Information AboutTeeth |
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Types of teeth
Teeth (singular: '''tooth''') are structures found in the Jaw s of many Vertebrate s. They have various structures to allow them to fulfill their many different purposes. The primary function of teeth is to tear and chew Food and in some animals, particularly Carnivore s, as a weapon. The roots of the teeth are covered by Gum s. Teeth are covered by a protective structure, called the Enamel , that helps to prevent cavities on the teeth. Adult teeth naturally darken as the person matures, the Pulp within the tooth shrinks and Dentin is deposited in its place. The form teeth take and their mode of development in a species is called the species' Dentition . Dentists sometimes refer to the inner surface of teeth as the ''lingual'' surface (meaning towards the Tongue ), and the outer surface as the ''labial'' surface (meaning towards the Lips ) or "buccal" (meaning towards the cheek). Other terms are ''mesial'' (toward the midline), ''distal'' (away from the midline), ''occlusal'' (the top surface), ''incisal'' (the cutting surface), "gingival" (toward the gumline), and "pulpal" (toward the center). Types of tissue in teeth '' In Human s ''
'' In Aardvark s''
Teeth are among the most distinctive features of different Mammal species, and one that Fossilizes well. Paleontologists use them to identify Fossil species and, often, their relationships. The shape of the teeth is related to the animal's diet, as well as its Evolutionary descent. For example, plant matter is hard to digest, so Herbivore s have many molars for Chewing . Carnivore s need canines to kill and tear and since meat is easy to digest, they can swallow without the need for molars to chew the food well. While humans only have two sets of teeth, some animals have many more: Shark s grow a new set of teeth every two weeks. Some other animals grow just one set. Rodent teeth grow and wear away continually through the animal's gnawing, maintaining constant length. HUMAN TEETH Humans grow two sets of teeth. The first (a.k.a. ''baby'', ''milk'', ''primary'' or '' Deciduous '') set of teeth appears at about six months of age, although some babies are born with one or more teeth already visible. This stage is known as Teething and can be quite painful for an infant. Human children have 20 milk teeth evenly distributed across the quadrants. Each quadrant of 5 teeth consists of The second, permanent set is formed between the ages of six and twelve years. The new set replaces the 20 teeth of the old set. A new tooth forms underneath the old one, pushing it out of the jaw. Apart from this another 8-12 teeth grow. This set can last for life if cared for properly through a regular program of dental hygiene, including brushing with water or Toothpaste as well as periodic professional cleaning by a dentist or hygienist. If a person's teeth are susceptible to decay, for example if the molars include deep pits and fissures, then complete prevention of decay may require treatment with Dental Sealants . Adult humans have 32 permanent teeth evenly distributed across the quadrants which are made of different tissues that are often mistakingly confused for bone. It is true that teeth are attached to the underlying bone of the Jaw (via a ligament called the Periodontal Ligament ), though the teeth themselves have no bone component to them. Unlike bone, the teeth are made up of constituents that are specialised to resist the harsh environment of the oral cavity, and withstand the large forces imposed upon them by Mastication , or chewing. The white part of the tooth which can be seen in the mouth is Enamel . Immediately 1-3 mm below this layer of enamel is a slightly softer, yellow tissue called Dentine . Dentine is supported by the Pulp (commonly called 'the nerve' - although it contains many other structures which are not nerves), which lies in the centre of the tooth. It is worth noting that the third molars ( Wisdom Teeth ) are the final teeth to erupt in the human dentition (usually at around the age of 20). However, it is common for the wisdom teeth not to erupt at all - this is often the case in people with small jaws, as there is not enough room in the jaw to support the extra teeth. Additionally, it is possible, though rare, for a person to have 4th molars, and there have been instances where 5th molars have been present in the dentition. Each quadrant of 8 teeth consists of these types of tooth:
The last molar of each quadrant (i.e. the third molar and commonly referred to as Wisdom Teeth ) may or may not erupt. |