Presentation (3).pptx for calcium hydroxide
- 2. Dental waxes Dental waxes: A low molecular weight ester of fatty acids derived from natural or synthetic components that soften to a plastic state at a relatively low temperature.
- 5. Composition of inlay wax Paraffin(40./. to 60./.):Main ingredient Used to establish the melting point Melting point increased with increase in its molecular weight It flakes when trimmed, does not produce smooth , glossy surface Therefore other waxes are added for modification
- 6. Gum Damar(1./.): Natural resin Improves smoothness Renders resistance to cracking and flaking Enhances the smoothness and luster of the surface. Carnauba wax(25./.): Quite hard, has high melting point Combined with Paraffin to decrease the flow at mouth temperature. Agreeable odour and gives glossiness to the surface
- 7. Candelila wax: Added to replace carnauba wax Has same qualities as carnauba wax but this has low melting point and is not as hard as carnauba wax. Carnauba wax is often replaced with synthetic waxes- Montan waxes. It is substituted to increase the melting point of the Paraffin wax
- 8. Ideal requirements When softened the wax should be uniform Colour should contrast with die Wax should not flake or crumble when softened Wax should not chip,flake or tear during carving During burnout (at 500 degree Celsius),it should vaporizer completely without residue Wax pattern should be completely rigid and dimensionally stable until it is eliminated
- 9. Should be sufficiently plastic slightly above mouth temperature and becomes rigid when cooled to mouth temperature. Should have good flow when heated and set slightly when cooled.
- 10. Types of inlay wax Type I- medium wax employed in Direct technique Type II-Soft wax employed in Indirect Technique
- 12. Manipulation of wax DIRECT TECHNIQUE: Soften the wax ,by holding the stick of wax over visible flame The wax is then shaped to the form of the prepared cavity. After inserting the wax into the cavity it is held under finger pressure while it solidifies Allowed to cool gradually at mouth temperature A cold carving instrument should be used Withdraw the wax pattern carefully In the Long axis of the preparation.
- 13. INDIRECT TECHNIQUE: Pattern is prepared over lubricated die Dipping method:In case of full crowns,the doe can be dipped repeatedly into hot liquid wax.The wax is allowed to cool,Carved and removed from die. Softening in warm water:Not recommended. Addition:The wax is melted and is added in layers using a spatula or a brush. In all the methods the pattern must be invested immediately after removal from the mouth or from the die
- 14. Flow One of the desirable properties of type I inlay wax is that it should exhibit a marked plasticity or flow atba temperature slightly above that of the mouth The temperature at which the wax is plastic is indicated by the Time- Temperature cooling curve for a typical type I wax. Each Wax exhibits a sharp transition Temperature at which it loses its plasticity
- 16. The maximum flow permitted for type I waxes at 37 degree Celsius is 1./. This temperature permits carving and removal of the pattern from the prepared cavity at oral temperature without distortion Both type I and type II waxes at 45 degree Celsius must have a minimal flow of 70 percentage.
- 17. Thermal properties Thermal conductivity is low and so sufficient time must be allowed both to heat them uniformly and to cool them to body or to room temperature They have higher coefficient of thermal expansion 0.7./. With increase in temperature of 20 degree Celsius Curve A represents the thermal expansion of onlay wax as a function of temperature The expansion rate increases abruptly above approximately 35 degree Celsius The temperature at which a change in rate occurs is known as Glass transition Temperature
- 19. Wax Distortion Distortion of a wax pattern results from occluded air in the pattern,physical deformation,release of stress trapped during previous cooling,excessive storage time and extreme temperature changes during storage. The wax pattern should be retained on the die for several hours to avoid distortion and to ensure that equilibrium conditions are established.
- 20. Wax tend to return partially to their original shape after manipulation.This is known as Elastic memory. To demonstrate this effect , a stick of inlay wax can be softened over a Burden burner,bent into a horseshoe shape and chilled. It is then floated in room temperature water for a number of hours, the horseshoe will open.