Table of Contents
POLYMERIZATION Chemical reaction in which monomers of a low molecular weight are converted into chains of polymers with a high molecular weight. Monomer molecules are bonded by covalent bonds.
What is the most common form of polymerization in dentistry?
Addition polymerization is the most common form of polymerization for dental materials.
What is polymerization method?
polymerization, any process in which relatively small molecules, called monomers, combine chemically to produce a very large chainlike or network molecule, called a polymer. The monomer molecules may be all alike, or they may represent two, three, or more different compounds.
What are three types of polymerization?
There are 3 principal classes of polymers – thermoplastics, thermosets, and elastomers.
What is polymerization shrinkage in dentistry?
A polymer occupies less volume than the monomers, the effect of which is well known as polymerization shrinkage. During polymerization the distance between monomer chains is reduced when the weak van der Waals forces are converted into covalent bonds.
What are the stages of polymerization?
Polymerization shrinkage. The polymerization reaction consists of three stages: (1) initiation, (2) propagation, and (3) termination.
Why must dentures be relined periodically?
Porosity is a result of loss of monomer or inadequate pressure during processing. Dentures must be relined periodically because: Dentures become loose over time as the alveolar bone of the ridges resorbs.
Why are polymers used in dentistry?
The primary use of polymers has been the construction of prosthetic appliances such as denture base. However they are also used in artificial tooth, restoration, cements, elastics, inlay patterns, implants, impression materials, dies, temporary materials, endodontic filling etc.
Which polymer is used in dental filling?
Fig. 13.4. Classification of dental filling composite materials. The organic (resin matrix) part is mainly made up of bisphenol-A- glycidyldimethacrylate (Bis-GMA).13.5. Composition of polymer composites for dental filling. Matrix Main chemical system Category Acid modified methacrylate Polar groups Compomers.
What is polymerization and examples?
A polymer is a large single chain-like molecule in which the repeating units derived from small molecules called monomers are bound together. The process by which monomers are transformed into a polymer is called polymerisation. For example ethylene polymerizes to form polyethylene.
Why does polymerization occur?
When a bond forms between two monomers, each monomer contributes part of the water molecule that is lost; one molecule provides a hydroxyl group, while the other provides a hydrogen. To make a polymer, this reaction is repeated as monomers are added to the chain one by one.
What is the important of polymerization?
A basic understanding of polymerization processes is important not only because polymerization affects structure, and hence properties, but also because some processing routes can convert monomers directly to a finished shape. They offer manufacturing industry considerable benefits both in direct and indirect costs.
What are the two methods of polymerization dental?
Polymerization Reactions The chemical reaction in which high molecular mass molecules are formed from monomers is known as polymerization. There are two basic types of polymerization, chain-reaction (or addition) and step-reaction (or condensation) polymerization.
What are the type of polymerization?
There are two general types of polymerization reactions: addition polymerization and condensation polymerization.
Where are polymers used?
Polymers are used in almost every area of modern living. Grocery bags, soda and water bottles, textile fibers, phones, computers, food packaging, auto parts, and toys all contain polymers. Even more-sophisticated technology uses polymers.
What factors affect polymerization?
Many factors affect the degree of polymerization of RBCs, including the shade, light curing duration, increment thickness, light unit system used, cavity diameter, cavity location, light curing tip distance from the curing RBC surface, substrate through which the light is cured (e.g., curing through ceramic, enamel, or 07-Mar-2017.
How can polymerization be reduced?
Polymerization shrinkage is inherent to the curing of methacrylates. The only known methods to reduce shrinkage are to reduce the number of methacrylates or utilize a new polymerization chemistry. The silorane-based restoratives (Filtek Silorane, 3M) are an example of novel chemistry in a commercial composite resin.
What is soft start polymerization?
Soft-start polymerization modes that employ an initial. exposure of low-intensity light followed by high-intensity. light exposure may increase flow and delay hardening of. restorative material, thereby reducing polymerization. stress,22 gap formation, and microleakage,12,34 thus.
What are the 4 steps of polymerization?
Production Addition Polymerisation. Initiation. The polymerisation reaction is initiated through the addition of a free radical. Propagation. Following initiation, the process continues with the successive addition of monomer units to the chains. Termination.
How do you initiate polymerization?
Initiation is the mechanism which starts the polymerization process. Vinyl monomers are quite easily polymerized by a variety of activating methods. Styrene, for example, can be converted to solid polymer simply by heating, and ultraviolet light can have exactly the same effect.
What is chain reaction polymerization?
3.02. A ‘chain polymerization’ is a chain reaction in which the growth of a polymer chain proceeds exclusively by reaction(s) between monomer(s) and active site(s) on the polymer chain with the regeneration of the active site(s) at the end of each growth step.
How many times can dentures be relined?
A denture reline should occur, at most, every two years. However, if you’re feeling any discomfort or your dentures just don’t fit right and are loose, getting a reline will most likely fix the problem and get you back to feeling comfortable with your new teeth.24-Dec-2018.
How are dentures relined?
Hard Denture Reline All Full Dentures should have a reline every two years. Denture Care Clinic in Neutral Bay removes a layer of plastic from the Dentures interior surface, and then fills the Denture with a putty-like material which conforms to the contours of your mouth creating an accurate impression.06-Aug-2018.
Can you reline dentures yourself?
Can You Reline Dentures Yourself? Obviously, it’s best to have your dentist do your denture reline. But, if it’s too inconvenient or too expensive to go that route, it is possible to reline your dentures at home. The benefits of doing a reline yourself are obvious — cheaper and more convenient.13-Jul-2019.
Is dental composite a polymer?
Dental composites, or resin-based composites, are synthetic materials that combine polymeric matrix with a dispersion of glass, mineral, or resin filler particles and/or short fibers by coupling agents. Just like dental amalgam, they are used to restore tooth structure lost through trauma, caries, or other diseases.
What are the three stages of addition polymerization?
Addition polymerization (also known as free-radical polymerization) has three stages: initiation, propagation and termination.
What are the two categories of polymers?
Polymers fall into two categories: thermosetting plastic or thermoset. thermoforming plastic or thermoplastic.
