- 作者：Alex ; ra Grigore ; Stefanie Spallek ; Anselm Petschelt ; Benjamin Butz ; Erdmann Spiecker ; Ulrich Lohbauer
- 关键词：Y-TZP ; X-ray diffraction ; Martensitic transformation ; Sandblasting ; Bur drilling ; Annealing
- 刊名：Dental Materials
- 出版年：2013
- 出版时间：November, 2013
- 年：2013
- 卷：29
- 期：11
- 页码：1098-1107
- 全文大小：3142 K
Objective
Clinical studies reveal that veneer chipping is one major problem associated with zirconia based dental restorations, the underlying mechanisms being still investigated. We semi-quantitatively analyzed the effects of different surface treatments (thermal etching, 35/105 ¦Ìm sandblasting and coarse bur drilling (150 ¦Ìm)) on the microstructure of a zirconia veneered dental ceramic.Methods
The relative monoclinic content on zirconia surfaces was determined using X-ray diffraction (XRD). The microstructure at the zirconia-veneer interface has thereafter been investigated using transmission electron microscopy (TEM). Selected area electron diffraction (SAED) was used to qualitatively assess the depth of the stress-induced phase transformation.
Results
Sandblasting or bur drilling significantly roughened the zirconia surface. A reverse transformation of already transformed monoclinic zirconia grains back into the tetragonal polymorph has been observed after thermal veneering treatment. In TEM, the mechanically treated samples revealed a highly damaged area of 1-3 ¦Ìm from the interface. The presence of monoclinic phase in veneered zirconia samples has been observed in SAED up to depths of 4 ¦Ìm (35 ¦Ìm sandblasted), 11 ¦Ìm (105 ¦Ìm sandblasted) and 9 ¦Ìm (150 ¦Ìm diamond drilled) below the interface.
Significance
Regardless of the treatment protocol and produced roughness, the veneering ceramic perfectly sealed the zirconia surface. XRD showed an increased amount of monoclinic phase on the surface treated zirconia. However after thermal treatment, the monoclinic phase was re-transformed into the tetragonal polymorph. TEM/SAED analysis has found indication for a greater extend of the monoclinic transformation into the bulk zirconia compared to the treatment related defective zone depth.