Had a mini ct scan of sinus and 2 dental office ct scan of tooth in one year am i high risk for brain cancer due to this ?

No, not even 9 scans: Patients get CT scans all over the world, every day. As long as there is a good reason for the scan, it is fine to do. If repeated scans are planned, to follow some sort of serious illness, a patient can ask his doctor what other options there are, in order to decrease the total number of scans in his lifetime. Having repeated CT scans, over and over, can add up to too much x-ray exposure.

Not problematic: Imaging is often required for knowledge, otherwise you are asking the practitioner to work blind. Radiation levels are carefully controlled to be a little as required for quality information. No, you are at virtually no risk of brain cancer from your tests. you probably had the equivalent of a couple of days background radiation. You have nothing to worry about.