Water Concentration in Self-etching Primers Affects their Aggressiveness and Bonding Efficacy to Dentin
N. Hiraishi1,4,
N. Nishiyama2,
K. Ikemura3,
J.Y.Y. Yau4,
N.M. King1,
J. Tagami5,
D.H. Pashley6, and
F.R. Tay1,*
1 Paediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong, Prince Philip Dental Hospital, 34 Hospital Road, Hong Kong SAR, China;
2 Department of Dental Materials, Nihon University School of Dentistry at Matsudo, Chiba, Japan;
3 Department of Research and Development, Shofu Inc., Kyoto, Japan;
4 Oral Biosciences, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China;
5 Department of Operative Dentistry, Tokyo Medical and Dental University, Tokyo, Japan; and
6 Department of Oral Biology and Maxillofacial Pathology, School of Dentistry, Medical College of Georgia, Augusta, GA, USA;
View larger version (60K):
[in a new window]
|
Figure 1. Microtensile bond strengths and representive SEM micrographs from the 5 experimental groups. (A) Microtensile bond strengths of the 5 two-step, experimental 4-AET/HEMA self-etching primer solutions: Group 9-0-1 (35.9 ± 7.5 MPa), Group 8-1-1 (43.1 ± 6.1 MPa), Group 7-2-1 (47.6 ± 6.6 MPa), Group 5-4-1 (42.3 ± 7.6 MPa), and Group 3-6-1 (22.6 ± 8.1 MPa). The number inside each bar represents the number of specimens tested for that group. There were no premature failures in any of the groups. Groups with the same upper-case letters are not statistically significant (P > 0.05). (B) SEM micrograph of an adhesive failure from the group with the highest mean bond strength (Group 7-2-1), showing the surface of the fractured hybrid layer that appeared comparatively solid. Hybridized smear plugs (arrows) can be seen within some dentinal tubules. (C) SEM micrograph of an adhesive failure from the group with the lowest mean bond strength (Group 3-6-1). The surface of the hybrid layer was porous (asterisk), and some incompletely infiltrated collagen fibrils (open arrowhead) can be identified along the fractured interface. The condition of the hybrid layer reflects the extensive nanoleakage observed in the TEM (Fig. 4D ). D: non-hybridized dentin.
|
|
View larger version (218K):
[in a new window]
|
Figure 2. TEM micrographs from (A-B) Group 9-0-1 (anhydrous), and (C-D) Group 8-1-1 (10 vol% water). C, composite; A, filled adhesive; D, dentin. Open arrowhead: F-PRG fillers. (A) Stained, demineralized section from Group 9-0-1 showing a 200-nm-thick, electron-dense hybrid layer (between open arrows). Some of the smear layer remnants (arrows) were not completely dissolved. (B) The corresponding unstained, undemineralized section, showing that the 200-nm-thick, partially demineralized zone (between open arrows) is heavily filled with silver deposits (nanoleakage). In addition, reticular silver deposits are sporadically present along the interfibrillar spaces (pointer) of the dentin beneath the hybrid layer. Such a feature could not be identified from the stained demineralized sections. (C) Stained, demineralized section from Group 8-1-1, showing a similar 200-nm-thick hybrid layer (between open arrows) with thicker regions containing smear layer remnants (asterisk). (D) The corresponding unstained undemineralized section, showing that the partially demineralized zone (between open arrows) is generally devoid of nanoleakage. Similar to Group 9-0-1, sporadic regions of silver-filled interfibrillar spaces (pointer) can be observed in the underlying intact, mineralized dentin.
|
|
View larger version (72K):
[in a new window]
|
Figure 3. TEM micrographs from the experimental group with the highest bond strength (Group 7-2-1; 20 vol% water). C, composite; A, filled adhesive; D, dentin; open arrowhead, fully pre-reacted glass-ionomer-type fillers (F-PRG) from the Fluoro-Bond bonding resin. (A) Stained, demineralized section showing a 500-nm- to 1-µm-thick hybrid layer (between open arrows). The smear layer was completely dissolved, and collagen fibrils (pointer) from the intact dentin exhibit a ‘shag carpet’ appearance. (B) The corresponding unstained, undemineralized section after tracer penetration, showing the overall absence of nanoleakage from the resin-dentin interface. The partially demineralized zone (between open arrows) corresponded to the hybrid layer depicted in the stained section. (C) A high-magnification view of Fig. 3B, showing the presence of minimal nanoleakage that existed in the form of isolated silver grains (arrow) within the partially demineralized zone (between open arrows).
|
|
View larger version (216K):
[in a new window]
|
Figure 4. TEM micrographs from (A-B) Group 5-4-1 (40 vol% water), and (C-D) Group 3-6-1 (60 vol% water). C, composite; A, filled adhesive; D, dentin. Open arrowhead: F-PRG fillers. (A) Stained, demineralized section from Group 5-4-1. There was an increased aggressiveness of the self-etching primer with increasing water concentration, with the formation of a 1.5- to 2-µm-thick hybrid layer (between open arrows). (B) The corresponding unstained undemineralized section revealed a 1.5- to 2-µm-thick partially demineralized zone (between open arrows) in which reticular patterns of nanoleakage could occasionally be seen. There were no silver deposits within the interfibrillar spaces of the underlying dentin. (C) Stained, demineralized TEM from Group 3-6-1, showing a similarly thick hybrid layer (between open arrows), but with further extensions to form peritubular cuffs (pointers) around the dentinal tubules. (D) The corresponding unstained, undemineralized TEM. The low resin concentration and the increased water content resulted in the extensive deposition of silver within the partially demineralized zone (between open arrows).
|
|
Copyright © 2005 Institutional Access Guidelines
