Chemical interaction between 10-methacryloyloxydecyl dihydrogen phosphate and methacryloxypropyltrimethoxysilane in one-bottle dental primer and its effect on dentine bonding

Are universal adhesives in etch-and-rinse mode better than old 2-step etch-and-rinse adhesives? One-year evaluation of bonding properties to dentin

OBJECTIVES

This study compared the bonding properties of dentin of three 2-step etch-and-rinse adhesives (2-ERAs) to those of three universal adhesives (UAs) applied with an etch-and-rinse strategy (ER), immediately and after 1 year of water storage.

METHODS

Sixty caries-free molars were divided into 6 groups according to the adhesive systems used (n = 10). The 2-ERA systems included were: 1) Adper Single Bond 2 (SB), 2) Tetric N-Bond (TB), and 3) Ambar (AM); and the UAs systems were: 4) Single Bond Universal (SBU) 5) Tetric N-Bond Universal (TBU), and 6) Ambar Universal (AMU). The occlusal third of each tooth was removed and the adhesives were applied. After the composite build-up, specimens were sectioned and tested for microtensile bond strength (µTBS) and nanoleakage (NL) immediately and after 1 year of water storage. In situ degree of conversion (DC) was only evaluated in the immediate time. For water sorption (WS), solubility (SO), and mass change (MC) tests, 48 disk-shaped specimens were prepared (n = 8) and assessed according to ISO 4049:2009.

RESULTS

UAs showed higher µTBS and lower NL values than 2-ERAs did after 1 year of water storage (p = 0.001). Regarding DC, 2-ERAs showed higher DC values than UAs (p = 0.001). Regarding WS, 2-ERAs showed higher WS values than those of UAs (p = 0.00001), except for AM and AMU. Lower WS was observed for AM than for other 2-ERAs (p = 0.00001).

CONCLUSION

The use of UAs applied with the ER strategy seems to be a more effective technique for maintaining adhesion to dentin substrate than 2-ERAS.

CLINICAL SIGNIFICANCE

This study may support clinicians in selecting the most adequate adhesive system to be used in ER strategy in dentin, demonstrating that UAs were more effective, considering the longevity of the resin restorations.

Role of 3-Methacryloxypropyltrimethoxysilane in Dentin Bonding

In this study, we aimed to examine the effect of 3-methacryloxypropyltrimethoxysilane (MPS) on dentin collagen and the impact of MPS and 10-methacryloyloxydecyl dihydrogen phosphate (MDP) together and separately on resin-dentin bonding. Eight groups of primers were prepared: control group, MDP, MPS5, MPS5 + MDP, MPS10, MPS10 + MDP, MPS15, and MPS15 + MDP. The potential interaction between MPS and collagen was assessed by molecular dynamics, contact angle measurement, zeta potential measurement, and chemoanalytic characterization using X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and ultraviolet-visible spectroscopy. Microtensile bond strength (μTBS) and nanoleakage were evaluated after 24 h or 12 months of water storage. In situ zymography was used to evaluate the enzyme activity at the bonded interface. According to chemoanalytic characterization and molecular dynamics, a weak interaction between MPS and collagen was observed. MPS enhanced the hydrophobicity and negative charge of the collagen surface (P < 0.05). Applying an MDP-containing primer increased μTBS (P > 0.05) and reduced fluorescence after 24 h of water storage. Water storage for 12 months decreased μTBS (P < 0.05) and increased nanoleakage for all groups. MPS conditioning did not change μTBS and nanoleakage after 24 h of water storage or aging. The MPS10 + MDP and MPS15 + MDP groups presented more silver nitrate and μTBS decrease than the MDP group (P < 0.05). These results indicated that MPS had a weak interaction with collagen that enhanced its surface negative charge and hydrophobicity without adversely affecting dentin bonding. However, compared to MDP alone, mixing MDP with MPS impaired their effectiveness and made the dentin bonding unstable.

Interactions of two phosphate ester monomers with hydroxyapatite and collagen fibers and their contributions to dentine bond performance

OBJECTIVES

To evaluate the interactions of two phosphate ester monomers [10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) and dipentaerythritol penta-acrylate phosphate (PENTA)] with hydroxyapatite and collagen and understand their influence on dentine bonding.

METHODS

Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, nuclear magnetic resonance, ultraviolet-visible, and molecular docking were applied for separately evaluating the interactions of two monomers with hydroxyapatite and collagen. Hydrophilicity tests and morphological observation were employed to characterize pretreated dentine. Microtensile bond strength (μTBS) and nanoleakage were investigated to evaluate the bonding performance. Hydroxyproline assay, in situ zymography, and matrix metalloproteinase-9 (MMP-9) activity assay were used to confirm the MMP inhibition.

RESULTS

Chemoanalytic characterization confirmed the interactions of 10-MDP and PENTA with hydroxyapatite and collagen. The interactions of PENTA were weaker than 10-MDP. PENTA possessed better dentine tubule sealing after etching than 10-MDP. Dentine treated with PENTA was more hydrophilic than 10-MDP. 10-MDP and PENTA treating significantly increased the initial μTBS than the control group without primer conditioning. μTBS decreased significantly during aging, and the decrease was more severe in the PENTA group than 10-MDP. The 10-MDP and PENTA groups exhibited relatively less fluorescence than the control. The relative inhibition percentages of MMP-9 decreased in the order of 10-MDP-Ca salt, 10-MDP and PENTA. The 10-MDP, PENTA, and 10-MDP-Ca salt groups showed significantly lower hydroxyproline contents than the control.

CONCLUSIONS

Although PENTA adsorbed on hydroxyapatite, it did not form a stable calcium salt. The interactions of 10-MDP with hydroxyapatite and collagen are different than those of PENTA.

CLINICAL SIGNIFICANCE

The sealing of dentinal tubules by PENTA and the inhibition of MMP by 10-MDP and its calcium salts contribute to improving the dentine bonding durability.