Making an Impression with Irreversible Hydrocolloid
Making an Impression with
Irreversible Hydrocolloid
Sharon Sparks Miss O’Keefe LB101 January 19, 2010
Irreversible Hydrocolloid impression material also called “alginate impression material” is a powder that is mixed with water to obtain a paste in order to make an exact copy of the mouth. This creates a negative dental impression of the mouth into which a gypsum/plaster is poured. These impressions are taken in order to construct preliminary impressions for complete dentures, partial dentures with clasps and orthodontic models and study models. It is not used for crown and bridge impressions because of the lack of accuracy.
The advantages of using alginate are that it is economical, easy to use, quick setting, has a fair taste, hydrophilic (having a strong affinity for water, hydrophilic colloids swell in water and are relatively stable), can displace blood and saliva and you can use stock trays. Some disadvantages are that they have limited detail reproduction, low tear resistance, single pour only, and quick pouring required and low dimensional stability.
Alginate impression material is generally easy to use; the powder is supplied in a can and shaken up before use for aeration. The “Water to Powder” ratio should be carefully followed as specified by the manufacturer per directions on label. What we call “working time” is the time from beginning of the mix until the setting reaction is complete. The “setting time”, is the time from beginning of the mix until the setting reaction is over. There are two mixes that you may encounter in the office. First, is regular set alginate which takes 1 min, 2.5 min, 3.5 min to set
Irreversible Hydrocolloid
Sharon Sparks Miss O’Keefe LB101 January 19, 2010
Irreversible Hydrocolloid impression material also called “alginate impression material” is a powder that is mixed with water to obtain a paste in order to make an exact copy of the mouth. This creates a negative dental impression of the mouth into which a gypsum/plaster is poured. These impressions are taken in order to construct preliminary impressions for complete dentures, partial dentures with clasps and orthodontic models and study models. It is not used for crown and bridge impressions because of the lack of accuracy.
The advantages of using alginate are that it is economical, easy to use, quick setting, has a fair taste, hydrophilic (having a strong affinity for water, hydrophilic colloids swell in water and are relatively stable), can displace blood and saliva and you can use stock trays. Some disadvantages are that they have limited detail reproduction, low tear resistance, single pour only, and quick pouring required and low dimensional stability.
Alginate impression material is generally easy to use; the powder is supplied in a can and shaken up before use for aeration. The “Water to Powder” ratio should be carefully followed as specified by the manufacturer per directions on label. What we call “working time” is the time from beginning of the mix until the setting reaction is complete. The “setting time”, is the time from beginning of the mix until the setting reaction is over. There are two mixes that you may encounter in the office. First, is regular set alginate which takes 1 min, 2.5 min, 3.5 min to set
Cited: 1. http://www.bing.com/images/search?q=dental++tray++pics&form=QBIR&qs=n, http://www.bing.com/images/search?q=dental+impression++pics&form=QBIR&qs=n, http://www.bing.com/images/search?q=alginate+tray+in+mouth+pics&go=&form=QBI R 2. Dental Assisting a Comprehensive Approach 3rd Edition: Donna J. Phinney, Judy H. Halstead 3. http://www.dent.ohio-state.edu/courses/d430/Impressions%20and%20Casts/alginate %20lecture%20.PDF 4. http://www.merriam-webster.com/medical/Hydrophilic 5. http://dentalcorp.com/dental/index.php/category/dental-impression-products/ 6. http://www.bothelldentallab.com/making.htm 7. http://www.dailyitem.com/0113_health_fitness/local_story_274001610.html