1. Mechanical grinding:
titanium chemical reactivity is high, low thermal conductivity, viscosity, mechanical grinding is relatively low, and easy to react with abrasive abrasives, ordinary abrasive is not suitable for titanium grinding and polishing, the best use of good thermal conductivity superhard abrasive, such as diamond, cubic boron nitride, polishing linear speed is generally 900-1800m/min. Otherwise, the surface of titanium is prone to grinding burns and microcracks.
2. Ultrasonic grinding: through ultrasonic vibration, the abrasive particles between the grinding head and the grinding surface and the grinding surface produce relative movement to achieve the purpose of grinding and polishing. The advantage is that grooves, pits and narrow areas that cannot be ground with conventional rotary tools become easier, but the grinding effect of larger castings is not satisfactory.
3. Electrolytic mechanical compound grinding: conductive grinding tools are used to apply electrolyte and voltage between the grinding tool and the grinding surface. Under the joint action of mechanical and electrochemical polishing, the surface roughness is reduced and the surface gloss is improved. The electrolyte is 0.9NaCl, the voltage is 5V, and the speed is 3000rpm/min. This method can only grind plane, and the grinding of complex denture bracket is still in the research stage.
4. Barrel grinding: using the centrifugal force generated by the revolution and rotation of the grinding barrel, so that the denture in the barrel and the abrasive relative friction movement to reduce the surface roughness of the grinding purpose. The grinding automation, high efficiency, but can only reduce the surface roughness and can not improve the surface gloss, grinding accuracy is poor, can be used with denture polishing before deburring and rough grinding.
5. Chemical polishing: Chemical polishing is through the REDOX reaction of metal in the chemical medium to achieve the purpose of leveling polishing. Its advantage is that chemical polishing has nothing to do with the hardness of metal, polishing area and structure shape, all parts in contact with the polishing fluid are polished, no special complex equipment, simple operation, more suitable for the complex structure of titanium denture bracket polishing. However, it is difficult to control the process parameters of chemical polishing, which requires a good polishing effect without affecting the accuracy of the denture. A better titanium chemical polishing solution is HF and HNO3 prepared in a certain proportion. HF is a reducing agent, which can dissolve titanium metal and play a leveling role. The concentration is less than 10%. Titanium polishing solution requires high concentration, low temperature and short polishing time (1 -- 2min.).
6. Electrolytic polishing: also known as electrochemical polishing or anodic dissolution polishing, due to the low conductivity of titanium, oxidation performance is very strong, the use of acidic water electrolyte such as HF-H3PO4, HF-H2SO electrolyte on titanium almost can not be polished, after the application of external voltage, titanium anode oxidation immediately, and the anode dissolution can not be carried out. However, anhydrous chloride electrolyte has a good polishing effect on titanium under low voltage. Small specimens can be polished with mirror surface, but for complex restorations, it is still impossible to achieve complete polishing. Perhaps changing the shape of cathode and adding cathode can solve this problem, which remains to be further studied.
