Paucity of Nanolayering in Resin-Dentin Interfaces of MDP-based Adhesives Adhesion of 10-MDP containing resin cements to dentin with and without the etch-and-rinse technique
Self-assembled nanolayering structures have been reported in resin-dentin interfaces created by adhesives that contain 10-methacryloyloxydecyl dihydrogen phosphate ( 10-MDP ) . These structures have been hypothesized to contribute to bond durability . The objective of the present study was to determine the extent of nanolayering in resin-dentin interfaces after application of commercialized  10-MDP-containing self-etch and universal adhesives to human dentin . Seven commercialized adhesives were examined :  Adhese Universal ( Ivoclar-Vivadent ) , All-Bond Universal ( Bisco , Inc. ) , Clearfil SE Bond 2 , Clearfil S3 Bond Plus , Clearfil Universal Bond ( all from Kuraray Noritake Dental Inc. ) , G-Premio Bond ( GC Corp. ) , and Scotchbond Universal ( 3 M ESPE ) . Each adhesive was applied in the self-etch mode on midcoronal dentin according to the respective manufacturer ’s instructions . Bonded specimens ( n = 6 ) were covered with flowable resin composite , processed for transmission electron microscopy , and examined at 30 r and om sites without staining . Thin-film glancing angle X-ray diffraction ( XRD ) was used to detect the characteristic peaks exhibited by nanolayering ( n = 4 ) . The control consisted of 15%wt , 10%wt , and 5%wt 10-MDP ( DM Healthcare Products , Inc. ) dissolved in a mixed solvent ( ethanol and water weight ratio 9:8 , with photoinitiators ) . Experimental primers were applied to dentin for 20 s , covered with hydrophobic resin layer , and examined in the same manner . Profuse nanolayering with highly ordered periodicity ( ~3.7 nm wide ) was observed adjacent to partially dissolved apatite crystallites in dentin treated with the 15 % 10-MDP primer . Three peaks in the 2θ range of 2.40 ° ( 3.68 nm ) , 4.78 ° ( 1.85 nm ) , and 7.18 ° ( 1.23 nm ) were identified from thin-film XRD . Reduction in the extent of nanolayering was observed in the 10 % and 5 % 10-MDP experimental primer-dentin interface along with lower intensity XRD peaks . Nanolayering and characteristic XRD peaks were rarely observed in specimens prepared from the commercialized adhesives . The sparsity of nanolayering in resin-dentin interfaces created by commercialized adhesives challenges its clinical effectiveness as a mechanism for improving bond longevity in dentin bonding PURPOSE This study evaluated the adhesion of 10-MDP containing self-etch and self-adhesive resin cements to dentin with and without the use of etch- and -rinse technique . MATERIAL S AND METHODS Human third molars ( N=180 ) were r and omly divided into 6 groups ( n=30 per group ) . Conventional ( Panavia F2.0 , Kuraray-PAN ) and self-adhesive resin cements ( Clearfil SA , Kuraray-CSA ) were bonded to dentin surfaces either after application of 3-step etch- and -rinse ( 35 % H3PO4 + ED Primer ) or two-step self-etch adhesive resin ( Clearfil SE Bond ) . Specimens were subjected to shear bond strength test using the universal testing machine ( 0.5 mm/min ) . The failure types were analyzed using a stereomicroscope and quality of hybrid layer was observed under a scanning electron microscope . The data ( MPa ) were analyzed using two-way ANOVA and Tukey 's tests ( α=.05 ) . RESULTS Overall , PAN adhesive cement showed significantly higher mean bond strength ( 12.5 ± 2.3 - 14.1 ± 2.4 MPa ) than CSA cement ( 9.3 ± 1.4 - 13.9 ± 1.9 MPa ) ( P<.001 ) . Adhesive failures were more frequent in CSA cement groups when used in conjunction with two-step self-adhesive ( 68 % ) or no adhesive at all ( 66 % ) . Hybrid layer quality was inferior in CSA compared to PAN cement in all conditions . CONCLUSION In clinical situations where bonding to dentin substrate is crucial , both conventional and self-adhesive resin cements based on 10-MDP can benefit from etch- and -rinse technique to achieve better quality of adhesion in the early clinical period
The 10-MDP monomer has the capacity to produce an acid-base resistant zone on the adhesive interface , which increases the response to acid-base challenges .
The adhesion established by these systems is stable over time .
The incorporation of functional monomers in dental adhesive systems promotes chemical interaction with dental substrates , result ing in higher adhesion forces when compared to micromechanical adhesion only .
The 10-MDP monomer , whose chemical structure allows for a polar behavior which is favorable to adhesion , also promotes the protection of collagen fibers through the formation of MDP-calcium salts .
This systematic review aim ed to characterize the interface created by 10-MDP containing adhesive systems through an evaluation of the following parameters : Formation of nano-layered structures , capacity to produce an acid-base resistant zone , and adhesion stability .