The thermal expansion coefficient of pure
titanium and ti-6al-4v titanium alloy decreased, and was 9.41×10-6℃-1 and 10.03×10-6℃-1, respectively. However, the thermal expansion coefficient of dental metal alloy and ni-cr alloy is about 13.7×10-6 ° c-1, and the matching porcelain powder cannot be used with titanium material, so special titanium porcelain porcelain must be developed. Currently, Ti-ceram, Vita Titankeramik and Proem are the main titanium ceramics used. As the bonding force between titanium oxide and titanium matrix formed on the surface of titanium material above 800℃ is significantly weakened, the roasting temperature of titanium porcelain on the surface is lower than 800℃, which is a low-temperature porcelain, and its bonding strength with titanium has reached the clinical requirements.
The weak link of titanium ceramic bonding is the titanium oxide layer, because the surface of titanium is very sensitive, and it is easily affected by oxygen or other components when heated or even treated at high temperature under the protection of argon, forming too thick oxidation film. In order to avoid excessive oxidation of titanium in porcelain sintering process, coating protection can be used. Currently, Zr is considered to be a promising coating material, which can form a dense ZrO2 on the surface of titanium and form a protective film. The main methods include splash method and electric transfer method.
In the combination of titanium and titanium alloy and ceramic the use of coupling agent, coupling agent and opaque porcelain for the same material, but its liquidity can improve the wetting effect of porcelain, to control the air bubbles interface, improve the bonding force, coupling agent can improve the gold porcelain thermal expansion coefficient and reduce the consistency of the interface and suppress too oxide formation, and strengthen the gold porcelain. Coupling agent is easier to oxidize than titanium, which can inhibit excessive oxidation to some extent. Mixing with ceramic particles in coupling agent can also reduce the difference between titanium and thermal expansion coefficient.
