Internal bleaching with a 30 percent hydrogen peroxide solution is aesthetically very successful in the short term; however, in the long term, the success rate falls below 50 percent. This procedure is associated with a risk of external root resorption, documented both clinically and experimentally. The etiology of resorption and the effects of 30 percent hydrogen peroxide on dental tissues suggest that this chemical should be avoided. Internal bleaching is possible using sodium perborate mixed with water. The aesthetic outcome is still acceptable and the potential for resorption may be minimized.