EDTA or H3PO4/NaOCl dentine treatments may increase hybrid layers' resistance to degradation: a microtensile bond strength and confocal-micropermeability study.
OBJECTIVE
The aim of this study was to reduce hybrid layer degradation created with simplified dentine adhesives by using two different methods to condition the dentine surface.


METHODS
A smear-layer was created on flat dentine surfaces from extracted human third molars with a 180-grit/SiC-paper. Dentine specimens were conditioned before bonding with the following procedures: 37% H(3)PO(4); H(3)PO(4)/0.5% NaOCl; 0.1M EDTA; 0.1M EDTA/0.5% NaOCl. Two etch-and-rinse adhesives: (Scotchbond 1XT or Optibond Solo Plus) were applied and light-cured. Composite build-ups were constructed. The bonded teeth were sectioned into beams, stored in distilled water (24h) or 12% NaOCl solution (90 min) and finally tested for microtensile bond strengths (microTBS). Additional dentine surfaces were conditioned and bonded as previously described. They were prepared for a pulpal-micropermeability confocal microscopy study and finally observed using confocal microscopy.


RESULTS
microTBS results revealed that both adhesives gave high bond strengths to acid-etched dentine before, but not after a 12% NaOCl challenge. Bonds made to acid-etched or EDTA-treated dentine plus dilute NaOCl, gave high microTBS that resisted 12% NaOCl treatment, as did EDTA-treated dentine alone. A confocal micropermeability investigation showed very high micropermeability within interfaces of the H(3)PO(4), etched specimens. The lowest micropermeability was observed in H(3)PO(4)+0.5% NaOCl and 0.1M EDTA groups.


CONCLUSIONS
The use of dilute NaOCl (0.5%) after acid-etching, or the conditioning of dentine smear layers with 0.1M EDTA (pH 7.4) produced less porous resin-dentine interfaces. These dentine-conditioning procedures improve the resistance of the resin-dentine bond sites to chemical degradation (12% NaOCl) and may result in more durable resin-dentine bonds.
Sauro
Salvatore
S
Dental Biomaterials Science, Biomimetics & Biophotonics, King's College London Dental Institute at Guy's, King's College and St Thomas's Hospitals, Floor 17 Guy's Hospital, London, UK. salvatore.sauro@kcl.ac.uk
Mannocci
Francesco
F
Toledano
Manuel
M
Osorio
Raquel
R
Pashley
David H
DH
Watson
Timothy F
TF
D000134:Acid Etching, Dental / Q000379:methods*; D001840:Dental Bonding / Q000379:methods*; D018772:Dental Marginal Adaptation; D003804:Dentin / Q000187:drug effects*; D003806:Dentin Permeability / Q000187:drug effects*; D017220:Dentin-Bonding Agents / Q000737:chemistry* / Q000627:therapeutic use; D004338:Drug Combinations; D004492:Edetic Acid / Q000627:therapeutic use; D006801:Humans; D008964:Molar, Third; D010756:Phosphoric Acids / Q000737:chemistry / Q000627:therapeutic use; D019279:Resin Cements / Q000737:chemistry; D016369:Smear Layer; D012973:Sodium Hypochlorite / Q000737:chemistry / Q000627:therapeutic use; D013718:Tensile Strength
D017220:Dentin-Bonding Agents; D004338:Drug Combinations; D010756:Phosphoric Acids; D019279:Resin Cements; D004492:Edetic Acid; D012973:Sodium Hypochlorite; C030242:phosphoric acid