Introduction
Metal allergies can cause inflammatory conditions affecting the skin and mucous membranes, often complicating diagnoses when associated with dental prostheses. Differentiating between allergic reactions to dental metals and other inflammatory lesions, such as oral lichen planus, can be difficult in the oral cavity. Oral lichen planus is a chronic inflammatory condition with multiple possible etiologies, including autoimmune responses, infections, medications, and, in some cases, metal allergies.
Previous studies have reported an association between dental metal restorations and oral lichen planus, leading to the recommendation of metal removal as a treatment option.1 However, the persistence of symptoms following metal removal suggests that other pathologies, such as oral lichen planus, may play a more significant role.2 This case report presents a patient with persistent oral lesions initially attributed to metal allergies, where treatment targeting the suspected allergy was unsuccessful, ultimately revealing oral lichen planus as the primary diagnosis.
Patients and Methods
Patient Information
A 55-year-old female patient presented with redness and pain in the buccal gingiva near the right mandibular first molar (#46). Her medical history included atrophic gastritis, and she had a known metal allergy. The patient had no previous history of oral lichen planus. The patient’s family history was unremarkable.
Present Illness
The patient was referred to our department from a dermatology clinic specializing in allergies and presented with symptoms suggestive of a metal allergy, including redness and lace-like white patches on the buccal gingiva adjacent to tooth #46. Redness and lace-like white patches were observed on the buccal gingiva near tooth #46, accompanied by pain and inflammation (Figure 1).
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Figure 1 Redness and lace-like white patches on the buccal gingiva near tooth #46, with associated pain and inflammation.
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Clinical Findings
Upon intraoral examination, full-cast crowns were identified on teeth #16, #17, #26, #27, #36, #37, #46, and #47, whereas partial-cast crowns were found on teeth #24, #25, #34, and #35 using the FDI two-digit tooth numbering system.3 Tooth #45 was restored with a composite resin, and the remaining teeth were natural (Figure 2). No extra-oral abnormalities were observed.
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Figure 2 Full cast crowns on teeth #16, #17, #26, #27, #36, #37, #46, and #47, and partial cast crowns on teeth #24, #25, #34, and #35. Composite resin restoration on tooth #45.
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Intraoral Metal Element Analysis
Samples were collected from all intraoral restorations using a silicone point (M3-28, Shofu, Kyoto) and analyzed using an X-ray fluorescence spectrometer (MESA-500W, HORIBA, Kyoto). The analysis detected the presence of Zn and Co in full-cast crowns on teeth #16, #17, #26, #27, #36, #37, #46, and #47, as well as in partially-cast crowns on teeth #24, #25, and #34 (Table 1).
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Table 1 Intraoral Metal Element Analysis of Dental Crowns
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Diagnosis and Treatment
Based on the intraoral metal element analysis, a diagnosis of metal allergy was confirmed.4 In September 2021, the metal crowns were removed and replaced with provisional restorations made of autopolymerizing resin. During the crown removal, suction, gauze, and an extraoral vacuum were employed to prevent exposure to metal fragments. No acute symptoms were observed postoperatively. Full-zirconia ceramic crowns were placed in December 2021. However, redness and pain persisted even eight months after crown placement (Figure 3).
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Figure 3 Persistent redness and pain in the buccal mucosa eight months after zirconia crowns were placed on teeth #46.
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Subsequently, in August 2022, the metal crown of the right mandibular second molar (#47) was removed and replaced with a full zirconia ceramic crown, similar to the approach used for tooth #46 (Figure 4). Despite these interventions, the symptoms did not subside, prompting reconsideration of the initial diagnosis. The patient was referred to the Department of Oral and Maxillofacial Surgery.
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Figure 4 White patches remained on the oral mucosa after the healing of oral lichen planus.
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Further Diagnostic Evaluation and Outcome
In November 2022, a punch biopsy was performed, which confirmed a diagnosis of oral lichen planus through histopathological analysis. Subsequently, the oral surgeon initiated steroid therapy, including dexamethasone 0.1% oral ointment and azunol 4% mouthwash. Regular follow-up (monthly) showed gradual resolution of the mucosal inflammation, and by March 2023, the oral lichen planus had fully healed (Figure 5). The patient was continuously monitored for recurrence.
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Figure 5 Oral cavity overview after the healing of oral lichen planus.
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Results
This case represents an unusual presentation of oral lichen planus that was initially diagnosed as a metal allergy-induced lesion. The removal of dental metals and their replacement with zirconia crowns did not lead to symptom improvement, suggesting that metal allergy was not the sole cause of the patient’s symptoms. Successful resolution following steroid therapy supports the hypothesis that oral lichen planus rather than metal allergy is the primary pathology.
Discussion
Dental metal allergies can manifest in various ways, and management approaches should take into account factors such as mucocutaneous symptoms, the involvement of allergy-positive metals, and individual patient response to the removal of dental metals.5 In this case, despite the detection of allergy-positive metals (Zn and Co), mucosal inflammation persisted following metal removal. This finding underscores the need for a comprehensive approach to diagnosing oral lesions, particularly in patients with complex presentations.6 Differential diagnoses considered included lichenoid contact reaction, systemic lupus erythematosus, and mucous membrane pemphigoid. These were ruled out based on clinical presentation and histopathological features. Oral lichen planus has been linked to various etiologies beyond metal allergies, including bacterial and viral infections, medications, stress, and autoimmune diseases.7 In cases where metal allergy is suspected, but symptoms persist despite the allergen removal, other potential causes, such as oral lichen planus, must be carefully evaluated. In this case, the efficacy of steroid therapy highlights the importance of considering alternative treatments, including immunosuppressants, antiviral medications, and biologics, especially in patients who do not respond to conventional therapies.8
Chronic oral lichen planus can severely impact a patient’s quality of life due to persistent pain and discomfort.9 Therefore, treatment goals should not only focus on symptom relief and recurrence prevention but also on improving the patient’s overall quality of life. Patient education and regular follow-ups are essential components of long-term management.10
Conclusion
This case highlights the need for a multidisciplinary approach to manage oral inflammatory conditions. Prosthodontists and dental practitioners should consider various perspectives and collaborate with other departments when facing persistent oral lesions, particularly when treatments targeting suspected metal allergies fail to yield positive results and desired outcomes. Alternative diagnoses, such as oral lichen planus, should be considered, and appropriate interventions should be implemented to achieve optimal patient care.
Acknowledgments
We would like to express our gratitude to Dr. Kitagawa from the Center of Oral Clinical Examination and Dr. Taguchi from the Department of Oral and Maxillofacial Surgery for their dedicated efforts in managing this condition.
Additionally, the patient provided written informed consent for the publication of this case report, including the use of clinical images. Ethical approval was not required for this case report, as no identifiable personal information is disclosed, and institutional guidelines at Hiroshima University Hospital do not require IRB review for single case reports.
Author Contributions
All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.
Disclosure
The authors report no conflicts of interest in this work.
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