Complete Dentures

Complete dentures are full-coverage oral prosthetic devices that replace a complete arch of missing teeth. The following are indications for this type of dental prosthesis:

• A full arch of missing teeth

• Dental implants that have been deemed inappropriate by patient and/or doctor because of financial constraints, a medically compromised status that contraindicates surgery, or inevitable damage to vital structures such as maxillary sinuses, nerves, and vessels

• Intraoral cancer that has caused a loss of gross intraoral tissue, resulting in an edentulous dental arch; the complete denture prosthesis would then not only replace teeth but also fill in the portion of missing tissue (eg, nasopharynx, hard palate)

  An edentulous maxillary ridge.

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  Maxillary complete denture used to restore the upper ridge and a mandibular partial cast denture placed to restore mandibular partial edentulous regions.

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Definitive contraindications to complete dentures have not been reported. However, the following factors should prompt a dentist to reconsider the use of a complete denture:

• Patient does not desire to have a removable appliance to replace missing teeth

• Patient has an allergy to the acrylic used in the fabrication of the complete denture

• Patient has a severe gag reflex (although this could be controlled with gag reflex desensitization)

• Patient has severely resorbed dental alveolar ridges, which would compromise retention with a complete denture alone

Many materials are necessary to fabricate a complete denture. These include spatulas, wax, casting ovens, impression material, adhesives, dental trays, border molding compound, shade guides, and a torch. The finished complete denture is composed of the following:

• Acrylic resin, which serves as the base of the complete denture, retains the denture teeth, and emulates the gingiva of supporting teeth

• Porcelain or acrylic denture teeth to emulate natural teeth

• In some cases, a cast metal base as part of a denture base

Conventional complete dentures

These are dentures that are fabricated using acrylic resin and that rely on the alveolar ridge, saliva, and other supporting structures for retention.

Immediate complete dentures

These are dentures usually delivered immediately after all remaining teeth of a dental arch are removed. During the healing process, this denture helps to confine the remodeling of the underlying ridge to the interior of the denture. Ordinarily, this type of prosthesis must be relined periodically as the underlying tissues heal and remodel. Usually, after 6 months, a conventional complete denture is indicated (ie, a new denture).

Overdentures

These are dentures that fit over usually two or more roots that have been salvaged and stabilized. These dentures can also fit over dental implants that have been placed. With overdentures, locator attachments are sometimes secured within the remaining roots or within placed dental implants, and these components are known to improve retention. Roots and dental implants help to preserve bone, and the added retention is known to be greater than conventional complete dentures alone. ^[1]

Metal-based dentures

These dentures have metal as a part of the base. The metal is usually placed on the tissue-bearing side. The advantages of the metal include a more accurate fit and better conduction of heat from foods, which may help aid in added pleasure during food consumption. ^[2] Another advantage is the added weight, which in particular helps to keep a mandibular (lower) denture in place. ^[2]

Various protocols and techniques are available for processing complete dentures. ^[3] Protocols vary by clinician preference and the technology being used. The authors hope to present here not a manual for the fabrication for a complete denture but rather an outline of principles.

Initial impression

A standard tray is used in recording the existing anatomy through an impression. The stock tray may need to be manipulated to accommodate for anatomical variances and constraints.

A study cast is synthesized from the impression.

The cast is evaluated for anatomical constraints, including, but not limited to, tori and undercuts.

A custom tray is fabricated from the study cast.

The custom tray circumscribes and accommodates for anatomy needed in the fabrication of the final denture.

Master impression

Border molding techniques are used for the recording of constraints imposed by muscular movements.

A custom tray applying balanced pressures registers the master impression. A custom tray mitigates distortions to the mucosal surface through accommodations for the impression material.

The master cast is fabricated from the recordings of the custom tray.

Wax rims

Wax rims are fabricated on the baseplates through the master cast.

The wax rims are used for the recording of the centric relationships in vivo.

Other anatomical landmarks such as the midline are marked on the wax.

Phonetics and esthetics are evaluated.

A facebow record is taken to triangulate and register the relationship of the maxillary cast to that of the mandibular transverse horizontal axis (terminal hinge axis).

Casts are mounted on an articulator, which emulates dynamic occlusal relationships.

Based on the registered information, denture teeth are installed on the wax rims.

Wax teeth try in

The patient and doctor examine the dentures’ ability to support extraoral tissues.

Phonetics are examined.

Occlusal relationships are evaluated. ^{[4, 5]}

The patient evaluates the esthetics.

Delivery

The processed denture is delivered to the patient.

Phonetics and occlusion are tested.

Pressure-indicating paste is used to identify excess or disproportionate pressures on mucosa.

Infringements on the neutral zones are relieved.

Follow-up and adjustments

Follow-ups are conducted at 24 hours, one week, and one month.

The denture is cleaned and examined, along with the patient’s oral health, every 6 months.

The denture is refabricated in 5-7 years.

The retention of a complete denture depends on several factors. The relative strengths of each retentive mechanism is debated in the literature. For the most part, surface tension and viscosity is seen as most vital for retention. ^[6] Cohesion, adhesion, friction, gravity, surface roughness, and atmospheric pressure are regarded as playing a lesser to no role in retention. ^[6]

The surface-tension model describes the interactions of a thin layer of fluid between two surfaces. In the case of a complete denture, the behavior of saliva along the denture-mucosa interface is theorized. As the complete denture is being drawn away from the mucosa, a liquid bridge develops along the periphery of the denture and mucosa. Such liquid bridges are similar to those that form when a water droplet is held between the fingertips.

Attempts had been made to model and approximate the capillary forces involved. ^{[7, 8]} A retentive pressure within the liquid-filled space develops and facilitates denture retention. This mechanism is independent and not related to that of atmospheric pressure differentials.

The surface-tension model is only one of many potential retentive forces, as it alone cannot account for retention from sheer-related displacements. In addition, capillarity would not apply when a denture, particularly a mandibular complete denture, is fully immersed in saliva.

Stefan’s law, ^[9] depicted in the image below, describes viscous tension eloquently. Although the model applies directly to relationships between two circular plates, it is not unreasonable to project such a relationship to the denture, saliva, and mucosa interfaces. ^[10]

Where "r" represents the radius of the plates, it is understood that an increase in the surface area of the denture-mucosa interface would improve retention by the power of 4. This coincides with the clinical practice of maximizing the denture base coverage but without infringing on the neutral zones. Where "k" represents the viscosity of the fluid, it is understood that higher viscosities improve retention. Denture adhesives, in addition to enhancing cohesion and adhesion more than saliva, improve denture retention through elevated viscosity values. ^[10] "V" represents velocity of displacement, helping to show that viscous tension is more effective in resisting high moments than prolonged displacements. Finally, but importantly "h," the distance between the denture base and mucosa, must be maintained at a minimum. The inversed cube relationship dictates that an accurate and intimate complete denture serves as a powerful retentive mechanism.

Because of the many variables that exist, it is difficult to know for certain how long complete dentures may last.

A review of the dental literature up to 1992 reveals that there is a lack of general consensus regarding the longevity of dentures. ^[11] Some estimates commonly reported by dentists include 5-7, 10, or even 10 plus years.

Research studies with sound parameters may help to create more reliable longevity estimates for dental clinicians to share with their patients. Certainly, over the years that a complete denture is worn, underlying alveolar bone will gradually resorb, teeth will wear down, and other normal wear-and-tear signs will be observed, ^[12] which is why regular dental checkups are necessary for the dentist to evaluate the patient’s existing dentures and to determine when intervention is necessary.

With meticulous attention to oral hygiene, responsible care and handling of the complete denture, and careful attention to a proper diet, dentures may conceivably last longer than expected. ^[12]

During the diagnostic phase of treatment, dentists may use the Prosthodontic Diagnostic Index (PDI) to assess the difficulty of a particular denture case. PDI considers factors such as patient's psychology, tongue anatomy, maxillomandibular relationship, arch morphology, muscle attachments, and interarch space. ^[2] Some factors that could lead to good prognosis according to the PDI include proper maxillary-to-mandibular relationship (ie, class I as opposed to class II), normal quantity and quality of saliva (as opposed to ropy saliva), U-shaped arch (as opposed to a V-shaped arch), prior use of dentures, and a positive mental attitude (as opposed to indifference or pessimism). ^[2]

A study by Andjelkovic et al suggested that wearing complete dentures caused a considerable increase of periodontopathic bacteria prevalence in elderly patients. ^{[13, 14]}

Immediately after completion of a complete denture, it is strongly advised that patients return for follow-up adjustments. In most cases, the first adjustment should occur within 24 hours of delivery of the complete denture. ^[12] This allows the practitioner to make finely tuned adjustments in areas where sore spots are noticed and to assess the patient’s psychological adjustment to the new prosthesis. ^[12]

It is not unusual for additional adjustments to be necessary after the first follow-up. Once adjustments have been completed, patients should see their dentist at least twice a year to evaluate the adequacy of the prosthesis. ^[12] If rocking is seen during subsequent visits, the dentist may recommend a reline to the base of the denture.

Additional instructions that patients must observe

Dropping the complete denture may cause fracturing of teeth or the acrylic base. Therefore, care must be taken when removing, cleaning, and reinserting the denture. When hovering over a sink, it is recommended to fill the sink with water or to have a towel placed underneath in case the prosthesis falls.

Generally, it is recommended to brush denture teeth with a soft bristled denture brush or soft bristled toothbrush after every meal to avoid stain and food debris accumulation. Hand soap or dishwashing soap may be used, but toothpastes are generally regarded as being too abrasive and should be avoided. ^{[2, 15]} Other denture cleaners are available, but caution should be exercised when using mild acids or hypochlorites, as they are known to corrode metals. ^[2] Oxygenating agents should be avoided if soft relines are present in dentures, as these will cause the soft reline to harden. ^[2]

Generally, it is recommended that complete dentures be removed at night to allow tissues to rest. ^[12] Failure to do so may contribute to the development of fungal infections and other intraoral tissue conditions.

Phonetics may change after insertion of the complete denture. ^[12] It is advised that patients practice reading out loud to allow quicker accommodation to the new prosthesis.

To allow for optimal functioning with the complete denture, it is recommended that patients place food bolus on both sides of the mouth and to chew with both sides. This will permit a more even distribution of stress throughout the masticatory system.

Avoid forcing the complete denture to seat in the mouth. If one finds that removing and inserting the denture is challenging, a follow-up appointment must be made with the dentist for further instruction.

When retiring for the night, the complete denture should be submerged in water to avoid the development of dimensional changes from dehydration. ^[12]

A study by Felix Gomez et al suggests that persons with dentures may be at risk for undernutrition. Two years after receiving dentures, they had lower serum albumin, calcium, and creatinine levels than persons without dentures. Those who were completely edentulous had a significant decline in serum albumin, creatinine, and blood urea nitrogen levels but an increase in estimated glomerular filtration rate. ^[16]