Diameter of dentinal tubules ranges from 2.5 microns to 0.5 microns. It's measurements with optical microscope is a very tough task, results could be unreliable. The best resolution for optical microscope is 0.2 microns, achievable only with immersion oil and good microscope. I never tried to observe dentin with immersion oil, so I cannot give a detailed advice. By all means, try to use SEM. In any case you need polished sections. Contrast will be much better if you impregnate your specimens with a resin (such as PMMA) before polishing.

Vladimir Dusevich thanks . i have lieca research microscope at my institution .trying oil immersion ,under bright field and phase contrast microscope for dentinal tubules .SEM would be very expensive as the sample size is 250 samples. . this is my hypothesis

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