Dentures are prosthetic devices constructed to replace missing teeth; they are supported by the surrounding soft and hard tissues of the oral cavity.
Dentures can help patients through:
Mastication or chewing ability is improved by replacing edentulous areas with denture teeth.
- Aesthetics, because 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.
- Phonetics, because replacing missing teeth, especially the anteriors, enables patients to speak better. There is especially improvement in pronouncing words containing sibilants or fricatives.
- Self-esteem, because improved looks and speech boost confidence in the ability to interact socially.
Fabrication of complete dentures
Modern dentures are most often fabricated in a commercial dental laboratory or by a denturist using a combination of tissue shaded powders polymethylmethacrylate acrylic (PMMA). These acrylics are available as heat cured or 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 an initial dental impression of the maxillary and mandibular ridges. Standard impression materials are used during the process. The initial impression is used to create a simple stone model that represents the maxillary and mandibular arches of the patient's mouth. This is not a detailed impression at this stage. Once the initial impression is taken, the stone model is used to create a 'Custom Impression Tray' which is used to take a second and much more detailed and accurate impression of the patient's 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 and mandibular ridges. A wax rim is fabricated to assist the dentist or denturist in 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 tested in the mouth so that adjustments can be made to the occlusion. After the occlusion has been verified by the dentist or denturist and the patient, and all phonetic requirements are met, the denture is processed.
Processing a denture is usually performed using a lost-wax technique whereby the form of the final denture, including the acrylic denture teeth, is invested in stone.
This investment is then heated, and when it melts the wax is removed through a spruing channel. The remaining cavity is then either filled by forced injection or pouring in the uncured denture acrylic, which is either a heat cured or cold-cured type. 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. After a curing period, the stone investment is removed, the acrylic is polished, and the denture is complete. The end result is a denture that looks much more natural, is much stronger and more 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 be highly porous and are only used as a temporary expedient until a more permanent solution is found. These types of dentures are inferior and tend to cost much less due to their quick production time (usually minutes) and low cost materials. 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
- 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 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 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.
- 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.
- When dentures no longer fit well, the correct action is to seek follow-up care. Using denture adhesive may improve the fit, but it tends to work better when only a small amount is used as covering the denture fitting surface in adhesive makes it stay in less well. Adhesives may compensate for gradual loosening of a denture, but it is only a temporary solution; it does not solve the problem. Fortunately, dentures can often be relined with relining materials to restore the proper fit, and this process costs less than creation of new dentures. Overall, a well-made denture should last about 5 years or more.
The fabrication of a set of complete dentures is a challenge for any dentist/denturist. There are many axioms in the production of dentures that must be understood; ignorance of one axiom can lead to failure of the denture. In the vast majority of cases, complete dentures should be comfortable soon after insertion, although almost always at least two adjustment visits are necessary to remove the cause of 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 an accurate model of the patient's edentulous arches. The dentist 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, a prosthodontist to make the denture.
Once the laboratory receives dental impressions of the patient's mouth, the laboratory creates plaster molds from them. The laboratory uses the molds to create the wax rims used to register the patient's bite. These wax rims are returned to the dentist, who uses them to register the patient's bite. The dentist may assist the patient in choosing the correct size of teeth for the dentures, or simply make the selection himself. Once 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, the result is a prefinished denture that looks almost like the finished product. This prefinished denture is usually returned to the dentist's office and the patient usually has a chance to approve the setup (for immediate or standard dentures) or to try the denture before it is finished. After approval by the patient, the dentist returns the pre-denture to the laboratory for final processing. The finished denture is then returned to the dentist's office for delivery to the patient.
Daily cleaning of dentures is recommended. Plaque and tartar can build up on false teeth, just as they do on natural teeth. Cleaning can be done using chemical or mechanical denture cleaners. Dentures should not be worn continuously, but rather left out of the mouth during sleep. This is to give the tissues a chance to recover. The main risk is development of fungal infection, especially denture-related stomatitis.