Tooth bleaching question ---why does it cause sharp stabbling nerve pain?

Possible cavity?: Sometimes patients will have sensitivity to the bleaching gel itself. But a sharp stabbing may be a sign of a tooth cavity, gum disease or a defective filling/crown. Consult your dentist.

A Crack/Root Exposed: There has to be a connection between the nerve tissue and the tooth surface where the bleaching gel is placed. When the peroxide hits the tissue it breaks down to water and oxygen and it is the pressure on the nerve from the gas release that causes the sharp pain. There are desensitizing gels and toothpastes you can use to seal the communications and bleach more slowly.

Material used: some patients react to the concentration of the peroxide component used. Usually this can be adjusted if a dentist is involved in the process