A Experimental Study On Chemical Polishing Of Dental Cast Titanium Prosthesis

Purpose: There are many disadvantages in the polishing of cast titanium prosthesis by mechanical burnishing method such as difficulties in burnishing, environmental pollution, and so on. In this study, we developed a new type chemical polishing solution, and then the related examination and clinical study were made in order that the polishing problems will be resolved when the solution is applied to clinic.Methods: To develop a new type chemical polishing solution, then the weight loss, surface roughness, surface condition, thickness of O-area, V micro-hardness and mechanical properties of castings were measured and analyzed after had been polished. At last the clinical use of chemical polishing method was tried. Results:1. The -wt% of castings of mechanical group, chemical group or electrolytic group was 1.129%, 2.768%, 2.503% respectively. In three groups, the -wt% of mechanical group was the least (p<0.01), and there was no significant difference between the other two groups (p>0.05).2. The Ra value of castings of mechanical group was 0.252um, which of chemical group was 0.092um, so we have reason to say that the castings of chemical group were glossier.3. Seen under the metallscope, there were some shallow or deep cutting traces on the surface of castings burnished by mechanical method, and there hadn't on which were polished by chemical solution.4. The thickness of O-area on the castings' surface in chemical group was about 7um, which was equal to and more uniform than that of castings' surface in mechanical group.5. One 25um thickness hard layer remained on the castings' surface after the3castings were sandblasted and burnished lightly. After the castings were polished, the hard layer had not existed. The results were accorded to which of O-area test.6. Compared control group with chemical polishing group, there was no significant difference in mechanical properties of castings, which includes tensile strength, yield strength and elongation rate.7. 150 cast titanium restorations were polished by chemical method in clinic. It was concluded that chemical polishing was an easy, efficient and no polluting method, and dentures remained gloss even after were heat-treated or used for some time. The exact dentures made patients to feel comfortable and esthetical. Conclusions:1. The chemical polishing solution was composed by hydrofluoric acid: nitric acid: additional :1:X.2. The results of five basic examinations proved that the polishing effects of chemical polishing are better than that of mechanical burnishing. Nice precise was acquired, and a uniform O-area was formed on the surface of castings, and the chemical polishing hadn't bad effect on titanium's mechanical properties.3. The use of chemical polishing in clinic showed that chemical polishing method was an easy, efficient and satisfactory method, and had clinical use and popularizing values.