A 72 years old male complained of gingival ulceration and whitish discoloration on the marginal and attached gingival epithelium of left mandibular premolar and molar area, where a porcelain-fused metal (PFM) crown and an ill-fitting gold crown were applied for 10 years, respectively. Recently he had a cancer phobia due to this whitish lesion unhealed even after intensive anti-inflammatory and antibiotic treatment. In the pathological examination the epithelium was hyperkeratotic and acanthomatous with severe inflammatory reaction, and subsequently its basement membrane was distorted and the intercellular spaces between keratinocytes were widened. Particularly, the nuclei of keratinocytes were elongated in the same direction towards the electric current between the dissimilar metallic crowns of PFM gold. In the immunohistochemistry KL1, β-catenin, and S-100 were strongly positive in the epithelium, but consistently weak for TNFα, HSP-70, and β-defensin-1, -2, -3. On the other hand, PCNA, p53, E-cadherin, and pAKT were rarely positive for the epithelium. Interestingly, the hyperkeratinized and inflamed epithelium was strongly positive for a calcium binding protein (S-100), while it showed almost reduced expression of protective molecules (HSP-70, β-defensin-1, -2, -3, and pAKT). Therefore, it was presumed that this localized lichenoid gingivitis was caused by the galvanic current phenomenon with lower cellular and immunological responses contrary to the ordinary oral lichen planus and leukoplakia

Ⅰ. Introduction
 Ⅱ. Case report
 Ⅲ. Discussion
 Ⅳ. References

• 김연숙(Department of Dental Hygiene, College of Health Sciences, Cheongju University) | Yeon Sook Kim
• 유제인(Department of Oral Pathology, College of Dentistry, Gangneung-Wonju National University) | Je In Yoo
• 이석근(Department of Oral Pathology, College of Dentistry, Gangneung-Wonju National University) | Suk Keun Lee correspondence