Paucity of Nanolayering in Resin-Dentin Interfaces of MDP-based Adhesives

• Published in: Journal of dental research 2016-04, Vol.95 (4), p.380-387
• Main Authors: Tian, F., Zhou, L., Zhang, Z., Niu, L., Zhang, L., Chen, C., Zhou, J., Yang, H., Wang, X., Fu, B., Huang, C., Pashley, D.H., Tay, F.R.
• Format: Article
• Language: English
• Subjects: Adhesives; Apatite; Bond strength; Chemical bonds; Crystals; Dental Enamel - chemistry; Dental Enamel - ultrastructure; Dental restorative materials; Dentin; Dentin - chemistry; Dentin - ultrastructure; Dentistry; Ethanol; Fourier transforms; Humans; Hydrophobicity; Hypotheses; In Vitro Techniques; Interfaces; Methacrylates - chemistry; Microscopy, Electron; Molar, Third; Nanostructures - chemistry; Nanotechnology - methods; NMR; Nuclear magnetic resonance; Periodicity; Primers; R&D; Research & development; Research Reports; Resin Cements - chemistry; Spectrum analysis; Surface Properties; Teeth; Transmission electron microscopy; X-Ray Diffraction
• ISSN: 0022-0345; 1544-0591
• DOI: 10.1177/0022034515623741

Self-assembled nanolayering structures have been reported in resin-dentin interfaces created by adhesives that contain 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP). These structures have been hypothesized to contribute to bond durability. The objective of the present study was to determine the extent of nanolayering in resin-dentin interfaces after application of commercialized 10-MDP-containing self-etch and universal adhesives to human dentin. Seven commercialized adhesives were examined: Adhese Universal (Ivoclar-Vivadent), All-Bond Universal (Bisco, Inc.), Clearfil SE Bond 2, Clearfil S3 Bond Plus, Clearfil Universal Bond (all from Kuraray Noritake Dental Inc.), G-Premio Bond (GC Corp.), and Scotchbond Universal (3M ESPE). Each adhesive was applied in the self-etch mode on midcoronal dentin according to the respective manufacturer’s instructions. Bonded specimens (n = 6) were covered with flowable resin composite, processed for transmission electron microscopy, and examined at 30 random sites without staining. Thin-film glancing angle X-ray diffraction (XRD) was used to detect the characteristic peaks exhibited by nanolayering (n = 4). The control consisted of 15%wt, 10%wt, and 5%wt 10-MDP (DM Healthcare Products, Inc.) dissolved in a mixed solvent (ethanol and water weight ratio 9:8, with photoinitiators). Experimental primers were applied to dentin for 20 s, covered with hydrophobic resin layer, and examined in the same manner. Profuse nanolayering with highly ordered periodicity (~3.7 nm wide) was observed adjacent to partially dissolved apatite crystallites in dentin treated with the 15% 10-MDP primer. Three peaks in the 2θ range of 2.40° (3.68 nm), 4.78° (1.85 nm), and 7.18° (1.23 nm) were identified from thin-film XRD. Reduction in the extent of nanolayering was observed in the 10% and 5% 10-MDP experimental primer-dentin interface along with lower intensity XRD peaks. Nanolayering and characteristic XRD peaks were rarely observed in specimens prepared from the commercialized adhesives. The sparsity of nanolayering in resin-dentin interfaces created by commercialized adhesives challenges its clinical effectiveness as a mechanism for improving bond longevity in dentin bonding.