1 / 18

Zinc Oxide Eugenol

Zinc Oxide Eugenol. Impression material. Zinc Oxide Eugenol. This material is used for recording edentulous ridges in a close fitting special tray or the patients existing dentures. The material is mixed in a 1:1 paste ratio and used in thin sections only (2-3mm) as a wash impression.

zahina
Télécharger la présentation

Zinc Oxide Eugenol

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Zinc Oxide Eugenol Impression material

  2. Zinc Oxide Eugenol • This material is used for recording edentulous ridges in a close fitting special tray or the patients existing dentures. The material is mixed in a 1:1 paste ratio and used in thin sections only (2-3mm) as a wash impression. • Vaseline is used as a separating agent on those areas requiring protection (soft tissues ,skin etc). Firm pressure is used during impression taking.

  3. Composition • Constituents of a typical zinc oxide eugenol paste are: • BASE PASTE • Zinc oxide • Inert oils (plasticiser) • Gum rosin (increases setting time and improves cohesion) • REACTOR PASTE • Eugenol • Zinc acetate/Mg Cl (accelerator) • Fillers (talc or kaolin) • Some pastes contain a substitute for eugenol e.g. a carboxylic acid./chlorothymolNON EUGENOL TYPEThe 2 pastes come in contrasting colours and are dispensed in a 1:1 ratio. They are mixed to give a paste of even colour.

  4. Setting reaction • Acid – base reaction. • Chelation reaction • Zinc oxide + water  zinc hydroxide • Zinc hydroxide + 2 eugenolBase Acid zinc eugenolate (chelate) (salt)

  5. Chelation: • Is the attachment of a molecule or ion to metal atom at more than one point. • The term is derived from the Greek word meaning “crab’s claw” indicating two pronged attachment. • A central zinc atom is held by two eugenol “claws”.

  6. Setting time • The set material contains both some unreacted zinc oxide and eugenol. • Any movement of the tray as the paste is hardening will lead to a deformed, inaccurate impression. • Setting time • Types: S.T • Type I: hard 10 minutes • Type II: soft 15 minutes • Accelerators: water, magnesium chloride, zinc acetate or alcohol. • Retarders: inert oils such as olive oils, mineral oil.

  7. Factors affecting the setting time • Setting time depends on: • 1. Accelerator additives (e.g. zinc acetate, acetic acid) • 2.Retarders (inert oils such as olive oils, mineral oil. 3. Exposure to moisture on mixing or the addition of water will accelerate the reaction4. Increasing temperature causes a faster setting reaction 5. Cooling the glass slab and mixing spatula will increase ST • Setting time is normally 4-5minutes.

  8. Manipulation.

  9. properties • Non toxic • Adherence to tissues • Good surface detail in thin section • Good dimensional stability (little or no dimensional change on setting, 0.1% dimensional change during setting) • Can be added to with fresh zinc oxide eugenol • Stable on storage and good shelf life

  10. Advantages & Disadvantages ADVANTAGES DISADVANTAGES • 1. Dimensional stability • 2. Good surface detail • 3. Can be added to • 1. Cannot be used in very deep undercuts • 2. Only sets quickly in thin section 3. Eugenol allergy in some patients

  11. Plaster of Paris (Non Elastic) • Uses: • Secondary impression or final wash in a special tray. • Composition of powder: • Calcium sulphate hemihydrate. • Potassium sulphate or nitrate: • Accelerator • Flavouring agent. • Colouring agents.

  12. Manipulation: • Water / powder ratio. • 55 to 60ml water to 100gm of powder. • Separating medium alcoholic solution of varnish. Or soap suspensions. • Properties. • Storage problems: kept in sealed containers.

  13. Reaction: Chemical reaction: crystalization CaSO4 ½ H2O + H2O  CaSO4.2H2O + heat Dimensional changes: Setting expansion can be reduced to + 0.06% by presence of K2SO4. Soluble impression plaster: Contains starch to facilitate the separation of impression from model by softening when immersed in hot H2O.

More Related