|
Sign In to gain access to subscriptions and/or personal tools.
|
Tubular Occlusion Optimizes Bonding of Hydrophobic Resins to Dentin
F.T. Sadek1,2,
D.H. Pashley3,
M. Ferrari2 and
F.R. Tay2,3,*
1 Department of Dental Materials, School of Dentistry, University of São Paulo, Brazil;
2 Department of Restorative Dentistry and Dental Materials, School of Dentistry, University of Siena, Italy; and
3 Department of Oral Biology & Maxillofacial Pathology, School of Dentistry, Medical College of Georgia, Augusta, GA 30912-1129, USA
View larger version (18K):
[in this window]
[in a new window]
|
Figure 1. Microtensile bond strength (means and standard deviations) obtained from the 6 experimental groups (N = 35). An experimental, three-step, etch-and-rinse hydrophobic adhesive was bonded to mid-coronal and deep acid-etched dentin by the ethanol wet-bonding technique under simulated pulpal pressure. The acid-etched dentin was pre-treated with de-ionized water (control), 3% potassium tetroxalate (oxalate), or poly(glutamic) acid-modified, diluted ceramicrete (PADC) prior to ethanol dehydration. Bond strengths for the 6 groups were 38.3 ± 8.2 MPa for the mid-coronal dentin control group, 19.8 ± 4.6 MPa for the deep dentin control group, 42.4 ± 8.4 MPa for the mid-coronal dentin oxalate group, 40.2 ± 9.4 MPa for the deep dentin oxalate group, 42.6 ± 7.9 MPa for the mid-coronal dentin PADC group, and 38.2 ± 7.7 MPa for the deep dentin PADC group. Groups identified with the same letter are not significantly different (p > 0.05).
|
|
View larger version (138K):
[in this window]
[in a new window]
|
Figure 2. A representative TEM micrograph taken from an unstained, undemineralized, silver-impregnated section in the control-deep dentin subgroup. Acid-etched deep dentin was bonded with the hydrophobic adhesive by the ethanol wet-bonding technique. A, adhesive layer; C, resin composite; D, mineralized intertubular dentin; E, space created when the adhesive-resin interface separated from the dentin, showing some voids (*) indicative of incomplete polymerization of the embedding epoxy resin, due to seepage of water from the interface during polymerization. Arrow: resin tags that pulled out of the tubules. Open arrowhead: silver deposits. The demineralized collagen matrix could not be identified clearly.
|
|
View larger version (79K):
[in this window]
[in a new window]
|
Figure 3. TEM micrograph taken from an unstained, undemineralized, silver-impregnated section from the oxalate-deep dentin subgroup. A, adhesive layer; C, resin composite; D, mineralized intertubular dentin; H, hybrid layer. (A) A low-magnification view showing the presence of calcium oxalate crystals (open arrows) in the dentinal tubules, about 5–8 µm from the tubular orifices, blocking water movement during dentin perfusion. (B) At a higher magnification, the dentin surface was completely devoid of oxalate crystals. Most of the oxalate crystals inside the dentinal tubules dislodged during ultramicrotomy, leaving empty spaces. Some of them, however, remained and appeared as electron-dense aggregates (open arrowhead). Only minimal nanoleakage could be identified as isolated, round silver grains (arrows) within the hybrid layer.
|
|
View larger version (56K):
[in this window]
[in a new window]
|
Figure 4. TEM micrograph taken from an unstained, undemineralized, silver-impregnated section of the poly(glutamic) acid-modified, diluted ceramicrete-deep dentin subgroup. A, adhesive layer; C, resin composite; D, mineralized intertubular dentin; H, hybrid layer. (A) An overall view of the resin-dentin interface, showing the generalized absence of silver nanoleakage. The dentinal tubules were coated along their peripheries with a layer of material (arrows) that had dislodged during ultramicrotomy, leaving electron-lucent spaces that were infiltrated with neither the adhesive resin nor the epoxy resin. The hybrid layer was only 2 µm thick, probably reflecting shrinkage that occurred during the stepwise chemical (ethanol) dehydration regime. (B) At a higher-magnification view, spaces occupied by the ceramicrete crystallite aggregates were seen on the dentin surface and inside the dentinal tubules (arrows). The use of poly(glutamic acid) resulted in the reduction in the sizes of these crystallites to the dimensions that were smaller than the diameters of the dentinal tubular orifices. Hence, they did not prevent resin infiltration into the tubules and demineralized collagen matrix. A fine layer of electron-dense ceramicrete crystallites could be seen within a tubule and could be readily discerned from the peritubular dentin (pointer). Only minimal nanoleakage could be identified as isolated, round silver grains (open arrowhead) within the hybrid layer. (C) At a very high magnification, electron-dense ceramicrete crystallites (open arrowheads), approaching the dimensions of dentin apatite crystals, could be seen attaching to the lamina limitans (arrows) of the dentinal tubules and trapped by resin.
|
|
Journal of Dental Research, Vol. 86, No. 6,
524-528 (2007)
DOI: 10.1177/154405910708600607
 CiteULike  Complore  Connotea  Del.icio.us  Digg  Reddit  Technorati  Twitter What's this?
|
|
