Swelling in the soft tissue
Lupus swells the gums and makes the teeth sensitive, also the medications affect teeth and gums, we also get sores on the inside of the mouth and nostrils.  This usually happens when we are in a flare or when the acidity in the body is too high.  Lupus medications, especailly prednisone,  are acid forming agents in the system, besiades causing the teeth and bones to soften with time, so we have to couteract their effects. 
Mouth and nose sores, acid reflux and many other symptoms, are caused by acidity in the body.  You have to regularize your Ph. One way to do this is eating an alkaline diet, usually white or pale foods are less acidic than spicy or brightly colored foods.  Procesed foods and red meat acidify the system while green vegetables and white meats keep it alkaline.  
Also, keep your mucus membranes moisturized by drinking water regularly and applying moisturizing oil or lotion inside your nose, especially in the winter when the heating is on.  In your house, keep steam moisturizers and always sleep with one in your room.
For the teeth and gums I brush with baking soda instead of tooth paste, that hurts less and regularizes the Ph in your mouth. Rinsing with warm water and baking soda or salt also helps.  Other products that can yied results are:
Sesodyne toothpaste
mouthwash to keep the sores from infecting
Calcium based antiacids, like tums, to curb acidity in the stomach and add calcium to teeth and bones, especially if taking prednisone (besides whatever your doctor recommends).
Based on the book Befriending the Wolf: The Guide to Living and Thriving with Lupus.