Photopolymerization dental applications

Composite resins allow for color matching, conservative cavity preparation, and simple preparation through intraoral photopolymerization. These advantages have made composites an increasingly popular substitute for amalgam in dental restorations, especially when aesthetics are of concern. In this article, we will focus on the actual process of forming dental composites, the properties of the composites that are formed, and a complete description of the photopolymerization of the multimethacrylates that produce the dental composite. We will only be focusing on the use of polymers as dental restorations. Other dental applications of polymers, e.g. dentures and ionomer cements (reviewed elsewhere by Scranton and Klier) will not be addressed. 

Photopolymerization of phosphorus-based (meth)acrylic monomers was largely investigated for dental applications (Scheme 1.4) 20,21,56 69 monomers bore one or two polymerizable groups and phosphoric acid ester, phosphonate, and phosphonic acid moieties were evaluated. When the phosphorus atom was directly linked to a hydrocarbon chain phosphonate ester), the monomers were more resistant to hydrolysis in comparison with phosphoric acid esters. 

Using a similar approach, Sahin et al prepared the acidic monomers PA-17, PA-18, and PA-19 (Scheme 8.8). The interaction of these monomers with HAP was investigated by both NMR and FTIR spectroscopies. It was shown that PA-18 was able to form a strong chemical bond with HAP. PA-17, PA-18, and PA-19 were copolymerized with GDMA. In this photopolymerization study, an increase of reactivity was observed when PA-17 was added to GDMA. This monomer could be a good candidate for dental applications. Unfortunately, no dental materials based on these PAs were developed. 

We chose to modify the anhydride monomers with photopolymerizable methacrylate functionalities. Methacrylate-based polymers have a long history in biomedical applications, ranging from photocured dental composites [20] to thermally cured bone cements [21]. Furthermore, photopolymerizations provide many advantages for material handling and processing, including spatial and temporal control of the polymerization and rapid rates at ambient temperatures. Liquid or putty-like monomer/initiator... 

In the 1960s, the photopolymerization of polyol acrylates found a variety of applications in dentistry, including dental composite resins, adhesives, dentures, and... 

Photopolymerization and photo-crosslinking are versatile and industrially useful reactions. Applications include drying or curing of coatings—paints and printing inks. In dentistry, u.v. hardening of dental filling is an example. Industrial applications of photochemical excitations are well known. 

Chapter 2 by Monge et al. details the synthesis and polymerization of phosphorus-containing (meth)acrylamide monomers. Compared to their (meth)aciylate homologues, this class of monomer is more hydrolytically stable and thus more interesting for a large variety of applications. Nevertheless, these monomers are less studied and most of the results mainly report their photopolymerization in order to develop stable self-etching dental primers. Future research on phosphorus-based (meth)acrylamide monomers is also discussed in this chapter and specifically the synthesis of block copolymers by controlled radical polymerization is investigated. 

Broer DJ, Mol GN, Challa G (1991) In-situ photopolymerization of oriented liquid-crystalline acrylates, 5. Influence of the alkylene spacer on the properties of the mesogenic monomers and the formation and properties of oriented polymer networks. Makromol Chem 192 59-74 Buruiana T, Melinte V, Costin G, Buruiana EC (2011) Synthesis and properties of liquid crystalline urethane methacrylates for dental composite applications. J Polym Sci A Polym Chem 49 2615-2626... 

---