Dentures are removable prosthetic devices designed to replace missing teeth and restore function and appearance. For a denture to work properly, it must maintain a secure and stable fit against the gums and underlying bone structure. Loss of stability causes slipping, rocking, or clicking, which impacts the ability to speak, eat, and feel confident. Instability is typically caused by changes in the appliance, changes in the mouth’s anatomy, or factors related to daily use and maintenance.
When the Denture No Longer Fits
A common reason for poor stability is that the denture appliance is no longer compatible with the mouth’s current shape. Although made of durable acrylic, dentures are subject to wear and tear, typically lasting five to seven years before needing replacement. Worn artificial teeth or warped surfaces that contact the gums can affect the balance and biting forces on the appliance.
Even a well-made denture requires periodic professional maintenance because the mouth is a dynamic environment. When the fit becomes loose due to minor changes in the gum line, a dental professional may recommend a reline. A reline involves applying a new layer of acrylic material to the fitting surface to conform to the current contours of the gums, improving comfort and stability.
A rebase is a more extensive adjustment where the entire acrylic base is replaced while keeping the original artificial teeth. This is necessary when the existing base is significantly weakened, cracked, or porous, or when the oral anatomy has changed substantially. Relying on excessive amounts of adhesive to manage a poor fit indicates that a reline or rebase is overdue.
How Bone and Gum Changes Affect Stability
The most significant biological factor affecting long-term denture fit is alveolar ridge resorption. This is the natural, progressive shrinkage of the jawbone that occurs after teeth are lost because the bone is no longer stimulated by the tooth roots. This chronic, irreversible bone loss causes the gums, which rest on the bone, to also shrink and flatten.
The loss of jawbone mass removes the vertical height and contours that provide the denture with its primary support and suction. Resorption continues gradually after tooth removal, meaning dentures custom-made years ago will eventually sit on a smaller, flatter surface. This gradual alteration inevitably leads to instability and a loose fit.
The lower jaw (mandible) is particularly susceptible to this issue. The reduced support area in the mandible makes lower dentures notably more challenging to keep stable than upper dentures, which rely on a larger surface area and palatal suction. Factors like general skeletal conditions and systemic diseases can also contribute to the speed of this bone loss.
Adhesion and User Technique Factors
Controllable factors related to daily habits and technique play a large role in maintaining denture stability. Denture adhesives are designed to enhance the fit of a reasonably well-fitting denture, not to compensate for a severely loose appliance. Adhesives work by forming a thin, moisture-activated layer that creates a bond between the denture and the gum tissue, providing increased retention.
A common mistake is using too much adhesive, which can lead to oozing and make the appliance difficult to clean. Proper technique involves applying a small amount of adhesive, whether cream or powder, to a clean, dry denture surface while avoiding the edges. Saliva also plays a role; since the adhesive is water-soluble, too little saliva (such as from dry mouth) or too much can interfere with the bonding process.
Eating and Speaking Techniques
Learning to use the facial muscles and tongue correctly is crucial for stability, especially when eating and speaking. When eating, take smaller bites and chew food simultaneously on both sides of the mouth to distribute pressure evenly and prevent rocking. Avoiding hard, sticky, or chewy foods can also prevent the appliance from being dislodged or damaged. Speaking clearly requires practice, often involving reading aloud to train the muscles and tongue to articulate sounds without causing the denture to move.