DENTAL ALGINATE – A clinical overview

Alginate Mixing Technique

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• Literally impression means the negative replica of the oral structures, so it must be accurate enough to simulate the surface and  surrounding structures with precision.

• IMPRESSION IS ALWAYS MADE BY A DENTIST/DENTAL ASSISTANT 

• Alginate is an elastic, irreversible hydrocolloid impression material

• They form a major bulk of our clinical practice ; therefore, it becomes mandatory to understand the material and follow certain fundamental guidelines for flawless, predictable impression.

• The most popular form of alginate is supplied as a powder, which is mixed with water. Many alginates are supplied with a reaction indicator that changes color of the impression when the material is set;.Paste type of alginate is also available. The best surface quality can be obtained with the paste-type material.

• Colder water can be used if longer working time is desired. Setting time should be controlled by varying water temperature, and not the consistency of mix. Mixing should be rapid with a wide-bladed spatula. The resultant mix should be creamy in consistency but must not drip off the spatula when lifted from the bowl

• Once set, the impression has to be removed with a firm, quick snap. During removal of the maxillary impression, the operator's index fingers (of both the hands) should be in the buccal sulci to break the seal while thumb holds the tray handle and the other fingers support the impression tray.

• A thin layer of dental stone powder can be sprinkled onto the surface of the impression. The stone adheres to saliva and acts as a disclosing agent. When impression is placed under running tap water, the saliva will be seen and can be removed by light brushing with wet camel's hair brush.

• Set alginate undergoes imbibition and syneresis if left in a normal clinical environment. The time before cast-pouring is critical. After being removed from the mouth, alginate impressions should be washed with a water spray, disinfected by means of the practitioner's choice of disinfection procedures, and dried until the shine just disappears. The impression has to be covered with damp gauze and left in a zip-lock plastic bag until the cast is poured. Cast-pouring must be delayed for 10 minutes, as the elastic recovery of alginate impression material is slow.

• The stone should be allowed to set in trays with the teeth down. If tray is turned upside down onto base of stone, there would be a tendency for water to rise to the highest point (cusp tips). This can result in faulty, very soft cusps on the model. Cast has to be removed immediately after adequate set; otherwise, the model would have “moth-eaten” appearance.

• Alginates should always be kept in an airtight container.

• The surface of d tissue should be free from any extra saliva or debris,

• While making the maxillary impression for d prepared tooth crown,,,,no need to load extra material in palatal area,as we need only d crown part impression,,,,,

• Its adviced to apply some mixed alginate nicely in the desired area before inserting the tray with the material.

Written by Dr. P. Kunal


Dr. Kunal did his BDS from Maruti Dental College, Bangalore. Currently he is pursuing private practice in New Delhi. He is a workaholic and loves dentistry!