Fracture strength of glass infiltrated-magnesia core porcelain.
OBJECTIVE
This study determined the fracture strength of magnesia-core porcelain after using a glass infiltration firing technique.


METHODS
Eighty refractory dies were replicated from a stainless steel master die milled to the dimensions of a maxillary premolar that had been prepared for a porcelain crown. The core porcelain was applied to the refractory dies using traditional condensation methods, and then formed into standardized copings using a centrifugal sculpturing device. The copings were vacuum-fired from 593 degrees C to 1 of 8 high temperatures. Five copings per temperature were then coated with a glass-infiltrate and ground back to a standard thickness. The finished copings were bonded to a duplicate die with an adhesive resin luting system and placed in an Instron testing machine and loaded to fracture.


RESULTS
Analysis of variance and Student-Newman-Keuls tests demonstrated significant differences among treatments and temperatures (P < 0.05). A significant increase in fracture strength was observed after glass infiltration of the magnesia-core porcelain. Sintering the copings to 871 degrees C or 899 degrees C prior to glass infiltration gave the highest fracture load values.


CONCLUSIONS
Glass infiltration significantly increased the fracture strength of the magnesia-core porcelain.
Evans
D B
DB
United States Air Force, Dental Corps, Kadena Air Base, Okinawa, Japan.
O'Brien
W J
WJ
D000704:Analysis of Variance; D003776:Dental Porcelain / Q000737:chemistry*; D005898:Glass / Q000737:chemistry; D006358:Hot Temperature; D008277:Magnesium Oxide / Q000737:chemistry*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning
C118364:Magcor; D003776:Dental Porcelain; D008277:Magnesium Oxide