What is the proper method to clean and kasher my mouth for Pesach?
By Rabbi Chaim Hillel Raskin, Rov of Anash in Petach Tikvah.
Heat facilitates a transmission of taste from food to utensil and vice versa. An absorbed taste is generally considered stale (pagum) after 24 hours and b’dieved won’t prohibit food subsequently cooked in the utensil (if it isn’t sharp food). Some hold that the taste of chametz prohibits on Pesach even after 24 hours, and the custom is to follow this view.
Poskim debate whether the heat of a kli sheni, transferred from the original cooking utensil, can facilitate a transmission of taste. L’chatchila we are stringent with a kli sheni, and by Pesach even a kli shlishi and further, yet in times of great need it is permitted b’dieved if 24 hours passed between the original transmission and the second use.
Some poskim hold that a utensil used primarily for cold food (e.g. a cup) and was sometimes used for hot, need not be kashered and it’s enough to clean it well. The custom is to be stringent, yet if it was used with hot food on Pesach without kashering, the food is permissible b’dieved if it was cleaned properly.
Teeth don’t become prohibited from absorption of chametz before Pesach since they are part of the human body, (of course, between the teeth must be thoroughly cleaned). However, fillings, braces or dentures aren’t part of the body, and some are concerned they may have absorbed hot chametz (above yad soledes bo) from a kli sheni or shlishi. Moreover, some hold that a hot solid food – slice of pizza – is always considered like a kli rishon.
Others write that fillings are made from a strong material that doesn’t absorb. Moreover, several of the above points can be combined to allow a lenient approach: (1) The basic halacha that taste doesn’t prohibit b’dieved after 24 hours; (2) Most of the foods one ate weren’t yad soledes; (3) The lenient view regarding an absorption in kli sheni including solids. This is widely accepted year-round between milchigs and fleishigs.
In practice, fillings or braces needn’t be kashered, though one must stop eating hot chametz 24 hours before the zman so that any taste in them should be pagum. Some have a hiddur for Pesach to kasher them somewhat by drinking a hot drink (above 113° F, or at least slightly hotter than one usually drinks) before the zman. Dentures should be kashered by pouring from a kli rishon, but if they might get damaged, they should be placed into a kli sheni.
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