Dentures

view of the same maxillary denture Dentures (also known as false teeth) are prosthetic devices constructed to replace missing teeth, supported by the surrounding soft and hard tissues of the oral cavity. Conventional dentures are removable (removable partial denture or complete denture). However, there are many denture designs, some of which rely on bonding or clasping onto teeth or dental implants (fixed prosthodontics). There are two main categories of dentures, the distinction being whether they fit onto the mandibular arch or on the maxillary arch.

view of the same maxillary denture]] Dentures (also known as false teeth) are prosthetic devices constructed to replace missing teeth, supported by the surrounding soft and hard tissues of the oral cavity. Conventional dentures are removable (removable partial denture or complete denture). However, there are many denture designs, some of which rely on bonding or clasping onto teeth or dental implants (fixed prosthodontics). There are two main categories of dentures, the distinction being whether they fit onto the mandibular arch or on the maxillary arch.

Medical uses

Dentures can help people via: Mastication: chewing ability is improved by the replacement of edentulous (lacking teeth) areas with denture teeth. Aesthetics: the presence of teeth gives a natural appearance to the face, and wearing a denture to replace missing teeth provides support for the lips and cheeks and corrects the collapsed appearance that results from the loss of teeth. Pronunciation: replacing missing teeth, especially the anteriors, enables patients to speak better, enunciating more easily sibilants and fricatives in particular. Self-esteem: improved looks and speech boost confidence in patients' ability to interact socially.

Complications

Tooth loss

People can become entirely edentulous for many reasons, the most prevalent being removal due to dental disease, which typically relates to oral flora control, i.e., periodontal disease and tooth decay. Other reasons include pregnancy, tooth developmental defects caused by severe malnutrition, genetic defects such as dentinogenesis imperfecta, trauma, and drug use. Periodontitis is defined as an inflammatory lesion mediated by host-pathogen interaction that results in the loss of connective tissue fiber attachment to the root surface and ultimately to the alveolar bone. It is the loss of connective tissue to the root surface that leads to teeth falling out. The hormones associated with pregnancy increases the risk of gingivitis and vomiting. Hormones released during pregnancy softens the cardia muscle ring that keeps food within the stomach. Hydrochloric acid is the acid involved in gastric reflux, also known as morning sickness. This acid, at a pH of 1.5-3.5, coats the enamel on the teeth, mainly affecting the palatal surfaces of the maxillary teeth. Eventually the enamel is softened and easily wears away. Dental trauma refers to trauma (injury) to the teeth and/or periodontium (gums, periodontal ligament, alveolar bone). Strong force may cause the root of the tooth to completely dislocate from its socket, mild trauma may cause the tooth to chip.

Types

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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" dentures, are made from crowns that are fitted on the remaining teeth. They act as abutments and pontics, and are made from materials resembling the missing teeth. Fixed bridges are more expensive than removable appliances but are more stable. Another option in this category is the flexible partial, which takes advantage of innovations in digital technology. Flexible partial fabrication involves only non-invasive procedures. Dentures can be difficult to clean and can affect oral hygiene.

Complete dentures

Complete 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—or, more commonly, in both arches. The full denture is removable because it is held in place by suction. They are painful at first and can take some time to get used to. There are two types of full dentures: immediate dentures and conventional dentures.

Materials

Dentures are mainly made from acrylic due to the ease of material manipulation and likeness to intra-oral tissues, i.e. gums. Most dentures are composed of heat-cured acrylic polymethyl methacrylate and rubber-reinforced polymethyl methacrylate. Coloring agents and synthetic fibers are added to obtain the tissue-like shade, and to mimic the small capillaries of the oral mucosa, respectively. However, dentures made from acrylic can be fragile and fracture easily if the patient has trouble adapting neuromuscular control. This can be overcome by reinforcing the denture base with cobalt chromium (Co-Cr). They are often thinner (therefore more comfortable) and stronger (to prevent repeating fractures).

George Washington

George Washington (1732–1799) suffered from problems with his teeth throughout his life, and historians have tracked his experiences in great detail. He lost his first adult tooth when he was twenty-two and had only one left by the time he became president. He had several sets of false teeth made, four of them by a dentist named John Greenwood. None of the sets, contrary to popular belief, were made from wood or contained any wood. The set made when he became president were carved from hippopotamus and elephant ivory, held together with gold springs. Prior to these, he had a set made with real human teeth, likely ones he purchased from "several unnamed Negroes, presumably Mount Vernon slaves" in 1784.

Prosthodontic principles

Support

Support is the principle that describes how well the underlying mucosa (oral tissues, including gums) keeps the denture from moving vertically towards the arch in question during chewing, and thus being excessively depressed and moving deeper into the arch. For the mandibular arch, this function is provided primarily by the buccal shelf, a region extending laterally from the back or posterior ridges, and by the pear-shaped pad (the most posterior area of keratinized gingival formed by the scaling down of the retro-molar papilla after the extraction of the last molar tooth). Secondary support for the complete mandibular denture is provided by the alveolar ridge crest. The maxillary arch receives primary support from the horizontal hard palate and the posterior alveolar ridge crest. The larger the denture flanges (that part of the denture that extends into the vestibule), the better the stability (another parameter to assess fit of a complete denture). 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, and ulcerations (denture sore spots).

Stability

Stability is the principle that describes how well the denture base is prevented from moving in a horizontal plane, and thus sliding from side to side or front to back. The more the denture base (pink material) is in smooth and continuous contact with the edentulous ridge (the hill upon which the teeth used to reside, but now 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 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 maxillary complete 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. Prosthodontists use a scale called the Kapur index to quantify denture stability and retention. Implant technology can vastly improve the patient's denture-wearing experience by increasing stability and preventing bone from wearing away. Implants can also aid retention. Instead of merely placing the implants to serve as blocking mechanism against the denture's 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. Available options include a metal "Hader bar" or precision ball attachments.

Fit, maintenance and relining

Generally speaking, partial dentures tend to be held in place by the presence of the remaining natural teeth and complete dentures tend to rely on muscular co-ordination and limited suction to stay in place. The maxilla very commonly has more favorable denture-bearing anatomy, as the ridge tends to be well formed and there is a larger area on the palate for suction to retain the denture. Conversely, the mandible tends to make lower dentures much less retentive due to the displacing presence of the tongue and the higher rate of resorption, frequently leading to significantly resorbed lower ridges. Disto-lingual regions tend to offer retention even in highly resorbed mandibles, and extension of the flange into these regions tends to produce a more retentive lower denture. An implant supported lower denture is another option for improving retention. Dentures that fit well during the first few years after creation will not necessarily fit well for the rest of the wearer's lifetime. This is because the bone and mucosa of the mouth are living tissues, which are dynamic over decades. Bone remodeling never stops in living bone. Edentulous jaw ridges tend to resorb progressively over the years, especially the alveolar ridge of the lower jaw. Mucosa reacts to being chronically rubbed by the dentures. Poorly fitting dentures hasten both of those processes compared to the rates with well-fitting dentures. Poor fitting dentures may also lead to the development of conditions such as epulis fissuratum. In addition, the occlusion (chewing surfaces of the teeth) tends to wear away over time, which reduces chewing efficacy and decreases the vertical dimension of occlusion (the "openness" of the jaws and mouth).

Brushing

After receiving dentures, the patient should brush them often with soap, water and a soft nylon toothbrush which has a small head, as this will enable the brush to reach into all the areas of the denture surface. The bristles must be soft in order for them to easily conform to the contours of the dentures for adequate cleaning: stiff bristles will not conform well and are likely to cause abrasion of the denture acrylic resin. If a patient finds it difficult to utilize a toothbrush, e.g. a patient with arthritis, a brush with easy-grip modifications may be used. Disclosing solutions can be used at home to make less obvious plaque deposits more visible to ensure thorough cleaning of plaque. Food dyes can be utilized as a disclosing solution when used correctly. Instead of brushing their dentures with soap and water, patients can use pastes designed for dentures or conventional toothpaste to clean their dentures. However, the American Dental Association advises against using toothpaste as it can be too harsh for cleaning dentures.

Immersion

Patients should combine the brushing of their dentures with soaking them in an immersion cleaner from time to time as this combined cleaning strategy has been shown to control denture plaque. Due to microbial invasion, the lack of use of immersion cleaners and inadequate denture plaque control will cause rapid deterioration of the soft linings of the denture.

Cleansers and methods

Liquid cleansers that dentures can be immersed in include: bleaches e.g. sodium hypochlorite; effervescent solutions e.g. alkaline peroxides, perborates and persulfates; acid cleaners.

Sodium hypochlorite cleansers

Sodium hypochlorite (NaOCl) cleansers have a disinfectant action and remove non-viable organisms and other deposits from the surface, but they are weak for eliminating calculus from the denture surface. Immersing dentures in a hypochlorite solution for more than 6 hours occasionally will eliminate plaque and staining. Furthermore, as microbial invasion is prevented, the deterioration of the soft lining material does not occur. Corrosion of cobalt chromium has occurred when hypochlorite cleansers have been used, and they may also result in the fading of the acrylic and silicone lining, but the softness or elastically of the linings are not greatly changed.

Effervescent cleansers

Effervescent cleansers are the most popular immersion cleansers and include alkaline peroxides, perborates and persulfates. Their cleansing action occurs by the formation of small bubbles which displace loosely-attached material from the surface of the denture. They are not very effective as cleansers and have a restricted ability to eliminate microbial plaque. Moreover, they are safe for use and do not cause deterioration of the acrylic resin or the metals used in denture construction. Despite this, they are able to cause rapid damage to some short-term soft lining. Discoloration of the acrylic resin to a white denture often occurs; however, this can be due to the use of very hot water with cleaning agents against manufacturer instructions.

Acid cleansers

Sulfamic acid is a type of acid cleanser that is used to prevent the formation of calculus on dentures. Sulfamic acid has a very good compatibility with many denture materials, including the metals used in denture construction. 5% hydrochloric acid is another type of acid cleanser. In this case, the denture is immersed in the hydrochloric cleanser to soften the calculus so that it can be brushed away. The acid can cause damage to clothes if accidentally spilt, and can cause corrosion of cobalt-chromium or stainless steel if immersed in the acid often and for long periods of time.

Other denture cleaning methods

Other denture cleaning methods include enzymes, ultrasonic cleansers and microwave exposure. A Cochrane Review found that there is weak evidence to support soaking dentures in effervescent tablets or in enzymatic solutions, and while the most effective method for eliminating plaque is not clear, the review shows that brushing with paste eliminates microbial plaque better than inactive methods. There is a need for studies to provide reports about the cost of materials and the negative effects that may be associated with their use, as these factors could affect the acceptability of such materials by patients which will in turn affect their effectiveness in a daily setting in the long term. Putting dentures into a dishwasher overnight can be a useful shortcut when away from home. Additionally, further studies comparing the different methods of cleaning dentures are needed.

See also

Full mouth extraction, the prophylactic removal of all teeth

References

External links

Text derived from https://en.wikipedia.org/w/index.php?oldid=1377330790 under CC BY-SA 4.0; modifications have been made.