Permanent teeth
Humans have two successive sets of teeth during life, primary and permanent ones. Permanent teeth are the second set of teeth. There are thirty-two permanent teeth that include four incisors, two canines, four premolars, and six molars in each jaw. (Britannica Online)
Types of Teeth
Incisor teeth are the teeth at the front of the mouth, which are adapted for cutting, tearing and holding. The wide and thin biting portion of an incisor makes a chisel-shaped cutting edge. The upper incisors have a sensitive tactile sense that allows identification of objects in the mouth by nibbling. (Britannica Online)
Canine teeth are found right next to the incisors on each side. The shape of the tooth is pointed and peg like in shape. It also has the function of cutting and tearing food. (Britannica Online)
Premolars and molars have a series of levels that are used for breaking up particles of food. Premolars are found right behind each canine and can cut and grind food. Each premolar consists of two cusps. The molars are used specifically for crushing and grinding, and are found the farthest back in the mouth. Each molar has four or five cusps. The number of roots for each type of tooth differs from one for incisors, canines, and premolars to two or three for molars. (Britannica Online)
Eruption of Permanent Teeth
The mixed dentition stage is when primary and permanent teeth are visible in the mouth at the same time. The permanent teeth begin erupting by the age of six and are fully replaced by the age of thirteen. Within the span of seven years, twenty baby teeth are replaced by twenty-eight permanent teeth. By the age of twenty-one four wisdom teeth will erupt completing the total number of thirty-two permanent teeth. (Simplyteeth)
Formation of Permanent Teeth
Permanent teeth begin to grown underneath primary teeth. Primary teeth roots begin to dissolve making the tooth loose. This process takes three and a half years to completely lose its roots and become replaced. The first part of the permanent tooth to develop is the crown and grows into the space previously occupied by the primary tooth. The permanent tooth root continues to develop. (Simplyteeth)
[edit] References
- Ash, Major M. and Stanley J. Nelson, 2003. Wheeler’s Dental Anatomy, Physiology, and Occlusion. 8th edition.
tooth. (2009). In Encyclopædia Britannica. Retrieved November 05, 2009, from Encyclopædia Britannica Online: http://www.britannica.com/EBchecked/topic/599469/tooth
The Eruption of Permanent Teeth. (2004). Simplyteeth Limited. Retrieved November 05, 2009, from Simplyteeth.com: http://www.simplyteeth.com/sitemap/index.html
