Mouth Ulcer Pics Is It Normal To Have A Mouth Ulcer For This Long?

Is it normal to have a mouth ulcer for this long? - mouth ulcer pics

I had a sore mouth for more than 3 weeks and shows no signs of disappearing. I saw my dentist about it when it first appeared and told me that he is infected, but soon disappear when I cleaned with salt water. It's not as painful as it was, but it still hurts when I brush my teeth to eat /. What is fever?