The oral mucosa is a component of the oral ecosystem, which can be aggressed by corrosion products released from the dental alloys used in prosthetic dentistry therapy. The purpose of this study was to compare the in vivo effect of nickel and copper compounds on the oral mucosa cells, including their ability to induce cell death, by analyzing the cytochrome c (cyt. c) immunohistochemical expression. Gingival mucosa fragments obtained from the subjects with dentures manufactured by nickel or copper casting alloys were processed through the histological technique of paraffin inclusion. The sections obtained were stained by usually histological methods in order to highlight the histopathological lesions and also analyzed using the immunohistochemical technique in order to study the cyt. c expression. The papillomatosis lesions were observed in the gingival mucosa fragments obtained from the subjects with nickel-based alloy dentures and the condyloma acuminata lesions were observed in those obtained from the subjects with copper-based alloy dentures. The cyt. c immunohistochemical expression was different in the epithelial layer of two types of mucosal fragments but it was the same in their lamina propria connective tissue. We can conclude that the two types of metal alloys have different effects on the adjacent gingival mucosa.