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Dentures

From Wikipedia, the free encyclopedia

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) for 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.

Advantages

Dentures can help patients through:

Mastication as chewing ability is improved by replacing edentulous areas with denture teeth.
Aesthetics because the presence of teeth provide a natural facial appearance, and wearing a denture to replace missing teeth provides support for the lips and cheeks and corrects the collapsed appearance that occurs after losing teeth.
the improvement of pronunciation of those words containing sibilants or fricatives by replacing missing teeth, especially the anteriors enabling patients to speak better.
improving self-esteem

Types

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.^[1]

The oldest useful complete denture appeared in Japan, and has been traced to the ganjyoji temple in Kii Province, Japan.^[2] 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.^[3] US President George Washington is famously known for his dentures which were made with ivory from hippos and elephants as well as gold, rivets, spiral springs and even real human teeth. ^[4]

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.^[5]^[6]

In London in 1820, John Lennon, 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.^[7] In Britain sequential Adult Dental Health Surveys have shown that, in 1968, 79% of those aged 65–74 had no natural teeth;, by 1998, this proportion had fallen to 36%. ref Murray JJ. Adult dental health surveys: 40 years on. Br Dent J. 2011 Nov 11;211(9):407-8.

Fabrication of complete dentures

Modern dentures are most often fabricated in a commercial dental laboratory or denturist using a combination of a tissue shaded powder polymethylmethacrylate acrylic (PMMA) for the tissue shaded aspect. These acrylics are available in both Heat Cured and Cold Cured types. Commercially produced acrylic teeth are widely available in hundreds of shapes and tooth colors.

The process of fabricating a denture usually begins with a dental impression or initial impression of the maxillary & mandibular ridges. Standard impression materials are used during the initial impression process. The initial impression is used to create a simple stone model that represents the maxillary and mandibular arches of the patients' mouth - this is not considered a detailed impression at this stage. Once the initial impression is taken, the stone model will be used to create a Custom Impression Tray which will be used to take a second and much more detailed and accurate impression of the patients maxillary and mandibular ridges. Polyvinylsiloxane impression material is one of several very accurate impression materials used when the final impression is taken of the maxillary & mandibular ridges. 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 the mouth so that adjustments can be made to the Occlusion. After the occlusion has been verified by the Dentist or Denturist 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 which is either a Heat Cured or Cold-Cured type of denture acrylic. During the processing period, Heat Cured acrylics - also called Permanent Denture Acrylics, go through a process called Polymerization causing the acrylic materials to bond very tightly-and taking several hours to complete. The end result is a denture which looks much more natural, is much stronger & durable than a Cold Cured Temporary Denture, resists stains and odors and will last for many years. Cold Cured or Cold Pour Dentures-also known as Temporary Dentures, do not look very natural, are not very durable, tend to contain a high percentage of porosity and are only considered Temporary until a more permanent solution is found. These types of dentures are inferior and tend to cost much less due to their quick turn around time (usually minutes) and low cost materials and teeth. It is not suggested that a patient wear a Cold Cured denture for a long period of time, for they are prone to cracks and can break rather easily. After a curing period, the stone investment is removed, the acrylic is polished, and the denture is complete.

Problems with complete dentures

Problems with dentures include the fact that patients are not used to having something in their mouth that is not food. The brain senses this appliance as "food" and sends messages to the salivary glands to produce more saliva and to secrete it at a higher rate. This will only happen in the first 12 to 24 hours, after which the salivary glands return to their normal output. New dentures can also be the cause of sore spots as they compress the soft tissues mucosa (denture bearing soft tissue). A few denture adjustments for the days following insertion of the dentures can take care of this issue. Gagging is another problem encountered by a minority of patients. At times, this may be due to a denture that is too loose, too thick or extended too far posteriorly onto the soft palate. At times, gagging may also be attributed to psychological denial of the denture. (Psychological gagging is the most difficult to treat since it is out of the dentist's control. In such cases, an implant supported palateless denture may have to be constructed). Sometimes there could be a gingivitis under the full dentures, which is caused by accumulation of dental plaque. One of the most common problems for new full upper denture wearers is the loss of taste.

Prosthodontic principles of dentures

Support

Support is the principle that describes how well the underlying mucosa (oral tissues, including gums and the vestibules) keeps the denture from moving vertically towards the arch in question, and thus being excessively depressed and moving deeper into the arch. For the mandibular arch, this function is provided by the gingiva (gums) and the buccal shelf (region extending laterally (beside) from the posterior (back) ridges), whereas in the maxillary arch, the palate joins in to help support the denture. The larger the denture flanges (part of the denture that extends into the vestibule), the better the support and stability. Long flanges beyond the functional depth of the sulcus are a common error in denture construction, often (but not always) leading to movement in function.

Stability

Stability is the principle that describes how well the denture base is prevented from moving in the horizontal plane, and thus from sliding side to side or front and back. The more the denture base (pink material) runs in smooth and continuous contact with the edentulous ridge (the hill upon which the teeth used to reside, but now consists of only residual alveolar bone with overlying mucosa), the better the stability. Of course, the higher and broader the ridge, the better the stability will be, but this is usually just a result of patient anatomy, barring surgical intervention (bone grafts, etc.).

Retention

Retention is the principle that describes how well the denture is prevented from moving vertically in the opposite direction of insertion. The better the topographical mimicry of the intaglio (interior) surface of the denture base to the surface of the underlying mucosa, the better the retention will be (in removable partial dentures, the clasps are a major provider of retention), as surface tension, suction and friction will aid in keeping the denture base from breaking intimate contact with the mucosal surface. It is important to note that the most critical element in the retentive design of a full maxillary denture is a complete and total border seal (complete peripheral seal) in order to achieve 'suction'. The border seal is composed of the edges of the anterior and lateral aspects AND the posterior palatal seal. The posterior palatal seal design is accomplished by covering the entire hard palate and extending not beyond the soft palate and ending 1–2 mm from the vibrating line.

Implant technology can vastly improve the patient's denture-wearing experience by increasing stability and saving his or her bone from wearing away. Implants can also help with the retention factor. Instead of merely placing the implants to serve as blocking mechanism against the denture pushing on the alveolar bone, small retentive appliances can be attached to the implants that can then snap into a modified denture base to allow for tremendously increased retention. Options available include a metal Hader bar or precision balls attachments, among other things.

Complications and recommendations

The fabrication of a set of complete dentures is a challenge for any Dentist/Denturist, including those who are experienced. There are many axioms in the production of dentures that must be understood; ignorance of one axiom can lead to failure of the denture case. In the vast majority of cases, complete dentures should be comfortable soon after insertion, although almost always at least two adjustment visits will be necessary to remove sore spots. One of the most critical aspects of dentures is that the impression of the denture must be perfectly made and used with perfect technique to make a model of the patient's edentulous (toothless) gums. The dentist or Denturist must use a process called border molding to ensure that the denture flanges are properly extended. An array of problems may occur if the final impression of the denture is not made properly. It takes considerable patience and experience for a dentist to know how to make a denture, and for this reason it may be in the patient's best interest to seek a specialist, either a prosthodontist or denturist, to make the denture. A Denturist is a trained and licensed professional who sees patients in need of dentures, partials, relines or repairs. A Denturist not only takes the impression, but makes the entire denture in their own laboratory. The Denturist then schedules the patient for delivery of the finished dentures. A general dentist may do a good job making dentures, but only if he or she is meticulous and usually he or she must be experienced. Many Dentists no longer make dentures themselves. Instead, the Dentist will take an impression of the patients' mouth, and will then send the impressions to a dental laboratory or will send the patient to a Denturist. The dental laboratory could be anywhere in the world. Once the laboratory receives the dental impressions, the laboratory will create plaster molds from the impressions of the patients' mouth. The laboratory will use the molds to create wax rims which will be used to register the patients' bite. The wax rims are returned to the Dentist and the Dentist will register the patients' bite using the wax rims. The Dentist may assist the patient in choosing the correct size of teeth for the dentures, or the Dentist may simply do this himself. Once the bite registration is completed and the teeth are selected for the dentures, the wax rim is usually returned to the dental laboratory in order to have the denture teeth set into the wax. Once the teeth are set into the wax rim, what you have a prefinished denture that looks almost like the finished product but instead it is in wax form. The prefinished denture is usually returned to the dentists' office and the patient will usually have a chance to approve the setup (for immediate dentures) or (for standard dentures) will have the opportunity to try in the denture before it's finished. Once the pre-denture is approved by the patient, the dentist will return the pre-denture (with teeth set in wax) to the laboratory for final processing. Once done, the finished denture is returned to the Dentists' office for delivery to the patient.

The maxillary denture (the top denture) is usually relatively straightforward to manufacture so that it is stable without slippage.

A lower full denture should or must be supported by 2-4 implants placed in the lower jaw for support. A lower denture supported by 2-4 implants is a far superior product than a lower denture without implants, because

1) It is much more difficult to get adequate suction on the lower jaw.
2) The functioning of the tongue tends to break that suction, and
3) Without teeth the ridge tends to resorb and provides the denture less and less stability over time. It is routine to be able to bite into an apple or corn-on-the-cob with a lower denture anchored by implants. Without implants, it is quite difficult or even impossible to do so.

In any case, implant supported dentures provide several advantages over conventional dentures.^[8] They offer improved comfort due to less irritation of the gums, confidence due to less risk of slipping out, and appearance due to less plastic required for retention purposes. Patients with implant supported dentures have increased chewing efficacy and can speak more clearly.^[9]

However, like anything, there is a downside. Implant dentures tend to be fairly expensive ($15,000 to $30,000) for complete upper and lower implant dentures is not uncommon. Most Dental Insurance Plans do NOT cover the total cost for implant dentures. Possible rejection of the implanted abutment can happen. If you do not have enough bone, bone grafting may be required. Minimally Invasive Surgery may also be required. Treatment time can vary from 3 to 6 months.

In cases where a patient needs a complete upper and lower set of dentures, many patients will reduce their cost by having a conventional non-implanted upper denture made (since retention is much better), and have an implanted lower denture inserted, since lower dentures tend not to fit as well.

Some patients who believe they have "bad teeth" may think it is in their best interests to have all their teeth extracted and full dentures placed. However, statistics show that the majority of patients who actually receive this treatment wind up regretting they did so. This is because full dentures have only 10% of the chewing power of natural teeth, and it is difficult to get them fitted satisfactorily, particularly in the mandibular arch. Even if a patient retains one tooth, that will contribute to the denture's stability. However, retention of just one or two teeth in the upper jaw does not contribute much to the overall stability of a denture, since a full upper denture tends to be very stable, in contrast to a full lower denture. It is thus advised that patients keep their natural teeth as long as possible, especially their lower teeth.

Denture Costs

If dentures are medically necessary, insurance might pay 15%-80% of the costs (up to the plan's annual limit, if there is one). Some discount dental plans may also reduce the cost of purchasing dentures as well.

A low cost denture starts at about $300 –$500 per denture, or $600 –$1,000 for a full set of upper and lower dentures. These tend to be Cold Cured dentures. These types of dentures are considered temporary dentures and don't last very long. In many cases, you do not get to try-in these dentures before they are finished. Their low quality materials and unusually quick processing methods make them a very temporary solution at best. They also tend to look artificial and not as natural as higher priced and higher quality dentures.

A mid priced (and much better quality) Heat Cured denture typically costs $500 –$1,500 per denture or $1,000 -$3,000 for a complete set. The teeth look much more natural and are much longer lasting than Cold Cured or Temporary dentures. In many cases, you get to Try-in the teeth before they are finished to ensure all the teeth occlude (meet) properly and look esthetically pleasing to you. These usually come with a 90 day to 2-year warranty and in some cases a money back guarantee if you are not satisfied. In some cases, adjustments to the dentures are also included.

Premium Heat Cured dentures can cost $2,000 -$4,000 per plate, or $4,000 -$8,000 or more for a set. Dentures in this price range are usually completely custom and personalized, use high-end materials to simulate the lifelike look of gums and teeth as closely as possible, last a long time and are warranted against chipping and cracking for 5–10 years or longer. Often the price includes several follow-up visits to fine-tune the fit.

Denture Care

Daily cleaning of dentures is recommended. Plaque and tartar can build up on false teeth, just as they do on natural teeth.^[10] Cleaning can be done by chemical or mechanical denture cleaners.