Investigation of the effect of titanium alloy surface coating with different techniques on titanium-porcelain bonding

Statement of Problem. The bond strength of dental porcelain to titanium is inadequate as a clinical alternative to conventional alloys for metal ceramic restorations. Purpose. The purpose of this in vitro study was to evaluate the effects of coating titanium surface with a micro-arc oxidation (MAO) technique and hydroxyapatite (HA) on the bond strength of porcelain to titanium surfaces. Material and methods. One hundred twenty machined titanium specimens with a dimension of 25x3x0.5 mm were prepared from grade 5 titanium as the metal substrate. Specimens were divided into 6 groups (n=20) according to the surface treatment used: airborne-particle abraded (control), coated with MAO for 5 minutes, coated with MAO for 15 minutes, coated with MAO for 30 minutes, coated with HA, and combination of MAO and HA. Each group was further divided into 2 subgroups (n=10) according to the type of porcelain used: Noritake Ti-22 porcelain or Vita-Titankeramik porcelain. The bond strength was tested with a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically with 2-way ANOVA and Tukey honest significant differences multiple comparison tests (alpha=.05). Results. For both porcelain groups, the 30-minute MAO groups showed higher bond strength values than those of the control groups (P<.05). In the Vita Titankeramik porcelain subgroup, the specimens coated with HA- did not show any statistical differences compared with those of the control group (P>.05). Surface roughness was affected significantly (P<.001) by the coating procedure compared to that of the the control group. Conclusions. Coating with either MAO or HA improved titanium-porcelain adhesion.