Skin certainly isn't the best medium for a tooth impression. Odontologists face some problems in making comparisons between known and unknown specimens of bites, in part because skin is elastic and is generally distorted when bitten. Patterns can be hard to identify Bite marks can be made with varying degrees of force, on different types of skin and on various parts of the body. Between the beginning and end of a bite, the teeth may slide on the skin, altering the impression by broadening the bite mark. All this adds to the pattern's variability.
Teeth have unique characteristics.
An expert can usually identify a bite mark by looking at the patterns made by a whole, or partial, set of teeth, and those made by individual teeth within the set. The whole or partial sets form an arc that follows the curvature of the upper and lower jaw. Photos taken at certain angles can distort the appearance of the bite, so the picture should be shot with the camera perpendicular to the mark. Molds of a suspect's dental impressions are made and then compared to photo images of the bite mark. There are several ways to do this, including the use of transparent overlays and computer image analysis.