In the general population, especially among women, the incidence of contact dermatitis and allergic reactivity to nickel is quite high. When inexpensive metal alloy crowns containing nickel are applied to these individuals, persistent redness, chronic swelling, burning sensation, and gum recession (periodontal reaction) occur locally in the gums where the crown touches. Systemically, the continuous release of nickel ions in the mouth can lead to unexplained chronic fatigue, skin rashes, triggered eczema flare-ups, and a constantly alarmed immune system. To minimize these risks in individuals with a history of allergies or those concerned about their biological health, zirconium or titanium substructures should be used.
