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Osmotic Blistering in Enamel Bonded with One-step Self-etch Adhesives
F.R. Tay1,*,
C.N.S. Lai1,
S. Chersoni2,
D.H. Pashley3,
Y.F. Mak1,
P. Suppa2,
C. Prati2 and
N.M. King1
1 Faculty of Dentistry, University of Hong Kong, Prince Philip Dental Hospital, 34 Hospital Road, Hong Kong SAR, China;
2 Department of Dental Science, University of Bologna, Italy; and
3 Department of Oral Biology and Maxillofacial Pathology, Medical College of Georgia, Augusta, GA, USA;
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Figure 1. Optical micrographs illustrating the phenomenon of osmotic blistering in enamel. (A,B) Optical microscopy photographs illustrating the phenomenon of osmotic blistering in enamel bonded with one-step self-etch adhesives such as (A) Adper Prompt and (B) iBond. Water blisters (pointers) are present between the adhesive and enamel (E) after the bonded specimen was immersed in water for 30 min. No water blisters can be observed in the bonded dentin (D). (C,D) A series of photographs taken from specimens bonded with One-Up Bond F, showing the effect of reversal of the osmotic gradient on existing water blisters. (C) Water blisters that were formed in enamel (pointer) but not dentin after immersion in distilled water for 30 min. (D) The same specimen after re-immersion in the CaCl2 solution for 10 min. Collapse of the blisters occurred due to the withdrawal of water from the blisters into the external salt solution.
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Figure 2. FE-ESEM micrographs demonstrating the appearance of osmotic water blisters after enamel bonded with different one-step self-etch adhesives was immersed in water. (A) A single water blister (arrow) in Adper Prompt that was found next to a large, irregular blister (pointer). The latter were more commonly observed in this adhesive and were probably formed by the coalescence of multiple smaller blisters. The surface texture of the adhesive (A) adjacent to the blisters was also altered (open arrowheads), and appears swollen and exhibits cracking, even when the specimen was examined under wet conditions. (B) Another view of a coalesced osmotic water blister (OB) in Adper Prompt, showing that the film coating that formed the blister wall was derived from, and is still connected with (arrows), the underlying adhesive resin (A). (C) A partially collapsed blister in Xeno-III-bonded enamel after the specimen was re-immersed in the concentrated CaCl2 solution. The top of the blister (asterisk) is partially collapsed. Connection of blister with the underlying adhesive can be clearly identified (arrows). A, adhesive. (D) Partial (arrow) and complete collapse of the pre-existing water blisters in iBond after re-immersion in the concentrated CaCl2 solution. Subsurface adhesive cratering (pointer) can be observed beneath the completely collapsed blisters.
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Figure 3. TEM micrographs demonstrating the pathways of water movement through one-step self-etch adhesives. The micrographs were taken from unstained undemineralized sections of adhesive-bonded enamel that were immersed in an ammoniacal silver nitrate tracer solution. Water trees (pointers) can be identified within the adhesives. In addition, isolated silver grains (open arrowheads), probably representing the hydrophilic resin domains, can be observed throughout the adhesive-enamel interfaces. They represent the pathways for water movement within the polymerized adhesives (A). (A) In the more aggressive self-etch adhesive, Prompt L-Pop, the enamel smear layer is completely dissolved, and water trees are seen along the surface of the enamel hybrid layer (R) and above the resin tags (T). (B) In the mild self-etch adhesive iBond, the enamel smear layer (arrow) is incompletely dissolved and separated from the adhesive during specimen preparation. S, empty grid space. (C) A high-magnification view of Fig. 3B , showing the hybridized enamel smear layer (ES) that separated from the adhesive and was probably embedded by the laboratory epoxy resin (XR). The hybridized smear layer consisted of fractured chips of enamel crystallites and can be distinguished from the underlying 300- to 500-nm-thick enamel hybrid layer (between open arrows) that comprised intact apatite crystallites.
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Figure 4. Clinical validation of osmotic blistering in enamel after the application of one-step self-etch adhesives. (A) Photograph of tooth 11 immediately after the application of iBond. (B). The same tooth surface after 1 hr, showing a rough texture (pointer). (C) A high-magnification view of the rough adhesive surface in tooth 11, showing the presence of osmotic blisters (open arrowheads). (D) SEM micrograph of an epoxy resin replica of the enamel surface of tooth 11, reproduced from a polyvinyl siloxane impression that was taken 3 hrs after the application of Xeno III. Osmotic blisters (open arrows) could be observed between the polymerized adhesive (A) and the enamel surface (E). (E) Epoxy resin replica of the same surface 24 hrs after the application of Xeno III. There was almost complete delamination of the adhesive from the enamel surface. Small, undisrupted blisters (open arrows) can still be seen from the fragments of retained adhesive (A). Striae of Retzius (pointer) were evident along the exposed enamel surface (E).
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Journal of Dental Research, Vol. 83, No. 4,
290-295 (2004)
DOI: 10.1177/154405910408300404
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