Suction dentures are specialized dental prostheses designed to remain securely in the mouth without adhesives. Retention relies on a sophisticated interplay of physical forces, primarily atmospheric pressure and a precise boundary known as the peripheral seal. This seal is created where the denture border contacts the soft, movable tissues of the mouth, preventing air from entering the space between the denture and the underlying mucosa. Establishing this airtight seal around the entire perimeter allows the denture to resist dislodging forces, which is especially important for lower dentures where stability is challenging.
Initial Assessment and Impression Taking
The first step in fabricating a suction denture is an initial assessment to ensure the patient’s oral tissues are healthy and suitable for the technique. The retention of the final denture depends on an impression that accurately captures the anatomy, including the specific areas that form the peripheral seal. This initial clinical phase involves taking a preliminary impression using a stock tray, which is then used by the laboratory to create a custom-fitted impression tray.
The custom tray covers the denture-supporting areas without extending into the movable tissue. Border molding is then performed, shaping the tray’s edges with a moldable material, such as green stick compound or high-viscosity silicone. The material is placed on the tray’s border, and the patient performs functional movements (e.g., smiling, swallowing, moving the tongue). These actions dynamically mold the impression material to the exact contour of the muscle attachments and soft tissue, creating the functional peripheral seal.
A final impression is then taken using a low-viscosity material, such as vinyl polysiloxane, within the now-border-molded custom tray. This material flows to capture the fine surface detail of the mucosa while the precisely formed borders maintain the seal. The resulting master cast, poured from this final impression, provides the dental technician with a three-dimensional blueprint of the patient’s mouth that includes the exact border extensions necessary to achieve the desired suction.
Establishing the Jaw Relationship and Aesthetics
With the accurate master casts prepared, the next clinical phase focuses on the functional and aesthetic design of the denture. This begins with fabricating wax bite rims on the casts, which serve as temporary bases for recording the relationship between the upper and lower jaws. Determining the correct vertical dimension of occlusion (VDO) is important, as it represents the height of the face when the teeth are in contact.
The VDO is calculated by subtracting the freeway space (usually 2 to 4 millimeters) from the resting vertical dimension of the jaw. An incorrect VDO can lead to discomfort, muscle strain, or poor aesthetics, such as a compressed or elongated facial profile. The dental professional also determines the centric relation, the most stable and repeatable position of the lower jaw relative to the upper jaw, which is necessary for the functional stability of the finished denture.
Aesthetics are finalized at this stage, including selecting artificial teeth based on size, shape, and color to harmonize with the patient’s facial features. The wax rims are contoured to provide appropriate lip and cheek support, restoring the patient’s facial profile. This stage transfers the patient’s functional and aesthetic requirements onto the articulated models, serving as the blueprint for the laboratory.
The Fabrication Phase: From Wax Trial to Final Acrylic
The laboratory phase begins once the dental professional approves the jaw relationship records and tooth selection. The technician mounts the master casts onto an articulator, a mechanical device that mimics the patient’s jaw movements, using the bite registration records. The artificial teeth are then set into the wax on the baseplates according to the established aesthetic and functional guidelines.
The wax setup is returned for a wax try-in, allowing the patient and professional to approve the fit, bite, and appearance before final processing. After approval, the wax trial denture is invested in a dental flask using plaster or dental stone, a process called flasking. The flask is then heated to boil out the wax, leaving a mold space that holds the artificial teeth in position.
Acrylic resin (polymethyl methacrylate or PMMA) is mixed into a dough-like consistency and packed into the mold space. The flask is subjected to high pressure and heat in a process called curing, which polymerizes the acrylic and converts the dough into the hard, durable denture base. Curing under pressure ensures maximum density, reducing porosity and providing the necessary strength for the final prosthesis.
Achieving the Seal: Delivery and Adjustments
Once cured, the acrylic denture is deflasked, finished by removing excess material, and polished to a smooth, high-gloss surface. The finished denture is delivered to the patient, marking the first opportunity to test the peripheral seal. The professional checks retention by attempting to dislodge the denture, confirming that the captured borders are functioning to maintain the atmospheric pressure differential.
A well-fitting upper denture relies on the posterior palatal seal, a feature where the denture presses slightly into the soft tissue at the back of the hard palate to complete the border seal. Minor adjustments are often needed immediately after delivery for both upper and lower dentures to relieve pressure points or refine the bite. Achieving the seal and comfort is an iterative process that requires follow-up appointments.
During subsequent visits, the fit is checked, and areas of tissue irritation are adjusted by selectively grinding the acrylic. The final success of the suction mechanism depends on the patient learning to use the tongue, cheek, and lip muscles to maintain the seal and keep the denture stable during speaking and eating. This adaptation ensures the long-term effectiveness and comfort of the suction denture.