Contact X-ray microradiography is the current gold standard for measuring mineral densities of partially demineralized tooth specimens. The X-ray sensitive film specified in the last J Res NIST publication on the subject is no longer commercially available. Objectives: develop a new microradiographic method by identifying a commercially available film with greater than 3000 lines/mm resolution, which is sensitive to X-ray, and develop correct film processing for X-ray microradiographic application. Methods: a holographic film was identified as a potential replacement film. Proper exposure was determined utilizing a thick nickel plate to create test-strips. Film development was bracketed around manufacturer suggestions. Film linearity was determined with aluminum step-wedges. Microradiographs of 100μm thick tooth sections, before and after acidic challenges, were a final test for film. Magnified images were captured with a digital microscope camera with 0.305 μm/pixel resolution. Results: Appropriate film exposure was 30 minutes at 80kV¬p and 3mA with a development time of 2 minutes. Step-wedge experiments show the system to be linear between (10% - 90%) grey-scale values (r2 =0.997) which encompasses the full exposure region of tooth tissue. Enamel sections were analyzed and show distinctive differences between erosion and demineralization. Spatial measurement standard error (S.E. = 0.193 μm) indicates that the image capture device resolution of 0.305 μm/pixel limits the system resolution. Conclusion: Use of the identified holographic film when combined with appropriate processing modifications is a significant improvement for use in the X-ray microradiographic method. Further improvements include the use of a higher resolution digital capture device. The method is appropriate for quantitatively measuring changes in mineral density and erosion.
Citation: Journal of Research of the National Institute of Standards and Technology
Pub Type: Journals
Enamel, dentin, x-ray microradiography, mineral density, caries