TERMINOLOGY:

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-Anterior teeth- Incisors and Canines
-Posterior teeth- Pre-molars and molars
-Buccal- tooth surfaces facing the cheek
-Lingual- tooth surfaces facing the tongue
-Distal (posterior)- tooth surfaces away from the oral cavity towards the back of the mouth
-Mesial (anterior)- tooth surfaces facing the oral cavity
-Cusp- having structural or functional occlusal area components delimited by developmental grooves and having independent apexes

4 Types of teeth are present in primates: incisors, canines, premolars, and molars.



Incisors: higher forms of primates have them placed at the front of the jaws. Prosimii (except tarsiers) have them spaced on the upper jaw. The length is much greater than the width. Pongidae have front crowns that are almost square in shape. All incisors are chiseled shaped and used for cutting off fragments of food substances. Daubentonia have long curved incisors of persistent growth. They are the most sensitive teeth because the sensory distinction is greatest at the front of the mouth.



Canines: They are long and project well beyond other teeth in most primates. They are used for aggression and defense. The presence of diastemata (a gap between the teeth) and larger canines usually occur in males. In primates, the whole tooth is fusiform (tapering toward each end). In Lemuroidea, the mandibular canine projects with the incisors. Hominids have small canines, but their roots still imply their ancestors had powerful teeth. Tupaiidae have some distance behind premaxillary structure and don't occlude with mandibular canines.



Premolars: These are the smaller of the cheek teeth. They commonly have 2 cusps (outer one being larger). The number or roots may be 3 (upper) or 2 (lower), but a single root with indication of division occurs in man. These teeth have the biggest range of function and structure. In Lemurs, the mandibular first premolar is canine like in form and function. Cercopithecidae's mandibular first premolar (this is seen in baboons) is elongated and has a powerful anterior root supporting a long sloping biting surface.



Molars: These are the most complex teeth. They are the larger of the cheek teeth. Their function is crushing or tearing food substances. Lemuridae have a tritubercular pattern. Lemur has a slight indication of a cingulum. Galagos have a quadritubercular form (also found in Northarctus). True hypocones are present in Adapinae. Lemuridaes usually have three primary cusps. Other primates usually have four or five cusps. An increase in cusps are explained as division of a previous cusp or an elevation of the cingulum. Ateles and Mycetes have upper molars that have an oblique ridge crossing the crown.

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The upper molar is a three cusped triangle consisting of the paracone, metacone, and protocone and is called the trigon. The lower molar has a trigonid consisting of the paraconid, metaconid, and protoconid. The talonid develops on the distal aspect of the trigonid and often bears three cusps, hypoconid, entoconid, and hypoconulid.

Source: (for terminology) Jaws and Teeth of Primates, by W. Warwick James. Please see "sources" page for more information.

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Enamel: This is the layer that covers the crown. It is smooth and varies in color from yellow to white. It is the hardest biological structure in an animal's body. This is why teeth are found more commonly than other parts of the body in the fossil record. Mature enamel is made of inorganic calcium phosphate (approx. 96%). Enamel's structure is made up of prisms. These prism structures occur in three different patterns that differ among the primates. This has been useful in classifying primates. Also, enamel thickness varies among primate groups. Taxa that feed on harder foodstuffs have thicker enamel than those who feed on softer foodstuffs.

Dentine: Dentine is softer than enamel, but still harder than bone. It makes up the majority of the tooth and its root. Dentine is comprised of collagen and hydroxyapatite. Therefore, it is more elastic than enamel.

Cementum: The next layer of the tooth is cementum. This develops around the dentine in the root region. There is both cellular and acellular cementum. It protects the underlying dentine, and adds to the size and strength of the tooth. One can use a technique to age a primate's tooth based on the lines in cementum.

Tooth roots: Primates usually have one, two, or three roots. Root formation begins after the development of enamel and dentine. An epithelial sheath will form, initiating root formation. The root has a pulp cavity and is surrounded by dentine and cementum.

Dental pulp: This fills the pulp cavity described above in the tooth roots. In the pulp resides arteries, veins, nerves, and lymphatic vessels.

The above image is a brief pictorial summary of the life cycle of a tooth. Click the picture above to enlarge.

Source: (for tooth anatomy information) Primate Dention, by Daris R. Swindler. Please see "sources" page for more information.

Sexual Dimorphism:

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In higher primates, canines can be linked to sexual dimorphism among species. Sexual dimorphism can be linked to the amount of competition amoung species of the same sex. Species with higher male-male competition (compared with female-female compeition) tend to have a greater degree of canine dimorphism. An example can be illustrated when comparing the polygynous baboons (dimorphic canines, and high male-male competition) and monogamous gibbons (monomorphic canines and male-male competition is less or equal to that of females).

Source: (for sexual dimorphism) Primate Adaptation and Evolution, Second Edition, by John G. Fleagle. Please see "sources" page for more information.

DENTAL FORMULAS:

Dental formulas can be defined as the following:

3. 1. 4. 3.

#incisors. # canines. # pre-molars. # molars.

This is for the half of the lower jaw. Dental formulas describe ½ of the jaw (usually an upper and lower jaw dental formula is given).

See below for list of dental formulas in primates