Resin–dentine interfacial morphology following CPP–ACP treatment

Abstract 

Objectives

To evaluate the quality of bonded resin–dentine interfaces produced by two self-etching primer adhesives after casein phosphopeptide–amorphous calcium phosphate (CPP–ACP) treatment, in comparison to untreated dentine.

Methods

Thirty-four adult molar teeth were sectioned to obtain dentine with tubule orientations parallel/oblique or perpendicular to the surface. The specimens were divided into ‘smear layer’ (1A, 1B) and ‘no smear layer’ groups, after treatment with 15% EDTA (2A, 2B). The specimens were then left either untreated (1A, 2A) or treated (1B, 2B) with CPP–ACP paste (Tooth Mousse, GC Corp.) for 60min×7 days. Each treatment group was divided into three subgroups and specimens etched/conditioned (no conditioning; 30–40% phosphoric acid (H₃PO₄); 20% polyacrylic acid) and bonded with either a 2-step self-etching primer adhesive (Clearfil SE Bond, Kuraray Medical) or an ‘all-in-one’ adhesive (G-Bond, GC Corp.) and a hybrid resin composite. After 24-h water storage, the bonded specimens were sectioned, polished up to 4000-grit abrasive silicon carbide paper and 0.25-μm diamond paste, prepared for FE-SEM using the acid–base technique, critical point-dried, gold-coated and examined. Bonded and fractured dentine interfaces were also prepared and examined.

Results

The 2-step adhesive produced a similar appearance of bonded resin–dentine interface irrespective of smear layer group, treatment or etching/conditioning. After polyacrylic acid conditioning, the ‘all-in-one’ adhesive exhibited more areas with bond failures. The bond failures were within the hybrid layer and more pronounced following CPP–ACP treatment.

Conclusion

The quality of the bonded resin–dentine interface produced after CPP–ACP treatment may depend on the adhesive system used.

Keywords: Dentine conditioners, Casein phosphopeptide–amorphous calcium phosphate, Interfacial morphology, Scanning electron microscopy, Self-etching primer adhesives, ‘All-in-one’ adhesives