Hi.. Can understand your concern.. As per your complain if you have a root piece slipped into the sinus it is definitely the cause of SINUSITIS and the removal of the root piece from the sinus cavity followed by antibiotic therapy to wean off the infection is necessary.. At times if the root piece can be retrieved through the socket itself the surgeon does it by placing a sterilized piece of gauze dipped in betadine into the sinus with the help of tweezers and retrieve the root piece followed by placing stitchess on the gum flap so that the healing takes place and the communication between the moth and sinus is closed.. In case if it is not possible a direct surgical approach by perforating the jaw bone near canine region and retrieving the root piece is done. You need not to be worried as a qualified oral surgeon can very well evaluate your case through a C T scan and decide the treatment plan as he gets the view of the sinus and the adjoining structures through different angulations in a C T Scan. If you are still not satisfied you can consult another oral surgeon for a second opinion before you decide to proceed for treatment.. Hope your query is solved.. If you find the answer helpful please write a positive review and click on find this answer helpful as a token of appreciation.. Thanks and regards.. Dr.Honey Nandwani Arora.