ABSTRACT

Like all mammals, humans generally have two sets of teeth during a lifetime. The first set, known as deciduous, primary, or ‘‘milk’’ teeth, begins to appear in infants between the age of 5 and 9 months. All 20 of these ‘‘baby’’ teeth are generally in place by age 21/2 years. The second set, or permanent teeth, forms within the gums during the period from infancy to puberty. These teeth, also known as succedaneous teeth, begin to erupt at around age 5, displacing the deciduous set as they appear. There are 32 permanent teeth. An individual will spend 91% of his or her lifetime chewing with these permanent teeth if they are properly cared for. Of the 32 permanent teeth, 16 are located in the upper jaw, or maxillary dental arch, which is part of the cranium, or skull, and is immoveable. The other 16 are located in the mandibular dental arch which is part of the lower jaw and is the moveable part of the skull. Each type of tooth is equally divided between these two dental arches (Figs. 1 and 2).