DCA02AR Allergic Reactions in Dental Patients _ _________________________________________________
A type I hypersensitivity reaction to natural rubber latex can occur without any prior hypersensitivity reaction, but there are certain indicators in a patient’s medical history that should raise a “red flag” for a potential allergy. Patients with a history of irritant or allergic contact dermatitis can develop a progressive sensitization to natural rubber latex components. Subsequent exposure to any latex product can precipitate a hypersensitivity reaction in these individuals. Patients who have undergone multiple surgeries for any reason, particularly beginning in childhood, have likely been repeatedly exposed to natural rub- ber latex and can develop a progressive sensitization. Also, as discussed, persons with an allergy to certain fruits (e.g., banana, avocado) are at an increased risk for latex hypersensitivity. The basis of this cross-reactivity is the structural similarity between the protein-composed enzymes that the rubber tree uses to defend itself against microbial colonization, particularly fungal organisms, and the protein-based enzymes that perform the similar antimicrobial function in these fruit trees/vines [40]. Some dental offices have minimized or stopped the use of any product that contains latex in order to protect patients and staff members. Clinicians who use gloves, rubber dams, or any other product that contains latex should be vigilant about the potential for allergic reactions and should be ready to provide emergency medical treatment, if necessary.
The buccal mucosa and the mucosa of the lateral surface of the tongue are the most frequently involved areas. Partial or complete resolution of oral lichenoid lesions occurs upon removal and replacement of the amalgam (or other triggering substance). Given the extensive number of dental amalgam restorations in the general population, the prevalence of oral lichenoid lesions is extremely low. Therefore, clinicians should not assume that all lesions that develop proximate to an amalgam are hypersensitivity reactions; histopathologic and immunohistologic assays are required for a definitive diagnosis. Oral lichenoid lesions should not be confused with the autoim- mune disorder oral lichen planus. The lesions of oral lichen planus feature delicate white lines that are slightly elevated above the mucosal surface (i.e., Wickham striae). These lesions occur bilaterally, with a predilection for the buccal mucosa, and their formation is not in response to contact with any dental material. Nickel Nickel is a metal with multiple uses in dentistry, as a soft metal (e.g., gold) can be made harder when combined with nickel. The combination of nickel and titanium allows for strength and flexibility, and this alloy is used in endodontic files, non-precious metal crowns and bridges, and cast-metal partial denture frameworks. Despite its widespread use, the American Contact Dermati- tis Society named nickel the contact allergen of the year in 2008, and it is a common cause of allergic contact derma- titis [45]. Nickel allergy is much more common in women (10%) than men (1% to 2%), likely due to sensitization from nickel-containing jewelry [46]. It is extremely rare for a nickel- containing crown or cast-metal partial denture framework to cause an immediate type I hypersensitivity reaction; the usual manifestation is a delayed type IV reaction (specifically, allergic contact dermatitis). The clinical presentation of a nickel allergy can vary depending on the severity and location of the exposure. When a non- precious metal crown extends to or below the gingival level, the adjacent tissue may appear erythematous and may bleed easily during brushing or flossing in hypersensitive patients. The erythema and inflammation cannot be resolved by meticulous hygiene or in-office scaling or root planing. Some patients may experience an itching or burning sensation at the site of the lesion. Patients who wear cast-metal partial denture frameworks may experience an erythematous reaction anywhere the partial denture overlies the oral mucosa. If testing by an allergist or a dermatologist reveals that the patient has a hypersensitivity to nickel or any other metal, the crown, bridge, or partial denture should be replaced with a more compatible prosthesis.
MATERIALS USED IN RESTORATIVE AND PROSTHODONTIC DENTISTRY
Many materials are used to restore carious teeth and replace lost teeth. Most of these materials are biocompatible with the teeth, gingiva, oral mucosa, and bone, so hypersensitivity reac- tions are uncommon and usually manifest as a localized reac- tion in the contiguous tissue. Rarely, a type I hypersensitivity reaction will develop secondary to contact with a restorative or prosthodontic dental material. Dental Amalgam Dental amalgam is an alloy composed of mercury, silver, copper, and other trace metals that has been used to restore carious lesions for more than 150 years [41]. The primary con- troversy associated with dental amalgam has been the release of mercury vapor during mastication, removal of old amalgams, and placement of new amalgams. The U.S. Food and Drug Administration has reviewed extensive scientific research and considers dental amalgam safe for use in adults and children 6 years of age and older, as the mercury exposure from dental amalgam is considerably less than the levels associated with adverse health effects [42]. In the oral soft tissue, the most common hypersensitivity reaction to dental amalgam is a type IV response known as oral lichenoid lesions. These erythematous lesions develop on the oral mucosa in direct contact with an offending material (e.g., dental amalgam, epoxy resins, composite restorations, orthodontic appliances) [43]. It is a T-cell mediated response that develops over time as mercury salts or other ions penetrate through the epithelial lining and incorporate into the surface proteins of the basal keratinocytes [44].
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