Contraindications for dental implant with thermi smooth?

Yes, you can use thermismooth if you have had dental implants in the past.  Dental implants are titanium rods that are inert.  Thermi works by using RF energy that penetrates the skin and not deep to the oral cavity

Having metal containing dental implants should not impact your ThermiSmooth treatments in anyway. ThermiSmooth is non invasive. It gently warms the skin to stimulate collagen production. 

Yes you could. That is a good question, but it is not a contraindication.Thermasmooth works with radio frequency but it is not that deep. If you really worry you may place a mouth guard prior to treatment.