The human mouth contains teeth, each with a specific role in speaking and eating. Understanding their location and types provides insight into oral anatomy and how dental professionals identify them, which is foundational for dental care.
The Basic Layout of Your Mouth
Teeth are organized within two dental arches: the upper (maxillary) and the lower (mandibular). The upper arch is fixed, while the lower arch is movable due to the temporomandibular joint. Dentists divide the mouth into four quadrants: upper right, upper left, lower right, and lower left, formed by an imaginary line between the central incisors in each arch.
Humans develop two sets of teeth. Children have 20 primary, or “baby,” teeth, which erupt around six months of age and are present by age three. These primary teeth eventually fall out, making way for the permanent teeth. Adults have 32 permanent teeth, which finish erupting by 21 years of age.
Identifying Different Tooth Types
The 32 permanent teeth in adults consist of four distinct types, each with a specialized shape and function. Incisors are the eight sharp, flat teeth positioned at the front of the mouth, four in the upper jaw and four in the lower jaw, used for biting and cutting food. Canines, located next to the incisors, are pointed teeth for tearing food, with two in the upper arch and two in the lower arch. These teeth are also called cuspids.
Behind the canines are the premolars, also known as bicuspids, which are larger and have ridges to chew and grind food. Adults have eight premolars, two on each side of both the upper and lower jaws. The molars are the largest teeth, found at the back of the mouth, featuring broad, flat surfaces with multiple cusps for grinding food into pieces before swallowing. There are twelve molars in the permanent dentition, including four wisdom teeth, or third molars, which are the last to emerge between ages 17 and 21. Children’s primary dentition includes eight incisors, four canines, and eight molars, but no premolars or third molars.
How Dentists Pinpoint Each Tooth
Dental professionals use numbering systems to identify each tooth, facilitating clear communication and accurate record-keeping. The Universal Numbering System, used in the United States, assigns a number to each permanent tooth from 1 to 32. Numbering begins with tooth #1, the upper right third molar, and proceeds clockwise around the upper arch to the upper left third molar (#16), then drops to the lower left third molar (#17), continuing to the lower right third molar (#32). For primary teeth, this system uses uppercase letters A through T, starting with the upper right second molar as ‘A’ and following a similar clockwise sequence.
The FDI World Dental Federation Notation, an international standard, employs a two-digit system for tooth identification. The first digit indicates the quadrant: 1 for the upper right, 2 for the upper left, 3 for the lower left, and 4 for the lower right in permanent dentition. The second digit specifies the tooth’s position within that quadrant, numbering from 1 (central incisor) to 8 (third molar). For primary teeth in the FDI system, quadrants are numbered 5 through 8, followed by a second digit from 1 to 5.
Another system, Palmer Notation, is used in the United Kingdom and utilizes a quadrant symbol alongside a number or letter. Adult teeth are numbered 1 to 8, starting from the central incisor in each quadrant, while primary teeth are designated by letters A to E. This method visually represents the tooth’s quadrant and its position from the midline.