Porcelain Bond Strengths to Four Noble Alloys using PoM Technique

Objective: The new press-on-metal (PoM) technique for applying porcelain to cast alloys should substantially reduce dental laboratory time for preparing metal-ceramic restorations (Tysowsky et al, Abstract 1555, IADR 2007). The objective of this study was to evaluate the bond compatibility index (bond strength) of four recently introduced noble alloys, one high-gold alloy and three more economical alloys, bonded to a compatible veneering porcelain, using the PoM technique. 

Method: (1) Aquarius Hard, a high-gold alloy (86.1Au-8.5Pt-2.6Pd-1.4In), (2) Evolution Lite, a reduced-gold alloy (40.3Au-39.3Pd-9.3In-9.2Ag-1.8Ga), (3) Callisto 75 Pd, a Pd-Ag-containing alloy (75.2Pd-2.5Au-7.1Ag-9.3Sn-1.0In), and (4) Aries, a conventional Pd-Ag alloy (63.7Pd-26.0Ag-7.0Sn-1.8Ga-1.5In) were selected for bonding to the veneering porcelain (IPS InLine) using the PoM technique. All products are marketed by Ivoclar Vivadent. Ten metal-ceramic specimens meeting the ISO 9693 standard were prepared for each alloy using recommended manufacturer techniques, and the three-point bending test in the ISO standard was used to determine bond strength. Values for the alloys were compared using one-way ANOVA (α = 0.05 for statistical significance). 

Result: Mean values with standard deviations for bond strength (units of MPa) were as follows: Aquarius Hard (33.7 ± 11.5); Evolution Lite (34.9 ± 4.5); Callisto 75 Pd (37.2 ± 11.9); Aries (30.7 ± 10.8). There was no significant difference (p > 0.05) in the bond strength for the four alloys. 

Conclusion: All four alloys had mean metal-ceramic bond strengths that substantially exceeded the 25 MPa minimum in the ISO standard, although one Aries specimen had a lower value than 25 MPa. It is important to note that the PoM technique for porcelain is not recommended by the manufacturer for alloys containing over 10% Ag.