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🏥 | Accuracy and issues of periodontal disease detection app Jointly developed by Tohoku University and DoCoMo

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Accuracy and issues of periodontal disease detection application Tohoku University and DoCoMo jointly developed [Latest medical technology that attracts attention even in corona disease]

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The temporomandibular joint disease detection AI is supposed to be an application for general users that detects from the opening and closing video data of the mouth, and the oral cancer detection AI is supposed to be a product that supports the diagnosis of dentists.

[Latest medical technology that attracts attention even in corona sickness] # 26 Periodontal disease is about 20% in the 40s, about 60% in the XNUMXs, in the XNUMXs ... → Continue reading

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Temporomandibular joint

Temporomandibular joint(Gakukansetsu,British: Temporomandibular joint) Is the joint that connects the mandibular fossa of the skull and the mandibular condyle of the mandible.


The temporomandibular jointExternal auditory canalIt is located in front of and consists of the following components.[1]

Mandibular fossa

The mandibular fossa is the temporomandibular joint of the skull (temporal bone) integrated with the maxilla and is located in front of the ear canal of the skull.The mandibular fossa has a concave shape in which the mandibular condyle fits.The shape of the indentation is that all surfaces are not uniform and the front angle is relatively gentle.

Joint nodules

The articular nodule is a raised portion of the bone located anterior to the mandibular fossa.The mandibular condyle can slide on the surface of the joint nodule.

Articular disk

The articular disk is a tough fibrous connective tissue without disc-shaped blood vessels that intervenes between the mandibular fossa and the mandibular condyle.The disk morphology is thin in the central part, thickened in a donut shape around it, and further thinned around it and transferred to the surrounding tissue.The articular disk has the property of withstanding strong pressure.The articular disk plays a role of smoothing the joint movement by moving with the movement of the joint.The sagittal cross-sectional morphology of the articular disk is thicker at the deepest part of the mandibular fossa (posterior thickening), thinner at the anterior (central stenosis), and slightly thicker at the anterior (anterior). Thickened part).The front edge of the articular diskLateral pterygoid muscleConnect with your headLateral pterygoid muscleThe contraction of the upper head causes the articular disk to move anteriorly.The posterior edge of the articular disk connects to the posterior tissue of the disk.The posterior disc tissue is composed of sparse connective tissue in which many blood vessels and nerves are distributed, and supports the disc from behind so that the disc does not move excessively forward.

Mandibular condyle

The mandibular condyle is a pair of articular process tips of the mandible and is oval.

Joint capsule

A membrane of fibrous connective tissue that surrounds the temporomandibular jointTemporal boneIt originates from around the mandibular fossa and attaches to the area around the mandibular condyle of the articular process to protect the glenoid and mandibular condyle.Its inner wall is thin, its front wall has unclear limits, and its rear wall is thick.[2]The joint capsule is a ligament that wraps around the temporomandibular joint and protects the inside.In addition, protect the temporomandibular jointligamentThe temporalis mandibular ligament (lateral ligament), the butterfly mandibular ligament, and the styloglossus mandibular ligament.ligamentCan be deformed to some extent, but has the property of being tough and non-stretchable.However, ligaments can stretch when large forces are applied, whether they are sudden or persistent.ligamentWhen the ligament is stretched, the ligament function is weakened and its function is reduced.


The temporomandibular joint has the following characteristics that are different from other joints.First, the left and right temporomandibular joints form a pair to support the mandible.Since the mandible is a mass, the left and right temporomandibular joints perform cooperative movements, and whenever one temporomandibular joint moves, the other temporomandibular joint also performs some kind of movement.Second, the temporomandibular joint can perform rotational movements and gliding movements at the same time as other joints.This gliding movement is a feature not found in other joints and allows complex movements of the mandible.Third, the movement of the temporomandibular joint is controlled by the contact of the teeth of the upper and lower jaws.

 From the above characteristics, the mandible supported by the temporomandibular joint can perform complex and characteristic movements.In addition, since it is affected by the contact between the upper and lower teeth, if the contact is abnormal, the temporomandibular joint may be improperly stimulated and suffer some damage.[3]


Okeson points out the need for an understanding of temporomandibular joint biomechanics.[4]..They cannot move one temporomandibular joint independently because a pair of temporomandibular joints are connected to a mass of mandible, and the left and right temporomandibular joints are under a complicated system that influences each other. The temporomandibular joint performs a combination of rotational movement and anterior movement around the left and right mandibular condyles, the mechanism by which the mandibular condyle stabilizes in the mandibular fossa, the structure and function of the posterior connective tissue, It is a basic concept related to the relationship between the movement of the articular disk and the superior temporal region of the lateral wing stab muscle, the stable state during the movement of the mandibular condyle, and so on.

Exercise of the temporomandibular joint

The mandibular condyle can perform simple rotational movements and anterior gliding movements within the mandibular fossa.The simple rotational movement of the mandibular condyle is the rotational movement of the mandible about the line connecting the centers of the temporomandibular joints on both sides.When the mandible performs this rotational movement, the components of the temporomandibular joint do not change their positional relationship with each other.On the other hand, the mandibular condyle can slide anteriorly and inferiorly on the anterior wall of the mandibular fossa.When the mandibular condyle glides anteriorly and inferiorly, the articular disk is pulled toward the lateral pterygoid humerus and moves anteriorly.If both mandibular condyles slide forward at the same time, the mandible will protrude forward.If only one mandibular condyle slides forward, the mandibular condyle will rotate laterally around the contralateral mandibular condyle.From the above, the rotational movement and the sliding movement of the temporomandibular joint enable the complicated mandibular movement that is a combination of the opening and closing movement of the lower jaw, the simultaneous sliding movement of the left and right, and the sliding movement of either the left or right.

Leverage between teeth, masticatory muscles and temporomandibular joints

The muscles that contract when biting a tooth are the masseter, temporalis, and medial pterygoid muscles.These muscles are located between the teeth and the temporomandibular joint, and work to pull up the lower jaw with the temporomandibular joint as the fulcrum.As a result, a person can chew noodles with his anterior teeth, chew meat with his canines, and eat food with his molars.

The relationship between teeth, muscles of mastication, and temporomandibular jointsLeverage principleCan be explained in.That is, the teethPoint of action, The muscles of masticationEmphasis, Temporomandibular jointPivotCorresponds to.The type of lever is classified into the third type, and there is a point of effort between the point of action and the fulcrum.In the third type lever, a force smaller than the force applied to the point of effort is transmitted to the point of action.Assuming that the pressure applied to the mandibular fossa is constant, the force to bite with the anterior teeth is small and the force to bite with the molars is large.The reason why the force of biting with the molars is stronger than the force of biting with the front teeth is that the distance between the point of action and the point of effort is short.


  1. ^ Shigehiko Uejo: Oral Anatomy 2 with Myology p9-25, Anatome, Tokyo, 1968.
  2. ^ Sayaya Hobo: Encyclopedia of Bites, Shorin, Tokyo, 1979,OCLC 674414476 National bibliographic number:79018772
  3. ^ Dawson PE: Functional Occlusion From TMJ to Smile Design, MOSBY, St. Louis, 2007, 12-15. ISBN 978-0-323-03371-8
  4. ^ Okeson JP: Management of Tenporomandibular Disorders and Occlusion Six Edition, MOSBY, St. Louis, 2008, 19-23, ISBN 978-0-323-04614-5

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