title: Flexural strength of the joint between glass-infiltrated alumina frames and the alumina-magnesia modifier.
abstract: OBJECTIVE
  The purpose of the present study was to evaluate the flexural strength of the joint between glass-infiltrated alumina frames and the experimental adjusting agent (MA modifier) that contains alumina and magnesia.
  
  
  METHODS
  A commercially available adjusting agent (Optimizer), a slurry of alumina powder (Alumina modifier), and a bulk specimen (joint-free alumina) were used as controls. Beam-shaped alumina specimens were machined from an alumina block. The ends of two alumina beams were positioned at an interval of 1.0 mm and joined with each adjusting agent. The joined specimens were subjected to sintering, glass infiltration firing, glass control firing, and then a three-point bending test was carried out to evaluate the flexural strength.
  
  
  RESULTS
  The maximum flexural strength was observed in the joint-free alumina, followed by MA modifier, Optimizer and Alumina modifier. With the exception for joint-free alumina, the failure modes after three-point bending test tended to shift from adhesive failure at substrate material-adjusting agent interface to cohesive failure within adjusting agent as the flexural strength increased.
  
  
  CONCLUSIONS
  The use of MA modifier significantly improved the flexural strength of joined glass-infiltrated alumina frame. The MA modifier could be applied for adjusting the margin as an alternative to Optimizer when fabricating crown and bridge substructures with In-Ceram Alumina system.
authors.affiliation: Applied Prosthodontics, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1, Sakamoto, Nagasaki 852-8588, Japan. yohsuke@nagasaki-u.ac.jp
authors.forename: Yohsuke
authors.initials: Y
authors.lastname: Taira
authors.forename: Junichi
authors.initials: J
authors.lastname: Fukui
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Odatsu
authors.forename: Kohji
authors.initials: K
authors.lastname: Kamada
authors.forename: Takashi
authors.initials: T
authors.lastname: Sawase
mesh_terms: D000537:Aluminum Oxide; D003764:Dental Materials; D005898:Glass; D008277:Magnesium Oxide; D008422:Materials Testing; D018583:Pliability
chemical_list: D003764:Dental Materials; D008277:Magnesium Oxide; D000537:Aluminum Oxide