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Dynamic covalent chemistry (DCC) in dental restorative materials: Implementation of a DCC-based adaptive interface (AI) at the resin–filler interface for improved performance
شیمی کووالانسی پویا (DCC) در مواد ترمیمی دندانپزشکی: اجرای یک رابط سازگار مبتنی بر (DCC )هوش مصنوعی در رابط رزین-پرکننده برای بهبود عملکرد-2020 Objective. Dental restorative composites have been extensively studied with a goal to improve
material performance. However, stress induced microcracks from polymerization shrinkage,
thermal and other stresses along with the low fracture toughness of methacrylate-based
composites remain significant problems. Herein, the study focuses on applying a dynamic
covalent chemistry (DCC)-based adaptive interface to conventional BisGMA/TEGDMA (70:30)
dental resins by coupling moieties capable of thiol–thioester (TTE) DCC to the resin–filler
interface as a means to induce interfacial stress relaxation and promote interfacial healing.
Methods. Silica nanoparticles (SNP) are functionalized with TTE-functionalized silanes to
covalently bond the interface to the network while simultaneously facilitating relaxation
of the filler–matrix interface via DCC. The functionalized particles were incorporated into
the otherwise static conventional BisGMA/TEGDMA (70:30) dental resins. The role of interfacial
bond exchange to enhance dental composite performance in response to shrinkage
and other stresses, flexural modulus and toughness was investigated. Shrinkage stress was
monitored with a tensometer coupled with FTIR spectroscopy. Flexural modulus/strength
and flexural toughness were characterized in three-point bending on a universal testing
machine.
Results. A reduction of 30% in shrinkage stress was achieved when interfacial TTE bond
exchange was activated while not only maintaining but also enhancing mechanical properties
of the composite. These enhancements include a 60% increase in Young’s modulus,
33% increase in flexural strength and 35% increase in the toughness, relative to composites
unable to undergo DCC but otherwise identical in composition. Furthermore, by combining
interfacial DCC with resin-based DCC, an 80% reduction of shrinkage-induced stress is
observed in a thiol–ene system “equipped” with both types of DCC mechanisms relative to
the composite without DCC in either the resin or at the resin–filler interface.
Significance. This behavior highlights the advantages of utilizing the DCC at the resin–filler
interface as a stress-relieving mechanism that is compatible with current and future devel-
opments in the field of dental restorative materials, nearly independent of the type of resin
improvements and types that will be used, as it can dramatically enhance their mechanical
performance by reducing both polymerization and mechanically applied stresses through-
out the composite lifetime. Keywords: Adaptive interface | Interfacial stress relaxation | Thiol–thioester exchange | Dynamic covalent chemistries | Composites |
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