Dental polymer part 1

All details about the dental polymer
Components and Composition
Molecular Weight
Polydispersity
Structure Of Polymer
Mechanical And Physical Properties Of Polymer,
Rheometric Properties
Solvation and dissolution Properties
Thermal Properties
Requirement Of Dental Resins
Dental Use Of Resins

1. DENTAL POLYMER PRESENTED BY :- DHANANJAY SINGH

2. DENTAL POLYMER Content:- * Introduction * Components and Composition * Molecular Weight * Polydispersity * Structure Of Polymer * Mechanical And Physical Properties Of Polymer * Rheometric Properties

3. * Solvation and dissolution Properties * Thermal Properties * Requirement Of Dental Resins * Dental Use Of Resins

4. INTRODUCTION .Polymers are formed through Chemical Reaction that convert large no. of Low Molecular weight molecules called Monomer or ‘Mer’ into Large very high Molecular weight Long chain Macromolecules.

5. Resins:- These are Composition of either monomer or Macromolecules blended with other Components.

6. On The Basis Of Type Of Mer Units- Polymers are of two Types! HOMOPOLYMER Polymers Containg same type of Monomer unit. COPOLYMER Polymers Containing 2 or more types of Monomer Unit.

7. Copolymer Structure. Copolymer can be further divided into 3 Types ! Random Copolymer ABBAAABBBAABABABABBBBAAAAAA Block Copolymer AAAAAABBBBBAAAAAAAABBBBBAAAAAAAA Branched/ Grafted Copolymer AAAAAAAAAAA | | B B B B B B

8. COMPONENTS AND COMPOSITION Backbone of Chain Extent Of Branching Cross Linking and Molecular weight Determines the Property of a Polymer.

9. . BACKBONE- Polymers are consist of very large macromolecules and that they are Chain like structure often called Backbone. In addition to C-chain macromolecules may also consist of Inorganic network ex- SiO2 in glass Silicate Ceramics. CHAIN BRANCHING- Branching is analogous to extra arms growing out of Polymer chain. CROSS LINKING- Cross Linking forms bridges between chains and dramatically increase Molecular weight, consequently physical and mechanical properties may vary.

10. Molecular Weight Molecular weight of polymer molecule equals the molecular weight of various mers multiplied by number of mers unit. They may range from thousands to millions of units depending on preparation condition.

11. Two types of average molecular weight are commonly used :- > Based on average number of mer units in a chain (Mn) > Based on molecular weight of average chain (Mw) > Mw is always greater than Mn except when all molecules are of same length ; thenMn =Mw

12. Polydispersity * Ratio of Mw/Mn is called polydispersity. * It is the measure of range and distribution of chain sizes. * Polymers of high polydispersity will began to melt at lower temperature and heavily larger temperature range of melting.

13. Effect of polymer chain length, branching and crosslinking on mechanical and physical properties.Rigidity,strenght and melting temperature increase as polymer chain length grows and molecular weight increases .

14. Structure Of Polymer There are three basic structures :- Linear polymer :- In these polymers monomers are linked with each other and form a long straight chain. These chains has no any side changes. Their molecules are closely packed and have high density, tensile strength, and melting point.

15. Branched polymer IN these polymer branching occurs by the replacement of a subunit. Branching may results from the formation of carbon-carbon or various type of other bonds. Branching some times occurs spontaneously during synthesis of polymer

16. Crosslinked polymer Crosslinking forms bridges between chains and dramatically increase molecular weight. Consequently physical and mechanical property vary with the composition and extent of crosslinking for a given polymer system. The three dimensional network of crosslinked polymers increase rigidity and resistance to solvents.

17. Mechanical And Physical Property Of Polymer These properties are grouped into four categories:- >Mechanical Properties >Rheometric Properties >Solvation And Dissolution Properties >Thermal Properties

18. Mechanical Properties Applied forces produce stresses within polymer that cause materials to deform (i.e. undergo strain) via :- Plastic strain- Irreversible deformation that cannot be recovered and result in a new permanent shape as the result of slippage(flow) among polymer chain .

19. Elastic strain- Irreversible deformation and will be completely recovered when the stress is eliminated as a result polymer chain uncoiling and then recoiling.

20. Visco Elastic - Combination of both elastic and plastic deformation, but only elastic portion is recovered when the stress is reduced.

21. Rheometric Properties The rheometry,or flow behavior of solid polymer involves a combination of elastic and plastic deformation followed by elastic recovery after stress is removed. The chain length,number of crosslinks,temprature, and the rate of force application determine which type of behavior dominates .

22. Solvation And Dissolution Properties *Polymers are usually slow to dissolve and clearly either soluble or insoluble in a particular liquid. *Solvation characteristic is sensitive to * Molecular Weight -> Molecular weight increases solvation decreases * Polydispersity –> (Mw/Mn) increases salvation decreases * Cross linking –> Cross linking increases , dissolution decreases * Chain Branching –> Branching increases , dissolution decreases

23. Thermal Properties * The physical properties of polymer are influenced by change in temperature. * Higher the temperature, the softer and weaker the polymers become.

24. Based on their thermal behavior they are divided into :- * Thermoplastic polymer:- * They undergo a reversible change. *These are rasins that can be repeatedly softened and molded under heat and pressure without chemical change occurring. They are soluble in organic solvents. *Example- polymethyl methacrylate , polyvinyl acrylics

25. * Thermosetting polymer:- * They undergo irreversible change when heated. * These are the rasins which can be molded only once. * They are set when heated * This cannot be softened by reheating * They are insoluble in organic solvent. * Example- Bakelite , Phenol Formaldehyde

26. Requirements Of Dental Resins It should be tasteless, non-toxic and non-irritant to the oral tissue Be esthetically satisfactory Be dimensionally stable Have enough strength ,resilience and abrasion resistance Be insoluble and impermeable to oral fluids Be easy to fabricate and repair Have coefficient of thermal expansion which match that of tooth structure

27. Dental Use s of resin * Prosthodontics:- > Denture base and teeth > Soft liners > Custom trays * Operative Dentistry:- > Glass- ionomer cements > Cavity fillings > Pit and fissure sealants * Orthodontics:- > Brackets > Bracket bonding resins and cement > Spacers *

28. * Endodontics:- >Gutta-percha points >Root canal Sealants >Rubber dams * Equipments:- >Mixing bowls >Mouth guard >Protective Eyewear