title: Microleakage comparison of glass-ionomer and white mineral trioxide aggregate used as a coronal barrier in nonvital bleaching.
abstract: OBJECTIVE
  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 barrier be used over the canal filling to prevent leakage of bleaching agents. Glass-ionomer (GI) is commonly used as a coronal barrier before nonvital bleaching. Because mineral trioxide aggregate (MTA) creates high alkalinity after 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 evaluate sealing ability of white mineral trioxide aggregate (WMTA) as a coronal barrier before nonvital bleaching.
  
  
  METHODS
  Root canals of one hundred thirty human maxillary incisors were instrumented and filled with gutta-percha without sealer. Gutta-percha was removed up to 3 mm below the cementoenamel junction (CEJ). The teeth 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 three bleaching agents was placed in the access cavity of each of the WMTA or GI groups. These three bleaching agents were 30% hydrogen peroxide, sodium perborate mixed with 30% hydrogen peroxide, and sodium perborate mixed with distilled water. The bleaching agents were replaced every 3 days for three times. In the positive controls, no coronal barrier was used. In the negative controls, all the tooth surfaces were covered by two layers of nail varnish. Microleakage was evaluated using protein leakage test. Statistical analyses were performed with the Kruskal-Wallis and Mann-Whitney tests.
  
  
  RESULTS
  The experimental groups showed minimum leakage which was not significantly more than tha in the negative controls. There was no statistically significant difference in leakage between the experimental groups (p<0.05).
  
  
  CONCLUSIONS
  This study indicated that different bleaching agents have no effect on sealing ability of WMTA.
authors: Research Center for Pharmaceutical Nanotechnology, Tabriz University (Medical Sciences), Tabriz, Iran.
authors: Sepideh
authors: S
authors: Vosoughhosseini
authors: Mehrdad
authors: M
authors: Lotfi
authors: Kaveh
authors: K
authors: Shahmoradi
authors: Mohammad-Ali
authors: MA
authors: Saghiri
authors: Vahid
authors: V
authors: Zand
authors: Masoumeh
authors: M
authors: Mehdipour
authors: Bahram
authors: B
authors: Ranjkesh
authors: Hadi
authors: H
authors: Mokhtari
authors: Amin
authors: A
authors: Salemmilani
authors: Sirvan
authors: S
authors: Doosti
mesh_terms: D017607:Aluminum Compounds; D017610:Calcium Compounds; D003763:Dental Leakage / Q000517:prevention & control*; D004338:Drug Combinations; D005899:Glass Ionomer Cements; D006801:Humans; D066298:In Vitro Techniques; D010087:Oxides; D017640:Silicates; D014073:Tooth Bleaching / Q000379:methods*
chemical_list: D017607:Aluminum Compounds; D017610:Calcium Compounds; D004338:Drug Combinations; D005899:Glass Ionomer Cements; D010087:Oxides; D017640:Silicates; C086631:mineral trioxide aggregate; C084541:Fuji glass-ionomer lining cement