Teeth

Teeth (singular tooth) are small, calcified, whitish structures found in the jaws (or mouths) of many vertebrates that are

used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The

roots of teeth are embedded in the Mandible bone or the Maxillary bone and are covered by gums. Teeth are made of multiple

tissues of varying density and hardness.

Teeth are among the most distinctive (and long-lasting) features of mammal species. Paleontologists use teeth to identify

fossil species and determine their relationships. The shape of an animal's teeth are related to its diet. For example, plant

matter is hard to digest, so herbivores have many molars for chewing and grinding. Carnivores, on the other hand, need

canines to kill prey and to tear meat.

Mammals are diphyodont, meaning that they develop two sets of teeth. In humans, the first set (also called the "baby",

"milk", "primary", and "deciduous" set) normally starts to appear at about six months of age, although some babies are born

with one or more visible teeth, known as neonatal teeth. Normal tooth eruption at about six months is known as teething and

can be painful.

Some animals develop only one set of teeth (monophyodont) while others develop many sets (polyphyodont). Sharks, for example,

grow a new set of teeth every two weeks to replace worn teeth. Rodent incisors grow and wear away continually through

gnawing, which helps maintain relatively constant length. The industry of the beaver is due in part to this qualification.

Many rodents such as voles (but not mice) and guinea pigs, as well as rabbits, have continuously growing molars in addition

to incisors.

Anatomy

Dental anatomy is a field of anatomy dedicated to the study of tooth structure. The development, appearance, and

classification of teeth fall within its field of study, though dental occlusion, or contact among teeth, does not. Dental

anatomy is also a taxonomic science as it is concerned with the naming of teeth and their structures. This information serves

a practical purpose for dentists, enabling them to easily identify teeth and structures during treatment.

The anatomic crown of a tooth is the area covered in enamel above the cementoenamel junction (CEJ). The majority of the crown

is composed of dentin (dentine in British English) with the pulp chamber in the center. The crown is within bone before

eruption. After eruption, it is almost always visible. The anatomic root is found below the CEJ and is covered with cementum.

As with the crown, dentin composes most of the root, which normally have pulp canals. A tooth may have multiple roots or just

one root (single-rooted teeth). Canines and most premolars, except for maxillary first premolars, usually have one root.

Maxillary first premolars and mandibular molars usually have two roots. Maxillary molars usually have three roots. Additional

roots are referred to as supernumerary roots.

Humans usually have 20 primary teeth and 32 permanent teeth. Among primary teeth, ten are found in the maxilla and the rest

in the mandible. Teeth are classified as incisors, canines, premolars and molars, the dental formula being: Upper: 2.1.2.3,

lower: 2.1.2.3. In the primary set of teeth, there are two types of incisors - centrals and laterals - and two types of

molars - first and second. All primary teeth are replaced with permanent counterparts. Among permanent teeth, 16 are found in

the maxilla & the other 16 are in the mandible. The maxillary teeth are the maxillary central incisor, maxillary lateral

incisor, maxillary canine, maxillary first premolar, maxillary second premolar, maxillary first molar, maxillary second

molar, and maxillary third molar. The mandibular teeth are the mandibular central incisor, mandibular lateral incisor,

mandibular canine, mandibular first premolar, mandibular second premolar, mandibular first molar, mandibular second molar,

and mandibular third molar. Third molars are commonly called "wisdom teeth" and may never erupt into the mouth or form at

all. If any additional teeth form, for example, fourth and fifth molars, which are rare, they are referred to as

supernumerary teeth.

Most teeth have identifiable features that distinguish them from others. There are several different notation systems to

refer to a specific tooth. The three most common systems are the FDI World Dental Federation notation, the universal

numbering system, and Palmer notation method. The FDI system is used worldwide, and the universal is used widely in the

United States.

The bottom teeth are used more for the grinding of food and the top front teeth are mainly used for biting.

Zahnaufhellung

Bleaching