Effect of laser welding on the titanium composite tensile bond strength

Effects of Different Surface Treatments on Bond Strength of Resin Cement to Machined Pure Titanium

PURPOSE

To investigate the effects of grit blasting, acidic or alkaline/heat treatments, and metal primer application on the shear bond strength (SBS) of resin cement to machined commercially pure titanium (CP-Ti).

MATERIALS AND METHODS

Titanium plates were machined and received one of the following treatments: grit-blasting (GB), or grit-blasting followed by either acidic treatment (GB/AC) or alkaline/heat treatment (GB/AH). The specimens were randomly divided into 4 groups and treated with Rely X Ceramic Primer (RCP), Z Prime Plus (ZPP), and Alloy Primer (ALP), or without primer as the control. The pairs of titanium plates were cemented together with the Rely X Unicem cement. SBS was measured before and after thermocycling between 5°C and 55°C for 5000 cycles.

RESULTS

SEM observation showed that honeycomb-shaped pores formed on the surface of machined CP-Ti after GB/AC treatment, whereas a uniform net-like pattern formed after GB/AH treatment. In descending order, the surface roughness was GB, GB/AC, and GB/AH. The GB/AH group showed the highest SBS among all the treatments. As for primers, ALP group showed the highest SBS, while the RCP group showed the lowest. GB followed by ALP presented the highest SBS.

CONCLUSION

A fine, uniform network structure was formed on the surface of CP-Ti following GB/AH treatment, providing an effective micromechanical interlocking mechanism for resin bonding. At the same time, after AH treatment, the -OH formed on the surface of the machined CP-Ti triggered a chemical reaction with the acid monomers in the resin adhesives, creating a chemical bond. As a result, GB/AH treatment significantly improved the bond strength relative to GB/AC treatment. In addition, ALP treatment facilitated the formation of hydrogen bonds, which further improved the chemical bond strength. Finally, the combination of the effects mentioned above resulted in the most robust bond between machined CP-Ti and the resin adhesives.

Adhesive bonding of resin cements to cast titanium with adhesive primers

The purpose of this study was to evaluate the effects of adhesive primer applications on the bond strength of resin cements to cast titanium. Four adhesive primers - Metaltite, Metal Primer II, Alloy Primer and Ceramic Primer - and their respective resin cements - Bistite II DC, Link Max, Panavia F 2.0, RelyX Unicem and RelyX ARC - were tested. Cast plates were prepared from titanium ingots (n=6 specimens/cement) and had their surfaces airborne-particle abraded with Al2O3 (50 μ m). Three resin cement cylinders were built on each bonded titanium surface, using a cylindrical translucent tubing mold and were subjected to micro-shear testing. Data were analyzed statistically by two-way ANOVA and Tukey's post-hoc test (α=0.05). The application of Metal Primer II and Ceramic Primer resulted in significant higher bond strength for Link Max and RelyX Unicem resin cements, respectively, than nonuse of adhesive primers. Panavia F 2.0 and RelyX ARC yielded high bond strength means with or without adhesive primers. The use of adhesive primers might increase the bond strength to cast titanium depending on the resin cement used.

Effect of laser welding on the titanium ceramic tensile bond strength

Titanium reacts strongly with elements, mainly oxygen at high temperature. The high temperature of titanium laser welding modifies the surface, and may interfere on the metal-ceramic tensile bond strength.

OBJECTIVE

The influence of laser welding on the titanium-ceramic bonding has not yet been established. The purpose of this in vitro study was to analyze the influence of laser welding applied to commercially pure titanium (CpTi) substructure on the bond strength of commercial ceramic. The influence of airborne particle abrasion (Al2O3) conditions was also studied.

MATERIAL AND METHODS

Forty CpTi cylindrical rods (3 mm x 60 mm) were cast and divided into 2 groups: with laser welding (L) and without laser welding (WL). Each group was divided in 4 subgroups, according to the size of the particles used in airborne particle abrasion: A - Al2O3 (250 µm); B - Al2O3 (180 µm); C - Al2O3 (110 µm); D - Al2O3 (50 µm). Ceramic rings were fused around the CpTi rods. Specimens were invested and their tensile strength was measured at fracture with a universal testing machine at a crosshead speed of 2.0 mm/min and 200 kgf load cell. Statistical analysis was carried out with analysis of variance and compared using the independent t test (p<0.05).

RESULTS

Significant differences were found among all subgroups (p<0.05). The highest and the lowest bond strength means were recorded in subgroups WLC (52.62 MPa) and LD (24.02 MPa), respectively.

CONCLUSION

Airborne particle abrasion yielded significantly lower bond strength as the Al2O3 particle size decreased. Mechanical retention decreased in the laser-welded specimens, i.e. the metal-ceramic tensile bond strength was lower.