Dentist here, after a wisdom tooth was extracted and sterilized, I proceeded to slice the tooth using discs until 0.5 mm thick. Placed the tooth slice between 2 polarizer filters turned aprox 90 degrees to each other backlit with a flash. This effect is called birefringence or double refraction creating a rainbow of colors as the light refracts from the enamel crystals. Shot handheld on Nikon D3500 105mm macro lens at 1/200 sec, f22 and iso 100 and contrast, clarity and vibrancy boosted in post.