Free radical polymerization dentin

Calcium Chelates (Salicylates). Several successhil dental cements which use the formation of a calcium chelate system (96) were developed based on the reaction of calcium hydroxide [1305-62-0] and various phenohc esters of sahcyhc acid [69-72-7]. The calcium sahcylate [824-35-1] system offers certain advantages over the more widely used zinc oxide—eugenol system. These products are completely bland, antibacterial (97), facihtate the formation of reparative dentin, and do not retard the free-radical polymerization reaction of acryhc monomer systems. The principal deficiencies of this type of cement are its relatively high solubihty, relatively low strength, and low modulus. Less soluble and higher strength calcium-based cements based on dimer and trimer acid have been reported (82). 

To conclude, phosphorus-based (meth)acrylamide monomers were involved in free radical polymerization and the resulting polymers proved to have interesting applications, in particular as new dentin adhesives. Nevertheless, the main drawback of conventional radical polymerization is the lack of control over the molecular weight, and the impossibility to achieve complex polymeric structures. As a result, controlled radical polymerization of phos-phonated-containing (meth)acrylamides was also investigated. 

Furthermore, monomers for restorative composites or composite cements should exhibit a low volume contraction during polymerization, excellent mechanical properties after polymerization, and low water solubility. The water sorption of the formed polymer should also be low. The currently used direct restorative composites, composite cements, and enamel/dentin adhesives are largely based on methaciylate chemistiy using mixtures of different methacrylates, such as crosslinking and functionalized methacrylates, which can be cured by free-radical polymerization. ... 

This monomer showed enhanced hydrolytic stability as well as great adhesive properties. Nowadays, PA-12 is incorporated in some commercially available adhesives from Ivoclar Vivadent AG (AdhESE, Excite). Although it does not impair its adhesive potential, PA-12 tends to slowly hydrolyze in water to form the compound PA-13 (Scheme 8.7). To overcome this problem, we synthesized the monomers PA-14, PA-15, and PA-16, which were totally stable in aqueous solutions (Scheme 8.7). Unfortunately, PA-14 and PAIS showed a significant lower reactivity in radical homopolymerization than PA-12. Adhesives based on PA-14 and PA-15 were formulated PA-15 provided a similar SBS to dentin as PA-12, whereas PA-14 exhibited veiy poor adhesive properties. The higher stability of PA-16 in comparison with PA-12 is due to the steric hindrance of the mesityl group. The presence of this mesityl group also induces a decrease of reactivity. Indeed, PA-16 has been shown to be less reactive in free-radical polymerization than MMA or PA-12. ... 

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