Microstructural changes produced by abrading Y-TZP in presintered and sintered conditions.
OBJECTIVE
To evaluate the effect of abrading before and after sintering using alumina-based abrasives on the surface of yttria-tetragonal zirconia polycrystals. Particular attention was paid to the amount of surface stress-assisted phase transformation (tetragonal→monoclinic) and the presence of microcracks.


METHODS
Pre-sintered zirconia ceramic specimens (ZirCAD; Ivoclar Vivadent) were first surface-ground flat with #600-800-1000-grit SiC paper. They were then surface-treated with different grain size abrasives before and after the sintering step. Samples that underwent no surface treatment were used as controls. For each condition, eight specimens were prepared. The physical/mechanical characteristics of zirconia material were determined by measuring density, porosity, grain size, hardness, and fracture toughness. The effects of surface treatments were assessed by surface roughness measurements, quantitative X-ray diffraction analysis, and scanning electron microscopy.


RESULTS
With increased dimensions of the abrasive particles, the abraded surfaces of zirconia specimens exhibited a widespread system of microcracks and an increased monoclinic zirconia quantity. These structural changes likely affect the aging of the material during its clinical service.
Department of Oral Sciences, Division of Prosthodontics and Maxillo-facial Rehabilitation, University of Bologna, Via S. Vitale 59, 40125 Bologna, Italy. carlo.monaco2@unibo.it
Carlo
C
Monaco
Antonella
A
Tucci
Leonardo
L
Esposito
Roberto
R
Scotti
D000465:Algorithms; D000537:Aluminum Oxide / Q000737:chemistry; D017554:Carbon Compounds, Inorganic / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D055598:Chemical Phenomena; D003461:Crystallography; D045662:Dental Etching / Q000379:methods*; D003764:Dental Materials / Q000737:chemistry*; D006244:Hardness; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D016062:Porosity; D017655:Silicon Compounds / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014961:X-Ray Diffraction; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
D017554:Carbon Compounds, Inorganic; D003764:Dental Materials; D017655:Silicon Compounds; C499362:yttria stabilized tetragonal zirconia; D015019:Yttrium; D012822:Silicon Dioxide; D015040:Zirconium; D000537:Aluminum Oxide; C022088:silicon carbide