO2|
The clinical failures of zirconia dental restorations are often caused by extrinsic artifacts introduced by processing. The aim of this study was to investigate the micro-defects and residual stresses generated during the multistep process of zirconia dental restorations.
Materials and Methods
Thermal spray granulated 3Y-TZP powders were dry pressed by two tools exhibiting distinctly different Young′s moduli, cold isostatic pressed (CIP-ed), and pressure-less fully sintered. The green bodies pressed by a stiff tool were treated with different procedures: direct milling (green milling) followed by fully sintering; half-sintering and milling (raw milling) with or without fully sintering; and fully sintering followed by grinding. The fully sintered 3Y-TZP crowns were clinically adjusted using both a diamond bur and SiC bur, respectively. Phase composition and microstructure of the pressed, milled, and ground surfaces were studied by XRD and SEM.
Tetragonal phase was the main phase of all detected 3Y-TZP specimens. Excessive residual stresses introduced by raw milling and grinding were confirmed by a strained T (111) peak, monoclinic phase, and obviously changed I(002)(t)/I(200)(t) ratio. The residual stresses would form a compressive stress layer, while it was too shallow to inhibit crack propagation even for ground specimens. Large voids with high-coordination numbers were the common packing micro-defects. Once formed, they were barely healed by CIP-ing and sintering. A stiff pressing tool was confirmed to be useful for reducing the surface packing voids. Milling removed the surface voids, but was no help for the interior ones. Raw milling introduced more serious chippings, most originating from the existing packing voids, than green milling due to its brittle failure and was less recommended for production. Grinding dense 3Y-TZP caused surface grain refinement and much more severe micro-defects, especially when clinical adjustment was applied by diamond bur compared to SiC bur.
Micro-defects and residual stresses are introduced and accumulated through the entire production chain and determine the final microstructure of zirconia dental restorations. Several procedural improvements are offered and expected to reduce processing micro-defects.
|资助机构||China Scholarship Council (Beijing, China) ; Swedish Research Council through the Berzelii Center EXSELENT (Stockholm, Sweden)|
|作者单位||1.Peking Univ Sch & Hosp Stomatol, Dept Prosthodont, Beijing, Peoples R China|
2.Stockholm Univ, Dept Mat & Environm Chem, Arrhenius Lab, S-10691 Stockholm, Sweden
3.Peking Univ Sch & Hosp Stomatol, Dept Gen Dent, Beijing, Peoples R China
|Zhao Jing,Zhang Ke,Liu Yihong,et al. Effect of Multistep Processing Technique on the Formation of Micro-defects and Residual Stresses in Zirconia Dental Restorations[J]. JOURNAL OF PROSTHODONTICS-IMPLANT ESTHETIC AND RECONSTRUCTIVE DENTISTRY,2014,23(3):206-212.|
|APA||Zhao Jing,Zhang Ke,Liu Yihong,&Shen Zhijian.(2014).Effect of Multistep Processing Technique on the Formation of Micro-defects and Residual Stresses in Zirconia Dental Restorations.JOURNAL OF PROSTHODONTICS-IMPLANT ESTHETIC AND RECONSTRUCTIVE DENTISTRY,23(3),206-212.|
|MLA||Zhao Jing,et al."Effect of Multistep Processing Technique on the Formation of Micro-defects and Residual Stresses in Zirconia Dental Restorations".JOURNAL OF PROSTHODONTICS-IMPLANT ESTHETIC AND RECONSTRUCTIVE DENTISTRY 23.3(2014):206-212.|