Objective      To produce nitrogen-doped titania (TiO

2-x

N

x

) film on MBT straight wire appliance and to evaluate its biocompatibility.        Methods      Radio-frequency magnetron sputtering was applied to produce TiO

2-x

N

x

film on the surface of raw material of MBT straight wire applian

ce. Biocompatibility was evaluated as follows: (1) The film material (raw material of MBT straight wire appliance with TiO

2-x

N

x

film) and the control material (raw material of MBT straight wire appliance) were fixed on the surface of rat oral mucosa

which were examined macroscopically and histologically after 2 weeks. (2) Mice were given the extracted liquids of the film material and the control material and normal saline by lavage for 1 week

respectively. The clinical symptoms were observed

body weight was recorded and viscera were dissected and observed in the mice to evaluate the short-term systemic toxicity of the film material. (3) The hemolysis of the film material was evaluated with rabbit blood in vitro. (4) Mice were given the extracted liquids of the film material and the control material and normal saline by lavage twice in 24 h

respectively

and the bone marrow slides of the mice were prepared to evaluate the teratogenicity and mutagenicity of the film material.       Results      The appetite and movement of the rats were normal

and the histological morphology of rat oral mucosa of the film material group showed no significant difference from that of the control material group

which suggested the film material had no oral mucosa irritation response. The growth rate of mouse body weight was not significantly different between the film material group and the control material group (P0.05)

and neither toxic signs nor apparent abnormality of pathological examination was found

revealing that the film material had no obvious short-term systemic toxicity. The hemolytic rate was less than 5%

and the breaking up of red blood cells was not found in the film material group

indicating that the film material had no hemolytic reaction. The micronuclear rates in the polychromatic erythrocytes (PCE) of the mouse bone marrow of the negative control group

the film material group and the control material group were 1.48

2.08  and 2.16

respectively

which were all less than 5

but th

ere was no significant difference between the three groups (P0.05).       Conclusion      MBT straight wire appliance with nitrogen-doped titania TiO

2-x

N

x

film has good biocompatibility without oral mucosa irritation response

short-term systemic toxicity

hemolysis and genotoxicity.