Denture adhesives provide a stronger, more secure bond between the denture plate and the gum tissues, offering wearers increased stability. For many years, many adhesive creams and powders contained zinc as a functional ingredient. Public health concerns arose when neurological symptoms were linked to the chronic, excessive use of these products. The issue is not the presence of zinc itself, which is an essential nutrient, but the potential for overexposure when the product is misused. This article explores why zinc is included, the health risks involved, and steps wearers can take for safe use or to choose zinc-free alternatives.
Why Denture Adhesives Contain Zinc
Zinc is included in certain denture adhesives purely for its beneficial physical properties. Zinc acts as a stabilizer and binder, improving the strength and durability of the bond between the denture and the underlying oral tissues. This function helps the adhesive maintain its integrity and holding power over a longer period, resisting the forces of chewing and saliva. This mechanical benefit contributes to a more secure fit for the denture wearer.
How Excessive Use Leads to Overexposure
The harm associated with zinc stems from applying far greater amounts than recommended over a long period. When dentures become ill-fitting due to natural changes in the gum ridge, users often apply progressively more adhesive to compensate. This practice greatly increases the amount of zinc available for systemic absorption through the mucous membranes of the mouth and the gastrointestinal tract.
The resulting cumulative exposure can cause the total daily intake of zinc to significantly exceed the tolerable upper intake level (UL) of 40 milligrams per day for adults. Case reports of toxicity have involved individuals using as much as two tubes of adhesive per week. This chronic, high-dose exposure is the direct cause of hyperzincemia, a state of elevated zinc levels in the body.
Specific Health Risks Associated with High Zinc Intake
The primary health risk from zinc overexposure is its interference with the body’s absorption and metabolism of copper. High levels of zinc induce the production of a protein called metallothionein in the intestinal cells, which binds tightly to copper and prevents it from entering the bloodstream. This leads to an acquired copper deficiency, known as hypocupremia, which is the underlying cause of the most serious symptoms.
Copper is an essential mineral required for the proper functioning of many enzymes involved in nerve and blood cell health. When copper levels drop too low, it can lead to hematological issues like anemia and neutropenia (a reduction in a type of white blood cell). More concerning are the neurological symptoms that arise from the degeneration of nerve fibers.
The resulting neurological condition, copper deficiency myeloneuropathy, manifests as peripheral neuropathy. Symptoms typically begin with numbness and tingling sensations, particularly in the hands and feet. This can progress to muscle weakness, difficulty walking, loss of balance, and gait disturbances. While the hematological issues often respond well to copper supplementation, the nerve damage can sometimes be permanent, even after zinc exposure is stopped.
Steps for Safe Application and Zinc-Free Options
To mitigate the risk of overexposure, denture wearers should always apply the minimum effective amount of adhesive, using short strips or a light dusting of powder as directed by the product label. If the adhesive oozes out from under the denture when inserted, this is a clear sign that too much product has been used. It is important to clean all residual adhesive thoroughly from the mouth and the denture plate daily.
A more effective long-term solution is ensuring the denture fits properly, which reduces the reliance on large amounts of adhesive. Dentures should be professionally examined and refitted or relined regularly, as the gum tissue and underlying bone naturally change shape over time. Individuals who want to eliminate the risk of zinc overexposure entirely can select from the many zinc-free denture adhesives now widely available. Several manufacturers offer zinc-free pastes, powders, and strips, which provide secure adhesion without the risk of systemic zinc absorption.