tooth definition: Any of the hard bony structures in the mouth used to grasp and chew food and as weapons of attack and defense. In mammals and many other vertebrates, the teeth are set in sockets in the jaw. In fish and amphibians, they grow in and around the palate.
A hard structure, embedded in the jaws of the mouth, that functions in chewing. The tooth consists of a crown, covered with hard white enamel; a root, which anchors the tooth to the jawbone; and a “neck” between the crown and the root, covered by the gum. Most of the tooth is made up of dentin, which is located directly below the enamel. The soft interior of the tooth, the pulp, contains nerves and blood vessels. Humans have molars for grinding food, incisors for cutting, and canines and bicuspids for tearing.
Twenty primary (baby) teeth come in by age 2 1/2 and fall out between ages 5 and 13 to be replaced by 32 permanent teeth. The incisors, in front, are shaped mostly for biting, the pointed canines for tearing, and the premolars and molars for grinding food. The teeth are subject to caries (decay), caused by acid from bacteria in plaque, a yellowish film that builds up on teeth. Misalignment of teeth between the upper and lower jaws can grind down the teeth and cause problems in chewing. Elsewhere, it is a cosmetic problem.Both can be treated with braces.
In humans the primary dentition (20 teeth) consists of four incisors, two canines, and 
four molars in each jaw. The primary molars are replaced in the adult dentition by the premolars, or bicuspid teeth. The 12 adult molars of the permanent dentition erupt (emerge from the gums) behind the primary teeth and do not replace any of these, giving a total of 32 teeth in the permanent dentition. The permanent dentition is thus made up of four incisors, two canines, four premolars, and six molars in each jaw.
four molars in each jaw. The primary molars are replaced in the adult dentition by the premolars, or bicuspid teeth. The 12 adult molars of the permanent dentition erupt (emerge from the gums) behind the primary teeth and do not replace any of these, giving a total of 32 teeth in the permanent dentition. The permanent dentition is thus made up of four incisors, two canines, four premolars, and six molars in each jaw.
incisor teeth are the teeth at the front of the mouth, and they are adapted for 
plucking, cutting, tearing, and holding. The biting portion of an incisor is wide and thin, making a chisel-shaped cutting edge. The upper incisors have a delicate tactile sense that enables them to be used for identifying objects in the mouth by nibbling. Next to the incisors on each side is a canine, or cuspid tooth. It frequently is pointed and rather peg like in shape and, like the incisors, has the function of cutting and tearing food.
plucking, cutting, tearing, and holding. The biting portion of an incisor is wide and thin, making a chisel-shaped cutting edge. The upper incisors have a delicate tactile sense that enables them to be used for identifying objects in the mouth by nibbling. Next to the incisors on each side is a canine, or cuspid tooth. It frequently is pointed and rather peg like in shape and, like the incisors, has the function of cutting and tearing food.
Premolars and molars have a series of elevations, or cusps, that are used for breaking up particles of food. Behind each canine are two premolars, which can both cut and grind food. Each premolar has two cusps (hence the name bicuspid). The molars, by contrast, are used exclusively for crushing and grinding. They are the teeth farthest back in the mouth. Each molar typically has four or five cusps.
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