A COMPARISON OF METALS, CERAMICS AND POLYMERS.pptx

comparison of metals ceramics and polymers

1. A COMPARISON OF METALS, CERAMICS AND POLYMERS Aishwarya Kulkarni 1 st year MDS Dept. of Prosthodontics

2. CONTENTS Introduction Glossary Basic classification Ceramics Metals Polymers Summary table References 2

3. INTRODUCTION 3 FAMILY TRAITS

4. GLOSSARY Alloy Amorphous Ceramic Cross linking Crystalline Dislocation Intermetallic compound Metal metallic bond Modulus of elasticity Polymer Stress raiser Water absorption 4

5. BASIC CLASSIFICATION 5 A tree diagram classifying the three basic materials.

6. 6 Predicted strength Actual strength 1 million to 3 million pounds per square inch (psi) or about 7 to 21 GPa . Actual strengths of most materials are ten to 100 times lower.

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8. CERAMICS 8

9. 9 The groove or other irregularity is called a stress raiser

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11. Clinical applications of ceramics 11 must not be subjected to large tensile stresses

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13. METALS 13

14. 14 In a ductile material, something happens before the theoretical strength of the material is reached at the tip of the stress raiser

15. Mechanism of ductile behavior 15

16. 16 This ripple in the lattice structure is called a dislocation , and it is responsible for the ductile behavior of metals.

17. Electrical and thermal conductivity 17

18. 18 Amorphous Crystalline Intermetallic compounds ?

19. Clinical applications of metals This ductility allows the margins of castings to be burnished, orthodontic wires to be bent, and partial denture clasps to be adjusted. 19

20. POLYMERS 20

21. Modulus of elasticity 21

22. Thermal expansion 22 When strong bonds are present between atoms, the atoms vibrate over a small amplitude Eg. Ceramics and Metals When weak bonds are present, the atoms vibrate over a large amplitude. Eg. Polymers

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24. Compensates for 0.5% processing shrinkage that occurs during the fabrication of heat-cured denture bases Water absorption Because of the weak secondary bonds in polymer materials, water molecules are able to penetrate between the polymer chains in a process called water absorption . 24 Water is responsible for the hydrolytic degradation of polymers break down more quickly or to become stained or malodorous.

25. Effect of cross-linking A way to improve weak bonds between polymer chains would be to link chains together with primary chemical bonds. This method, called cross-linking. Improve strength, resistance to water absorption, abrasion resistance, and other properties of polymers. 25

26. 26 Alloy Amorphous Cross linking Crystalline Dislocation Intermetallic compound metallic bond Modulus of elasticity Stress raiser Water absorption

27. SUMMARY 27 A comparison of the properties of metals, ceramics, and polymers   Metals   Ceramics     Polymers Properties Alloys Intermetallic compounds   Inorganic salts Crystalline   Glasses Rigid Rubbers Hardness Medium to hard Hard   Medium Hard   Hard Soft Very soft Strength Medium to high Medium   Medium High   High Low Low Toughness High Low   Low Most low, some high   Low Low Medium Elastic modulus High High   High High   High Low Very low Electrical conductivity High High   Low Low   Low Low Low Thermal conductivity High High   Low Low   Low Low Low Thermal expansion Low Low   Low Low   Low High High Density High High   Medium Medium   Medium Low Low Translucency None None   Medium High   High High Low Examples Gold-copper Amalgam phases   Gypsum, zinc phosphate SiO 2 , Al 2 O 3   Dental porcelain Poly (methyl methacrylate) (PMMA) Impression materials

28. REFERENCE Dental Materials and Their Selection - 3rd Ed. (2002) by William J. O'Brien 28

29. 29 THANKYOU