A major problem was that the impression shape was distorted upon removal.ġ871 – Taking Impressions of the Mouth (republished in 1894) Hot water was required to soften the wax for insertion. This became a common thermoplastic molding material to use for making impressions. He also added talc as an inert filler to strengthen and “add to the texture” of the material, and a red coloration 9,10. It was introduced by Edwin Truman as a material for making dental impressions, but it was not very satisfactory for the intended purpose because it had a tendency to distort upon removal from the patient’s mouth, and to shrink upon cooling.Ĭharles Stent, an English dentist, developed an impression (modeling) compound as an attempt to improve gutta-percha by adding stearin, a substance made from animal fat, to improve plasticity and stability. This is a natural latex obtained from tropical trees native to Southeast Asia and northern Australia. He says that this will give “an exact impression.” A Bunsen burner or a spirit stove was used to soften the wax for insertion (Figure 5). In A System of Dental Surgery by Samuel Sheldon Fitch, he writes that one should take a piece of wax, usually beeswax, and to soften it in warm water on in a flame, after which it is pressed on the teeth and gums 8. A Bunsen burner named after Robert Bunsen, is a common piece of laboratory equipment that produces a single open gas flame, used for heating, sterilization, and combustion. Although plaster was an accurate impression material, it had the distinct disadvantage of being inflexible, typically fracturing during removal.įigure 5. It seems certain that plaster of Paris was first used to pour up dental impressions before it was used as an impression material. One source traces it roots to the very early 1800s 6, but the use of Plaster of Paris was well-established for taking dental impressions by 1844, and was the most commonly-used impression material in 1904 7. Isaac John Greenwood and bother Clarke (sons of Isaac Greenwood) are reported to first use plaster of Paris (so named because one of the most extensive deposits was found in the “Paris Basin,” near Paris, France) in 1820 5 for dental work, but its first use as impression material is uncertain. Wax is a poor impression material by today’s standards, but it seemed to have functioned adequately in its day. Isaac Greenwood’s ad in the New York Daily Advertiser – “persons at any distance may be supplied with artificial teeth by sending an impression, taken in wax, of the places where wanted…” 5 The use of impressions, specifically related to teeth, has been credited to another German, Philipp Pfaff (1713-1766), a dentist to Frederick the Great of Prussia (mid-to-late 1700s) 5. History shows that the taking of ear impressions, and the materials used, followed that of the dental profession where impressions were made to provide models and prostheses of the teeth, but, records are sketchy.ġ684 – Wax of unknown type, but most probably, beeswax.Ī first description of using wax impressions for modeling prosthetic appliances was reported to have been made by Matthaus Purmann (1648-1711), a German surgeon 5.ġ700s (mid-to-late) – sealing wax, softened in water The Contribution of Dentistry to Hearing Rehabilitation And besides, the intent in this post is to determine the origin and history of ear impression materials and procedures, a necessary component of any custom earmold.Īs stated, this post is more interested in the history of impression materials used for taking ear impressions, and any related procedure used for its insertion, and not on the specifics of the procedure (preparation, placement of otoblock, etc.). patents provide no confirmation that other custom earmolds had not already been made. We are left to assume that they were made using plaster of Paris or hydrocolloid, common materials for ear impressions used at the time. Lieber’s contribution related to a patent intended to improve earpieces for hearing aids using a flexible material (such as soft rubber) that may yield somewhat and thereby adapt itself to the individual ear, and to reduce the number required to three (Figure 4).Īs like Halsey, Lieber does not reference any ear impression material or procedure. Lieber reported that “stock” earpieces consisted generally of anywhere from three-to-six different sizes (right and left ears), formed of hard rubber or Bakelite – fixed, unyielding forms. “Stock” earpieces were made for hearing aids at least by 1931 4. Hugo Lieber patent of “stock” hearing aid earmolds, made of flexible material (such as soft rubber) that may yield somewhat and thereby adapt to the individual ear, and to reduce the number required to three
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