Ultrastructure of the dentin-adhesive interface after acid-base challenge.
OBJECTIVE
To observe the ultrastructure of the dentin-adhesive interface after in vitro sequential challenge by acidic and basic chemicals around adhesive restorations.


METHODS
Box-shaped cavities were prepared in bovine root dentin and restored as follows: Reactmer Bond and Reactmer Paste (RB/RP), Clearfil SE Bond and Clearfil AP-X (SE/APX), ABF (experimental) and APX (ABF/APX), Single Bond and APX (SB/APX). After the specimens were stored in water for 1 week, the integrity of the bonds tested by sequential immersion were placed in an artificial demineralizing solution (pH 4.5) for 20 min and in 5% NaOCl for 20 min. The specimens were sectioned, polished, then argon-ion etched for 7 min, and gold sputter coated for SEM examination of the dentin-adhesive interface.


RESULTS
The morphological results indicated tight bonding between the cavity wall dentin and the adhesive. For the fluoride-releasing restoration, RB/RP, a thick acid-resistant zone was clearly observed adjacent to the restoration; however, the bonding resin, RB, was partially degraded by the acid-base challenge. For SE/APX, ABF/APX and SB/APX, the bonding resins were resistant to the acid-base challenge. With the self-etching adhesive systems, SE and ABF, a thin band of acid-base resistant dentin less than 1 microm thick was observed beneath the hybrid layer. With the wet bonding system, SB, the hybrid layer was partially degraded by the acid-base challenge.


CONCLUSIONS
SEM observation is useful for observing the reactions of adhesives to acid-base challenge. Prevention of secondary caries around a restoration may be influenced by the physical properties of the restorative and adhesive materials, quality of the hybrid layer, and fluoride-release.
Tsuchiya
Satoko
S
Cariology and Operative Dentistry, Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
Nikaido
Toru
T
Sonoda
Hidekazu
H
Foxton
Richard M
RM
Tagami
Junji
J
D019342:Acetic Acid / Q000494:pharmacology; D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate; D002417:Cattle; D003188:Composite Resins; D001840:Dental Bonding; D003731:Dental Caries / Q000517:prevention & control*; D003793:Dental Restoration, Permanent / Q000379:methods*; D003804:Dentin / Q000187:drug effects / Q000648:ultrastructure*; D003806:Dentin Permeability; D017220:Dentin-Bonding Agents; D005899:Glass Ionomer Cements; D008689:Methacrylates; D008855:Microscopy, Electron, Scanning; D011726:Pyridinium Compounds; D019279:Resin Cements; D012973:Sodium Hypochlorite / Q000494:pharmacology
C112828:Clearfil AP-X; C438313:Clearfil SE Bond; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D005899:Glass Ionomer Cements; D008689:Methacrylates; D011726:Pyridinium Compounds; D019279:Resin Cements; C447779:reactmer bond; C465006:reactmer paste; C115612:single bond; C001524:Laurosept; D017438:Bisphenol A-Glycidyl Methacrylate; D012973:Sodium Hypochlorite; D019342:Acetic Acid