Effect of surface treatment on bond strength of low-fusing porcelain to commercially pure titanium

Abstract

Due to the pronounced oxidative nature of titanium at high temperatures, an excessively thick layer of TiO(2) may form on the surface. This oxide layer could adversely affect titanium-porcelain bonding. The purpose of this study was to investigate the effect of bonding agent and surface treatment using airborne-particle abrasion and hydrochloric acid on the bond strength between a low-fusing porcelain and commercially pure cast titanium. A casting unit was used to cast 60 specimens of commercially pure titanium (25.0 x 3.0 x 0.5 mm). The specimens were equally divided into 3 groups. The first group received no surface treatment and served as the control, the second group was subjected to airborne-particle abrasion, and the third group was treated with hydrochloric acid. The specimens in each group were further divided into 2 subgroups of 10 each. Ten specimens were treated with bonding agent (Noritake), and 10 specimens were not treated with bonding agent. Low-fusing porcelain (Noritake) was fired onto the surface of the specimens. A universal testing machine was used to perform the 3-point bending test. The titanium-ceramic interfaces were subjected to scanning electron microscopic analysis. The bond failure data (MPa) were analyzed with a 2-way analysis of variance and Tukey multiple range tests (alpha=.05). Four specimens from each group were selected for scanning electron microscopic examination. The debonding test showed that surface treatment with airborne-particle abrasion followed by application of a bonding agent resulted in the strongest (35.60 +/- 8.15 MPa) titanium-ceramic bond (P<.001), followed by airborne-particle abrasion alone (25.6 +/- 5.4 MPa) and bonding agent alone (24.7 +/- 6.3 MPa). Hydrochloric acid surface treatment provided no beneficial effect to the titanium-ceramic bond strength compared to untreated specimens (P=.975). The photomicrographs of the titanium surface after debonding demonstrated residual porcelain retained on the metal surface for all groups. Surface treatment using either airborne-particle abrasion or bonding agent alone enhanced the bond strength of cast commercially pure titanium to low-fusing porcelain. The combination of airborne-particle abrasion and bonding agent provided the greatest improvement in titanium-ceramic bond strength. Titanium surface treatment with hydrochloric acid, with or without bonding agent, produced values that were not statistically different than the control.