Effect of bleaching agents on bonding to pulp chamber dentine.
OBJECTIVE
To determine the effect of intracoronal bleaching agents on adhesion of bonding agents to pulp chamber dentine.


METHODS
Forty extracted human maxillary anterior teeth were randomly divided into four groups of 10 teeth each. Bleaching agents were sealed in pulp chambers for 7 days, as in clinical use. Group 1 (control): distilled water, group 2: 35% hydrogen peroxide, group 3: sodium perborate mixed with water, and group 4: sodium perborate mixed with 35% hydrogen peroxide. Teeth were stored in saline at 37 degrees C for 7 days. After the bleaching agent was removed, teeth were leached in water for a further 7 days prior to bonding. The crown was cut vertically from mesial to distal and the labial pulp chamber dentine was prepared for bonding with Clearfil SE-Bond and filled with resin composite (Clearfil AP-X). The bonded specimens were kept moist at 37 degrees C for 24 h. Microtensile bond strengths were determined using a universal testing machine. Additional teeth were prepared using the same bleaching procedures to investigate the scanning electron microscopic appearance of the dentine surface.


RESULTS
Mean values (+/-SD) of microtensile bond strength for the experimental groups were: group 1: 5.29 +/- 2.21 MPa, group 2: 5.99 +/- 1.51 MPa, group 3: 9.17 +/- 1.65 MPa and group 4: 3.99 +/- 1.31 MPa. Dentine treated with sodium perborate in water (group 3) had significantly higher mean bond strength when compared with the other three groups (P < 0.05, Tukey's test). Mean bond strength was lowest when dentine was treated with sodium perborate plus hydrogen peroxide (group 4).


CONCLUSIONS
In terms of subsequent bond strength during restoration, sodium perborate mixed with distilled water appears to be the best intracoronal bleaching agent.
Timpawat
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S
Department of Operative Dentistry, Faculty of Dentistry, Mahidol University, Bangkok, Thailand. dtstp@mahidol.ac.th
Nipattamanon
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Kijsamanmith
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K
Messer
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D001881:Borates / Q000494:pharmacology*; D003188:Composite Resins; D001840:Dental Bonding; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D003804:Dentin / Q000187:drug effects* / Q000648:ultrastructure; D003806:Dentin Permeability / Q000187:drug effects; D017220:Dentin-Bonding Agents; D004338:Drug Combinations; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008422:Materials Testing; D008689:Methacrylates; D008855:Microscopy, Electron, Scanning; D016877:Oxidants / Q000494:pharmacology*; D011897:Random Allocation; D019279:Resin Cements; D018709:Statistics, Nonparametric; D013718:Tensile Strength; D014073:Tooth Bleaching / Q000379:methods*; D019228:Tooth Crown
D001881:Borates; C112828:Clearfil AP-X; C438313:Clearfil SE Bond; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D004338:Drug Combinations; D008689:Methacrylates; D016877:Oxidants; D019279:Resin Cements; D006861:Hydrogen Peroxide; C027707:sodium perborate