The first permanent teeth begin to emerge into the mouth at the age of 6 and for the following 6–12 years the primary (deciduous) teeth are gradually replaced by the permanent ones. After the emerging of the second molars the permanent dentation is considered complete1. The age of the maturation and eruption of the most distal (third) molars is variable between populations2,3 and the complete eruption (stage D) is rarely observed in all four quadrants4.
1Nelson S, Ash M. Wheeler's Dental anatomy, physiology and occlusion. 9th ed. Elsevier, 2010, p.1.
Skull with full set of permanent teeth that is rarely seen in real life. The anterior & lateral aspect. Click the images above to see the teeth with the roots. Note the relative size and spatial orientation of the roots in the alveolar bone.
Tooth Surfaces and Numbering System
On the past two centurires, many classifications of tooth numeration have been proposed1–3 and some new ones are still emerging4. To avoid confusion, we use only one classficationon on this website — the most commonly used tooth numbering system recommended by the World Dental Federation5.
According to that classfication each permanent tooth is encoded by the combination of two digits: the first refers to the quadrant (1—maxillar right; 2—maxillar left; 3—mandibular left; 4—mandibular right). and the second refers to the order number of tooth, starting from the midline:
1Zsigmondy A. A practical method for rapidly noting dental observations and operations. Br J Dent Sci, 1874, 17:580–582.
Another point worth mentioning is the specific terminology used to describe the surfaces and other landmarks of the teeth. The teeth surround the oral cavity and do not coincide with the anatomical planes (sagittal, coronal, horisontal). For this reason, terms such as "anterior", "posterior", "medial" and "lateral" are not used in dental anatomical terminology and are substituted by "lingual" (facing the tongue), "buccal/labial" (facing the cheeks or lips), "mesial" & "distal":
Surfaces and directions
Please note that the outer (vestibular) surface of teeth is devided into the "labial" and "buccal", as the angulus oris projects slightly lateral to the canine tooth
The list of terms:Facies vestibularis s. facialis – Vestibular, or facial surface Facies buccalis – Buccal surface Facies labialis – Labial surface Facies lingualis – Lingual surface Facies occlusalis s. masticatoria – Occlusal, or masticatory surface Directio mesialis – Mesial direction Directio distalis – Distal direction Facies approximalis – Approximal surface Area congingens – Contingent area
Detailed Review of the Permanent Incisors, Canines, Premolars et Molars
Incisors
Тhe permanent set of teeth has two incisors in each quadrant. The maxillar incisors are noticeably larger, than mandibular ones. The main feature of the incisor is the single sharp edge at the top of the crown. Other features, such as a single root, or absence of the cusps are less specific. The main function of the incisors is to pierce and cut the food during mastication process.
Right maxillary first incisor.
Note the presence of so-called "cingulum", connecting the marginal crests on the lingual surface of incisors and canines. This structure represents the rudimentary lingual cusp. To get an impression of well-developed lingual cusps, refer to the premolar teeth.
The list of terms:Corona dentis – Crown of tooth Cervix dentis – Neck of tooth Radix dentis – Root of tooth Apex radicis dentis – Apex of root of tooth Foramen apicis radicis dentis – Apical foramen of root of tooth Tuberculum dentis – Dental tubercle Fossa lingualis – Lingual fossa Margo incisalis – Incisal margin Crista marginalis – Marginal crest Cingulum
Canines
The permanent dentition has one canine in each quadrant. These are the longest teeth and the maxillary canine teeth are not much larger than the mandibular ones. The main feature of the crowns is the massive single pointed cusp. The word originate from the Latin canis — dog, emphesizing the carnivorous nature of this type of teeth, related to the piercing and tearing the food during mastication process. But the most important function of these teeth for humans is to guide the teeth into the intercuspal position (occlusion) through the mechanism called "canine guidance"*.
*Ash M, Ramfjord S. Occlusion. 4th ed, Saunders, Philadelphia, 1995
Right maxillary canine.
Note the groove on the mesial aspect of the canine root. In about 5% of cases* this groove is deep enough to completely split the root and the canal – the variant called a bifurcated root.
The list of terms:Corona dentis – Crown of tooth Cervix dentis – Neck of tooth Radix dentis – Root of tooth Apex radicis dentis – Apex of root of tooth Foramen apicis radicis dentis – Apical foramen of root of tooth Apex cuspidis – Apex of cusp Crista cuspidis mesialis – Mesial cusp ridge Crista cuspidis distalis – Distal cusp ridge Crista marginalis mesialis – Mesial marginal ridge Crista marginalis distalis – Distal marginal ridge CingulumCrista lingualis – Lingual ridge Fossa mesiolingualis – Mesiolingual fossa Fossa distolingualis – Distolingual fossa
Premolares
The premolars are located distal to the canines, two in each quadrant in the permanent dentition. The main peculiarity of premolars is the presence of two cusps, so sometimes the term premolar is substituted with "bicuspid". However, the term can be misleading, as mandibular premolars can have three, or even four cusps*.
Right maxillary first premolar.
The number of roots varies between premolars. Clasically the maxillary first premolar is described as a tooth with two roots. Recent studies based on computed-tomography have confirmed this in European1 and Arab2 (~60% prevalence), but not in Chinese populations (~30% prevalence)2. All other premolars (second maxillar and both mandibular) have only one root in more than 80% of cases1–4.
The molars are largest and best anchored teeth, performing the main portion of work in mastication process. The maxillary first and second molars each have three full sized roots (two buccal and one lingual), while the mandibular first and second molars usually have only two roots, mesial and distal. The third molars are usually smaller, with greater variability and occasionally appear as anomalies with little or no resemblance to neighboring teeth*.
*Nelson S, Ash M. Wheeler's Dental anatomy, physiology and occlusion. 9th ed, Saunders, St. Louis, 2010, p.184, p.203.
Right upper & lower first molar.
The main feature of the molar crown is 4-5 well-developed cusps, due to which crowns of molars are the largest among all other teeth. Currently, International Anatomical Terminology for molars is insufficient in terms of detailed terminology for the occlusal aspect1. The terminology presented in the illustration above is largely based on terms published in Wheeler's textbook of dental anatomy2.