Sol-Gel Materials, 1. Synthesis and Hydrolytic Condensation of New Cross-Linking Alkoxysilane Methacrylates and Light-Curing Composites Based upon the Condensates

Self Cite

204

110

The currently used commercial self‐etching enamel‐dentin adhesives and restoratives composites are mainly based on a mixture of various monofunctional and cross‐linking dimethacrylates. New developments of enamel‐dentin adhesives concern the improvement of technique insensitivity and storage stability. Improvements of restorative composites are focused on the reduction of the polymerisation shrinkage, as well as the improvement of wear resistance, biocompatibility, and processing properties. In the past five years, many research efforts have been carried out to develop new monomers and tailor‐made components for filling materials, such as fillers or initiators. New phosphonic acid ether acrylates and cross‐linking bis(acrylamide)s enable the preparation of self‐etching enamel‐dentin adhesives with improved storage stability. With free‐radically polymerisable cyclic monomers, such as bicyclic cyclopropyl acrylates or cyclic allyl sulfides, low‐shrinkage storage‐stable restorative composites could be prepared. In case of the cationic polymerisable cyclic monomers, like siloxane‐based cycloaliphatic epoxides, the lower curing rate, stronger exothermic effect and lower curing depth compared to dimethacrylate‐based composites presently prevent their dental application. Designed methacrylates with tailor‐made properties and sol‐gel polycondensates can also contribute to the improvement of the currently used restorative composites. Radical polymerisable dental materials are initiated by light curing and by redox initiator systems. Under acidic conditions amine containing initiator systems are deactivated by acid‐base reaction. Non amine‐based initiators have to be developed for acidic monomer containing dental materials. The use of discrete nano‐filler particles mainly concerns the reinforcement and, in some cases, the increase of X‐ray opacity of composite filling materials.magnified image

Section: Organic-inorganic Components For Dental Restorative Materialsmentioning

confidence: 99%

Recent Developments of New Components for Dental Adhesives and Composites

Moszner¹,

Salz²

2007

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204

110

“…the preparation of the network precursor is separated from the initiation of its curing process. [17,18] However, the batch vitrified rapidly and often caused incomplete consumption of double bonds. The studies of chemical reactions of reactive groups attached to a polymer backbone have shown, in many cases, a lower extent of reaction in comparison with low molecular reactants.…”

Section: Residual Unsaturationmentioning

confidence: 99%

“…[12] Furthermore, the composites should be stabilized against premature curing. The residual silanol groups make MSiP macromonomers less stable during storage [18] and should be removed by silylation with alkylchlorsilanes. On the other hand, the addition of free radical scavengers suppresses the spontaneous spreading of thermal double bond polymerization.…”

Section: Introductionmentioning

confidence: 99%

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Photocrosslinking Polymerization of Methacrylate Modified Triethoxysilanes Polycondensates and Multifunctional Methacrylates

Pavlineč

Moszner

2003

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Densely crosslinked polymer networks were prepared by fast, visible light‐induced polymerization at 20–22 °C. The two methacrylate functionalized triethoxysilanes polycondensates (MSiP) either alone, or in a mixture with methacrylate modified oxozirconium clusters, were polymerized separately and as comonomers to multimethacrylate monomers in a weight ratio of 1:0.9. Pure organic networks based on 1,6‐bis(2‐hydroxy‐3‐methacryloyloxyethoxycarbonylamino)‐2,2,4‐trimethylhexane (UDMA) were used for comparison in the same ratio to other comonomers. The networks based on organic bifunctional monomers showed high, around 85% conversion of double bonds. Nevertheless the non‐reacted monomer that migrates to the toluene amounts from 5.6 to 11.65 wt.‐%. Copolymerization of UDMA with tetrafunctional components resulted in networks with higher residual unsaturation up to 27.7%. This result points out the important role that functionality and the spacer structure between the monomer double bonds play in the extent of reaction. Based only on modified inorganic SiOSi nano‐structures the networks are characterized by nearly complete building up of MSiP in the network, extreme crosslinks density, and mostly less than 1 wt.‐% of soluble substances. However, residual unsaturations exceeded 22%. The advantage of copolymerization of MSiP with proper organic comonomers as potential solvent free matrices for dental composites was demonstrated by a network consisting of MSiP II and UDMA. The 13.7% of unreacted double bonds and 99.65 wt.‐% gel content approximated efforts to minimize residual unsaturation and maximize monomer conversion in cured networks.Monomers used for the synthesis of the densely crosslinked polymer.magnified imageMonomers used for the synthesis of the densely crosslinked polymer.

“…[30,31] A series of new hydroxylated monomers was obtained from Michael addition of ethanolamine, diethylene glycol amine, triethylene glycol amine, tetradecylamine, 1-adamantanamine, 1,6-hexanediamine with AHM. [29] Using the same approach, we synthesized a new derivative via Michael addition of APTES to the acrylate group of AHM at room temperature without any solvent and catalyst (Scheme 2).…”

Section: Synthesis Of Monomersmentioning

confidence: 99%

Synthesis and Photopolymerizations of New Crosslinkers for Dental Applications

Yağcı

Ayfer²,

Albayrak

et al. 2006

Summary: Five new crosslinkers for use in dental composites were synthesized. Four are based on TBHMA: 1 via reaction of TBBr and Bisphenol A; 2 by hydrolysis of t‐butyl groups of the first monomer to give a diacid derivative; 3 by conversion of the first monomer to an amide derivative using benzyl amine; 4 by conversion of the first monomer to amide derivative using APTES. The AHM‐based monomer 5 was synthesized from the Michael addition of APTES to AHM. The photopolymerization behaviors of the synthesized monomers with Bis‐GMA, TEGDMA and HEMA were investigated using photodifferential scanning calorimetry at 40 °C using DMPA as photoinitiator. The polymerization rates and degrees of conversion for mixtures of any of the monomers 1–4 with Bis‐GMA:TEGDMA were found to be similar to Bis‐GMA:TEGDMA, higher than Bis‐GMA:HEMA, and also higher than mixtures with Bis‐GMA:HEMA. The incorporation of TBHMA‐based monomers into the conventional resin mixture (Bis‐GMA and TEGDMA) reduced the polymerization shrinkages. Monomer 5 and its mixtures polymerized much faster and to higher degrees of conversion than the other investigated systems, however, this system exhibited the largest volume shrinkage.Structures of some of the new crosslinkers synthesized.magnified imageStructures of some of the new crosslinkers synthesized.