Wow, I could have written this this myself. You are not alone! I am going the same symptoms following the same procedure on a premolar with the same history. Although my cheek is not hot to touch, I feel that something is wrong and it seems like an infection to me. The OS is more concerned about the gum healing closed because I would not have an opening from my mouth to the sinus cavity anymore. I don't feel confident that when this heals closed it will stop the symptoms with all the sinus fluids.