It is rare to find a full set of teeth in which every tooth met all the anatomic criteria of what a perfect tooth should be; too much variation occurs among individual teeth. When studying tooth identification, it is important to remember the extreme amounts of variation possible. The individual tooth you are trying to identify may meet most of the criteria of a maxillary central incisor, may be missing certain criteria for a maxillary central incisor, and may even meet some of the criteria of a maxillary canine or lateral incisor, yet it may still be a maxillary central incisor. Only after compiling all of the characteristics of the tooth in question and categorizing these characteristics can the individual tooth be identified—and then only after it becomes apparent that the tooth meets more characteristics of one type of tooth than another.
Following is a description of general characteristics of each of the teeth by their respective groupings: incisors, canines, premolars, and molars.* In identifying teeth, it is necessary to be able to differentiate among the left and right teeth in any particular group.
4. Mandibular anterior teeth tend to wear on their labial incisal edges, whereas maxillary teeth wear on their lingual incisal edges. Unless a person has a class III occlusion, the maxillary teeth are facial to the mandibular teeth.
5. Permanent molars are generally smaller in height and have fewer cusps the more posteriorly they are positioned. For example, the permanent first molar usually has five cusps and is larger than a second or third molar. A mandibular first molar has a distal cusp on its facial surface, and a maxillary first molar has a cusp of Carabelli. The second and third molars are less likely to have these cusps; however, when they do, cusps are less well developed and are more like tubercles than cusps.
6. Permanent molars tend to have more secondary and tertiary anatomy the more posterior they are positioned. Secondary anatomy consists of extra grooves and pits in addition to the main primary developmental anatomy. These grooves and pits are more shallow than the primary anatomy and are more likely to be found on second and third molars. Tertiary anatomy refers to the extremely shallow and even more numerous grooves, pits and lines that third molars often have, giving them a more wrinkled appearance than first or second molars.
7. The roots of molars tend to be shorter and closer together the more posterior the molars are positioned, and the roots are often fused into one. First molars have the widest and longest roots of all molars.
8. The more posterior the molars are positioned, then the more variation of the anatomy is evident. Third molars are more wrinkled and unpredictable in shape than second or first molars; they could have six cusps or one single conical cusp. They are also more likely to be congenitally missing than other molars.