Dental Impression Materials

Excerpt

Impression materials are used to copy the teeth and surrounding oral structures by creating a dental impression poured with dental plaster to fabricate a dental cast. This procedure provides a tridimensional and accurate mouth replica, allowing dental work even in the absence of the patient.

Dental models enable dentists to perform a better diagnosis and treatment planning since the teeth can be meticulously visualized and studied from angles that are difficult to see in the patient's mouth. Particular treatment, such as removable and fixed prostheses, can be executed thanks to dental casts. The final restoration or prosthesis fit depends on how accurately the impression material has recorded the tissue details.

History of Impression Materials

Wax was the only impression material used in dentistry until the mid-19th century when gutta-percha first appeared. Then in 1857, Charles Stent created a thermoplastic modeling compound similar to today's impression compound. Still, the problem with this material was that it was rigid and could not reproduce undercut areas. All the impression materials used until that date became rigid after setting and could not copy the oral tissues accurately. Thus, there was always a need for an impression material that could remain elastic even after setting. That is when agar, a reversible hydrocolloid manufactured from algae, was introduced in dentistry. Although this jelly-like material was elastic, it required a complicated procedure to be used as an impression material.

When the algae used to manufacture agar was unavailable during the second world war, Americans used local algae to manufacture another elastic impression material known as alginate, which has gained popularity since then.

Alginate and agar have disadvantages, like dimensional instability and low tear strength, which led to the manufacture of elastomeric (also known as rubber-based) impression materials. First came polysulfide, then condensation silicone followed by polyether, and then addition silicones.

With the advancement in technology, digital dentistry is also making its way into the field. However, there is always a scope for new impression materials, as no impression material is 100% accurate until the date.