How do you treat baby bottle tooth decay?

Clean the teeth. If caught early enough, the tooth decay process can be stopped and even repaired. Brush teeth thoroughly at least once a day to remove acid causing bacteria, stay away from sugars, breads and sodas (even diet!), use a small amount of Fluoride ( in toothpaste and water) to help calcium and phosphate in the saliva to repair the acid damage.
Depends on severity. If mild it can be treated preventively by changing bottle habits, improving diet and oral hygeine practices and home applications of topical fluoride. If more severe then dental restorations and possible tooth extraction may be required in addition to preventive measures. Long term ongoing dental care will be needed. These children are much more susceptible to additional cavities later in life.
That depends. Baby bottle tooth decay is an emotionally and physically devastating disease. Very often by the time we see the child for the first time the front teeth are so destroyed that they do need to be extracted. We can usually save the back teeth with stainless steel crowns. These children are also more prone to future cavities and need constant follow up dental care.
Xylitol. Prevention is most important. In addition to brushing the baby teeth and no bottle in the bed, you can use xylitol to prevent decay. Xylitol is a natural sugar available in granular form, mints, chewies or gum. It inhibits the bacteria that causes decay from growing.
Prevention & dentist. First - go see a pediatric or your general dentist asap. Next prevent future decay by never putting a baby to bed with a bottle of milk, formula or juice. If you must put a baby down with a bottle it can only be water. In addition to tooth decay, this is the beginning of the path toward obesity and diabetes.