About a month ago, I bit down on an apple, and experienced pain in my lower jaw. It radiated up to my ear. The pain subsided. My dentist took x-rays, saw no infection, but put me on Keflex 500 mg, which I took till finished. FYI--my sinuses flared up (headaches) & my ears ached, for a while....both have since subsided. In the last week, my teeth have (overall) were sensitive. I've also developed a lump, below the gum line, in the same area, that I originally felt pain. I called the dentist again, and he has me rinsing 2x daily with Chlorhexidine 0.12% He did not renew the Keflex. My tooth sensitivity has subsided. The lump is still there, but seems to be improving. Is the mouth rinse effective in treating problems BELOW the gum line? i.e. lumps & is more keflex recommended? Thanks! Nancy