It's also possible that you have the correct application on your PC, but .afp files aren't yet associated with it. In this case, when you try to open a .afp file, you can tell Windows which application is the correct one for that file. From then on, opening a .afp file will open the correct application.
Dentin is found underneath the enamel surface of the tooth and underneath the cementum that forms along a tooth's roots. Made of living cellular material and tissue, dentin is what makes up the majority of a tooth's structure. Dentin is a bone-like substance that contains microscopic tubules. Unlike enamel, exposed dentin is highly susceptible to the bacteria that cause dental cavities and can cause tooth sensitivity. Cementum.
Cavities: Holes or structural damage in the two outer layers of a tooth called the enamel and the dentin. The enamel is the outermost white hard surface and the dentin is the yellow layer just beneath enamel. Both layers serve to protect the inner living tooth tissue called the pulp, where blood vessels and nerves reside. Cavities are caused by bacteria in the mouth. Small cavities may not cause pain, and may be unnoticed by the patient. Larger cavities can collect food, and the inner pulp of the affected tooth can become irritated by bacterial toxins, foods that are cold, hot, sour, or sweet - causing toothache.