Teeth are the hard, calcified, whitish structures found in the mouth. They are used for biting, tearing, grinding and chewing. They help keep the facial profile by supporting facial muscles. They are also needed to pronounce certain words thereby helping in speech too.
Humans develop two sets of teeth. The primary teeth (milk teeth or deciduous teeth) start to appear at about six months of age. There are a total of 20 primary teeth. The second set of teeth that usually start to appear in the mouth at around six years of age is called the permanent teeth (adult teeth). There are thirty-two permanent teeth.
The visible part of the tooth (above the gums) is called the crown of the tooth. The root of the tooth is that part of the tooth which lies inside the alveolar bone under the gums. Tooth enamel is the highly mineralized outer most protective covering of the crown of the tooth. It is the hardest of all the tissues of our body. Cementum is the outermost yellowish layer covering the root of a tooth. It is hard as bone. Underneath the enamel and cementum lies the dentin, a bone-like mineralized connective tissue, which makes up the majority of the tooth structure. The core of the tooth is formed by the pulp, often referred to as the nerve of the tooth. The pulp is a soft connective tissue and is made up of blood vessels, nerves and cells like odontoblasts, fibroblasts, macrophages, etc.
The supporting structures of the teeth, collectively called periodontium, keep them firmly placed in the mouth.