Complete dentures have a longstanding record for rehabilitation of edentulous jaws, but are frequently associated with problems of retention and stability. Patients with these issues may be referred for implant therapy often without first addressing problems of inadequate design and fit of the complete prostheses. Improving the design and construction of the prostheses may alleviate problems of retention and stability without the need for implants. Therefore, the first step in the rehabilitation of edentulous arches is to establish whether or not the prostheses are adequate.

A complete denture is defined as a removable dental prosthesis that replaces the entire dentition and associated structures of the maxilla or mandible. Complete removable dentures must be designed as ideally as possible. This module will address two aspects of optimal prostheses design: the patient's denture requirements and the professional design considerations for construction of the prostheses. This module is a prerequisite to the Learning Module titled 'Complete Removable Overdentures: Implant Configuration and Retention'.

After completing this ITI Academy Module, you should be able to describe the denture requirements from the patient's perspective, discuss the importance of denture base fit and extension for denture retention and support, describe the aspects of denture design that aid in restoring the patient's overall physiognomy and oral function, and explain the static and dynamic occlusal schemes that contribute to denture stability and chewing efficiency.

The patient's concerns and wishes will most often be related to changes in the appearance of their face and teeth and changes in their functional ability and social well-being. The patient may also have specific concerns about their ability to handle and maintain their dentures.

Changes in facial appearance are a concern to most patients. Complete tooth loss leads to substantial changes in the patient's physiognomy, affecting their facial form, features, and expressions. The patient will therefore be seeking restoration of both facial harmony and esthetics. The patient may describe the facial changes in different ways, but they will often mention loss of lip support, sunken lips or face, and decreased lower facial height as well as a more prominent chin.

Most patients will have an inherent desire to conceal that they are wearing dentures. This makes the freedom to communicate and smile confidently in social situations all the more important. The appearance and form of the denture teeth are closely related to both communication and smiling. The patient may have very specific expectations and desires for the appearance of their teeth.

The patient will be hopeful that they can be assured of the freedom of a full range of oral functions. This includes spontaneous laughing without fear of the denture coming loose. Equally important is the ability to speak clearly and to be understood without effort, which are fundamental aspects of communication. Patients value the feeling that their food choices are not restricted, particularly when eating out. It is further important for the patient to feel free to engage in normal daily activities such as singing and swimming or in specific hobbies such as parachute jumping without fear of losing their teeth in an embarrassing or irretrievable way.

Insertion and removal of the dentures can pose a challenge to some patients. Such patients may also struggle with the demands of daily denture care. The patient may worry that the food will accumulate under the denture. This can be painful, and it is not always easy to find privacy in order to take out the dentures and remove the retained food. Most patients will be keen on keeping their dentures clean. Therefore, the patient should be made aware that a denture that has been finished with more complex and natural-looking contours will place extra demands on daily cleaning to avoid buildup of stains and calculus.

Patient Denture Requirements, Key Learning Points: Changes in facial appearance are a primary concern to most patients. The patient's esthetic wishes are often related to a desire to conceal denture wearing. Clear speech and freedom to eat a variety of foods are key denture functions. Dentures should be easy to handle and clean and should resist buildup of food and stains.

We now move on to the professional design considerations for the complete denture. These comprise a number of features intended to ensure that the prostheses are optimal for every given patient. These features will be discussed in order of denture construction, as follows: Fit and extension of denture bases, Facial support and position of incisors, Jaw relationship, Denture occlusion, Features and contours of the denture body.

The fit and extension of the denture base have a direct bearing on denture support and retention. The aim is to gain as much support as possible for the denture base, but the extent of support depends on the anatomical situation and the denture supporting area. The anatomical situation for any given edentulous patient is a reflection of the degree of atrophy of the alveolar ridge following loss of the teeth.

The degree of atrophy is usually classified according to the following broad descriptions: With a minimal degree of atrophy, the alveolar ridges are high and well-rounded. However, as a result the interarch space for the prostheses may be limited. With a moderate degree of atrophy, the interarch space is more favorable, but the width and/or height of the alveolar ridge is significantly reduced. The result may be a knife-edge or low ridge form. With advanced or severe atrophy the interarch space is large, and the ridge form is likely to be flat. The residual ridges may also be depressed or concave, which is a sign that the atrophy extends into the basal bone beyond the original tooth-supporting alveolar process.

The retention of the prostheses depends on the scope for a peripheral seal. In the maxillary arch in particular the degree of retention offered by an optimum seal can be excellent, supplanting the need for adjunct implant assistance. This seal prevents air and liquids from gaining access to the fit surface of the denture. The seal is achieved through a combination of the shape and extension of the vestibular denture flanges, a tightly fitting inner seal, and a posterior palatal seal. The palatal seal is achieved by the postdam denture area, which compresses the palatal mucosa. The postdam denture area is located immediately anterior to the vibrating line between the hard and soft palate. The exact position and shape of the palatal seal area must be determined in the patient's mouth. Similarly, the extent of the vestibular flanges is determined by the functional mobility of structures such as the frenula and muscles.

Achieving a peripheral seal for a mandibular prosthesis can be more of a challenge. The nature of the denture-supporting area is less favorable for preventing access of air and liquids to the fit surface. However, the scope for careful extension and shaping of the denture base and flanges should be explored in each patient. The flanges need to allow for functional mobility of adjacent muscles and frenula, but a surprisingly effective seal can be achieved with inclusion of a dam across the retromolar pads.

This video clip demonstrates the degree of retention in a mandibular complete denture that can be achieved by a careful compression seal across the retromolar pads. Note the considerable pressure needed to release the seal, and listen for the audible click at the point of release.

Restoration of facial support is achieved through a combination of upper and lower lip support. This is illustrated in these two images. In the left image, only the maxillary prosthesis has been inserted, and the lower lip still lacks support. This has been corrected in the right image, where both maxillary and mandibular prostheses are in place. The position of the incisors is guided by a combination of esthetic and functional requirements. The three-dimensional positioning of the incisors is aided by an assessment of facial proportions and lines, including the level of the lips at rest and when smiling. The functional relationship of the upper and lower incisors in speech can also be helpful. Reference to existing dentures and old photographs from the patient’s dentate past can lend important guidance through information and comparison.

As part of restoring the patient's overall physiognomy and oral function, it is also important that the complete dentures are constructed within a correct lower face height and comfortable jaw relationship. Restoration of the three-dimensional relationship between the upper and lower jaws relies on a series of reference planes and points. These include the inclination of the occlusal plane, the vertical dimension of occlusion, and the temporomandibular joint position when the complete dentures are in maximum intercuspation. The Camper plane, which is parallel to the ala-tragus line, is the most frequently used reference for determining the inclination of the occlusal plane, as demonstrated in this clinical image. The vertical dimension of occlusion should aim to restore the lower face height while maintaining a freeway space that is compatible with speech; for example, in pronunciation of the letter 's' the incisors should come into close proximity without touching. For healthy temporomandibular joints without internal disc displacement, the centric occlusion of the complete dentures should be coincident with centric relation of the mandibular condyles within the joints.

Complete denture occlusion aims to stabilize the position of the mandible against the maxilla. This is important during both static and dynamic occlusion. The principles of setting up posterior denture teeth are aimed at addressing transfer of load and control of the dentures when they come into contact. The position of the posterior teeth should transfer the occlusal load as effectively as possible to the underlying ridges to aid stability of the dentures and enhance chewing efficiency.

Equally, the dynamic occlusion should assist the patient in avoiding dislodgement of the dentures in eccentric movements. The dynamic occlusion in dentures is therefore often set up as a balanced occlusal scheme to allow greater freedom in excursive movements. Examples of a bilaterally balanced occlusion are shown in these images. In the upper images the maxillary and mandibular dentures make simultaneous contacts on both right and left sides during a left lateral excursion. The lower images show the corresponding occlusal contact patterns as marked by articulating paper.

The features and contours of the denture body should restore the missing tissue volume. Proper contours also assist the patient with muscular control of the denture. The shape of the denture body and its polished surfaces should be formed with both of these factors in mind. Speech and taste may also benefit when the palatal denture surface is contoured to mimic the morphology of the underlying palatal tissues; this feature provides the patient with a more natural feel. However, not all patients prefer inclusion of these palatal details. The denture shown here includes replication of the incisive papilla, rugae, and midline palatal raphe. On the other hand, it is equally important to avoid contours and crevices that may encourage retention of food and buildup of extrinsic stains and complicate removal of bacterial biofilm.

Clinician Denture Requirements, Key Learning Points: The prosthesis should have optimal support and retention from peripheral and inner seals, and the scope for these seals must be evaluated in the individual patient. Proper upper and lower lip support, correct lower face height, and a comfortable jaw relationship all contribute to restoring the patient's overall physiognomy and oral function. The static and dynamic occlusal schemes should aid in the stability of the dentures; in dynamic occlusion, a bilaterally balanced occlusal scheme is recommended. The denture body should be formed to aid in patient denture control and replace tissue volume while avoiding crevices that encourage food and plaque buildup.

Design Principles for Complete Removable Dentures, Module Summary: The design of denture prosthesis must address both patient concerns and prosthetic features relevant to the clinician. The patient is usually concerned about changes in their appearance, functional ability, and social well-being as well as their ability to handle and maintain their dentures. Denture support and retention depends greatly on the fit and extension of the denture base and in particular on the peripheral seal. Oral function and physiognomy are restored through adequate upper and lower lip support, correct three-dimensional relationship between the upper and lower jaws, and a bilaterally balanced occlusal scheme. A denture body that resists buildup of food, stains, and calculus is valued by both patient and clinician.