Polymers dental composites

In the first portion of this section, we will focus on the materials and processes used to form polymer dental composites. This section will be followed by a discussion of the problems associated with polymer composite materials. An overview of the photopolymerization behavior and the polymer structure of these highly crosslinked materials is presented in Sects. 3 and 4. Lastly, some of the properties of current composite resin formulations are presented. 

N. Moszner, U. Salz, New developments of polymer dental composites. Prog. Pol)rm. Sci. 

Applications. The applications sought for these polymers include composites, stmctural plastics, electronics/circuit boards, aircraft/spacecraft coatings, seals, dental and medical prosthetics, and laser window adhesives. However, other than the early commercialization by Du Pont of the NR-150 B material, Httie development has occurred. These polymers are quite expensive ( 110 to 2200 per kg for monomers alone). 

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... 

Crosslinked polymers are widely used as dental materials (1-31. Perhaps the most challenging application is in the restoration of teeth (4). The monomers must be non-toxic and capable of rapid polymerization in the presence of oxygen and water. The products should have properties comparable to tooth enamel and dentin and a service life of more than a few years. In current restorative materials such properties are sought using so-called "dental composites" which contain high volume fractions of particulate Inorganic fillers (5-71. However in the present article attention is concentrated on one commonly used crosslinked polymeric component, and on the way in which some of its properties are influenced by low volume fractions of fillers. 

With over 200 million dental restorations performed each year, the importance of developing a restorative material with tooth-like appearance and properties cannot be underestimated. In this article, the use of poly (multimethacrylates) as dental composites is summarized from both fundamental and practical sides. Detail is provided regarding the utilization, procedures, and problems with polymeric composite restoratives, and a complete discussion of the polymerization kinetics and the polymer structural evolution is presented, fn the final sections, properties of current composite materials and suggestions for what areas of research would prove most promising are presented. 

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. 

The majority of resins are composed of two dimethacrylate monomers, 2,2 -bis [4(2-hydroxy-3-methacryloyloxypropyloxy)phenyl] propane (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) [22-28]. Typically, TEGDMA or other methacrylate monomers are added as viscosity modifiers to Bis-GMA to make the solution less viscous and more appropriate for clinical use. These diluents also allow for better distribution of the components during manufacture of these composite systems. Another common monomer used to make dental composites, especially those manufactured in Europe, is urethane dimethacrylate [24,29, 30], Ethoxy bisphenol A dimethacrylate is another modification of the Bis-GMA monomer that can be used to make a more hydrophobic polymer that would better withstand the wet oral environment. Other diluents include low viscosity diacrylates and dimethacrylates. Table 1 lists some of these monomers [31-37]. 

Lewandowski et aL (2) prepared containing polymers of carbosilane and methacrylate derivatives, (II), which were effective in dental compositions and had a Watts shrinkage of less than 2%. Crosslinkable carbosilane methacrylate monomers, (HI), effective in dental compositions were also prepared by Lewandowski et al. (3) in an earlier investigation that had a Watts shrinkage of less than 2%. Carbosilane derivatives effective in dental compositions were prepared by Bissinger et aL (4) and are described. 

Title Dental Compositions Containing Carbosilane Polymers... 

Nozawa et al. (5) prepared reactive methacrylate monomers containing isocyanate functions, (IV), which were used in dental compositions for preparing low-shrinkage polymers. 

Oxathiocin 771 and related compounds were used to produce polymers, co-polymers, or block polymer to manufacture adhesive, dental compositions, and optical lenses <1996WO 9471>. 

Poly(propylene oxide) is typically obtained by base catalyzed anionic polymerization of propylene oxide [12]. Both stereospecific and atactic forms are known. The polymer is used as a soft polyether unit in polyurethane elastomers and foams in polymer electrolytes as surfactants (lubricants, dispersants, antistatic agents, foam control agents) in printing inks, as solubilizers in hydraulic fluids, coolant compositions in various medical applications (protective bandages, drug delivery systems, organ preservation, dental compositions), etc. 

Geltedi Silica Powd. [Geltech] Silica for dental composites, biomedical applies., light dil ers, polymer composites for electronic iy)plics. 

The majority of the polymerization of a dental composite resin occurs very quickly, typically during the 20-40 s or so of light irradiation from the dental cure lamp. However, free radicals within the material do not terminate immediately the lamp switches off. Hence they are able to continue their propagation steps for some time after this initial cure, as growing polymer molecules containing free radical centres continue to incorporate extra monomer molecules [24]. Shrinkage, which is associated with polymerization, has been shown to continue for up to 24h after initial setting [25] in a process known as post-polymerization [26]. 

K. Anseth, S.M. Newman, C.N. Bowman, Polymeric dental composites properties and reaction behaviour of multimethacrylate dental restorations, Adv. Polym. Sci. 122(1995) 177-217. 

K. Arakawa, Shrinkage forces dne to polymerization of light-cured dental composite resin in cavities, Polym. Test. 29 (2010) 1052-1056. 

Storage Protect from light refrigerate store away from heat store 4 C Uses Crosslinking agent in inks, adhesives, textile prod, modifiers, photoresists modifiers for castings, polyesters, fiberglass, or radiation-cured prods. in dental composite materials, prosthetics, sealants Manuf./Distrib. ABCR Aldrich Alfa Aesar Monomer-Polymer Dajac Labs... 

Abstract This chapter focuses on dental biomaterials designed for permanent placement in the mouth. The development of flowahle polymer-ceramic composites is traced and their rheological properties, such as pseudoplasticity and thixotropy, discussed. Also considered are some materials that are being developed for root canal therapy, including calcium phosphate cements. There is vast scope for research into materials development, clinical applications and fundamental mechanisms. 

PMMA and other methacrylate and acrylate polymers are widely used in dentistry. PMMA is used for dentures and root canal sealants. Polymers of 2,2-bis[4-(2-hydroxy-3-methacry-loyolxypropoxy)phenyl]propane (BisGMA), triethyleneglycol dimethacrylate (TEGDMA), and urethane dimethacrylate (UDMA) are used in dental composite resins, most commonly with a silica filler. Such composite resins are used for filling cavities, reshaping, and restoring teeth and for full and partial crowns. 

The maximum value of Rp (between 10% and 30% conversion) is one of the reliable parameters to measure the reactivity of the formulation. FTIR profiles also provide the amount of unreacted functional groups remaining in the cured system, which is a parameter that strongly affects the final properties of the polymer. Real-time FTIR is also well suited for dark polymerization reactions that occur immediately after light exposure. One of the disadvantages of this technique appears in composite systems, in which the presence of additives may interfere with the transmission of the light by the polymer system, such as in dental composites. ... 

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