Thermal analysis is a branch of materials science where the properties of materials are studied as they change with temperature. Several methods are commonly used –these are distinguished from one another by the property which is measured:
In materials science,a thermosetting polymer,often called a thermoset,is a polymer that is obtained by irreversibly hardening ("curing") a soft solid or viscous liquid prepolymer (resin). Curing is induced by heat or suitable radiation and may be promoted by high pressure,or mixing with a catalyst. Heat is not necessarily applied externally,but is often generated by the reaction of the resin with a curing agent. Curing results in chemical reactions that create extensive cross-linking between polymer chains to produce an infusible and insoluble polymer network.
Dental products are specially fabricated materials,designed for use in dentistry. There are many different types of dental products,and their characteristics vary according to their intended purpose.
Dental restoration,dental fillings,or simply fillings are treatments used to restore the function,integrity,and morphology of missing tooth structure resulting from caries or external trauma as well as to the replacement of such structure supported by dental implants. They are of two broad types—direct and indirect—and are further classified by location and size. A root canal filling,for example,is a restorative technique used to fill the space where the dental pulp normally resides.
Dental composite resins are dental cements made of synthetic resins. Synthetic resins evolved as restorative materials since they were insoluble,of good tooth-like appearance,insensitive to dehydration,easy to manipulate and inexpensive. Composite resins are most commonly composed of Bis-GMA and other dimethacrylate monomers,a filler material such as silica and in most applications,a photoinitiator. Dimethylglyoxime is also commonly added to achieve certain physical properties such as flow-ability. Further tailoring of physical properties is achieved by formulating unique concentrations of each constituent.
In dentistry,inlays and onlays are used to fill cavities,and then cemented in place in the tooth. This is an alternative to a direct restoration,made out of composite,amalgam or glass ionomer,that is built up within the mouth.
A photopolymer or light-activated resin is a polymer that changes its properties when exposed to light,often in the ultraviolet or visible region of the electromagnetic spectrum. These changes are often manifested structurally,for example hardening of the material occurs as a result of cross-linking when exposed to light. An example is shown below depicting a mixture of monomers,oligomers,and photoinitiators that conform into a hardened polymeric material through a process called curing.
Synthetic resins are industrially produced resins,typically viscous substances that convert into rigid polymers by the process of curing. In order to undergo curing,resins typically contain reactive end groups,such as acrylates or epoxides. Some synthetic resins have properties similar to natural plant resins,but many do not.
Polybenzoxazines,also called benzoxazine resins,are cured polymerization products derived from benzoxazine monomers.
Curing is a chemical process employed in polymer chemistry and process engineering that produces the toughening or hardening of a polymer material by cross-linking of polymer chains. Even if it is strongly associated with the production of thermosetting polymers,the term "curing" can be used for all the processes where a solid product is obtained from a liquid solution,such as with PVC plastisols.
A luting agent is a dental cement connecting the underlying tooth structure to a fixed prosthesis. To lute means to glue two different structures together. There are two major purposes of luting agents in dentistry –to secure a cast restoration in fixed prosthodontics,and to keep orthodontic bands and appliances in situ.
In dentistry,the configuration factor refers to the number of bonded surfaces in an adhesive dental restoration. Because adhesive dental restorative material will adhere to the walls of a cavity preparation made available to it during polymerization,competing forces can arise during restoration of the tooth that can have both short and long term effects that correlate to the configuration of the cavity preparation.
Polymer engineering is generally an engineering field that designs,analyses,and modifies polymer materials. Polymer engineering covers aspects of the petrochemical industry,polymerization,structure and characterization of polymers,properties of polymers,compounding and processing of polymers and description of major polymers,structure property relations and applications.
Dental cements have a wide range of dental and orthodontic applications. Common uses include temporary restoration of teeth,cavity linings to provide pulpal protection,sedation or insulation and cementing fixed prosthodontic appliances. Recent uses of dental cement also include two-photon calcium imaging of neuronal activity in brains of animal models in basic experimental neuroscience.
Dental compomers,also known as polyacid-modified resin composite,are used in dentistry as a filling material. They were introduced in the early 1990s as a hybrid of two other dental materials,dental composites and glass ionomer cement,in an effort to combine their desirable properties:aesthetics for dental composites and the fluoride releasing ability for glass ionomer cements.
Derek W. Jones is a Professor Emeritus of Applied Oral Science and Biomaterials at Dalhousie University in Halifax,Nova Scotia,Canada
Expanding monomers are monomers which increase in volume (expand) during polymerization. They can be added to monomer formulations to counteract the usual volume shrinking to manufacture products with higher quality and durability. Volume Shrinkage is in first line for the unmeltable thermosets a problem,since those are of fixed shape after polymerization completed.
Bis-GMA is a resin commonly used in dental composite,dental sealants. and dental cement. It is the diester derived from methacrylic acid and the bisphenol A diglycidyl ether. Bearing two polymerizable groups,it is prone to form a crosslinked polymer that is used in dental restorations. For dental work,highly viscous bis-GMA is mixed with aluminosilicate particles,crushed quartz and other related acrylates;changes to component ratios lead to different physical properties in the end product. Bis-GMA was incorporated into composite dental resins in 1962 by Rafael Bowen. Until matrix development work in the early 2000s,bis-GMA and related methacrylate monomers were the only options for organic matrix composition.
Lizymol Philipose Pamadykandathil is an Indian dental materials scientist. Her work has been recognised with a Nari Shakti Puraskar - the highest civilian honour exclusively for women in India.
Jimmy W. Mays is an American polymer scientist,academic,and author. He is a Professor Emeritus at the University of Tennessee.
