Proper lip support from dentures is fundamental to prosthetics, going beyond simply replacing missing teeth. This support restores the correct projection and fullness of the lips and surrounding lower facial tissues. Achieving proper support is necessary for both aesthetics—preventing a sunken or prematurely aged look—and function, allowing natural speaking and eating.
The Anatomical Basis of Lip Support
The underlying support for the lips and facial muscles is the alveolar ridge, the bone that once held the natural teeth. When teeth are lost, the functional stimulus maintaining this bone structure is removed, leading to alveolar ridge resorption. This bone loss is a natural consequence, as bone mass adapts to the levels of mechanical strain it receives.
Resorption is significant and occurs rapidly. Studies indicate the width of the ridge can decrease by up to 50% within the first year, with the most dramatic changes happening in the first three months. Since the outer (buccal) bone plate is thinner, it resorb more quickly than the inner plate, causing the ridge to shrink predominantly toward the tongue.
This loss of underlying bone causes the entire structure of the lower face to collapse inward. The orbicularis oris muscle, the ring of muscle surrounding the mouth, loses its foundation, contributing to the characteristic “sunken face” or prematurely aged appearance. Dentures must mechanically replace the lost volume of bone and soft tissue to restore muscle contour and achieve a natural facial profile.
Denture Design Elements That Restore Facial Contour
The correct design of a new denture relies on precise measurements and structural components to recreate lost facial support. One significant factor is the Vertical Dimension of Occlusion (VDO), the distance between the upper and lower jaws when the teeth are in contact. An insufficient VDO, often caused by tooth wear or long-term missing teeth, results in facial collapse, requiring the new denture to accurately restore this vertical height.
The denture’s acrylic base, known as the flange, is the primary element providing physical lip support. The flange extends from the artificial teeth and rests against the gum tissue and underlying bone ridge. Prosthodontists meticulously control the thickness and contour of this labial (lip-side) flange to push the lip outward to the correct natural position. This process is guided by the relation between the residual ridge and the depth of the lip vestibule.
The precise positioning and angulation of the anterior artificial teeth also play a defining role in lip aesthetics. The front teeth must be set at an angle and distance that supports the lip without causing an unnatural bulge, which signals excessive support. To achieve a natural appearance, the placement of the upper front teeth is often determined by measuring their distance from specific anatomical landmarks. The combined effect of the correct VDO, the contoured flange, and the artificial tooth position determines the fullness and natural drape of the lips.
Addressing Insufficient Support in Existing Dentures
Patients who have worn dentures for several years may notice a gradual loss of support due to continued bone resorption underneath the appliance. If existing dentures are otherwise sound, a dental professional may suggest a corrective procedure rather than constructing a new set. These procedures focus on re-adapting the denture base to the changing oral anatomy.
One common method is relining, which involves adding a new layer of acrylic material to the internal, tissue-fitting surface of the denture. This addition fills the space created by shrunken gum tissue, restoring the close fit and improving stability. While primarily intended to enhance retention, relining can provide a minor correction to the facial contour by slightly increasing the denture base thickness.
A more extensive procedure is rebasing, which replaces the entire acrylic base while preserving the original artificial teeth and their established relationship. Rebasing is typically chosen when the existing base material is deteriorated, stained, or when underlying tissue changes are too significant for a minor reline. Both relining and rebasing are performed without altering the patient’s established bite or VDO, which differentiates them from a full denture remake.
For localized under-support, a dentist can perform a direct modification of the labial flange by adding self-curing acrylic material directly beneath the lip. This chairside modification allows the professional to build up the flange contour to increase projection in a specific area. These adjustments ensure the appliance continues to provide adequate facial tissue support as the jawbone changes over time.
Consequences of Poor Lip Support and When to Consult a Professional
Ignoring inadequate lip support can lead to negative outcomes affecting both appearance and health. Aesthetically, insufficient support results in a compressed lower face, causing deep wrinkles and folds around the mouth that can make a person look older. Functionally, the collapse of soft tissues can interfere with proper speech, making certain sounds difficult to pronounce clearly.
A health consequence of poor support is the increased risk of angular cheilitis. This inflammation at the corners of the mouth occurs because inadequate denture support allows the jaw to over-close, deepening the folds. Saliva then pools in these moist environments, leading to tissue breakdown and creating a favorable site for fungal or bacterial infection.
Any time a denture wearer notices a change in facial contour, new difficulty with speaking, or persistent irritation and cracking at the corners of the mouth, they should consult a dental professional. A dentist or prosthodontist can assess if the issue stems from an ill-fitting appliance and recommend the appropriate adjustment, relining, or replacement to restore comfort and facial harmony.