A removable prosthesis (such as a complete or partial denture) is designed to rest on the soft tissues and underlying bone of the mouth. A “pressure point” is a highly localized area of acute pain, irritation, or soreness that develops beneath the device. This discomfort occurs when the force that should be distributed evenly across the supporting tissues becomes concentrated on a small spot, often exceeding the tissue’s pressure-pain threshold. While some initial soreness is common as the mouth adapts, persistent pressure points signal a mechanical or biological mismatch. These issues must be addressed promptly by a dental professional to prevent serious problems like tissue inflammation, chronic sores, or accelerated bone loss.
Problems with the Initial Fit and Design
Pressure points can arise immediately after a new prosthesis is placed due to issues originating in the design or manufacturing process. One common issue is over-extended borders, where the edges of the acrylic base (flanges) press excessively into the soft tissues. This over-extension can impinge on sensitive areas like the pterygomaxillary notch or interfere with muscle attachments, such as the mylohyoid muscle, leading to pain and displacement.
Another factor is a lack of precision during the creation of the prosthesis, often starting with inaccurate impressions. An imperfect impression can result in a denture base that does not conform intimately to the underlying tissues, causing localized spots of high pressure. Rough spots or small acrylic nodules on the tissue-contacting surface, typically arising from poor finishing, can also act as concentrated pressure points.
Occlusal disharmony, or incorrect alignment of the upper and lower biting surfaces, is another cause related to design. When the teeth do not meet properly during chewing, the forces are distributed unevenly across the supporting ridges. This uneven distribution creates excessive stress, which can exceed the pressure-pain threshold of the underlying mucosa and accelerate bone resorption. These issues are usually corrected by the dental professional through chairside adjustments, which involve identifying high-pressure areas using indicator paste and carefully reducing the acrylic.
Anatomical Changes Over Time
Even a perfectly fitted prosthesis will eventually cause discomfort due to changes occurring within the mouth over time. The most significant long-term cause of ill-fitting dentures and pressure points is alveolar bone resorption. After natural teeth are lost, the jawbone no longer receives the necessary stimulation, leading to a natural process where the bone gradually shrinks and loses density.
This ongoing bone reduction means the foundation on which the prosthesis rests is constantly changing shape, causing the once-snug denture base to lose contact with the tissue. As the denture becomes loose, it begins to rock or shift during function, concentrating the masticatory forces onto small, localized areas of the ridge, which then become painful pressure points. For instance, in the lower jaw, resorption is often more extensive, averaging between 0.01 to 2.4 millimeters per year, making the fit particularly unstable.
Bone resorption can also cause bony prominences to become more exposed and susceptible to irritation. As the residual ridge flattens, structures like the mylohyoid ridge or a bony growth known as a torus can become covered by only a thin layer of mucosa. The pressure from the denture base, which was once distributed over thicker tissue, now directly compresses this thin, sensitive layer against the hard bone, resulting in acute, persistent pressure points.
Accidental Damage or Improper Handling
Pressure points can also develop suddenly as a result of external factors or improper patient care. The most common accidental damage is physical trauma, such as dropping the prosthesis onto a hard surface, which can cause chips, cracks, or fractures in the acrylic base. Even a minute crack or a sharp edge resulting from such damage can create an intense, highly focused point of irritation on the underlying gum tissue.
Another frequent issue is the warping of the acrylic material, which typically occurs due to improper cleaning methods. Acrylic resin is sensitive to heat, and exposing the prosthesis to excessively hot or boiling water during cleaning can distort the plastic base. This distortion immediately alters the precise fit of the denture, causing it to press unevenly against the oral tissues and generate new pressure areas.
Patient habits, such as the misuse of denture adhesives, can also inadvertently lead to localized pressure. While adhesives temporarily stabilize a loose denture, applying too much or distributing it unevenly can push the prosthesis out of alignment. This misalignment creates an artificial high spot, which concentrates the chewing force and results in a painful pressure point. Continuing to wear a damaged or ill-fitting prosthesis, rather than seeking maintenance, can accelerate the development of chronic gum problems and tissue sores.