Characterization of foreign body materials in oral and maxillofacial biopsies using FT-IR spectroscopy
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Foreign materials in tissue sections are common findings in routine Oral and Maxillofacial Pathology practice. Most foreign materials in tissue sections in this study were localized to sites where biomaterials had been placed previously for therapeutic purposes. These foreign particles were easily identified under light microscopy on hematoxylin & eosin (H&E) stained, 5&mgr;m thick sections of fixed, paraffin embedded tissue as a reliable diagnostic modality for localizing foreign materials. It is also possible in some cases to localize but not accurately identify these particles based on pattern recognition gained over years of experience. Improved methodology is required for accurate and reliable foreign matter diagnosis, a complicated process because of the vast number of potential foreign bodies that can find their way into oral tissues. In addition, the list of available biomaterials is increasing rapidly with the advancing field of materials science. This study evaluated Fourier Transform Infrared (FTIR) spectroscopy as a diagnostic tool for characterizing foreign materials in oral and maxillofacial biopsies. A pilot study first compared spectral and visual similarities/differences between unstained (both paraffinized and non-paraffinized) and stained (hematoxylin and eosin) 5&mgr;m thick sections. Although close spectral resemblance was found between de-paraffinized, unstained sections and de-paraffinized, H&E stained sections, there was greater visual advantage in using de-paraffinized, H&E stained sections. New sections prepared for experimentation in this study were 5&mgr;m thick, hematoxylin and eosin stained and mounted on special silver coated (low-e) glass slides. The light microscope function of the FTIR microspectroscope unit was utilized to localize the foreign material of interest. Thereafter, each case was FTIR analyzed for covalently bonded material compositions by obtaining three spectra (background, sample and ratio) from an average of 100 spectra, using an analytical area of 100 &mgr;m x 100 &mgr;m. FTIR spectra were analyzed using IR energy ranging from 600/700-4000 cm-1 in transmission mode. Secondary analysis by Energy Dispersive X-Ray Spectroscopy (EDS) was employed to obtain elemental information and was used in conjunction with the FTIR spectra to arrive at additional conclusions regarding foreign material chemistry. Six selected cases were evaluated in greater detail, supplemented by additional literature review. These foreign materials were identified: 1) Canal sealing material, most consistent with commercial product AH 26; 2) Consistent with polysulfone-based impression material; 3) Oxidized iron fragments; 4) Oxidized endodontic silver point; 5) Obturant material with Bi and Ba compounds as filler particles and 6) Chromic acid tanned catgut suture material. FTIR spectral and EDS analyses provided unique chemical information about material composition, not available by light microscopic evaluation only. These results provide convincing evidence that applications of these techniques can be cost effective, time efficient, diagnostically specific and technically feasible.