Intermediate Plaxus

7/30/2019 Intermediate Plaxus

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INTERMEIDATE PLEXUS


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The dental literature of the 18th and 19th

centuries showed that there existed a strong

intervening membrane, commonly called the

periosteum, between the root of a tooth and itsbony socket.

Black has coined the terms "principal fibers" and

"indifferent tissue" in describing the histologicalappearance of the peridental membrane implying

that this membrane was more than a periosteum.


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Noyes has referred to Black's work but has used

the terms "alveolo-dental periosteum" and

"alveolo-dental membrane synonymously.

Noyes has attributed three functions to the

alveolo-dental membrane.

These were to hold the tooth in position, to be

the seat of sensation for the tooth, and to be asource of formative elements for the alveolus and

the cementum.


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Waugh has stated that the principal fibers of thealveolo-dental membrane were responsible forholding the tooth in its socket.

These fibers passed from the alveolar wall to thecementum and firmly suspended the tooth in itssocket.

He has described the fibers as lying parallel withone another except where they deviated to make

room for vessels and nerves. He has stated that the principal fibers passed

directly from the alveolus to the cementum.


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The idea of the periodontal membrane beingsomething other than a periosteum had not beenfully accepted by the beginning of this century.Cupit has discussed the similarity of the

periodontal membrane to the periosteum ofbones in that it is both bone forming andnourishing. In further discussions of the"peridental membrane," as he has preferred to

call it, Cupit has men-tioned that it consisted oftwo parts, the pericementum and the alveolarperiosteum.


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He did not describe the histology of such an

arrangement with regard to the passing of the

fiber bundles from the alveolus to the tooth.

Widdowson has used the terms "periodontal

membrane" and "alveolo-dental membrane"

interchangeably.


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C. S. Tomes has described the alveolodental

periosteum as being synonymous with the

term "periodontal membrane" and has stated

that the soft tissues investing the root and

lining the socket were one and the same

membrane.


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In his opinion there was a marked difference

in the histological character of the alveolo-

dental fiber bundles lying next to the alveolar

bone as compared to those fibers next to the

cementum, but that there was no break in the

continuity of the fiber bundles as they passed

from the alveolus to the cementum.


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He has mentioned that the fibers attached

both to the cementum and the alveolar bone

were imbedded into the calcified tissues much

like the fibers are imbedded into other bone

and could also be called "Sharpey's fibers."


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PERIODONTAL FIBERS

The most important element of periodontal ligamenthas principal fibers, the principal fibers arecollagenous in nature and a arranged in bundles andfollow a wavy course.

Collagen is a high molecular weight protein.

Collagen macromolecules are rod like and are

arranged in form of fibrils. Fibrils are packed side byside to form fibers.

Vitamin C help in formation and repair of collagen.10


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Half life of collagen fibers is between 3 to 23 days

and collagen imparts a unique combination of

flexibility and strength to tissue.

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TYPES OF PERIODONTAL LIGAMENT FIBERS

1. TRANSEPTAL GROUP

These fibers extend interproximally over alveolarbone crest and are embedded in the cementum of

adjacent teeth.

They are reconstructed even after the destructionof alveolar bone resulting from periodontal disease.

These fibers may be considered as belonging to thegingiva because they do not have osseousattachment.

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DIAGRAM OF PRINCIPAL FIBER GROUPS

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ALVEOLAR CREST GROUP

These fibers extend obliquely from the cementum

just beneath the junctional epithelium to alveolar

crest.

Fibers also run from the cementum over the alveolar

crest and to fibrous layer of periosteum covering

alveolar bone.

The alveolar crest fibers prevent extrusion of tooth

and resist lateral tooth movements. The incision of these fibers during periodontal

surgery does not increase tooth mobility unless

significant attachment loss has occurred.14


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3. HORIZONTAL GROUP

Horizontal fibers extend at right angles to long axis of tooth

from the cementum to alveolar bone.

4. OBLIQUE GROUP

Oblique fibers, the largest group in periodontal ligament,

extend from cementum in a coronal direction obliquely to bone.

They bear the brunt of vertical masticatory stresses and

transfer them into tension on the alveolar bone.

5. APICAL GROUPThe apical fibers radiate in a rather irregular manner from the

cementum to bone at apical region of the socket. They do not

occur on incompletely formed roots.15


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INTER-RADICULAR FIBERS

The interradicular fibers fan out from thecementum to the tooth in furcation areas of

multirooted teeth.

The remodeling of fibers take place in

intermediate plexus. This allows adjustments

in the ligament, which accommodate smallmovements of tooth.

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OXYTALAN FIBERS

These are immature elastic fibers restricted to

walls of blood vessels and are oriented in an

axial direction.

The function is to support the bloods vessels

in the periodontal ligament.

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STRUCTURES PRESENT IN THE


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STRUCTURES PRESENT IN THE

CONNECTIVE TISSUE

BLOOD VESSELSMain blood supply is from superior and inferioralveolar arteries. The blood vessels are derivedfrom the following:

1. BRANCHES FROM APICAL VESSELSVessels supplying the pulp.

2. BRANCHES FROM INTRA-ALVEOLARVESSELS:- Vessels run horizontally and penetratethe alveolar bone to enter into the periodontalligament.

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3. BRANCHES FROM GINGIVAL VESSELS:- Thearterioles and capillaries ramify and form a richnetwork. Rich vascular plexus is found at the apex

and in cervical part of ligament.

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NERVE SUPPLY

Nerves found in ligament pass through foramina in

alveolar bone.

The nerves are the branches of second and thirddivision of fifth cranial nerve (trigeminal nerve)

and follow same path as blood vessels.

These nerve fibers provide sense of touch, pressure,

pain and proprioception during mastication.

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Intermediate Plaxus