Effect of surface treatments on adhesion of low-fusing porcelain to titanium as determined by strain energy release rate

Objective

This study evaluated the effect of different chemical surface treatments on the surface characteristics of commercially pure titanium (cp Ti) and the adhesion of the porcelain–titanium system by means of strain energy release rate (G-value, J/m²). Surface roughness and morphology of treated cp Ti were additionally evaluated.

Methods

Two hundred and thirty specimens of machined cp Ti plates grade II were prepared. The specimens were divided into ten groups in each test according to the surface treatment used; Gr 1 (control; machined), Gr 2 (sandblasted), Gr 3 (CH₂Cl₂ for 5 min), Gr 4 (CH₂Cl₂ for 10 min), Gr 5 (10% H₂O₂ for 5 min), Gr 6 (10% H₂O₂ for 10 min), Gr 7 (30% H₂O₂ for 5 min), Gr 8 (30% H₂O₂ for 10 min), Gr 9 (9% HF for 5 min) and Gr 10 (9% HF for 10 min). Titanium–porcelain (Vita Titankeramik) was applied to each group for testing the adhesion. The G-value (J/m²) was measured with a four-point bending configuration. Following fracture testing specimens were examined with a scanning electron microscope (SEM). Surface roughness and SEM analysis were carried out. Data were analyzed using ANOVA and Tukey's test.

Results

Groups treated with 9% HF or CH₂Cl₂ baths for 10 or 5 min showed the highest adhesion values (J/m²) (34.23 ± 4.31, 30.75 ± 4.91, 28.92 ± 4.33 and 22.54 ± 3.58) respectively among the groups. The machined groups demonstrated the lowest value (8.18 ± 1.95) (J/m²). SEM analysis indicated a combination of cohesive and adhesive fractures for 9% HF, CH₂Cl₂, sandblasted and 30% H₂O₂ (10 min) groups, while mainly adhesive fractures were found with the other groups. There was no direct correlation between surface roughness and adhesion.

Significance

Adhesion between porcelain and cp Ti can be improved by the use of certain chemical surface treatments prior to porcelain firing as alternative techniques to sandblasting treatment.