All people have two sets of teeth. The primary dentition, (sometimes called "baby teeth" or deciduous teeth) consists of 20 teeth that are eventually lost or exfoliated. They are replaced with a permanent dentition, which starts to erupt around six years of age. There are 32 teeth in the permanent dentition.
The teeth are arranged in a semi-circle (arches) in the mouth both on the top (maxillary) and bottom (mandibular) jaws (arches). The top teeth are referred to as maxillary teeth and the bottom teeth are referred to as mandibular teeth. Both arches have 18 teeth, although some adults may never have had all of their teeth erupt or they may be missing some permanent teeth. A prime example of this is the wisdom teeth (third molars). Many adults have them, but they never erupt into the oral cavity.
In addition, the maxillary and mandibular teeth are divided into quadrants. There are four quadrants in the oral cavity. There are two quadrants in the maxilla, and two quadrants in the mandible. The quadrants are divided by a midline at the center of the mouth.
Another distinguishing factor is the teeth in the front of the mouth nearest the lips are referred to as anterior teeth. The posterior teeth are the ones nearest the throat.
When biting the teeth together, we can see the relationship between the maxillary and mandibular teeth. This is referred to as the occlusion. This relationship is one of the determining factors in recommending orthodontics (braces) to correct abnormalities concerning the way the arches come together.
The teeth are recognized by name and either a number (permanent dentition) or letter (primary dentition).
The incisors are the front teeth in the mouth and are responsible for biting and cutting food. There are four incisors in each arch. The two at the midline are referred to as central incisors. The ones next to the central incisors, are referred to as lateral incisors. The canines, form the corners of the mouth and tear the food. There are four total canines (two in each arch). The premolars, which are also referred to as bicuspids, help to crush and chew food. There are four premolars, in each arch (two per quadrant) for a total of eight premolars. The premolars next to the canines are called first premolars and the ones behind the first premolars are the second premolars. The most posterior teeth in the oral cavity are the molars. These teeth grind our food. There are three molars in each quadrant for a total of 12 molars. They are called the first, second and third molars. The third molar is often referred to as a "wisdom tooth."
Directional descriptions are useful in reference to areas of the oral cavity. One directional description is the surfaces of the teeth that are on the tongue side. These are called lingual surfaces. The surfaces on the cheek side are called facial or buccal surfaces. Sometimes, in the anterior area near the lips, the term labial is used instead of the term facial. The surface next to the lips is the labial. We describe the surfaces that are toward the midline as mesial and away from the midline as distal. The chewing surfaces of the posterior teeth are referred to as the occlusal surfaces. The biting edges of the anterior teeth are known as the incisal edges. Also, as we look at certain areas of the oral cavity, we can refer to these surfaces with the following terminology. Interproximal refers to the area between two teeth. This area usually is not visible by directly looking at the area. The area referred to as proximal is the area near the interproximal surface that you can see in the oral cavity.
As we look in Mr. Smith’s mouth, we see that he has 31 teeth. Three of his third molars are present, but we do not see his maxillary right third molar.
Jamie to Mr. Smith: "Mr. Smith, as I was recording which teeth you have present, I see that you are missing your upper right wisdom tooth. Did you have it extracted?"
Mr. Smith to Jamie: "No, it just never came in."
Jamie to Mr. Smith: "OK, I will make a note and when the dentist does your dental examination, he may want to have an x-ray taken of that area to determine if it is present and possibly impacted."