title: Surface structure and mechanical properties of impaction-modified Y-TZP.
abstract: OBJECTIVE
  The objectives of the study were to describe the surface structure and the chemical surface composition of Y-TZP ceramics produced by using the modified additive technique and to evaluate the flexural strength of Y-TZP with or without surface modification and with different pretreatments: etching before or after sintering combined with or without an adhesive cement system.
  
  
  METHODS
  Y-TZP discs were used for surface analysis (n=48) and for biaxial flexural strength testing (n=200). The specimens were divided into groups depending on the cementation surface of Y-TZP: unmodified, sandblasted or glass-modified Y-TZP surfaces, and according to the production process: etching before or after sintering.
  
  
  RESULTS
  The surface structure and the chemical composition of glass-modified Y-TZP differ; a rougher surface and phase transformation was identified compared to unmodified Y-TZP. The unmodified Y-TZP groups showed significantly higher flexural strength compared to the glass-modified groups (p<0.001) and showed increased flexural strength after sandblasting (p<0.001). Furthermore, by adding cement to the surface, the value increased even further in comparison with the sandblasted non-cemented specimens (p<0.01). After thermocycling, however, the cement layer on the unmodified and the sandblasted surfaces had air pockets and regions with loose cement.
  
  
  CONCLUSIONS
  A rougher surface structure, superficial glass remnants and a higher content of m-phase was present in the cementation surface of glass-modified Y-TZP. The glass modification creates a bondable cementation surface that is durable. By etching the glass-modified Y-TZP before sintering, a more homogenous surface is created compared to one that is etched after sintering.
authors: Department of Materials Science and Technology, Faculty of Odontology, Malmö University, Carl Gustafs väg 34, 205 06 Malmö, Sweden. Electronic address: evaggelia.papia@mah.se.
authors: Evaggelia
authors: E
authors: Papia
authors: Department of Prosthodontics, Faculty of Odontology, Malmö University, Carl Gustafs väg 34, 205 06 Malmö, Sweden. Electronic address: ryo.jimbo@mah.se.
authors: Ryo
authors: R
authors: Jimbo
authors: Department of Prosthodontics, Faculty of Odontology, Malmö University, Carl Gustafs väg 34, 205 06 Malmö, Sweden. Electronic address: bruno.chrcanovic@mah.se.
authors: Bruno R
authors: BR
authors: Chrcanovic
authors: Department of Chemical and Biological Engineering, Applied Surface Chemistry, Chalmers University of Technology, Kemivägen 10, 412 96 Gothenburg, Sweden. Electronic address: martin.andersson@chalmers.se.
authors: Martin
authors: M
authors: Andersson
authors: Department of Materials Science and Technology, Faculty of Odontology, Malmö University, Carl Gustafs väg 34, 205 06 Malmö, Sweden. Electronic address: per.vult@mah.se.
authors: Per
authors: P
authors: Vult von Steyern
mesh_terms: D008422:Materials Testing; D018625:Microscopy, Atomic Force; D013499:Surface Properties; D015019:Yttrium; D015040:Zirconium
chemical_list: C499362:yttria stabilized tetragonal zirconia; D015019:Yttrium; D015040:Zirconium
keywords: Compressive strength; Dental bonding; Dental cements; Dental ceramics; Materials testing; Yttria-stabilized tetragonal zirconia