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DENT MAT 10 22
| Question | Answer |
|---|---|
| Elastic Impression Materials | (Hydrocolloid Impressions) |
| TWO General Types of ELASTIC Impression Materials: | 1. Hydrocolloids 2. Rubber Impressions or Elastomers |
| are classified as a fourth state of matter,__because of their difference in structure, constitution and reaction. | Colloids, the colloidal state, |
| exist in one phase, when we mix solute and solvent. | True solutions |
| Colloids and suspension have TWO phases: | A. Dispersed Phase B. Dispersion Medium |
| The size of colloidal particles ranges from | 1 to 200nm |
| Types of Colloids (5) | 1. Aerosols – liquids or solids in air 2. Lysols – gases, liquids or solids in liquids 3. Foams – gases in solid 4. Solid Emulsion – liquids in solid 5. Solid Suspension – solids in solid |
| liquids or solids in air | AEROSOLS |
| gases, liquids or solids in liquids | LYSOLS |
| gases in solid | FOAMS |
| liquids in solid | SOLID EMULSION |
| solids in solid | SOLID SUSPENSION |
| The colloidal materials used for making impressions are either, _they are known therefore as_ | AGAR or ALGIN dissolved in water, HYDROCOLLOIDS. |
| HYDROCOLLOIDS (2) | a. IREVERSIBLE hydrocolloids or Alginate b. REVERSIBLE hydrocolloids or Agar |
| Alginate Impression Material | ( Irreversible Hydrocolloid) |
| ADVANTAGES ( Irreversible Hydrocolloid) (7) | 1. easy to mix and manipulate, has good viscosity and is low in adhesive qualities. 2. Requires little armamentarium 3. it allows for undercuts 4. the process is not time consuming |
| ADVANTAGES ( Irreversible Hydrocolloid) (7) SUMPAY | 5. it makes an accurate impression 6. cheap and it causes no great pain to the patient 7. inexpensive to the dentist |
| DISADVANTAGES ( Irreversible Hydrocolloid) (2) | 1. cannot be used in making metal dies 2. less production of surface details to gypsum dies as agar and elastomers |
| PRODUCT OF CHEMICAL REACTION (3) | 1. calcium alginate 2. sodium sulfate 3. water |
| PROPERTIES: ( Irreversible Hydrocolloid) (7) | 1. Mix should be smooth and creamy 2. permanent deformation 3. flexibility 4. strength 5. dimensional change 6. reproduction of detail 7. disinfection |
| OBJECTIVES FOR TAKING IMPRESSIONS (5) | 1. all teeth in the upper and lower arch 2. the entire alveolar process 3. the retromolar pad of the lower arch 4. the area of the hamular notch in the upper arch 5. a detailed, undistorted, and bubble-free reproduction of the tissues |
| STEPS IN TAKING AN ALGINATE IMPRESSION (5) | 1. Selection of impression tray 2. Proportioning of alginate and water 3. Mixing the alginate 4. Loading the tray 5. Taking the impression |
| HANDLING OF THE IMPRESSION: (7) | 1. Rinse the impression with cold water. 2. Cut away any unsupported alginate 3. Disinfect alginate impression 4. Rinse disinfected impression with cold water |
| HANDLING OF THE IMPRESSION: (7) SUMPAY | 5. Remove excess water 6. Pour gypsum model 7. If stored, the impression should be places so that the alginate is supported by the tray. |
| the FIRST successful elastic impression | Agar (Reversible Hydrocolloid) |
| Accuracy (2) | 1. Syneresis - formation of exudate on surface of the gel. 2. Imbibition – absorption of water in impression |
| a phenomenal physical property of a material having different liquefaction temperature and solidification temperature. | HYSTERESIS |
| are a supplement to the oral examination | DIAGNOSTIC CASTS |
| THREE steps of obtaining a diagnostic cast: | 1. an alginate impression is made directly in the patient’s mouth producing a NEGATIVE mold. 2. The impression is poured in dental stone, producing a POSITIVE cast. 3. The cast is inspected for defects, repaired if possible, and trimmed to the proper si |
| is an impression material that is supplied in POWDER FORM and mixed with WATER. is classified as IRREVERSIBLE HYDROCOLLOID is sensitive to higher temperature and moisture contamination. | ALGINATE |
| because it consists of particles of a gelatinous (colloidal) state in water (hydro) and irreversible because once it has jelled, it cannot be returned to a liquid solution. | HYDROCOLLOID |
| The alginate particles are comprised of: (4) | 1. Salt of alginic acid, a product of marine kelp. 2. An activator, usually CALCIUM SULFATE. 3. An inert filler to reduce stickiness, produce a smooth texture and add strength. 4. FLAVORING |
| is reversible hydrocolloid because it can pass repeatedly between highly viscous gel and low viscosity sol simply through heating and cooling. | AGAR |
| once converted to the gel form cannot be converted back into the sol. | ALGINATE |
| Calcium sulfate in the alginates is a : | REACTOR |
| The size of colloidal particles ranges from: | 1 to 200nm |
| It is an accurate replication of the anatomic form of the maxillary or mandibular dental arch showing the relationships of the remaining teeth and the surrounding tissues. | DIAGNOSTIC CAST |
| The fact that the temperature of gelation of reversible hydrocolloid is lower than the temperature of liquefaction is known as: | HYSTERESIS |
| Mostly widely used to take preliminary impressions: | ALGINATE |
| TECHNIQUES OF TAKING IMPRESSION USING AGAR: (2) | Wet Field Technique Laminate technique |
| combination of alginate and agar. The syringe type of agar will be injected to the dental arch and the alginate is used as the tray material loaded to the stock tray. | Laminate technique |
Created by:
docbritzh