Organic Chemistry: Polymers - Research Paper Example

Polymers in Dentistry Chemistry Research Paper Polymers in Dentistry The term polymer is defined, as large molecules that consist of small chemical units called monomers linked together repetitively like a string of beads (Darvell, 2009). Usually, polymers are made up of more than five monomers, and the chain may consist up to thousands of monomers (Shalaby & Salz, 2006). Although many people of polymers as mere plastics used in making household objects and packaging, polymers have a variety of application in everyday life. Polymers and composites, i.e., materials that result from a combination of more than two materials, are essential to the modern dentistry industry (Anusavice & Phillips, 2012; Van Noort, 2013). The term amalgam refers to a mixture of metals and specifically means mercury alloy. A dental amalgam comprises of 50% mercury, 30% silver and other elements such as copper, zinc and tin in smaller percentages (Geier et al., 2012a). For the last sixteen decades, amalgam has had a large role in dentistry industry for filling teeth (Geier et al., 2013). An amalgam is so strong that it can withstand the pressure exerted by the molar during chewing and crunching process. In making amalgam, silver, copper, tin and zinc are dissolved in liquid mercury. The Process of Amalgamation In the amalgamation process, copper, silver, zinc and tin are mixed with liquid mercury either on an amalgamation table or amalgamation drum, where mercury bonds with the other metals to form mercury amalgam. The metals need to be ground to powder form fine enough to increase the exposure surface area of the metal to the mercury. The preferred mesh is between 100 and 325. Water is added to the metal mixture to help in the dispersion of the ore and promotion of a better metal to the interface of mercury. Polymers Used In Dentistry Synthetic polymers are the ones that are used in dentistry. Synthetic polymers are prepared either via addition or step-growth polymerization process. In addition, polymerization monomers that contain double bond join to form a polymer. The double bond in the monomer offers the active center where the process starts. During the process, the π-bond present in the monomer is changed to σ-bond in the polymer molecule. Monomer addition to the end of the developing chain is a fast and exothermic process. Addition polymerization can be anionic, cationic or free radical polymerization (Shalaby & Salz, 2006). Step-growth polymerization involves monomers containing different functional groups. The process occurs by via the reaction of functional groups in a conventional manner. In this type of polymerization, a minimum of two functional per monomer is needed, and every monomer has the same probability to react. The monomers are combined in an alternating structure, and once the elementary reaction takes place, the ability of the polymer to grow remains constant. The process is slower than the addition process, and the polymers formed are mostly of lower molecular weight (Shalaby & Salz, 2006). Components of Teeth and the Decay Process Apart from human bones, teeth are the hardest tissues in the human body. They are made partly inorganic and partly of organic material. The main inorganic component of human teeth is called hydroxyapatite with a simple formula of Ca5(PO4)3(OH). The teeth’s outer layer called enamel is the hardest material in the human body. Approximately 92% of the enamel is made up of hydroxyapatite. Beneath the enamel lies the dentin. The dentine is a composite material that is majorly made up of and a mixture of hydroxyapatite, salts, water and an organic substance called collagen (Van Noort, 2013). Human teeth are one of the tissues that function in the most inhospitable environs. Human teeth are subjected to larger variations in temperature than any other part of the human body. They can withstand low temperatures such as those of ice (0 °C) as well as high temperatures such as those of hot coffee and tea. Apart from variations in temperature, human teeth also encounter variations in pH, i.e., pH ranges of 0.5 to 8. They also encounter large mechanical stresses during the crunching and chewing process. All these environmental stresses contribute to the decay process in one way or another (Van Noort, 2013). The decay process occurs mostly when the teeth are often exposed to foods rich in carbohydrates. Some of the carbohydrates include ice cream, milk, cakes, some soft drinks, some fruits, juices, and vegetables. The presence of bacteria in the mouth of human being is the sole source of plaque, a film on the human teeth where reproduction of bacteria occurs. The interaction between plaque and food deposits left on teeth produce acids over time. After a given period, the acids dissolve the hydroxyapatite present in the teeth thus damaging the tooth enamel. Although the saliva in the mouth can partly counter the acids formed by plaque, these acids dissolve the enamel and creating holes (cavities). Usually, the cavities are painless until there is a large growth that destroys the nerve and blood vessels present in the teeth. There, it is important to fill any hole that forms in the teeth as soon as possible to avoid further damage to them. Health Issues Related to Mercury Although there is scientific evidence that the mercury metal present in amalgam for teeth filling is inactive, it cannot be disputed that mercury is poisonous in the human body in large quantities. Proper placement of the amalgam in small quantities during teeth filling has demonstrated minimal clinical harm. The removal of the existing amalgam can neither hinder the ill health nor reverse the existing disease effects (Brownawelll et al., 2005). Even though the mercury present in the amalgam is strongly bonded to the other metals, it can be released or freed from the amalgam during the chewing or brushing process. In case this happens, the mercury vaporizes from the filling and can be inhaled by the user. During the process of filling and removal, the mercury vaporizes too. The process of removing the amalgam involves drilling into the teeth, and the friction created between the amalgam, and the drill vaporizes some mercury present in the filling. Currently, research is being conducted to examine any existing relationship between diseases such as Alzheimer’s disease, multiple sclerosis and amalgam filling in the teeth. Various disadvantages have been associated with the use of amalgam and hence the declined use in the current decade. Disadvantages of amalgam (Brownawelll et al., 2005) i. Disposal of the old filling amalgam containing mercury is a potential environmental hazard. ii. The amalgam is made up of metal that conduct heat resulting in pain experience among individuals with amalgam filling. iii. The dentist has to drill a cavity in the teeth to keep the filling in place because it cannot stick to the tooth. iv. The silver color of the amalgam is no longer considered aesthetical. v. Mercury present in the amalgam is poisonous. Composite Fillings In recent practice, dentists no longer make use of amalgam in teeth filling but use white composite in teeth filling. A composite is defined as substance made of a combination of more than two materials (Ferracane, 2011). Generally, the composite used for teeth filling are made of glass particles or silica that is bound together with a polymer resin. The methacrylic acid monomer forms the base of the polymer resin used in composite for teeth filling. Glass filler of 35 to 85% is used to fill the polymer resin. The Procedure Used In Composite Filling A number of steps are followed in filling the teeth with a composite. The first step involves preparation of the tooth by etching it with acid to get rid of the debris and application of an adhesive followed by evaporation of the solvent in the adhesive. In the second step, the cavity is filled with the composite in the form of a paste followed by shining a beam of light on it to harden it. The UV light shone on the composite initiates a chemical reaction between the monomer molecules to form various cross-links between the chains of the polymer. The photocuring process takes place converting the glass filler-containing polymer into a three-dimensional cross-linked polymer that fills the cavity in the tooth. During the polymerization process, the resin shrinks a little allowing addition of several layers of the composite successively. The photocuring process is essential because it gives the dentist enough time to build and shape the material well before exposure to light. Once the dentist is done with the filing process, the filling is hardened by shining the light on it. The third step involves polishing of the filling. Advantages of Composite Filling i. The following advantages make composite filling better than amalgam ii. It does not contain mercury, which is considered a poisonous element. iii. It can be used to change the size, shape and color of the teeth to improve the smile of the user. iv. The color and texture of the composite fill can be matched to the user’s teeth. v. Less drilling is done in comparison to the amalgam. Other Applications of Composite Filling Applications in Civil Engineering The use of fiber composite structures, i.e., a plastic polymer that is reinforced with fiber has been used in the restoration and replacement of traditional structures that are degrading (Awad, 2012). Application in Lithium-ion Battery Composite separator enhanced by inorganic fiber offers thermal stability to the separator. The relative affinities that exist between the submicron inorganic fibers and the electrolyte, the polyvinylidene fluoride binder and the electrolyte ensure a superior wettability of the final product (separator) by the liquid electrolyte. The effective ionic conductivity of the composite separator is due to its high porosity and the open porous structure (Huang & Hitt, 2013; Yi et al., 2013). Application in Gas and Liquid Separation Zeolitic imidazolate frameworks are a class of metal-organic frameworks that is made of imidazolates that are bridged by tetrahedral metal ions. This class of frameworks exhibits some permanent porosity and slightly high chemical and thermal relative stability, a property that makes them applicable in many industries. Most composite membranes possess excellent performance in both liquid separation and gas separation (Yao & Wang, 2014). Applications in Energy Absorption Most composite sandwich specimens fabricated from glass fiber, epoxy resin and polystyrene foam have been shown to exhibit high capability for specific energy absorption and the absorbed crash energy (Tarlochan et al., 2012). Applications in Solar Cells A Cu2O/TiO2 composite prepared by depositing Cu2O on a TiO2 film via the electrochemical deposition method is used as a photon absorber for application in solar cells. The Cu2O particles, in this case, are deposited near the interface of TiO2/substrate rather than on the film surface of TiO2 (Zainun et al., 2012). Application in Bone Tissue Engineering A composite scaffold made of carbon nanotubes and poly(lactide-co-glycolide) has been used for bone repair due to its controllable surface roughness and mechanical strength. Preparation of this composite involves the dispersion of carbon nanotubes in a solution of poly(lactide-co-glycolide). A composite scaffold carbon nanotubes/poly(lactide-co-glycolide) has a higher mechanical strength in comparison to poly(lactide-co-glycolide). The presence of carbon nanotubes enhances surface roughness resulting in improved proliferation and attachment of osteoblasts (Cheng et al., 2013). Environmental Effects of Polymers Polymers have both positive and negative effects on the environment depending on their type and usage. Positive effects of polymers Super absorbent polymers cause better enlargement and growth of plants resulting in increased yield under water stress conditions and normal irrigation. This polymer increases the water storage capacity of soil, reduces evaporation of water from the soil, reduces wastage of water and nutrients in the soil and increases soil aeration (Sarvas et al., 2007; Azarpour et al., 2014). Chelating polymers are used in soil and water remediation. The incorporation of chelating groups into the polymeric backbone enhances their remediation ability. The selectivity, retention efficiency and affinity of metal ion are governed by the pH, ligand density and type, solubility and structure of the polymer (Zander, 2009). Most wastewater from dental-operatory contains mercury (Hg), and its removal is an issue of environmental concern for many dental clinics. Studies conducted on polymers have shown their efficacy in removing mercury contaminants from wastewater stream of dental units (Pederson et al., 1999) Negative Effects of Polymers on the Environment Non-biodegradability; synthetic polymers like Teflon take long time to degrade in the environment. Apart from biological degradation, chemical degradation is another problem associated with synthetic polymers. Degradation of polythene is a very slow process involving the chemical breakdown of polythene into smaller parts that can be eaten by microbes (Azwa et al., 2013). Toxic effects; polymers obtained from crude oil and synthesized into plastics are known to release toxins during their decomposition process. The burning of plastics that are synthesized from the feedstock of crude oil results in the production of dioxins and carbon dioxide, which contributes to global warming (Vinu & Madras, 2012). Chemicals present in plastic can cause a structural change in hormones if absorbed by the human body. The seafaring creatures ingest debris of plastics present in the sea, and the chemicals present in them can be poisonous to all manner of wildlife. Harmful chemicals leached from plastics buried in landfills can find their way into ground water and further into the water supply thereby contaminating the water (Delfosse et al., 2012; Cole et al., 2013). References Anusavice, K. J., & Phillips, R. W. (2012). Phillips science of dental materials. New York: Elsevier Health Sciences. Retrieved from http://books.google.com/books?hl=en&lr=&id=gzUeKDhP-KQC&oi=fnd&pg=PP1&dq=Polymers+in+dentistry+and+the+tooth+filling&ots=BfNWt1HIn0&sig=6N154sY7dmC5WW-xfpNo16Q4SmY Awad, Z. K., Aravinthan, T., Zhuge, Y., & Gonzalez, F. (2012). A review of optimization techniques used in the design of fiber composite structures for civil engineering applications. Materials & Design, 33, 534-544. Retrieved from http://www.sciencedirect.com/science/article/pii/S026130691100330X Azarpour, E., Moraditochaee, M., & Bozorgi, H. R. (2014). Effects of super absorbent polymer and combining plant growth promoting rhizobacteria and chemical nitrogen fertilizer under irrigation management of peanut (Arachis hypogaea L.). Advances in Environmental Biology, 8(16), 24-31. Retrieved from http://connection.ebscohost.com/c/articles/99785825/effects-super-absorbent-polymer-combining-plant-growth-promoting-rhizobacteria-chemical-nitrogen-fertilizer-under-irrigation-management-peanut-arachis-hypogaea-l Azwa, Z. N., Yousif, B. F., Manalo, A. C., & Karunasena, W. (2013). A review on the degradability of polymeric composites based on natural fibers. Materials & Design, 47, 424-442. Retrieved from http://www.sciencedirect.com/science/article/pii/S0261306912007832 Brownawell, A. M., Berent, S., Brent, R. L., Bruckner, J. V., Doull, J., Gershwin, E. M., & Karol, M. H. (2005). The potential adverse health effects of dental amalgam. Toxicological reviews, 24(1), 1-10. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/16042501 Cheng, Q., Rutledge, K., & Jabbarzadeh, E. (2013). Carbon nanotube–poly (lactide-co-glycolide) composite scaffolds for bone tissue engineering applications. Annals of biomedical engineering, 41(5), 904-916. Retrieved from http://link.springer.com/article/10.1007%2Fs10439-012-0728-8 Cole, M., Lindeque, P., Fileman, E., Halsband, C., Goodhead, R., Moger, J., & Galloway, T. S. (2013). Microplastic ingestion by zooplankton. Environmental science & technology, 47(12), 6646-6655. Retrieved from http://pubs.acs.org/doi/abs/10.1021/es400663f Darvell, B. W. (2009). Materials science for dentistry. New York: Elsevier. Retrieved from http://books.google.com/books?hl=en&lr=&id=paijAgAAQBAJ&oi=fnd&pg=PP1&dq=Materials+Science+for+Dentistry+&ots=Le5HwNVV8s&sig=p2kr9hSqI_qPrLyqdvnkmFPgcOo Delfosse, V., Grimaldi, M., Pons, J. L., Boulahtouf, A., Le Maire, A., Cavailles, V., & Balaguer, P. (2012). Structural and mechanistic insights into bisphenols action provide guidelines for risk assessment and discovery of bisphenol A substitutes. Proceedings of the National Academy of Sciences, 109(37), 14930-14935. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/22927406 Ferracane, J. L. (2011). Resin composite—state of the art. Dental materials, 27(1), 29-38. Retrieved from http://www.demajournal.com/article/S0109-5641%2810%2900463-X Geier, D. A., Carmody, T., Kern, J. K., King, P. G., & Geier, M. R. (2012a). A dose-dependent relationship between mercury exposure from dental amalgams and urinary mercury levels: a further assessment of the Casa Pia Children’s Dental Amalgam Trial. Human & experimental toxicology, 31(1), 11-17. Retrieved from http://het.sagepub.com/content/31/1/11.long Geier, D. A., Carmody, T., Kern, J. K., King, P. G., & Geier, M. R. (2013). A significant dose-dependent relationship between mercury exposure from dental amalgams and kidney integrity biomarkers A further assessment of the Casa Pia children’s dental amalgam trial. Human & Experimental Toxicology, 32: 434-440. Retrieved from http://het.sagepub.com/content/32/4/434.long Huang, X., & Hitt, J. (2013). Lithium-ion battery separators: Development and performance characterization of a composite membrane. Journal of Membrane Science, 425, 163-168. Retrieved from http://www.sciencedirect.com/science/article/pii/S0376738812006989 Pederson, E. D., Stone, M. E., & Ovsey, V. G. (1999). The removal of mercury from dental-operatory wastewater by polymer treatment. Environmental Health Perspectives, 107(1), 3. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1566316/ Sarvas, M., P avlenda, E. Takacova, J. (2007). Effect of hydrogel application on survival and growth of pine grainling in reclamations. Journal of Forest Science, 53(5), 204-209. Retrieved from http://www.agriculturejournals.cz/publicFiles/00192.pdf Shalaby, S. W., & Salz, U. (Eds.). (2006). Polymers for dental and orthopedic applications. New York: CRC Press. Retrieved from http://books.google.com/books?hl=en&lr=&id=kuPKBQAAQBAJ&oi=fnd&pg=PP1&dq=Polymers+for+Dental+and+Orthopedic+Applications&ots=XxL2QZWFQK&sig=1NA4_NIRGFD6WJ88D_jugo_FCnc Tarlochan, F., Ramesh, S., & Harpreet, S. (2012). Advanced composite sandwich structure design for energy absorption applications: Blast protection and crashworthiness. Composites Part B: Engineering, 43(5), 2198-2208. Retrieved from http://www.sciencedirect.com/science/article/pii/S1359836812001813 Van Noort, R. (2013). Introduction to Dental Materials4: Introduction to Dental Materials. New USA: Elsevier Health Sciences. Retrieved from http://books.google.com/books?hl=en&lr=&id=Qm1pzS0ZN20C&oi=fnd&pg=PP1&dq=Polymers+in+dentistry+and+the+tooth+filling&ots=1sj8Mj8ASh&sig=oEX6uk_H9-8g67gVE76Js1CVQzY Vinu, R., & Madras, G. (2012). Environmental remediation by photocatalysis. Journal of the Indian Institute of Science, 90(2), 189-230. Retrieved from http://journal.iisc.ernet.in/index.php/iisc/article/viewFile/95/92 Yao, J., & Wang, H. (2014). Zeolitic imidazolate framework composite membranes and thin films: synthesis and applications. Chemical Society Reviews, 43(13), 4470-4493. Retrieved from http://pubs.rsc.org/en/content/articlelanding/2014/cs/c3cs60480b Yi, R., Dai, F., Gordin, M. L., Chen, S., & Wang, D. (2013). Micro‐sized Si‐C composite with interconnected nanoscale building blocks as high‐performance anodes for practical application in lithium‐ion batteries. Advanced Energy Materials, 3(3), 295-300. Retrieved from http://onlinelibrary.wiley.com/doi/10.1002/aenm.201200857/abstract Zainun, A. R., Tomoya, S., Noor, U. M., Rusop, M., & Masaya, I. (2012). New approach for generating Cu 2 O/TiO 2 composite films for solar cell applications. Materials Letters, 66(1), 254-256. Retrieved from http://www.sciencedirect.com/science/article/pii/S0167577X11009359 Zander, N. E. (2009). Chelating polymers and environmental remediation (No. ARL-CR-0623). DYNAMIC SCIENCE INC PHOENIX AZ. Retrieved from http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA495762 Read More