Microleakage comparison of glass-ionomer and white mineral trioxideaggregate used as a coronal barrier in nonvital bleaching

ABSTRACT

Objectives: There is some evidence that the pH at the root surface is reduced by intracoronal placement of bleaching pastes, which is known to enhance osteoclastic activity. Therefore, it is recommended that a protective barrierbe used over the canal filling to prevent leak age of bleaching agents. Glass-ionomer (GI) is commonly used asa coronal barrier before nonvital bleaching. Because mineral trioxide aggregate (MTA) creates high alkalinityafter mixing with water, using MTA as a protective barrier over the canal filling may not only prevent leakage of bleaching agents and microorganisms, but may prevent cervical resorption. The aim of this study was to evaluates ealing ability of white mineral trioxide aggregate (WMTA) as a coronal barrier before nonvital bleaching.Study design: Root canals of one hundred thirty human maxillary incisors were instrumented and filled withgutta-percha without sealer. Gutta-percha was removed up to 3 mm below the cementoenamel junction (CEJ). Theteeth were randomly divided into six experimental groups of 20 teeth each and two control groups of 5. In three experimental groups, WMTA was packed into the canal to the level of CEJ. In the remaining experimental groups,glass-ionomer (GI) was used as a coronal barrier. After a 24-hour incubation period, one of the following threebleaching agents was placed in the access cavity of each of the WMTA or GI groups. These three bleaching agentswere 30% hydrogen peroxide, sodium perborate mixed with 30% hydrogen peroxide, and sodium perborate mixedwith distilled water. The bleaching agents were replaced every 3 days for three times. In the positive controls, no (..) (AU)