Bonding to Er-YAG-laser-treated Dentin
L. Ceballos1,*,
M. Toledano1,
R. Osorio1,
F.R. Tay2, and
G.W. Marshall3
1 Department of Dental Materials, University of Granada, Granada, Spain;
2 Conservative Dentistry, Faculty of Dentistry, University of Hong Kong, Hong Kong SAR, China; and
3 Division of Biomaterials and Bioengineering, Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, CA, USA;
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Figure 1. TEM micrographs of bonding of Single Bond to acid-etched, deep dentin. The demineralized, epoxy-resin-embedded sections were stained with phosphotungstic acid and uranyl acetate. (a) A low-magnification overall view of the resin-dentin interface. Phase separation of the polyalkenoic acid copolymer (P) component of the adhesive could be seen as globular structures within the adhesive layer (A) and as a continuous layer (arrow) over the surface of the bonding substrate. A 3- to 4-µm-thick hybrid layer (H) could be seen above the laboratory demineralized dentin (D). Bar = 1 µm. (b) A high-magnification view showing the presence of intact, banded collagen fibrils within the hybrid layer. A, adhesive layer. Bar = 300 nm.
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Figure 2. TEM micrographs of bonding of Single Bond to laser-ablated, deep dentin. (a) A low-magnification overall view of the resin-dentin interface. A 3- to 5-µm-thick laser-modified layer (Ab) could be observed that had separated from the underlying intertubular dentin (D). The resultant space (S) was infiltrated by the laboratory-embedding resin. Remnant dentinal tubules (arrow) could be seen within the laser-modified layer. A, adhesive layer. Bar = 1 µm. (b) A high-magnification view of the superficial part of the laser-modified layer that was partially infiltrated by the polyalkenoic acid copolymer (P). Roughly parallel plates of rippled materials could be identified (arrow). Bar = 1 µm. (c) A high-magnification view of the basal portion of the laser-modified layer. Collagen fibrils in this region were fused together to form an amorphous layer (F) that was completely devoid of interfibrillar spaces. This layer probably restricted resin infiltration into the laser-ablated intertubular dentin (D). Above the fused layer, a circumferential layer of mineral-rich peritubular dentin (arrow) could be seen around a dentinal tubule (T). Because of its higher mineral content, peritubular dentin was ablated to a lesser extent than the adjacent collagen-rich intertubular dentin. E, epoxy resin. Bar = 300 nm. (d) A very high-magnification view of the base of the laser-modified layer. Beneath the fused layer (F), collagen fibrils from the subsurface intertubular dentin were also partially denatured and appeared as unraveled, microfibrillar strands (arrow). No collagen banding could be seen along the intact collagen fibrils in the subsurface zone for several microns in the underlying dentin. Bar = 100 nm.
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Figure 3. TEM micrographs of bonding of Single Bond to laser-ablated, acid-etched, superficial dentin. (a) A low-magnification view showing the absence of the surface laser-modified layer after acid-etching. However, the extent of laser treatment extended into the subsurface intertubular dentin. These partially denatured collagen fibrils could not be removed by phosphoric acid and probably interfered with resin infiltration. A, adhesive layer; P, polyalkenoic acid copolymer; D, demineralized intertubular dentin. Bar = 300 nm. (b) A high-magnification view of the region marked with an asterisk in (a). Despite the presence of collagen fibrils with intact microfibrillar architecture (arrow), collagen banding could not be observed from the majority of the fibrils. These subsurface collagen fibrils were probably partially denatured by the heat generated during laser treatment. Bar = 100 nm.
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