I recently read up on this issue, and wiping seems unnecessary.
How old is your son? Has he had problems with cavities?
One study compared the decay-causing levels (sorry can't think of a better way to put that) of different substances. Water was 0.0 and sugar water was 10.0. Breastmilk was 0.1, so basically the same as water.
Breastfeeding at night doesn't cause tooth decay.
llli.org has some articles on this issue that are a good read.
thanks for the replies. my ds is almost 10 months, so we haven't went to dentist and probably wont til 2 yrs. does that seem a right time to visit dentist? otherwise, how would i even know he has cavities?