Dental polymer part 2

all details about the chemistry of polymerization
Addition polymerization
Chemical Stages of polymerization
induction
propagation
chain transfer
termination
Inhibition of polymerization
Ring-opening polymerization,
Step growth/Condensation polymerization
Copolymerization
Acrylic resins
Methylmethacrylate
Polymethylmethacrylate{PMMA}
Multifunctional Methacrylate and Acrylate resins

1. DENTAL POLYMER PRESENTED BY:- DHANANJAY SINGH

2. CHEMISTRY OF POLYMERIZATION Content:- *Introduction * Addition polymerization * Chemical Stages of polymerization: -induction -propagation -chain transfer -termination * Inhibition of polymerization * Ring-opening polymerization * Step growth/Condensation polymerization

3. Content:- * Copolymerization * Acrylic resins * Methylmethacrylate * Polymethylmethacrylate{PMMA} * Multifunctional Methacrylate and Acrylate resins *conclusion

4. Introduction:- *polymers are finding increased application in almost every field of dentistry these are being used successfully. *New type of resins are being developed in regular basis, it is important us to know the basic chemistry of polymer.

5. Additional polymerization:- *In addition polymerization monomers react to form a polymer without formation of by-products. *The addition polymerization takes place in free radical mechanism.(R.) *Most dental resins are polymerized by additional polymerization.

6. * Chemical stages of polymerization 1.Induction:- *Two process control the induction stage(activation and initiation). *free radicals can be generated by the activation of radical-producing molecule like heat, visible light, chemical agents.

7. *The free radicals are produce by reactive agents called initiators. *The free radicals reacts with a monomer and initiates the polymerization process. *Initiators which is used extensively in dental polymers is Benzoylperoxide.

8. 2.Propagation:- The resulting free radical-monomer complex then act as a new free radical center when it approaches another monomer to form a dimer, which is also becomes a free radicals.

9. 3.Chain Transfer:- *In the process the active free radicals of a growing chain is transferred to another molecule.

10. 4.Termination:- *Although chain Termination can result from chain transfer. *Addition polymerization reactions are most often terminated either by direct coupling of two free radical chain ends. *Both molecules combine and become deactivated by formation of a covalent bond.

11. Inhibition of polymerization:- *An impurity can react with activated initiator or any activated nucleus, or with an activated growing chain to prevent further growth. * Ex -the addition of a common inhibitor such as Hydroquinone, to the monomer inhibits spontaneous polymerization. Presence of oxygen (air) also inhibit polymerization.

12. Ring opening polymerization:- *It is a second type of addition polymerization used with current dental products. *Ring opening monomer containing more than three atoms in the ring.

13. *two types of three atom ring monomer use in dentistry- 1.Imines -It used in the polyether impression materials. 2.Epoxy -it used in the silorane restorative and bonding resins.

14. Step-Growth/ Condensation Polymerization:- *Reaction between two or more molecules to produce a large molecule with formation of by-products such as- water, alcohols, halogen acids, and ammonia. *The process can repeat itself and form macromolecules.

15. COPOYMERISATION:- *Two or more chemically different monomers, each with some desirable property, Can be combined to yield specific physical property of polymer. As defined earlier, the polymer formed is a copolymer, and the process is known as copolymerization.

16. *Many useful resins are manufactured by copolymerization. *Methylmethacrylate , acrylic esters and methacrylic esters all copolymerization readily.

17. ACRYLIC RESINS:- The acrylic resins are derivatives of ethylene and contain a vinyl group in their structural formula. 1.Acrylic acid, CH 2 =CHOOH 2.Methacrylic acid, CH 2 =C(CH 3 )COOH

18. The effect of esterification on the softening point of poly(methacrylate) compound

19. METHYLMETHACRYLATE:- *The monomer methymethacrylate is a liquid at room temperature, with following physical properties;

20. *Metylmethacrylate exhibits a high vapor pressure and is an excellent organic solvent. *A volumetric shrinkage of approximately 21% occurs during the polymerization of pure methylmethacrylate, which a problem for accuracy of fit.

21. POLY(METHYLMETHACRYLATE){PMMA}:- *PMMA is a transparent resin of water like clarity that is transparent to light in the visible and ultraviolet range down to a wavelength of 250nm. *Its noncrystalline structure possesses a high internal energy

22. *Density 1.19g/cm3. *It is a hard resin 18-20KHN *Tensile strength approximately 60MPa. *A modulus of elasticity of approximately 2.4GPa.

23. *PMMA is easy to handle, tough, wear resistant, able to sterilized, easily cleaned, biologically safe, and very durable. *PMMA is a linear polymer, it is soluble in organic solvents such as chloroform and acetone. *PMMA also absorbs water imbibition. [shown an increase in 0.5% of weight after immersion in water for 1week]

24. MULTIFUNCTIONAL METHACRYLATE AND ACRYLATE RESINS:- *BIS-GMA, also known as Bowens resins, is one of the first multifunctional methacrylates introduced in dentistry. * (PENTA-P) used in dentin bonding agents. *PAA used in light-curable glass ionomer cement.

25. Conclusion :- * Polymer are very rarely used in their pure form. *Modification are carried out to improve the properties of polymers. *Some of the fairly good properties of the polymer make, use in dentistry.

26. THANK YOU