There are some interesting background around bathing actually...http://www.accesstoinsight.org/lib/auth ... .ch01.html
Bathing. Although Pc 57 forbids a bhikkhu from bathing at intervals of less than half a month, we noted in the discussion of that rule that it was apparently intended as a temporary disciplinary measure for bhikkhus who had inconvenienced King Bimbisāra when he wanted to bathe in the hot spring near Rājagaha. When the Buddha later added exemptions to the rule, he so relaxed it that he virtually rescinded it. In addition, Mv.V.13 explicitly rescinds the rule in all parts of the world outside of the central Ganges Valley.
Care of the teeth. Toothbrushes, dental floss, toothpaste, and tooth powders were unknown in the time of the Buddha. However, there is an allowance for tooth wood, which is the same thing as the tooth-cleaning stick discussed under Pc 40. The Buddha extolled the virtues of using tooth wood as follows: "There are five advantages in chewing tooth wood: It makes the mouth attractive, the mouth does not smell foul, the taste buds are cleaned, bile and phlegm do not coat one's food, one enjoys one's food." At present, toothbrushes and dental floss would come under the allowance for tooth wood. Because tooth wood should not be less than four fingerbreadths long, many Communities extend this prohibition to include toothpicks less than four fingerbreadths as well. Toothpaste and tooth powder, because they are composed of mineral salts, would come under the allowance of salts for medicine.