Variations in collagen fibrils network structure and surface dehydration of acid demineralized intertubular dentin: effect of dentin depth and air-exposure time.
OBJECTIVE
The aim was to characterize the variations in the structure and surface dehydration of acid demineralized intertubular dentin collagen network with the variations in dentin depth and time of air-exposure (3, 6, 9 and 12 min). In addition, to study the effect of these variations on the tensile bond strength (TBS) to dentin.


METHODS
Phosphoric acid demineralized superficial and deep dentin specimens were prepared. The structure of the dentin collagen network was characterized by AFM. The surface dehydration was characterized by probing the nano-scale adhesion force (F(ad)) between AFM tip and intertubular dentin surface as a new experimental approach. The TBS to dentin was evaluated using an alcohol-based dentin self-priming adhesive.


RESULTS
AFM images revealed a demineralized open collagen network structure in both of superficial and deep dentin at 3 and 6 min of air-exposure. However, at 9 min, superficial dentin showed more collapsed network structure compared to deep dentin that partially preserved the open network structure. Total collapsed structure was found at 12 min for both of superficial and deep dentin. The value of the F(ad) is decreased with increasing the time of air-exposure and is increased with dentin depth at the same time of air-exposure. The TBS was higher for superficial dentin at 3 and 6 min, however, no difference was found at 9 and 12 min.


CONCLUSIONS
The ability of the demineralized dentin collagen network to resist air-dehydration and to preserve the integrity of open network structure with the increase in air-exposure time is increased with dentin depth. Although superficial dentin achieves higher bond strength values, the difference in the bond strength is decreased by increasing the time of air-exposure. The AFM probed F(ad) showed to be sensitive approach to characterize surface dehydration, however, further researches are recommended regarding the validity of such approach.
Fawzy
Amr S
AS
Dental Biomaterials Department, Faculty of Dentistry, Ain Shams University, Cairo, Egypt. amrshf@hotmail.com
D000134:Acid Etching, Dental / Q000379:methods*; D000268:Adhesiveness; D000328:Adult; D000388:Air; D003094:Collagen / Q000187:drug effects / Q000648:ultrastructure*; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry; D003804:Dentin / Q000187:drug effects / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D003890:Desiccation; D000431:Ethanol / Q000737:chemistry; D006801:Humans; D008689:Methacrylates / Q000737:chemistry; D018625:Microscopy, Atomic Force; D036103:Nanotechnology; D010756:Phosphoric Acids / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013314:Stress, Mechanical; D013718:Tensile Strength; D013997:Time Factors
D003188:Composite Resins; D003764:Dental Materials; D017220:Dentin-Bonding Agents; C420130:Excite cement; D008689:Methacrylates; D010756:Phosphoric Acids; D012997:Solvents; C121818:Tetric ceram; D000431:Ethanol; D003094:Collagen; C030242:phosphoric acid