Vulcanite
Background
One of the most significant advancements for dental prosthesis in the 19th century was the development of vulcanite as a base for dentures. The history of vulcanite or “rubber” dentures begins with the discovery of “india rubber” or caoutchouc in 1735. (11) For many years it was only used to erase pencil marks on paper. In the 1820s however, it was discovered that caoutchouc became hard and brittle in cold weather and sticky in hot weather. Many experiments were carried out in light of these properties. (12) These experiments eventually culminated in the discovery of vulcanite by Charles Goodyear in 1843 when he applied heat to a compound of caoutchouc and sulfur. (12) The combination of sulfur and caoutchouc preserved the elasticity of the latter in extreme temperatures, such as the heat of a furnace. In the years following, vulcanite was used to make everyday items such as buttons and combs because of this very elasticity, making it a desirable and cheap material to work with. (11)
Eventually, dentists experimented with vulcanite as well. Vulcanite dentures came to the notice of the profession by 1853 (9) and enjoyed widespread usage by 1863. (11) Importantly, the “vulcanite” in vulcanite dentures does not refer to the mineral vulcanite but rather hardened rubber obtained through a process called “vulcanizing”. Vulcanizing involves combining caoutchouc with a vulcanizing agent (sulfur) and then heating this compound to create a hardened rubber material. (5) This “vulcanite” was also referred to as “ebonite”. (13)
Advantages
Some advantages of vulcanite as a dentures base were that it is was easy to manipulate and repair. They were also inexpensive in terms of their material and labour cost, meaning that they were accessible to patients who could not afford metal-base dentures. In addition, vulcanite bases were unsusceptible to fluids of the mouth and materials that were expected to interact with dentures (ie. food). (11) Thus, vulcanite became a popular base for dentures because of their durability, affordability, strength, elasticity, and lightness. (12) (11)
Disadvantages
Despite these virtues, vulcanite dentures had a few disadvantages as well. For one, vulcanite was a poor thermal conductor, meaning it prevented heat from reaching the mouth properly which lead to weakened mouth tissues over time. (12) Additionally, patients’ dentures needed to be re-vulcanized at some point. However, vulcanite-base dentures shrink in the vulcanization process, which then interfered with the patient-dentures adaptation process. (12) Lastly, vulcanite dentures lacked the natural colors of the gums. (10) (12)
