ImageJ analysis of dentin tubule distribution in human teeth

• Dentin tubules in human incisors and molars were observed by light-microscopy.
• Distance-intervals of dentin tubules in incisor and molar were measured and compared.
• Dentin tubules in molars displayed a greater density than that observed in incisors.
• Numerical data is measured by combining routine histology and photomicroscopy with ImageJ.

Mapping the distribution of dentin tubules is vital to understanding the structure–function relationship of dentin, an important indicator of tooth stability. This study compared the distances between and density of tubules in the external dentin located in the crown region of an adult human incisor and molar to determine if analysis could be conducted using light-level microscopy. Teeth were processed for routine histology, cut in cross-section, images captured using Advanced SPOT Program, and microstructure was analyzed using ImageJ (NIH). Intratubular (peritubular) dentin with or without odontoblast processes were observed and although incisor and molar images appeared visually similar, plot profile graphs differed. Distance-intervals between tubules in the incisor (5.45–7.67 μm) had an overall range of 2.22 μm and in the molar (7.43–8.42 μm) an overall range of 0.99 μm. While molar tubule distribution displayed a tighter overall range, there was a smaller distance between most incisor tubules. The average densities observed in incisors were 15,500 tubules/mm2, compared with 20,100 tubules/mm2 in molars. ImageJ analysis of prepared histology microscopic slides provides researchers with a rapid, inexpensive assessment tool when compared with advanced/ultrastructural methodologies. By combining routine histological processing and light microscopic observations followed by ImageJ analysis, tooth structure can be converted into numerical data and easily mastered by laboratory personnel.