Dentures rest upon the gum tissue and the underlying jawbone, known as the alveolar ridge. The primary factor necessitating adjustments is alveolar ridge resorption, the natural shrinkage of the jawbone after teeth are lost. This occurs because the bone tissue, lacking stimulation from tooth roots, is gradually broken down by the body. While bone loss is most rapid during the first year after extraction, it continues throughout the denture wearer’s life.
This reduction in bone height and width alters the contour of the denture foundation. The lower jaw (mandible) typically resorbs four times faster than the upper jaw (maxilla), making lower dentures especially prone to becoming loose. As the underlying structure changes, the gum tissue shifts, leading to a loss of the snug seal necessary for stability and retention.
The denture material itself also contributes to poor fit. The acrylic base can degrade or warp due to constant exposure to temperature changes and chewing stresses. Furthermore, artificial teeth wear down over time, disrupting the bite alignment and placing uneven pressure on supporting tissues.
Clinical Procedures for Reshaping Dentures
When a denture loses its fit, dental professionals use clinical methods to reshape the appliance and restore adaptation to the oral tissues. The most common procedure is a reline, which adds new acrylic material to the tissue-fitting surface of the existing base. This technique fills the gap created by resorbed bone and tissue changes, improving the denture’s suction and stability.
Relining uses either hard or soft material and can be completed directly in the office or indirectly in a laboratory.
Hard Relines
A chairside (direct) hard reline uses a self-curing acrylic resin for a quicker fix. An indirect hard reline involves sending the denture to a lab for processing with a heat-cured resin, which offers a denser, longer-lasting surface.
Soft Relines
Soft relines use a flexible material, such as silicone or a specialized polymer. These are often recommended for patients experiencing chronic soreness or highly sensitive gum tissues.
A more extensive reshaping procedure is rebasing, which replaces the entire pink acrylic base material while preserving the original artificial teeth. This is necessary when the base is significantly deteriorated or discolored, or when substantial tissue conditioning is required, provided the existing bite relationship remains correct. Dentists also perform minor chairside adjustments, which involve selectively grinding and polishing small areas of the denture base or border to eliminate localized pressure points.
Signs That Replacement is Necessary
While relining and rebasing can greatly extend the life of a denture, limitations exist that necessitate complete replacement. One clear sign is extensive physical deterioration, such as deep cracks, severe chipping, or a base fractured beyond simple repair. Furthermore, if artificial teeth are severely worn down, which reduces the vertical dimension of the bite, a new denture is required to re-establish proper jaw alignment.
Persistent pain, chronic sores, or instability that cannot be corrected after multiple reline procedures suggest drastic changes in jaw anatomy. Severe alveolar ridge resorption may leave the remaining bone too flat to provide adequate retention or support for the denture, rendering relining or rebasing ineffective. Additionally, if the teeth are positioned incorrectly, causing significant speech difficulties or an unappealing appearance, the entire appliance must be remade to correct these foundational design issues.