Nonvital bleaching: general considerations and report of two failure cases.

This paper describes the rationale and procedures for noninvasive treatment of discolored nonvital teeth using the walking bleach technique. The limitations of this procedure and, in particular, the unpredictable color stability following non-vital bleaching are discussed and illustrated with two cases of rapid discoloration relapse. The possible reasons for treatment failure are examined and show that current knowledge regarding the origin and prevention of discoloration is limited.