According to the 'Adhesion-Decalcification' concept, specific functional monomers within dental adhesives can ionically interact with hydroxyapatite (HAp). Such ionic bonding has been demonstrated for 10-methacryloyloxydecyl dihydrogen phosphate (MDP) to manifest in the form of self-assembled 'nano-layering'. However, it remained to be explored if such nano-layering also occurs on tooth tissue when commercial MDP-containing adhesives (Clearfil SE Bond, Kuraray; Scotchbond Universal, 3M ESPE) were applied following common clinical application protocols. We therefore characterized adhesive-dentin interfaces chemically, using x-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDS), and ultrastructurally, using (scanning) transmission electron microscopy (TEM/STEM). Both adhesives revealed nano-layering at the adhesive interface, not only within the hybrid layer but also, particularly for Clearfil SE Bond (Kuraray), extending into the adhesive layer. Since such self-assembled nano-layering of two 10-MDP molecules, joined by stable MDP-Ca salt formation, must make the adhesive interface more resistant to biodegradation, it may well explain the documented favorable clinical longevity of bonds produced by 10-MDP-based adhesives.

The aim of this study was to investigate the bactericidal effect of a dentin primer incorporating the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) against bacteria in human dentinal carious lesions. To evaluate the antibacterial activity of MDPB against anaerobes, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) against obligate anaerobes and facultative anaerobic strains of lactobacilli were determined. Bacteria were recovered from carious dentin samples obtained from the teeth of patients, and the bactericidal activities of the experimental primer containing 5% MDPB and three commercially available primers were compared by counting the number of viable cells after contact with diluted solutions of each primer for 30 s. MDPB showed strong antibacterial activity against anaerobes, the MIC and MBC values ranging from 3.9 to 31.3 micrograms/ mL-1 and 15.6-125 micrograms/ mL-1, respectively. Experimental primer containing MDPB was the most bactericidal among the materials tested (ANOVA, Fisher's PLSD test, P < 0.05) and was able to kill the bacteria completely even when diluted 40 times, while the three commercial products exhibited little activity at 40 times dilution. These results indicate that incorporation of MDPB into dentin primer could be beneficial for eliminating the residual bacteria in cavities.

No abstract

Previous research, in which the bonding effectiveness of the 3 self-etch monomers HAEPA, EAEPA, and MAEPA was determined, showed that MAEPA was most effective. In this study, the molecular interactions of these monomers with hydroxyapatite and dentin were investigated by combining x-ray diffraction, infrared spectroscopy, and scanning electron microscopy. We tested the null hypothesis that the bonding performance of these monomers does not correlate to the formation of monomer-calcium salts and to hydrolytic stability of these monomer-calcium complexes. Monomer/ethanol/water solutions were prepared and applied to synthetic hydroxyapatite and dentin. While HAEPA and EAEPA dissolved dentin considerably and deposited unstable calcium-phosphate salts (DCPD), MAEPA formed hydrolysis-resistant monomer-calcium salts that remained attached to the dentin surface even after being washed. The chemical stability of the monomer-Ca salts was thought to contribute in particular to the bond durability, but this study shows that the formation of stable monomer-calcium salts also enhances the 'immediate' bonding performance of self-etch adhesives.

The purpose of this study was to estimate the effect of three types of different adhesive systems on enamel adhesion. Scotchbond Multi-Purpose (MP) as a traditional system, Single Bond (SB) as a wet-bonding system and Clearfil SE Bond (SE) and Unifil Bond (UB) as self-etching priming systems were used. Bovine enamel was treated with each system and tensile bond strength (TBS) of resin to the enamel was measured. The conditioned enamel surfaces and resin-enamel interfaces were also morphologically observed with scanning electron microscope (SEM). The mean TBS for MP, SB, SE and UB were 15.3, 13.7, 14.3 and 11.6 MPa, respectively. There was no significant difference in mean TBS among all products but the traditional system showed the most stable TBS. In SEM observations, self-etching primer created a weaker etched pattern on the enamel surface than phosphoric acid. At the resin-enamel interfaces, thick tag-like extensions penetrated into the enamel etched with phosphoric acid regardless of using the wet-bonding technique, while self-etching primer created thin lamina-like resin penetrations. These results indicate that the traditional system with phosphoric acid etching exhibits the most stable enamel adhesion although the enamel-bonding promoting abilities of these adhesive systems are equivalent to each other.

Fluoride-releasing materials can be expected to inhibit the secondary caries. The aim;of this study was to evaluate the effect of fluoride-releasing adhesives on inhibition of secondary caries in outer and wall lesions. Two commercial fluoride-releasing adhesives, Reactmer bond (RB) and One-up bond F (OB), and a commercial adhesive without fluoride release, Mac-bond II (MB), were used prior to placement of restorative materials without fluoride release, Lite-fil II A (LF) and Estelite (EL), and a fluoride-releasing restorative material, Reactmer paste (RP). Class V cavities prepared on extracted human premolars were restored with various combinations of the materials: MB/EL, OB/EL, RB/LF and RB/RP. The restored teeth were incubated in bacterial medium containing sucrose with Streptoccus mutans for 14 days. Microradiographs of specimens showed no wall lesions in all groups and an acid-resistant layer adjacent to the restoration in the caries-like lesion. OB/EL, RB/LF and RB/RP groups showed thicker layers than the MB/EL group. The RB/RP group formed the shallowest outer lesion among all groups. These results indicate that fluoride-releasing adhesives are effective in the prevention of wall lesions but exhibit little outer lesion inhibition. Therefore, combined restoration using a fluoride-releasing adhesive and fluoride-releasing restorative material should be selected to inhibit secondary caries.

The purpose of this study was to analyse quantitatively the early bacterial plaque formed on resin composite and human enamel in vivo, using a confocal laser scanning microscope. Test pieces of resin composite and human enamel were retained at the buccal surfaces of the upper first molars of three volunteers for 4, 8 and 24 h to allow plaque formation. Then, the specimens were immersed in propidium iodide in phosphate-buffered saline to stain adherent bacteria and observed with a confocal laser scanning microscope. The ratios of the area occupied by microorganisms to the whole area of the optical field were calculated using a photo-image analysis system. The thickness of the plaque was also measured. Quantitative analysis revealed that the resin composite showed significantly higher bacterial adherence than human enamel throughout the test period. A difference was noticed in the morphology of the bacteria between the two groups. Our findings suggest that resin composite shows higher bacteria adherence during early plaque formation compared with human enamel. In addition, the present findings may suggest a presence of the difference in bacterial composition of plaque in both specimens.

The aim of this study was to evaluate the effect of fluoride-releasing adhesive systems on human decalcified dentin in vitro. Two fluoride-releasing adhesive systems, Reactmer bond (RB, Shofu) and ABF (AF, Kuraray), an experimental system, and a commercial adhesive system without fluoride release, SE bond (SE, Kuraray), were used in this study. The amount of fluoride release from adhesive in deionized water was measured every week for 10 weeks. Class V cavities were prepared on extracted human pre-molars and decalcified dentin was promoted by using a bacterial caries induction system at the cavity floor. The cavities preserving decalcified dentin were restored with resin composite (AP-X, Kuraray) after treatment by each adhesive system. The specimens without treatment by adhesive system and restoration were used for control. The specimens with restoration were then incubated for 4 weeks at 37 degrees C, 100% humidity. Microradiographs of the specimens showed that the radiopacities of the decalcified dentin layers in RB and AF groups with fluoride release were significantly higher than those in SE or control groups without fluoride release. This result suggested that the fluoride-releasing adhesive systems enhanced mineralization of decalcified dentin.