<P> As a result, any given tooth has three different ways to identify it, depending on which notation system is used . The permanent right maxillary central incisor is identified by the number "8" in the universal system . In the FDI system, the same tooth is identified by the number "11". The palmer system uses the number and symbol, ┘, to identify the tooth . Further confusion may result if a number is given on a tooth without assuming (or specifying) a common notation method . Since the number, "12", may signify the permanent left maxillary first premolar in the universal system or the permanent right maxillary lateral incisor in the FDI system, the notation being used must be clear to prevent confusion . </P> <P> In 1891 Victor Haderup devised a variant of eight tooth quadrant system in which plus (+) and minus (-) were used to differentiate between upper and lower quadrants, and between right and left quadrants (e.g., + 1 = upper right central incisor; 1 - = lower left central incisor). Primary teeth were numbered as upper right (05 + to 01 +), lower left (- 01 to - 05). This system is still used in Denmark . </P> <P> The term "crown" of a tooth can be used in two ways . The term "anatomic crown" of a tooth refers to the area above the cementoenamel junction (CEJ) or "neck" of the tooth . It is completely covered in enamel . The term "clinical crown" often is convenient in referring to any part of the tooth visible in the mouth, but as a rule the unqualified term "crown" refers to the anatomic crown . The bulk of the crown is composed of dentin, with the pulp chamber within . The crown is enclosed within bone before the tooth erupts, but after eruption the crown is almost always visible in an anatomically normal and clinically healthy mouth . </P> <P> The anatomic root is found below the cementoenamel junction and is covered with cementum, whereas the clinical root is any part of a tooth not visible in the mouth . Similarly, the anatomic root is assumed in most circumstances . Dentin composes most of the root, which normally has pulp canals . The roots of teeth may be single in number (single - rooted teeth) or multiple . 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 . The tooth is supported in bone by an attachment apparatus, known as the periodontium, which interacts with the root . </P>

What term refers to the visible part of the tooth