The upper jaw, known as the maxillary arch, contains teeth essential for the initial mechanical breakdown of food. Understanding the standard count provides a baseline for recognizing a healthy, complete set of permanent teeth. This information clarifies the typical number of teeth in the upper arch and explores the various roles and reasons for common variations.
The Standard Adult Upper Arch Count
The typical, complete set of teeth in a healthy adult mouth includes 32 permanent teeth, evenly divided between the upper and lower arches. The standard number of teeth in the upper jaw is 16, provided all third molars (wisdom teeth) have erupted. These 16 teeth are arranged symmetrically across the arch, with eight teeth on the left side and eight on the right side.
The upper arch contains four distinct categories of teeth. At the front are four incisors, followed by two canines. Moving further back, there are four premolars (bicuspids), and finally six molars, which include the first, second, and third molars on each side.
Functions of the Upper Teeth
Each type of tooth in the maxillary arch has a specialized shape that determines its function. The four incisors, positioned at the very front, have sharp, flat edges designed primarily for biting and cutting food. They are the first teeth to make contact with food, cleanly separating pieces from a larger item.
The canines, located immediately beside the incisors, are notably pointed and are used for tearing and gripping food. Their robust, single root helps them withstand the heavy forces involved in shearing tougher foods. Behind the canines are the four premolars, which feature a transitional shape, possessing two cusps. They engage in both tearing and crushing food, acting as an intermediary between the front and back teeth. The six molars, the largest teeth, are situated furthest back and have broad, flat surfaces with multiple cusps. Their purpose is the extensive grinding and crushing of food, preparing it for swallowing and digestion.
Common Reasons for Variation in Number
It is common for an adult to have fewer than the standard 16 teeth in the upper arch. The most frequent reason for a lower count is the surgical removal of the third molars, or wisdom teeth. These teeth are often extracted due to impaction, crowding, or pain, which reduces the upper count from 16 to 14. Variations can also be due to orthodontic treatment, where premolars are sometimes removed to create space and alleviate crowding.
Beyond surgical removal, some people are born with hypodontia, which is the congenital absence of one or more permanent teeth. Conversely, a person may have a higher count due to hyperdontia, characterized by the presence of extra teeth, known as supernumerary teeth. These supernumerary teeth are most commonly found in the upper jaw. They can cause issues like crowding and displacement of other teeth, often requiring professional removal. Both hypodontia and hyperdontia are often linked to genetic factors affecting tooth formation.
The Upper Arch in Childhood
The count in the upper arch is different during childhood when primary teeth are present. A child’s upper jaw typically contains a total of 10 primary teeth. This temporary set includes four incisors, two canines, and four molars.
A distinct difference from the adult arch is the complete absence of premolars in the primary dentition. The primary molars serve the function of grinding food until they are naturally lost. The eruption of these upper primary teeth usually begins around six months of age and replacement by permanent teeth typically starts around age six.