block 5 ospe revisio pob fyb hijbg n.pptx

Vhb

1. Block 5 2 nd year dental materials

2. polymers 1 question

3. identification Acrylics Acrylic powder Acrylic liquid Prosthesis such as dentures of custom trays made with acrylic

4. Based on Behavior polymer Reshaped by heat treatment Setting reaction Solubility in organic solvents Abrasion resistance Example thermoplastic yes Physical change yes low Impression compound Thermoset No after final setting Chemical reaction no high Epoxy resins

5. Stages of Polymerization

6. Types of Copolymerization

7. Composition of acrylics Powder Polymer Polymethylmethacrylate beads Initiator A peroxide such as benzoyl peroxide (approximately 0.5%) Pigments Salts of cadmium or iron or organic dyes Liquid Monomer Methylmethacrylate Cross-linking agent Ethyleneglycoldimethacrylate (approximately 10%) Inhibitor Hydroquinone (trace) Activator* N N ′-dimethyl- p -toluidine (approximately 1%)

8. Types

9. Stages of acrylic mixing

10. Heat cure vs self cure

11. Bonding and adhesion 1 question

12. Enamel etch patterns as type 1, type 2, type 3 Type I Dissolution of the prism cores leaving the prism peripheries intact. Type II Dissolution of the prism peripheries leaving the prism cores intact. Type III No prism structures are evident.

13. Understand dentin smear layer on SEM

14. Hybrid zone

15. Electron microscopy image annototion

16. Smear layer Cut dentinal surface form a unique structure called as the ‘smear layer’. It is composed of debris of hydroxyappatite crystals and denatured collagen. Smear layer is on the freshly cut dentinal/ enamel surface Will be removed by dissolution in 37% concentration of phosphoric acid in 15 sec etch

17. Composites 1 question

18. Filler classification Classification According to Size:- MACROFILLERS 10 TO 100 um MIDIFILLERS 1 TO 10 um MINIFILLERS 0.1 TO 1 um MICROFILLERS 0.01 TO 0.1 um NANOFILLERS 0.005 TO 0.01 um

19. Reduce stress Internal stresses can be reduced by, 1) ‘Self start’ Polymerisation 2) Incremental placement 3) Use of stress breaking liners such as:- a)Filled Dentinal Adhesives b)RMGI .