Alginate impressions are among the most commonly used ones in dentistry. Alginate is a special material that belongs to the group of irreversible hydrocolloids. It is a regular part of many dental procedures. With the impression, the dentist gets a negative copy from the oral cavity of the patient. They use that, to get a mold which will replicate the exact situation in the mouth. From there on, they use them to plan further treatment or start a certain restoration. The most common uses of the alginate impression are to get a study model, getting an impression from opposing teeth, for bleach trays, preliminary impressions for partial and total dentures, orthodontic models, preliminary impressions for crowns, bridges and more. Also, a lot of dentists tend to use them with patients that have an excessive saliva flow and alveolar bones with undercuts. The procedure is very simple and lasts for a short time. It is not painful, and the patient doesn’t feel discomfort.
Dentists usually use alginate materials to take preliminary impressions for dentures. Another widespread use is for patients that produce a lot of saliva. Dental arches with undercuts are also a strong indication of an alginate impression. Partial dentures with clasps are also often based on an alginate impression. Other uses include a mold for inspection, diagnosis and planning, mold from opposing teeth, duplicate molds and more.
The alginate material is actually a powder, that is mixed with water. After the mixing, dentists get a paste that is placed in a tray for impressions. The powder contains sodium and potassium salts of alginic acids. Once mixed with water, the chemical reaction starts and during the mixing, dentists have to be very careful to provide a constant movement with the hands to avoid trapped air bubbles in the material.
One of the biggest advantages is that alginate materials are inexpensive and everyone can afford them. Another great thing is the good detailed impression they provide. They don’t have the power to apply a lot of pressure to the tissues, so there is a minimal possibility for the material to dislocate the tissues. Alginates have a pleasant smell and can be delivered in a number of flavors, mostly derived from fruits such as strawberry and more. They can be used even in the presence of saliva. Patients ding them very comfortable. The alginate impressions are very easy and simple to take.
The main disadvantage is that alginate has a very poor dimensional stability. That is mainly due to the ingredient list. There is a slight evaporation that leads to shrinkage of the material. Dentists and dental technicians should pour the mold as soon as possible. Since the material has a low strength it is susceptible to tear. Alginate impressions have to be done with at least 3mm of material in every area. It is not recommended for cases where the dentist needs a high accuracy. They have a low adhesion power, so if the tray is not perforated, the dentist has to use additional measures to provide adhesion.