Effect of opaque porcelain thickness bond strength of porcelain to Ni-Cr alloys
Objectives Metal-ceramic restorations are the standard by which all esthetic restorations are measured. Fracture of dental restorations is a
multifactorial problem, which is serious and costly. Debonding of porcelain from the metal substructure and the bond strength depend on
many factors. The purpose of this study was to determine whether the opaque porcelain thickness has a significant effect on metal ceramic
bond strength utilizing the ISO 9663 standard crack initiation test.
Methods Thirty rectangular Ni-Cr metal bars (25 × 5 × 0.3 mm) were fabricated according to ISO 9663 standards. The metal bars were
divided into three groups of 10. Opaque, body and enamel Noritake porcelain were applied on the middle of the bar according to ISO 9663
standards up to 1 mm porcelain thickness. The opaque porcelain thicknesses were 0.1, 0.2, and 0.3 mm, respectively in the three groups.
The 3-point bending test was applied according to the ISO 9663 standards and fracture strength (Ffail) was measured using a universal
testing machine with a cross head speed of 1.5 mm/minute.
Results Analyses of the data by one-way ANOVA demonstrated no significant differences in bond strength among the three experimental
groups (P = 0.26).
Conclusion Within the limitations of this study, it is concluded that 0.1 mm opaque porcelain provides sufficient bond strength between
metal and ceramic in metal-ceramic restorations.