What are some of the types and common causes of failures encountered with the alginate impression materials?

What are the advantages and disadvantages of alginate impression material?

Alginate

It is inexpensive and can produce impressions with reasonable surface detail. Disadvantages: poor dimensional stability, poor tear strength, distortion if unsupported, requires good mixing otherwise air bubbles, minimum 3mm thickness required.

What is a disadvantage of alginate?

Their disadvantages include less accurate reproduction of details as compared with elastomeric impression materials, poor dimensional stability, and that they are messy to work with.

What are types of alginate impression material?

The two forms of alginate available are powder, the most common form, and paste. This latter is available in two styles separated by viscosity. Tray viscosity is the thicker of the two and intended for use in standard impression trays. The syringe is the other viscosity available.

What causes drags in impressions?

Drag marks can be caused by several factors. One source of these types of errors is movement of the impression material in the mouth before the set is complete. If there is a drag mark behind the back molar, make sure the tray is completely off your patient's teeth before pulling it out of their mouth.

Prosthodontics | Impression Materials | INBDE, NBDE Part II

What are the common errors in impression taking?

Internal Bubbles. Marginal Tears. Choosing the Wrong Impression Material. Rushing the Impression.

What are the most common impression errors?

What are 3 classifications of impressions used in dentistry?

There are three main types of dental impressions — preliminary, final, and bite registration.

What are the properties of alginate impression material?

Properties: Taste & odor: ·Pleasant. Flexibility:·lower w/p ratio results in lower flexibility. Elasticity & elastic recovery: highly elastic, permanent deformation less if the impression is removed from the mouth quickly.

How can distortion of alginate impression be avoided or minimized?

On the lower arch, make sure that that the border of the tongue is not trapped by the impression tray by having the patient to pull the tip outside the mouth. As soon as the tray is in position, muscle trim and keep it there without pressure and movement during the setting time of the alginate to avoid distortion.

What are the types of impression materials?

By their composition, the impression materials are divided into three major groups: nonaqueous elastomers, hydrocolloids, and inelastic materials. Elastomers include polysulfide, condensation and addition silicone, and polyether. Hydrocolloids are alginate and agar.

How long can alginate impressions last?

Numerous studies have evaluated the dimensional accuracy of conventional alginates [2,7–15]. Some studies show that it is possible to store a hydrocolloid impression for up to 1, 2 and even 4 hours [8–10].

What are the different types of impression materials?

Four types of elastomeric impression materials are available in the market: addition silicone, also known as polyvinyl siloxanes (PVS), condensation silicone, polyether, and polysulfide. Elastomers can present in different consistencies, including putty, heavy body, medium body, and light body.

Why is alginate impression material one of the most common forms used in dentistry?

Alginate impression materials are easy to use, less expensive and have more rapid setting times. The reaction time and therefore the setting time can be controlled with the temperature of the water used.

Why is it important to understand the different types of impression materials?

Understanding the chemistry of each type makes it easier to match the material to the case in the chair and make a good impression that leads to excellent patient outcomes.

What precaution should be observed while softening the impression compound?

softening of the material , the outside will soften first & inside last. So to ensure uniform softening the material should be kept immersed for a long time in water bath. The layer adjacent to the mouth tissue swill remain soft. Therefore Its imp to cool the compound thoroughly before removing the impression.

What happens when an alginate impression is stored in water?

If an alginate impression is stored in water or in a very wet paper towel, the alginate will absorb additional water and expand. This condition is called imbibition. If an alginate impression remains in the open air, moisture will evaporate from the material, causing it to shrink and distort.

Which factor should be examined when evaluating the quality of an impression?

Which factor should be examined when evaluating the quality of an alginate impression? The presence of the retromolar area and maxillary tuberosity are recorded. Anatomical detail is sharp and not distorted. Surfaces are free from voids.

What are the three types of impression evidence?

What are the 3 classifications of impressions?

Of the 3 classifications of impressions, which can the EFDA legally take? The 3 classifications consist of preliminary, final and occlusal or (bite) registration. The EFDA can legally take preliminary & bite registration.

Which dental impression material is most affected by moisture?

Conclusions: Although moisture may not adversely affect the dimensional accuracy of either PE or hydrophilic PVS material, the evidence suggests that PE material is more likely to produce impressions with superior detail reproduction in the presence of moisture.

What causes bubbles in alginate?

Causes: 1. Bubbles occur while the impression material is being distributed, due to the mixing tip being lifted out of the material mid process, creating a hollow void under the material now placed on top. 2.

How do you prevent bubbles in alginate impressions?

We recommend the following steps to take an accurate impression: Smear the impression material (ex: alginate) onto the occlusal surfaces of the teeth and into undercuts by finger pressure before the impression tray is placed. This prevents the occurrence of trapping bubbles in the impression.

What is a distorted impression?

2 to alter or misrepresent (facts, motives, etc.) 3 (Electronics) to reproduce or amplify (a signal) inaccurately, changing the shape of the waveform. (C16: from Latin distortus misshapen, from distorquere to turn different ways, from dis-1 + torquere to twist) ♦ distorted adj.