Detection and Chemical State Analysis of Trace Elements Contained in the Oral Lichen Planus and Oral Lichenoid Lesion Using Quantum Beams

Oral lichen planus (OLP) is common inflammatory lesions in oral mucosa. These are characterized by interlacing white lines clinically, and three classic features histopathologically; overlying keratinization, band-like layer of chronic inflammatory cells within the underlying connective tissue and liquefaction degeneration of the basal cell zone. The cause of OLP is unknown. On the other hand, there are various lesions resembling OLP clinically and histopathologically. These lesions are usually referred to as oral lichenoid lesion, which encompass several clinical type; (1) Oral lichenoid contact lesions (OLCL) as a result of allergic contact stomatitis, (2) Oral lichenoid drug reactions (OLDR) which occur owing to certain medication, (3) Oral lichenoid lesions of graft-versus-host disease (OLL-GVHD), and so on. Clinical and pathological findings of OLP and OLCL are quite similar, so OLCL is difficult to distinguish from OLP and their diagnostic criteria are not accurately established. The relationship between OLCL and metal allergy has been suggested, in Japan, most of OLP patients with metallic restorations are diagnosed as OLP not OLCL by the reason of no direct contact between diseased area and metals. Patch test is widely used for the metal allergen diagnosis, but its reliability is not high. The frequency of these diseases is relatively high and these involve some risk for malignant transformation. Therefore, the establishment of diagnostic criteria of OLCL with trace metallic elements detection is required. However, there is no information about the concentration and distribution of metallic elements in OLP and OLCL. The purpose of this study is to detect the metallic elements derived from the restorations contained in the OLP and OLCL and reveal their influence to the lesions using highly sensitive analysis methods, such as synchrotron radiation excited X-ray fluorescence analysis (SR-XRF), particle induced X-ray emission (PIXE) and X-ray absorption fine structure (XAFS).

Twelve paraffin embedded samples were collected, consisted five OLPs, six OLCLs and one normal sample as control. These were sliced in 8μm-thickness and placed over the dedicated film. Elemental distribution analyses were carried using SR-XRF and PIXE, and chemical state of detected metallic elements were estimated using XAFS. These elemental distributions were compared with histopathological H-E staining images. SR-XRF analysis was carried at BL-4A of KEK-PF (Tsukuba, Japan), PIXE analysis at National Institute of Radiological Science (Chiba, Japan) and XAFS analysis at BL-4A and PF-AR NW10A of KEK-PF. This study was carried out with the permission of the Ethical Committee of the Jichi Medical University Hospital and Nihon University School of Dentistry Dental Hospital.

In OLCL specimens, the metallic elements, e.g. Ag, Ni, Cr and Cu, were clearly detected and those were localized in the limited regions of specimens. Those elements are the major component of dental alloys. With XAFS analyses, Ag was existed as the sulfide and Ni, Cr and Cu were existed in the ionic condition. Therefore, the eroded ions accumulation from the metallic restorations into OLCL lesions was suggested. In contrast, no localization of metallic elements was detected in OLP and control specimens.

In this study, we succeeded to detect the accumulated metallic elements into OLCL lesions derived from the erosion of the metallic restorations. OLP showed no significant accumulation of such metallic elements. This is the first report to indicate the direct effect of the erosion of the metallic restorations to the mucosal lesions. From above results, the differentiation of OLCL from OLP would be possible with the analysis of trace metallic analysis in the lesions.

References

van der Meij EH, et al. Oral Oncol 43: 742, 2007.

Al-Hashimi, et al. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 103: S25.e1, 2007.