I am 46 and have only had one cavity in my life. I was put on several medications in January of 2013. Now my bottom front teeth are starting to darken at the gumline. They do not hurt like a cavity. It started with just one tooth but is now spreading to the ones beside it. I am on KlorCon, Lasiks, MagOxide, Oxycodone, Baclofen, Lactulose and Alprazolam. I also take Vitamin C, B12 and Milk Thistle daily. Could one of these be causing the problem with my teeth?