Dentures

Dentures (also known as false teeth) are prosthetic devices constructed to replace missing teeth, and which are supported by surrounding soft and hard tissues of the oral cavity. Conventional dentures are removable; however there are many different denture designs, some which rely on bonding or clasping onto teeth or dental implants. There are two main categories of dentures, depending on whether they are used to replace missing teeth on the mandibular arch or the maxillary arch.

Causes of tooth loss

Patients can become entirely edentulous (without teeth) due to many reasons, the most prevalent being removal because of dental disease typically relating to oral flora control, i.e. periodontal disease and tooth decay. Other reasons include tooth developmental defects caused by severe malnutrition, genetic defects such as Dentinogenesis imperfecta, trauma, or drug use.

Types of dentures

Removable partial dentures

Removable partial dentures are for patients who are missing some of their teeth on a particular arch. Fixed partial dentures, also known as "crown and bridge", are made from crowns that are fitted on the remaining teeth to act as abutments and pontics made from materials to resemble the missing teeth. Fixed bridges are more expensive than removable appliances but are more stable.

Complete dentures

Conversely, complete dentures or full dentures are worn by patients who are missing all of the teeth in a single arch (i.e. the maxillary (upper) or mandibular (lower) arch).

History

Around 700BC, Etruscans in northern Italy made dentures out of human or other animal teeth. These deteriorated quickly but, being easy to produce, were popular until the mid 19th century.

The oldest useful complete denture appeared in Japan, and has been traced to the ganjyoji temple in Kii Province, Japan. It was a wooden denture made of Buxus microphylla, and used by Nakaoka Tei (–20 April 1538). This wooden denture had almost the same shape as modern dentures retained by suction. It also shaped to cover each condition of teeth loss. Wooden dentures were used in Japan up until the Meiji period.

London's Peter de la Roche is believed to be one of the first 'Operators for the Teeth', men who fashioned themselves as specialists in dental work. Often these men were professional goldsmiths, ivory turners or students of barber-surgeons.

The first porcelain dentures were made around 1770 by Alexis Duchâteau. In 1791 the first British patent was granted to Nicholas Dubois De Chemant, previous assistant to Duchateau, for "De Chemant's Specification", "a composition for the purpose of making of artificial teeth either single double or in rows or in complete sets and also springs for fastening or affixing the same in a more easy and effectual manner than any hitherto discovered which said teeth may be made of any shade or colour, which they will retain for any length of time and will consequently more perfectly resemble the natural teeth." He began selling his wares in 1792 with most of his porcelain paste supplied by Wedgwood.

In London in 1820, Claudius Ash, a goldsmith by trade, began manufacturing high-quality porcelain dentures mounted on 18-carat gold plates. Later dentures were made of Vulcanite from the 1850s on, a form of hardened rubber (Claudius Ash’s company was the leading European manufacturer of dental Vulcanite) into which porcelain teeth were set, and then, in the 20th century, acrylic resin and other plastics. In Britain in 1968 79% of those aged 65–74 had no natural teeth, by 1998 this proportion had fallen to 36%.

Fabrication of complete dentures

Modern dentures are most often fabricated in a commercial Dental Laboratory using a combination of a tissue shaded powder polymethylmethacrylate acrylic for the tissue shaded aspect, and commercially produced acrylic teeth available in hundreds of shapes and tooth colors.

The process of fabricating a denture usually begins with a dental impression of the maxilla or mandible. This impression is used to create a stone model that represents the arch. A wax rim is fabricated to assist the dentist or denturist with establishing the vertical dimension of occlusion. After this a bite registration is created to marry the position of one arch to the other.

Once the relative position of each arch to the other is known, the wax rim can be used as a base to place the selected denture teeth in correct position. This arrangement of teeth is tried in to the mouth so that adjustments can be made to the Occlusion. After the occlusion has been verified by the doctor with the patient, and all phonetic requirements are met, the denture is processed.

Processing a denture is usually performed in a lost-wax process whereby the form of the final denture, including the acrylic denture teeth, is invested in stone. This investment is then heated, and the wax is removed through a sprue when it melts. The remaining cavity is then either filled by forced injection or pouring of the uncured denture acrylic. After a curing period, the stone investement is removed, the acrylic is polished, and the denture is complete.