Dentures are constructed from polymethyl methacrylate (PMMA), a durable acrylic resin. This porous material is designed to absorb a small amount of water, typically 0.5% to 2.4% of its weight. This absorbed water is an integrated component of the denture’s structure, helping to maintain its shape and size. Without this moisture, the acrylic can become compromised, leading to structural and dimensional problems that affect the appliance’s function and comfort. Proper moisture retention is necessary for the long-term health and fit of any acrylic denture.
The Timeframe for Denture Dehydration
The process of moisture loss from an acrylic denture begins almost instantly upon exposure to air, making the timeframe for significant drying a matter of hours. This dehydration is influenced by ambient factors such as temperature, which speeds up evaporation, and low relative humidity, which increases the moisture gradient between the denture and the surrounding air. Measurable dimensional changes in conventional acrylic resin can be detected after as little as eight hours of continuous dry storage.
A few hours of air exposure initiates a cycle of water loss and subsequent material change. The most intense changes in moisture content occur within the first 24 hours of a new storage condition. Leaving a denture out overnight, a standard eight-hour period, is sufficient time for the material to begin shrinking and distorting. This rapid initial moisture loss explains why dental professionals advocate for immediate immersion when the appliance is not being worn.
How Drying Out Affects Denture Fit and Structure
The water absorbed by the PMMA acrylic resin acts as a plasticizer. This absorbed moisture partially compensates for the minute shrinkage that occurs when the resin is initially cured during manufacturing. When the denture dries out, the water molecules evaporate, and this plasticizing effect is reversed, causing the polymer chains to pull closer together.
This contraction results in the acrylic base shrinking. A shrunken denture base will no longer conform precisely to the contours of the patient’s gum tissues. This results in an unstable fit and the potential for movement.
A dry denture becomes significantly more brittle and susceptible to damage. The loss of internal moisture increases the material’s rigidity, making it less able to withstand normal chewing forces. This increased brittleness often manifests as hairline cracks, which can quickly propagate into larger fractures, compromising the structure. Furthermore, a poor fit from drying causes irritation, leading to sore spots and inflammation of the underlying oral tissues.
Recommended Methods for Denture Storage
Dentures must be stored in a liquid environment whenever they are removed from the mouth. The simplest and most accessible method is to submerge the appliance completely in clean, room-temperature tap water. The water acts as a barrier, preventing the evaporation of moisture content from the porous acrylic.
A more effective method for both hydration and hygiene involves using a specialized denture soaking solution. These solutions, often in tablet form, are formulated to clean the appliance while ensuring it remains fully hydrated. Whether using plain water or a solution, the liquid should be contained in a clean, sturdy denture case to protect the appliance from accidental damage.
Avoid using hot or boiling water for cleaning or storage, as elevated temperatures can rapidly distort the acrylic base. Household cleaning agents like bleach should not be used, as they can weaken the PMMA and potentially damage any metal components. The storage container should be kept in a safe, temperature-controlled environment away from direct heat sources.