Permanent teeth, which are also known as adult teeth, are the second and final set of teeth in the human mouth. There are generally 32 permanent teeth in an adult mouth—16 in the upper jaw and 16 in the lower jaw. The permanent teeth replace the 20 primary teeth, which are also known as baby teeth, milk teeth, or deciduous teeth.
In the mouth, a combination of hard and soft tissue areas form the occlusion (bite). The teeth, along with upper and lower jaw bones, are among the hard tissues. The soft tissue includes the gums, tongue, and salivary glands.
Teeth, both primary and permanent, are used to chew and swallow food. Each tooth is divided into a crown and root. The crown is visible. The root grows below the gum and is attached to the jawbone. A pulp chamber located in the center of the crown houses pulp tissue.
The crown is covered with enamel, the hardest substance in the body. It is 95% calcified (mineralized). Cementum, a thinner material, surrounds a portion of the root.
The shape of the crown determines the purpose of the tooth:
The development of both primary and permanent teeth starts long before these teeth are visible. When a child is born, the primary teeth are partially formed, and development of permanent teeth has started in the jaw bone.
At about the age of six, a child begins losing primary teeth and permanent teeth erupt (appear). The primary teeth fall out (exfoliate) to make room for the permanent teeth to erupt. Generally, girls' teeth develop before boys, and lower teeth grow through the gums before upper teeth. Development of this second set of teeth can sometimes continue into adulthood. A delay in the development process of two years or more could be a symptom of hormonal deficiencies.
TOOTH DEVELOPMENT IN THE UPPER JAW. According to the American Dental Association (ADA), permanent teeth in the upper jaw generally erupt in this order:
| Permanent teeth: development and eruption | ||||
| Hard tissue | Root | |||
| formation | Eruption | completed | ||
| begins | (years) | (years) | ||
| SOURCE: Ash, M.M. Wheeler's Dental Anatomy, Physiology, and Occlusion. 6th ed. Philadelphia: W.B. Saunders Co., 1984. | ||||
| Maxillary | Central incisor | 3–4 mos. | 7–8 | 10 |
| Later incisor | 10 mos. | 8–9 | 11 | |
| Canine | 4–5 mos. | 11–12 | 13–15 | |
| First premolar | 1.5–1.75 yrs. | 10–11 | 12–13 | |
| Second premolar | 2–2.25 yrs. | 10–12 | 12–14 | |
| First molar | at birth | 6–7 | 9–10 | |
| Second molar | 2.5–3 yrs. | 12–13 | 14–16 | |
| Third molar | 7–9 yrs. | 17–21 | 18–25 | |
| Mandibular | Central incisor | 3–4 mos. | 6–7 | 9 |
| Lateral incisor | 3–4 mos. | 7–8 | 10 | |
| Canine | 4–5 mos. | 9–10 | 12–14 | |
| First premolar | 1.75–2 yrs. | 10–12 | 12–13 | |
| Second premolar | 2.25–2.5 yrs. | 11–12 | 13–14 | |
| First molar | at birth | 6–7 | 9–10 | |
| Second molar | 2.5–3 yrs. | 11–13 | 14–15 | |
| Third molar | 8–10 yrs. | 17–21 | 18–25 | |
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Author Info: Liz Swain, The Gale Group Inc., Gale, Detroit, Gale Encyclopedia of Nursing and Allied Health, 2002 |