Issue 57, 2016, Issue in Progress

Self-strengthening hybrid dental adhesive via visible-light irradiation triple polymerization

Abstract

A self-strengthening methacrylate-based dental adhesive system was developed by introducing an epoxy cyclohexyl trimethoxysilane (TS) which contains both epoxy and methoxysilyl functional groups. The experimental formulation, HEMA/BisGMA/TS (22.5/27.5/50, wt%), was polymerized by visible-light. Real-time Fourier transform infrared spectroscopy (FTIR) was used to investigate in situ the free radical polymerization of methacrylate, ring-opening cationic polymerization of epoxy, and photoacid-induced sol–gel reactions. Among the three simultaneous reactions, the reaction rate of the free radical polymerization was the highest and the hydrolysis/condensation rate was the lowest. With 40 s-irradiation, the degrees of conversion of the double bond and epoxy groups at 600 s were 73.2 ± 1.2%, 87.9 ± 2.4%, respectively. Hydrolysis of the methoxysilyl group was initially <5%, and increased gradually to about 50% after 48 h dark storage. Photoacids generated through the visible-light-induced reaction were effective in catalyzing both epoxy ring-opening polymerization and methoxysilyl sol–gel reaction. The mechanical properties of copolymers made with TS concentrations from 5 to 35 wt% were obtained using dynamic mechanical analysis (DMA). In wet conditions, the storage moduli at 70 °C and glass transition temperature were significantly higher than that of the control (p < 0.05); these properties increased with TS concentration and storage time. The post reaction of hydrolysis/condensation of alkoxysilane could provide persistent strengthening whether in a neutral or acidic environment and these characteristics could lead to enhanced mechanical properties in the oral environment. The cumulative amount of leached species decreased significantly in the TS-containing copolymers. These results provide valuable information for the development of dental adhesives with reduced leaching of methacrylate monomers and enhanced mechanical properties under the wet, oral environment.

Graphical abstract: Self-strengthening hybrid dental adhesive via visible-light irradiation triple polymerization

Supplementary files

Article information

Article type
Paper
Submitted
17 Apr 2016
Accepted
24 May 2016
First published
25 May 2016

RSC Adv., 2016,6, 52434-52447

Self-strengthening hybrid dental adhesive via visible-light irradiation triple polymerization

L. Song, Q. Ye, X. Ge, A. Misra, C. Tamerler and P. Spencer, RSC Adv., 2016, 6, 52434 DOI: 10.1039/C6RA09933E

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