Could i do ct scan if i have orthodontic appliance ?

Sure, unless your CT: ...is focused on the oral cavity, in which case your braces may promote scatter of the xray beam.

Depends: What kind of scan and what part of your body in relation to the appliance?

Yes, generally so: An orthodontic appliance itself is generally not contraindicated for CT scanning. An important thing to keep in mind is that foreign material, especially high density such as metal, can produce artifacts on CT scanning that can limit the images. If the CT scan is for a part of the body far away from metal then there should be no problem. For imaging closer to the area of metal, it may interfere

Yes, but...: The ortho appliance will show up on the CT, and may have side-effects on the accuracy of the images. Discuss this with your provider and you will be able to make the right decision.