Animal studies and fewer human studies have shown that NaChs change their expression and distribution after nerve and inflammatory lesions, and these changes are implicated in the generation of pain states. We are using the extracted human tooth as a model system to further evaluate NaCh expression in normal and painful samples. In qualitative pilot studies we noted significant changes in the pattern of NaCh expression in painful teeth, particularly with respect to small axonal NaCh clusters (accumulations), as well as the general expression level on nerve fibers. Here, we quantitatively compare NaCh expression found in nerves from extracted normal wisdom teeth and diseased molar teeth with severe, spontaneous pain and large carious lesions. Pulpal nerve sections from normal and diseased samples (n=10 of each) were double-labeled for indirect immunofluorescence with a pan-specific antibody that identifies all NaCh isoforms, and an anti-caspr antibody to visualize nodes of Ranvier. A z-series of optical sections were obtained with a confocal microscope. Each optical section image was analyzed using ImageJ software to determine; 1) overall NaCh immunofluorescence intensity in nerve fibers, and 2) the total number of NaCh accumulations that had four or more contiguous pixels of maximum intensity. Quantitative analysis showed both a significant increase in the intensity of overall fiber staining, and a greater variability in density of large/brightly stained accumulations in painful samples when compared to normals. This variability in painful samples included a subpopulation with high NaCh density, and another with low density presumably secondary to necrosis. All painful samples included the presence of NaCh accumulations at altered caspr sites, most likely involving the remodeling of NaChs at demyelinated sites. This study demonstrates a plasticity in the expression of and a remodeling of NaChs in painful human nerve samples. Support: NIDCR (DE-015576). Animal studies and fewer human studies have shown that NaChs change their expression and distribution after nerve and inflammatory lesions, and these changes are implicated in the generation of pain states. We are using the extracted human tooth as a model system to further evaluate NaCh expression in normal and painful samples. In qualitative pilot studies we noted significant changes in the pattern of NaCh expression in painful teeth, particularly with respect to small axonal NaCh clusters (accumulations), as well as the general expression level on nerve fibers. Here, we quantitatively compare NaCh expression found in nerves from extracted normal wisdom teeth and diseased molar teeth with severe, spontaneous pain and large carious lesions. Pulpal nerve sections from normal and diseased samples (n=10 of each) were double-labeled for indirect immunofluorescence with a pan-specific antibody that identifies all NaCh isoforms, and an anti-caspr antibody to visualize nodes of Ranvier. A z-series of optical sections were obtained with a confocal microscope. Each optical section image was analyzed using ImageJ software to determine; 1) overall NaCh immunofluorescence intensity in nerve fibers, and 2) the total number of NaCh accumulations that had four or more contiguous pixels of maximum intensity. Quantitative analysis showed both a significant increase in the intensity of overall fiber staining, and a greater variability in density of large/brightly stained accumulations in painful samples when compared to normals. This variability in painful samples included a subpopulation with high NaCh density, and another with low density presumably secondary to necrosis. All painful samples included the presence of NaCh accumulations at altered caspr sites, most likely involving the remodeling of NaChs at demyelinated sites. This study demonstrates a plasticity in the expression of and a remodeling of NaChs in painful human nerve samples. Support: NIDCR (DE-015576).