The general arrangement of teeth is referred to as the dentition. Primary dentition refers to the 20 deciduous teeth, often called baby teeth. Secondary dentition refers to the 32 permanent teeth (Figs. 4-1 and 4-2).
The dentition is divided into upper and lower arches. The teeth anchored within the upper jaw belong to the maxillary arch. The mandible is the bone that supports the lower arch of teeth, hence the name mandibular arch.
The mandibular and maxillary arches each compose one half of the dentition. In the permanent dentition of 32 teeth, each arch comprises 16 teeth. How many teeth are in an arch of the primary dentition? How many teeth compose the total primary dentition? Each arch is further divided into a right and a left half, making four quadrants, two in each arch. In the Palmer notation system, the quadrants are determined by the intersection of a vertical and a horizontal line. The maxillary quadrants are represented by numbers or letters above the horizontal line, and the mandibular quadrants are indicated below the line. The technical term for the dividing line between the right and left sides of the body is the midsagittal plane. In dentistry this is called the midline, or median line, of the face. The right and left quadrants are separated by this vertical line, which represents the midline of the skull when facing the patient. Thus each quadrant consists of one fourth of the dentition and has a mirror image on the other side of the arch and an opposing quadrant in the opposite arch.
Note that a permanent dentition quadrant has eight teeth: central and lateral incisor; canine; first and second premolar; and a first, second, and third molar. A deciduous (primary) quadrant has five teeth: two incisors, canine, and first and second molar. No deciduous premolars are evident.
The permanent teeth that replace or succeed the deciduous teeth are called succedaneous teeth. The permanent molars are called nonsuccedaneous teeth. They do not have predecessors, and they do not succeed or replace deciduous teeth. The permanent premolars replace the deciduous molars. How many teeth in the secondary dentition are nonsuccedaneous? How many are in each arch? How many are in each quadrant?
A mixed dentition refers to one that comprises some permanent teeth and some deciduous teeth. After a child’s permanent teeth begin to erupt, several years of mixed dentition follow. Not all the deciduous teeth are replaced at one time. Some adults may also have a mixed dentition; this occurs when a deciduous tooth is retained even though the remainder of the teeth are permanent. If any combination of primary and secondary teeth are in the same dentition, then a mixed dentition is present.
When identifying a specific tooth, list the dentition, arch, quadrant, and tooth name in that order (e.g., permanent [dentition], mandibular [arch], right [quadrant], central incisor [tooth]. Therefore permanent mandibular right central incisor is the correct wording over right mandibular permanent central incisor.
Each dental team should be familiar with the various systems of naming and coding teeth. Although each office may use only one system, the staff should be familiar with all systems so that communication among dental offices is possible. Therefore the most popular systems are discussed here.
The Universal system uses the Arabic numerals 1 through 32 for permanent teeth and the letters A through T for the primary teeth. The number 1 is assigned to the most posterior molar on the upper right, the permanent maxillary right third molar. The highest number is given to the permanent mandibular right third molar (Fig. 4-3). Likewise, the letter A is given to the primary maxillary right second molar, and the letter T to the primary mandibular right second molar (Fig. 4-4).