Cusp (anatomy)

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Cusp
Cusp tips.JPG
The teeth of the right side of the mouth, shown contacting the teeth in the opposing jaw with their cusp tips.
Details
Identifiers
Latin cuspis dentis
TA98 A05.1.03.010
TA2 925
FMA 56481
Anatomical terminology
1. Tooth
2. Enamel
3. Dentin
4. Dental pulp
5. cameral pulp
6. root pulp
7. Cementum
8. Crown
9. Cusp
10. Sulcus
11. Neck
12. Root
13. Furcation
14. Root apex
15. Apical foramen
16. Gingival sulcus
17. Periodontium
18. Gingiva
19. free or interdental
20. marginal
21. alveolar
22. Periodontal ligament
23. Alveolar bone
24. Vessels and nerves
25. dental
26. periodontal
27. alveolar through channel Cross sections of teeth intl.svg
1. Tooth
2. Enamel
3. Dentin
4. Dental pulp
5. cameral pulp
6. root pulp
7. Cementum
8. Crown
9. Cusp
10. Sulcus
11. Neck
12. Root
13. Furcation
14. Root apex
15. Apical foramen
16. Gingival sulcus
17. Periodontium
18. Gingiva
19. free or interdental
20. marginal
21. alveolar
22. Periodontal ligament
23. Alveolar bone
24. Vessels and nerves
25. dental
26. periodontal
27. alveolar through channel

A cusp is a pointed, projecting, or elevated feature. In animals, it is usually used to refer to raised points on the crowns of teeth.

Contents

The concept is also used with regard to the leaflets of the four heart valves. The mitral valve, which has two cusps, is also known as the bicuspid valve, and the tricuspid valve has three cusps.

In humans

A cusp is an occlusal or incisal eminence on a tooth. Canine teeth, otherwise known as cuspids, each possess a single cusp, while premolars, otherwise known as bicuspids, possess two each. Molars normally possess either four or five cusps. In certain populations the maxillary molars, especially first molars, will possess a fifth cusp situated on the mesiolingual cusp known as the Cusp of Carabelli.

Buccal Cusp- One other variation of the upper first premolar is the 'Uto-Aztecan' upper premolar. It is a bulge on the buccal cusp that is only found in Native American Indians, with highest frequencies of occurrence in Arizona. The name is not a dental term; it comes from a regional linguistic division of Native American Indian language groups.

Buccal-The side of a tooth that is adjacent to (or the direction towards) the inside of the cheek, as opposed to lingual or palatal, which refer to the side of a tooth adjacent to (or the direction towards) the tongue or palate, respectively. Although technically referring only to posterior teeth (where the cheeks are present instead of lips, use of this term may extend to all teeth, anterior and posterior), this term may be employed to describe the facial surface of (or directions in relation to) anterior teeth as well.

Cusps on the molars of therian mammals

Right upper molar showing the four main upper molars cusps Tooth Picturewlabels.jpg
Right upper molar showing the four main upper molars cusps

There are 4 main cusps found on the molars of the upper dentition of therian mammals.

Hypocone

The hypocone is found on the distal lingual side of the tooth. It fits into the grooves of the lower dentition and is an adaptation for the overall grinding and tearing of foods using the occlusal (chewing side) of the tooth surface during occlusion or mastication (chewing). Its strength is due to the thickness of the enamel which differs among species of hominids. The hypocone appears to have evolved independently more than twenty times in different mammal groups during the Cenozoic period. [1]

Metacone

The metacone is a cusp on the molars of the upper dentition in hominids. It is found at the buccal distal area of the tooth. The crests between the cusps are adaptations for slicing food during occlusion or mastication (chewing).

Paracone

The anterior of the three cusps of a primitive upper molar that in higher forms is the principal anterior and outside cusp.

Protocone

The protocone is founding the molars of the upper dentition in Placental and Marsupial vertebrates. [2] It is found at the mesiolingual area of the tooth. The crests between the cusps are adaptations for slicing food during occlusion or mastication (chewing).

See also

Related Research Articles

Molar (tooth) Large tooth at the back of the mouth

The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name molar derives from Latin, molaris dens, meaning "millstone tooth", from mola, millstone and dens, tooth. Molars show a great deal of diversity in size and shape across mammal groups. The third molar of humans is sometimes vestigial.

Premolar Transitional teeth located between the canine and molar teeth

The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered transitional teeth during chewing, or mastication. They have properties of both the canines, that lie anterior and molars that lie posterior, and so food can be transferred from the canines to the premolars and finally to the molars for grinding, instead of directly from the canines to the molars.

Malocclusion Medical condition

In orthodontics, a malocclusion is a misalignment or incorrect relation between the teeth of the upper and lower dental arches when they approach each other as the jaws close. The English-language term dates from 1864; Edward Angle (1855-1930), the "father of modern orthodontics", popularised it. The word "malocclusion" derives from occlusion, and refers to the manner in which opposing teeth meet.

Maxillary first molar

The maxillary first molar is the human tooth located laterally from both the maxillary second premolars of the mouth but mesial from both maxillary second molars.

Maxillary second molar

The maxillary second molar is the tooth located distally from both the maxillary first molars of the mouth but mesial from both maxillary third molars. This is true only in permanent teeth. In deciduous (baby) teeth, the maxillary second molar is the last tooth in the mouth and does not have a third molar behind it. The function of this molar is similar to that of all molars in regard to grinding being the principal action during mastication, commonly known as chewing. There are usually four cusps on maxillary molars, two on the buccal and two palatal.

Mandibular first premolar

The mandibular first premolar is the tooth located laterally from both the mandibular canines of the mouth but mesial from both mandibular second premolars. The function of this premolar is similar to that of canines in regard to tearing being the principal action during mastication, commonly known as chewing. Mandibular first premolars have two cusps. The one large and sharp is located on the buccal side of the tooth. Since the lingual cusp is small and nonfunctional, the mandibular first premolar resembles a small canine. There are no deciduous (baby) mandibular premolars. Instead, the teeth that precede the permanent mandibular premolars are the deciduous mandibular molars.

Mandibular second premolar

The mandibular second premolar is the tooth located distally from both the mandibular first premolars of the mouth but mesial from both mandibular first molars. The function of this premolar is assist the mandibular first molar during mastication, commonly known as chewing. Mandibular second premolars have three cusps. There is one large cusp on the buccal side of the tooth. The lingual cusps are well developed and functional. Therefore, whereas the mandibular first premolar resembles a small canine, the mandibular second premolar is more alike to the first molar. There are no deciduous (baby) mandibular premolars. Instead, the teeth that precede the permanent mandibular premolars are the deciduous mandibular molars.

Mandibular first molar

The mandibular first molar or six-year molar is the tooth located distally from both the mandibular second premolars of the mouth but mesial from both mandibular second molars. It is located on the mandibular (lower) arch of the mouth, and generally opposes the maxillary (upper) first molars and the maxillary 2nd premolar in normal class I occlusion. The function of this molar is similar to that of all molars in regard to grinding being the principal action during mastication, commonly known as chewing. There are usually five well-developed cusps on mandibular first molars: two on the buccal, two lingual, and one distal. The shape of the developmental and supplementary grooves, on the occlusal surface, are describes as being 'M' shaped. There are great differences between the deciduous (baby) mandibular molars and those of the permanent mandibular molars, even though their function are similar. The permanent mandibular molars are not considered to have any teeth that precede it. Despite being named molars, the deciduous molars are followed by permanent premolars.

Mandibular second molar

The mandibular second molar is the tooth located distally from both the mandibular first molars of the mouth but mesial from both mandibular third molars. This is true only in permanent teeth. The function of this molar is similar to that of all molars in regard to grinding being the principal action during mastication, commonly known as chewing. Though there is more variation between individuals than that of the first mandibular molar, there are usually four cusps on mandibular second molars: two on the buccal and two lingual. There are great differences between the deciduous (baby) mandibular molars and those of the permanent mandibular molars, even though their function is similar. The permanent mandibular molars are not considered to have any teeth that precede them. Despite being named molars, the deciduous molars are followed by permanent premolars.

Curve of Spee

In anatomy, the Curve of Spee is defined as the curvature of the mandibular occlusal plane beginning at the canine and following the buccal cusps of the posterior teeth, continuing to the terminal molar. According to another definition the curve of Spee is an anatomic curvature of the occlusal alignment of the teeth, beginning at the tip of the lower incisor, following the buccal cusps of the natural premolars and molars and continuing to the anterior border of the ramus. It is named for the German embryologist Ferdinand Graf von Spee (1855–1937), who was first to describe the anatomic relations of human teeth in the sagittal plane.

Dental arch The arrangement and alignment of teeth

The dental arches are the two arches of teeth, one on each jaw, that together constitute the dentition. In humans and many other species; the superior dental arch is a little larger than the inferior arch, so that in the normal condition the teeth in the maxilla slightly overlap those of the mandible both in front and at the sides. The way that the jaws, and thus the dental arches, approach each other when the mouth closes, which is called the occlusion, determines the occlusal relationship of opposing teeth, and it is subject to malocclusion if facial or dental development was imperfect.

Dental anatomy is a field of anatomy dedicated to the study of human tooth structures. The development, appearance, and classification of teeth fall within its purview. Tooth formation begins before birth, and the teeth's eventual morphology is dictated during this time. Dental anatomy is also a taxonomical science: it is concerned with the naming of teeth and the structures of which they are made, this information serving a practical purpose in dental treatment.

Occlusion, in a dental context, means simply the contact between teeth. More technically, it is the relationship between the maxillary (upper) and mandibular (lower) teeth when they approach each other, as occurs during chewing or at rest.

This is a list of definitions of commonly used terms of location and direction in dentistry. This set of terms provides orientation within the oral cavity, much as anatomical terms of location provide orientation throughout the body.

Postcanine megadontia

Post-canine megadontia is a relative enlargement of the molars and premolars compared to the size of the incisors and canines. This phenomenon is seen in some early hominid ancestors such as Paranthropus aethiopicus.

Crossbite Medical condition

Crossbite is a form of malocclusion where a tooth has a more buccal or lingual position than its corresponding antagonist tooth in the upper or lower dental arch. In other words, crossbite is a lateral misalignment of the dental arches.

Serial extraction is the planned extraction of certain deciduous teeth and specific permanent teeth in an orderly sequence and predetermined pattern to guide the erupting permanent teeth into a more favorable position.

Tikitherium is an extinct genus of mammaliaforms from the Late Triassic. It is thought to be an insectivore and a close relative to Docodonta. Tikitherium refers to Tiki, the village located near the Tiki Formation where the specimen was found, and therium is Greek for “Beast”. The species was named copei in honor of Edward Drinker Cope for his pioneering discoveries towards understanding mammalian molars.

Orthodontic indices are one of the tools that are available for orthodontists to grade and assess malocclusion. Orthodontic indices can be useful for an epidemiologist to analyse prevalence and severity of malocclusion in any population.

Occlusion according to The Glossary of Prosthodontic Terms Ninth Edition is defined as 'the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues'.

References

  1. Hunter, JP; Jernvall, J (1995). "The hypocone as a key innovation in mammalian evolution". Proc. Natl. Acad. Sci. U.S.A. 92 (23): 10718–22. doi: 10.1073/pnas.92.23.10718 . PMC   40683 . PMID   7479871.
  2. Gavin Prideaux, "Systematics and Evolution of the Sthenurine Kangaroos" (April 1, 2004). UC Publications in Geological Sciences. Paper vol_146. http://repositories.cdlib.org/ucpress/ucpgs/vol_146 p.16

Bibliography