What Is a Periodontal Ligament?

The periodontal ligament is located in the dense connective tissue between the root of the tooth and the alveolar bone. It contains a thicker collagen fiber bundle, one end of which is embedded in human cementum, and the other end extends into the alveolar. Role. The periodontal ligament of the elderly often shrinks, causing the teeth to loosen or fall off.

Chinese name: Periodontal Ligament Overview
Foreign name: parodontium

Basic substance: Unstructured colloidal substance
Make up: Nerves, blood vessels, lymph and epithelial cells, etc.
Thickness: 0.15-0.38mm

Periodontal Ligament Overview

Periodontal ligament, also known as periodontal ligament, is the connective tissue located between the root of the tooth and the alveolar bone, which mainly connects the teeth and the alveolar bone.

Periodontal ligament is the connective tissue that connects teeth with alveolar bone, or periodontal ligament. It appears as a black line around the root of the tooth on the radiograph.

Structure of periodontal ligament The fibers in the periodontal ligament are aggregated into bundles and arranged in a certain direction, which is called the main fiber bundle. One end of the main fiber bundle is embedded in the cementum, and the other end is embedded in the alveolar bone, or distributed in the gums. According to the location and function, the main fiber bundles are arranged in different directions. The main fiber bundles are inclined at about 45 °. The high end is attached to the alveolar bone and the other end is attached to the cementum. When the teeth are under chewing pressure, the alveolar bone receives an average traction force due to the effect of this group of fibers. Normal main fiber bundles are slightly corrugated, so teeth can be slightly moved. With some elastic fiber dyeing methods, immature elastic fibers can be seen under an optical microscope, and this fiber is similar to a developing elastic fiber under an electron microscope. This fiber is arranged in a different direction than collagen fibers, with one end buried in bone or cementum and the other end in the blood vessel wall. It is arranged in a reticular pattern near the apex, and its function is unknown. The loose connective tissue between the main fiber bundles is the interstitial tissue, which includes blood vessels, nerves and lymphatic vessels. The periodontal ligament is rich in blood vessels, partly from the gums, partly from the alveolar, and partly from the same source as the apical vessels. There are abundant sensory nerve endings in the periodontal ligament, and sympathetic nerves innervate blood vessels. The periodontal ligament lymphatics are injected into the lymph nodes of each neck, so when the periodontal ligament is infected, it will cause local lymphadenopathy. Epithelial surplus is also called Malassez epithelial surplus, which is the remainder of the epithelial root sheath during root development. In the interstitial tissue, there are small strands or small clumps, which are generally stationary. These epithelial residues are often proliferated by trauma or infection, and they can also be the epithelial source of dental cysts or jaw tumors.

Function of Periodontal Ligament The periodontal ligament can form alveolar bone and cementum, which can be reconstructed after being destroyed; it can support teeth against chewing force, and can buffer external forces so that it does not directly affect alveolar bone. Periodontal ligament can also nourish cementum and alveolar bone. The function of periodontal ligament is closely related to its structure. For a tooth buried in the jawbone, or a tooth that has not been used for a long time, the main fiber bundle is underdeveloped or disappears, and the periodontal ligament is thinner, often below 0.1mm. However, for functional teeth, the main fiber bundles are thick and the periodontal membrane thickness is about 0.2 mm. Periodontal tissue has strong resistance to vertical pressure, but the lateral pressure is vulnerable to damage.

Periodontal ligament anatomy

It is composed of dense connective tissue, which is wrapped around the root of the tooth, closely connecting the cementum with the alveolar bone. Therefore, the periodontal ligament has a function of fixing teeth.

Also known as periodontal ligament, the connective tissue between the root of the tooth and the alveolar bone is a structure that connects the teeth and the alveolar bone. It appears as a black line around the root of the tooth on the radiograph. The fibers are aggregated into bundles and arranged in a certain direction, which is called the main fiber. One end of the main fiber is embedded in the cementum and the other end is embedded in the alveolar bone or distributed in the gums, so that the teeth are firmly implanted in the alveolar socket. Can form alveolar bone and cementum, can be reconstructed after being destroyed. Can support teeth to resist chewing force, and buffer external forces so that it does not directly affect the alveolar bone. It can also nourish cementum and alveolar bone.

The dense connective tissue located between the root and the alveolar bone is called the periodontal ligament, also known as the alveolar periosteum. The periodontal ligament is made of glial fibers, similar to ligaments. According to the distribution of glial fibers, periodontal ligament can be divided into main fibers and interstitial fibers. The main fiber has many colloidal fiber bundles arranged radially around the root of the tooth. One end of this fiber bundle is embedded in the shallow layer of cementum and the other end is embedded in the alveolar wall, so that the teeth are firmly embedded in the alveolar. When loose or damaged, the firmness of the teeth is affected. Interstitial fibers are distributed in the interstices of the main fibers and have a buffering effect on teeth during chewing with other loose connective tissues in the interstices. The periodontal ligament is rich in blood vessels and nerve endings, which plays an important role in dental nutrition.

Periodontal ligament composition

fiber

It is mainly composed of collagen fibers, which are mostly gathered into bundles and have a certain arrangement direction (main fiber bundle). Embedded in cementum and:

The main fiber bundle nU in the alveolar bone penetrates the fibers. The main fiber bundle can be divided into five groups:

(1) Alveolar crest fiber: It starts from the alveolar crest and tilts radially toward the crown, ending in the cementum of the neck. Visible on the lip (cheek) of the teeth and on the lingual surface, absent from the adjacent surface. Pull the teeth into the alveolar socket to prevent the teeth from tilting towards the lips.

(2) Alveolar transverse fiber: The root of the alveolar ridge fiber starts from the alveolar bone and stops horizontally around the tooth neck. Prevents teeth from tilting in any direction.

(3) Alveolar oblique fibers: a group of fibers with the largest number, the strongest force, and the widest distribution. It is inclined from the alveolar bone toward the apex and stops in the cementum. Its function is to suspend the teeth so that the teeth can withstand large chewing forces.

(4) Apical fiber: It starts from the alveolar bone around the apex and gathers on the crown to the cementum of the apex of the tooth. Can fix the position of the apex,

Protect blood vessels and nerves entering and exiting the apical foramen.

(5) Inter-root fibers: This fiber exists only in multiple teeth, starting from the root space, and ending at the cementum at the root bifurcation. Tooth can be pulled into the alveolar socket.

Matrix

It is an unstructured colloidal substance.

cell

(1) Fibroblasts: The most important cells in the periodontal ligament. Its function is to participate in the synthesis and absorption of collagen, so that the collagen in the periodontal ligament can be continuously updated. It is also related to matrix formation.

(2) Osteoblasts: located on the surface of the newly formed alveolar bone, can secrete collagen fibers and bone matrix, and become mineralized bone after mineralization. Can also become bone cells.

(3) Osteoclasts: located in the pit of the bone resorption site, which can absorb bone or cementum. When bone resorption stops, osteoclasts disappear.

(4) Odontoblasts: located in the periodontal ligament near the cementum. Its function is to form cement.

(5) Remainder of the epithelium: It is the residual part of the epithelial root sheath during the development of the tooth root. It is located in the fibrous space attached to the cementum, and is in the shape of a strand or a mass. When stimulated, it can proliferate into an epithelial source of odontogenic tumors or jaw cysts.

Cementum body

It is a round mineralized agglomerate, varying in number, free from periodontal ligament or attached to the surface of dry cementum. May be caused by mineralization of degenerate epithelial cells.

Blood vessels, lymphatic vessels, nerves

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