Hydroxyl radical activity in thermo-catalytically bleached root-filled teeth.

Intra-coronal bleaching of root-filled teeth has been associated with invasive cervical root resorption. It is considered that during bleaching hydrogen peroxide diffuses through the tooth structure into the cervical periodontium, resulting in periodontal tissue destruction and initiating a resorptive process. Hydrogen peroxide is capable of generating hydroxyl radical, an oxygen-derived free radical, in the presence of ferrous salts. Hydroxyl radicals are extremely reactive and have been shown to degrade components of connective tissue, particularly collagen and hyaluronic acid. The aim of the present study was to determine whether hydroxyl radicals are generated during the bleaching of root-filled teeth which have been discoloured by blood. Forty extracted human premolar teeth were root-filled with gutta-percha and AH26 sealer cement. Twenty of the teeth were experimentally discoloured by blood. All teeth were then thermo-catalytically bleached using 30% hydrogen peroxide while tooth roots were seated in a test solution of sodium salicylate. Hydroxyl radical generation was determined by the detection of reaction products of this radical with salicylate using high performance liquid chromatography with electrochemical detection (HPLC-ECD). The presence of hydroxyl radicals was detected in twenty-five of the teeth. There was a significant association between the production of hydroxyl radicals and the presence of tooth discolouration caused by blood components. Greatest yields of hydroxyl radicals occurred in teeth in which EDTA had been used to clean the pulp chamber prior to bleaching. It was concluded that hydroxyl radicals are generated during the thermo-catalytic bleaching of root-filled teeth. Generation of this toxic chemical species may be one mechanism underlying periodontal tissue destruction and root resorption after intra-coronal bleaching.

Incidence of invasive cervical resorption in bleached root-filled teeth.

Invasive cervical resorption, a form of external root resorption, has been reported to be associated with intra-coronal bleaching of root-filled teeth and this has raised concerns about carrying out such bleaching procedures. The purpose of the present study was to examine the incidence of invasive cervical resorption in root-filled teeth which had been bleached using a standardized technique. Three observers examined records and radiographs from a total of 158 patients, whose bleaching treatment had been carried out in a specialist endodontic practice. The sample comprised 204 teeth with a review period of between 1 and 19 years. One-hundred-and-fifty-one teeth (77.94 per cent) had an associated history of traumatic injury. All teeth had been treated with a combination of thermocatalytic and 'walking bleach' procedures using 30 per cent hydrogen peroxide. In 54.41 per cent of teeth, gutta-percha and AH26 root-fillings were kept at the height of the cemento-enamel junction while 18.63 per cent were below and 26.96 per cent were above the CEJ. Sealing cement was not placed over the gutta-percha and AH26 root-fillings in any of the teeth in the study. It was found that a total of four teeth from the sample group (1.96 per cent) had developed invasive cervical resorption during the review period. All of these teeth had a history of traumatic injury and the level of gutta-percha was at the CEJ.(ABSTRACT TRUNCATED AT 250 WORDS)