Periodontium refers to the tissues investing and supporting the teeth,

Periodontium refers to the tissues investing and supporting the teeth, including the cementum, periodontal ligament (PDL), alveolar bone and gingiva. PDL is a soft, specialized connective tissue which connects the tooth to the alveolar bone. Ligament is a fitting term; it comes from the Latin ligare meaning to bind or tie. Although the PDL bears this term because it anchors the tooth to the bone, it differs in many respects from the other ligaments in the body.This tissue has also been referred to as gomphosis in the literature. Gomphosis is not a connection between true bones but is considered a type of fibrous joint. (This term is not in usage, considering the lack of structural and functional resemblance.) The embryological origin of the PDL is from the dental follicle. The average width of the periodontal space (the space containing the PDL that is present around the tooth) is 0.1-0.25 mm (Fig. 40.1). It is widest at the mouth of the socket and at the apex, and narrowest at the axis of rotation of the tooth, which is located at the junction of the apical and middle third of the root. This space can increase because of excessive occlusal forces and can reduce in nonfunctional teeth. It can narrow down as age advances. This space is said to be wider in deciduous dentition - compared with in permanent teeth. The periodontal tissue is continuous with the gingival connective tissue coronally and extends to the level of the apical foramen apically. This is - important when considering the progression of - periodontitis from gingivitis and also the spread of inflammation from the pulp to the PDL.When a sound tooth is extracted from its socket, the PDL is torn, and the periodontal fibres inserted into the cementum are retained on the root surface. If the tooth were dipped into a diluted dye solution such as methylene blue, the fibres would turn dark blue. In healthy teeth, the whole length of the root would be stained. If the tooth is affected by advanced periodontal disease, in which the fibres are destroyed partially or completely, the apical portion of the root would be stained and the rest of the root portion would not take up the stain.This tissue is extensively investigated by various researchers as it is associated with various dental functions and is of clinical significance. This tissue is involved in inflammatory periodontal diseases (a common cause of tooth loss), and its possible reattachment consequent to disease is still a subject of interest to many researchers worldwide. Despite extensive research, this tissue remains enigmatic and has drawn much controversy. Without extra content only explain to me the things I provided and explain the points detailed

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Periodontium

The periodontium is the collective term for all the tissues that surround, invest, and support the teeth. It has four components:

Cementum
Periodontal Ligament (PDL)
Alveolar Bone
Gingiva

Each of these structures works together to keep the tooth anchored in its socket and to maintain oral function.

Periodontal Ligament (PDL) - Definition and Name

The PDL is a soft, specialized connective tissue that connects the tooth (specifically its root surface via cementum) to the surrounding alveolar bone.

The word "ligament" comes from the Latin ligare, meaning "to bind or tie."
The term is fitting because the PDL literally anchors (binds) the tooth to bone.
However, the PDL differs significantly from other ligaments in the body in both structure and function - it is far more metabolically active, contains cells of multiple types, and serves sensory and nutritive roles that typical ligaments do not.

Gomphosis

The PDL has also been referred to in literature as a gomphosis:

Gomphosis is classified as a type of fibrous joint.
Importantly, it is not a connection between two true bones - because the tooth (via cementum) is not a bone, even though it is embedded into bone.
This term is no longer in common usage because the PDL does not truly resemble other fibrous joints either structurally or functionally. It is therefore considered a poor fit as a descriptive term.

Embryological Origin

The PDL originates embryologically from the dental follicle - a sac of ectomesenchymal tissue that surrounds the developing tooth germ. This follicle gives rise not just to the PDL, but also to cementum and alveolar bone.

Width of the Periodontal Space

The periodontal space is the physical gap around the root of a tooth within the socket, and it contains the PDL.

Normal average width: 0.1 to 0.25 mm
The space is widest at two locations:
- At the mouth (crest) of the socket (near the gingival margin)
- At the apex of the root
The space is narrowest at the axis of rotation of the tooth, which lies at the junction of the apical and middle thirds of the root - this is the fulcrum point around which the tooth tilts under force.

Factors that change PDL width:

Condition	Effect on PDL Width
Excessive occlusal (biting) forces	Increases width
Non-functional teeth (e.g., unopposed)	Decreases width
Advancing age	Narrows the space
Deciduous (baby) teeth	Wider than in permanent teeth

Continuity with Adjacent Tissues

The PDL is continuous with surrounding tissues at both ends:

Coronally (towards the crown): it is continuous with the gingival connective tissue.
Apically (towards the root tip): it extends to the level of the apical foramen.

This continuity has two major clinical implications:

Gingivitis to periodontitis progression: Because the gingival connective tissue and PDL are continuous, inflammation starting in the gingiva (gingivitis) can spread into and destroy the PDL (periodontitis).
Pulp to PDL spread: Because the PDL connects to the apical foramen (the opening through which pulp nerves and vessels enter), inflammation from inside the tooth (pulpitis or pulp necrosis) can spread outward into the PDL and surrounding bone.

PDL Fibres and the Methylene Blue Test

When a healthy tooth is extracted from its socket:

The PDL is torn during extraction.
The periodontal fibres that were inserted into the cementum remain attached to the root surface.
If this extracted tooth is dipped into a diluted dye such as methylene blue, those fibres absorb the dye and turn dark blue.
In a healthy tooth, the entire length of the root will be stained, showing fibres all the way from crown to apex.
In a tooth with advanced periodontal disease, the fibres have been partially or completely destroyed by disease. Only the apical portion (which was unaffected or less affected) will stain, while the rest of the root surface will not take up the dye - visually demonstrating the extent of fibre destruction.

This is a simple but powerful way to visualize the extent of periodontal attachment loss.

Clinical Significance and Research Relevance

The PDL is one of the most investigated tissues in dentistry for several reasons:

It is involved in inflammatory periodontal diseases, which are among the most common causes of tooth loss worldwide.
After disease destroys the PDL and supporting bone, achieving reattachment (regeneration of the PDL and bone) is a major clinical and research goal - and remains a challenge.
Despite decades of research, aspects of the PDL remain poorly understood and controversial, making it an ongoing focus of scientific inquiry.

In summary, the PDL is a uniquely specialized tissue - not simply a "ligament" in the conventional sense - that plays structural, sensory, nutritive, and remodeling roles. Its anatomy, width, continuity with adjacent tissues, and response to disease all have direct clinical consequences in the practice of periodontics.

DEVELOPMENT OF THE PERIODONTAL LIGAMENT The dental follicle is composed of mesenchymal cells of the dental follicle proper in the centre and the perifollicular mesenchymal cells in the periphery (Fig. 40.2). As root formation continues, the perifollicular mesenchymal cells of the dental follicle gain polarity: Dental and exhibit enhanced synthetic activity. The cell elongates and demonstrates increased number of rough endoplasmic reticulum (RER), mitochondria and Golgi apparatus (GA) representing an actively secreting cell which progresses to synthesize and deposit collagen and glycoproteins and thus is called PDL fibroblast. rious ental issue eases ssible bject espite matic Development of the Alveolar Crest Group of Principal Fibres At the coronal third of the root, elaborated fibro-blasts from the dental follicle cells elongate. These cells orient themselves in an oblique direction to the long axis of the tooth and secrete collagen fibres. With the eruption of the tooth, these fibres form the alveolar crest group of fibres (Fig. 40.3). Development of Other Groups of Principal Fibres ymal d the cular larity First, small, fine, brush-like fibrils are found to arise from the cementum and extend into theperiodontal space. Simultaneously, from the surface of bone, a small number of thin collagen fibrils are seen arising. The number and thickness of fibrils on the side of the bone increase. The fibres originating from the cementum are still short while those extending from the bone gradually increase in length. Soon after, the fibres originating from the cementum increase in length and thickness, and blend with the fibres originating from the bone in the periodontal space forming the other group of fibres. The group of fibres in the coronal third of the root is established with the initial occlusal contact of the tooth and is called the horizontal group of fibres. The oblique group of fibres is still in the progress of formation. With definitive occlusion, the oblique group of fibres matures. Subsequently, the apical group of fibres is also established completing the architecture of the PDL. Oral Histology PDL Formation in Primary Tooth and Succedaneous Tooth The development of these fibres differs in teeth with predecessors compared with in those withoutpredecessors. These differences are due to the stage at which the alveolar bone is formed. In the development of teeth without predecessors such as permanent molars and primary teeth, the tooth crown erupts through the alveolar bone. The secondary teeth erupt through the bony crypt, lingual to the primary teeth. In addition, the alveolar bone must be deposited on the crypt lining before the formation of ligament fibres. Once the alveolar bone is deposited, the formation of the ligament is the same in teeth with predeces-sors and teeth without predecessors. Do the same like u did previously

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Development of the Periodontal Ligament (PDL)

The Dental Follicle - Starting Point

The PDL develops from the dental follicle, which has two distinct zones of cells:

Zone	Location	Cell Type
Dental follicle proper	Centre	Mesenchymal cells
Perifollicular mesenchyme	Periphery	Mesenchymal cells

As root formation begins and progresses, it is the perifollicular mesenchymal cells (the outer layer) that are activated. These cells:

Gain polarity - meaning they develop a defined orientation (a distinct "direction" to the cell), which is a prerequisite for organized tissue formation.
Show enhanced synthetic activity - the cell becomes metabolically very busy.

Transformation into a PDL Fibroblast

As these perifollicular cells become active, they undergo a visible transformation. Structurally, the cell:

Elongates in shape
Develops an increased number of rough endoplasmic reticulum (RER) - the organelle responsible for synthesizing proteins (especially collagen)
Develops more mitochondria - to supply energy for this high synthetic workload
Develops a prominent Golgi apparatus (GA) - responsible for packaging and secreting the synthesized proteins

This combination of features - elongated form, abundant RER, mitochondria, and Golgi - is the hallmark of an actively secreting cell. The cell proceeds to:

Synthesize and deposit collagen
Synthesize and deposit glycoproteins

At this point, the cell is now called a PDL fibroblast - the primary cell type of the mature periodontal ligament.

Development of Principal Fibre Groups

The principal fibres of the PDL do not all form at once. They develop in a specific sequence, tied to the stage of tooth eruption and occlusal contact.

1. Alveolar Crest Group - First to Form

Location: Coronal third of the root (nearest to the crown)

How it forms:

Fibroblasts elaborated from dental follicle cells in this region elongate.
They orient themselves in an oblique direction relative to the long axis of the tooth.
They secrete collagen fibres in this oblique orientation.
As the tooth erupts, these fibres mature and organize into the alveolar crest group of principal fibres.

2. Other Principal Fibre Groups - Sequential Formation

The remaining groups form through a well-coordinated, two-sided process:

Step 1 - Early fibrils from cementum:

Small, fine, brush-like fibrils emerge from the cementum surface and extend outward into the periodontal space.
At the same time, a small number of thin collagen fibrils begin arising from the surface of bone.

Step 2 - Bone-side fibres grow:

The fibrils on the bone side increase in both number and thickness progressively.
The cementum-side fibres are still short at this stage.

Step 3 - Cementum-side fibres catch up:

The fibres from the cementum also begin increasing in length and thickness.
Eventually, the fibres from both sides meet and blend together in the middle of the periodontal space.
This blending in the periodontal space is how the principal fibre groups are formed - from two ends growing toward each other and joining.

Step 4 - Horizontal group:

The fibres in the coronal third of the root become established when the tooth makes its first occlusal contact (initial bite contact).
This is called the horizontal group of fibres.
At this stage, the oblique group is still forming (not yet mature).

Step 5 - Oblique group:

With the establishment of definitive (full) occlusion, the oblique group of fibres matures.
This is the largest and most important group of PDL fibres in the fully erupted tooth.

Step 6 - Apical group:

After the oblique group is established, the apical group of fibres forms last.
Its formation completes the full architecture of the PDL.

Summary of Fibre Development Sequence:

Order	Fibre Group	Trigger for Formation
1st	Alveolar Crest Group	Tooth eruption
2nd	Horizontal Group	First occlusal contact
3rd	Oblique Group	Definitive occlusion
4th	Apical Group	After oblique group matures

PDL Formation: Primary Teeth vs. Succedaneous (Permanent) Teeth

The development of PDL fibres differs depending on whether a tooth has a predecessor (a primary tooth before it) or not.

Teeth WITHOUT Predecessors (e.g., Permanent Molars and Primary Teeth)

These teeth erupt directly through the alveolar bone.
There is no pre-existing tooth above them in the bone.
The alveolar bone must be deposited on the crypt lining first, before any ligament fibres can form.
Once the alveolar bone is laid down, fibre formation proceeds normally.

Teeth WITH Predecessors (Succedaneous Teeth - e.g., Permanent Incisors, Canines, Premolars)

These are the secondary (permanent) teeth that replace primary teeth.
They erupt through the bone lingual (tongue-side) to the primary teeth, not directly through them.
They emerge into an environment where a primary tooth still occupies the space above.
The same requirement applies - alveolar bone must be deposited on the crypt lining before ligament fibres form.

Key Point:

The difference between these two situations is due to the stage at which alveolar bone is formed in relation to the erupting tooth. However, once the alveolar bone is in place:

The formation of the ligament fibres follows the same process in both cases - regardless of whether the tooth had a predecessor or not.

In summary, PDL development is a precisely orchestrated sequence beginning with the activation of perifollicular mesenchymal cells, their transformation into fibroblasts, and the gradual, eruption-driven formation of fibre groups from the alveolar crest group all the way to the apical group. The presence or absence of a predecessor tooth affects the timing and environment, but not the fundamental mechanism of fibre formation once bone is available.

COMPONENTS OF THE PERIODONTAL LIGAMENT The PDL is a highly cellular and complex vascular structure composed of fibres which are principally collagenous. The ground substance contains cells, vessels and neural elements. Extracellular Matrix or Intercellular Substance This is a complex interactive compilation of proteins in a dynamic equilibrium that can regulate the gene expression of cells. Specific molecules in the extracellular matrix interact with genetically similar target cells to trigger a biological response that culminates in a distinct morphological and secretory result. The extracellular matrix is the intercellular substance of tissues and is composed of a diverse number of macromolecules. It regulates the cellular function by the following methods: 1. Binding of soluble growth factors 2. Mediating the adhesion of cells via integrins and proteoglycans, which provides cells with anchorage and directed migration 3. Providing signals for governing cell function The binding of growth factors to the matrix allows subsequent interaction with cells. The ability to localize and concentrate the growth factors with receptor-mediated cell binding to the matrix provides the organization of the tissue and also modulates the function of the tissue. In this way, the extracellular proteins are crucial for the dynamic progression of development and woundrepair as well as the initiation and progression of pathological alterations. The rapid expansion and identification of collagenous and noncollagenous proteins and proteoglycans suggest that the number and type of macromolecules in the periodontal matrix will continue to grow. Components of the Extracellular Matrix 1. Glycosaminoglycans and proteoglycans 2. Collagen 3. Oxytalan fibres 4. Noncollagenous proteins Functions of the Cell Surface Proteoglycans ar y 1. Cell adhesion 2. Cell-cell and cell-matrix interactions 3. Binding growth factors as coreceptors 4. Cell repair Fibres of the Periodontal Ligament As much as 90% of the fibres in the PDL are collag-enous. The remaining are oxytalan and reticulin fibres.Collagen Fibres Collagen is a proteinaceous, triple-helical structure composed of different amino acids such as glycine, proline, hydroxyproline and hydroxylysine. These are synthesized by fibroblasts, the cells of PDL. The formation of collagen can be understood as a two-step event: 1. Intracellular event: Proprotein formation (procollagen or tropocollagen) is similar to the formation of any other secretory protein of other cells. It is vitamin C dependent. 2. Extracellular events (a) Typical banded collagen microfibril formation (b) Fibril formation and fibre assembly Family of Collagen Proteins - The predominant extracellular matrix component of the periodontium is collagen. The collagen molecule consists of three distinct polypeptidechains called a-chains that form homotrimeric or heterotrimeric proteins. There are at least 27 types of collagen that have been identified so far in the human body. Of these, types I and III are found in abundance in the PDL and are classified as fibrous collagens. 1. Type I collagen forms the bulk (80%) of fibres in the PDL. 2. Small amounts of types V and VI and traces of types IV and VII have also been found in the PDL. 3. The rate of turnover of the collagen is faster in PDL compared with in all other connective tissues. The presence of type III perhaps explains this rapid turnover. The rate of turnover differs in various parts of the same tooth, the highest being at the root apex. The collagen fibres in PDL are about 5 µm in diameter. They are arranged in bundles running from the tooth to the bone. These fibres are known as the principal fibre bundles of the PDL. Theterminal portion of the principal fibres of the PDL inserted in the cementum and alveolar bone is known as Sharpey's fibres. These fibres are smaller at the cementum end compared with those at the alveolar bone end. The Sharpey's fibres in the acellular cementum are fully mineralized, whereas those in the cellular cementum and alveolar bone are partially mineralized. The mineralization occurs at about 90° to the long axis of the fibre. e f e e The principal fibres of the PDL can be grouped into five divisions according to how they are arranged. Table 40.1 lists the groups of PDL fibres (Fig. 40.4). Interstitial Spaces Interstitial spaces are found in between each prin-cipal fibre bundle and are appreciated in both. Oxytalan Fibres Oxytalan fibres are a form of immature elastin fibres, which are bundles of microfibrils of diameter ranging from 0.5 to 2.5 µm, comprisingabout 3% of the total extracellular fibre compo-sition. They seem to have type IV collagen and elastin components. These fibres run longitudi-nally from the cementum into the PDL proper which is parallel to the root surface and almost perpendicular to the oblique group of fibres. They terminate in the apical complex of vascular and neural components. Although the functions of these fibres are not completely understood, they are thought to be involved in the regulation of the vascular flow in the PDL. Also, they are found to be thicker in areas of heavy masticatory loads and orthodontic forces. Another form of immature elastin fibre, elaunin, is possibly seen within the PDL. Apart from the immature elastin fibres, smaller collagen fibres that are allied with larger principal collagen fibres and run in different directions forming a plexus are known. These are called indif-ferent fibre plexus. Do as same

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Components of the Periodontal Ligament

The PDL is described as a highly cellular and complex vascular structure. Its fibres are principally collagenous. The ground substance contains:

Cells
Blood vessels
Neural elements

Extracellular Matrix (ECM) / Intercellular Substance

The ECM is not a passive filler - it is a complex, dynamic, interactive compilation of proteins in a state of dynamic equilibrium. This means it is constantly being built up and broken down, and this balance can directly regulate gene expression in cells.

Specific molecules in the ECM can interact with genetically compatible target cells and trigger a biological response that leads to a specific:

Morphological result - a change in cell shape or structure
Secretory result - a change in what the cell produces

How the ECM Regulates Cellular Function:

The ECM regulates cells through three main mechanisms:

Binding of soluble growth factors - The matrix acts as a reservoir, capturing and holding growth factors. These bound growth factors can then interact with nearby cells when needed.
Mediating cell adhesion via integrins and proteoglycans - These molecules act as anchors, attaching cells to the matrix. They also provide directed migration - guiding cells to move in specific directions.
Providing signals for governing cell function - The matrix sends biochemical signals that tell cells what to do - whether to divide, differentiate, migrate, or stay dormant.

Why This Matters Clinically:

The ability of the ECM to localize and concentrate growth factors and mediate receptor-based cell binding allows it to:

Organize tissue architecture
Modulate tissue function

This makes the ECM critically important in:

Normal development
Wound repair
Initiation and progression of disease (pathological alterations)

Components of the Extracellular Matrix

The ECM of the PDL is made up of four major components:

Glycosaminoglycans (GAGs) and Proteoglycans
Collagen
Oxytalan fibres
Noncollagenous proteins

Proteoglycans - Functions of Cell Surface Proteoglycans

Proteoglycans are not just structural - they serve active functional roles:

Cell adhesion - help cells stick to the matrix
Cell-cell and cell-matrix interactions - mediate communication between cells and between cells and their surrounding matrix
Binding growth factors as co-receptors - work alongside receptors to capture and present growth factors to cells
Cell repair - involved in healing and tissue restoration

Fibres of the PDL

The fibre composition of the PDL is:

Fibre Type	Proportion
Collagenous fibres	~90%
Oxytalan and reticulin fibres	Remaining ~10%

Collagen Fibres

Structure of Collagen

Collagen is a proteinaceous, triple-helical structure - meaning it is made of protein and is wound into a triple helix. It is composed of specific amino acids:

Glycine
Proline
Hydroxyproline
Hydroxylysine

Collagen is synthesized by fibroblasts, the principal cells of the PDL.

Formation of Collagen - A Two-Step Process

Step 1 - Intracellular Event (Proprotein Formation):

The cell first makes a precursor protein called procollagen (also called tropocollagen).
This process is similar to how any other secretory protein is made in any cell.
Importantly, this step is vitamin C (ascorbic acid) dependent - a deficiency of vitamin C impairs collagen synthesis (which is why scurvy causes connective tissue breakdown).

Step 2 - Extracellular Events: Once the procollagen is secreted outside the cell, two things happen:

(a) Typical banded collagen microfibril formation - the precursor molecules assemble into microfibrils with a characteristic banded pattern.
(b) Fibril formation and fibre assembly - microfibrils bundle together to form fibrils, and fibrils bundle further to form full collagen fibres.

Family of Collagen Proteins

The collagen molecule is made of three polypeptide chains called alpha (α) chains, which can form:

Homotrimeric proteins - all three chains are identical
Heterotrimeric proteins - chains are of different types

There are at least 27 types of collagen identified in the human body. In the PDL specifically:

Collagen Type	Abundance/Role in PDL
Type I	Forms 80% of PDL fibres - the bulk
Type III	Present in significant amounts; explains the rapid collagen turnover in PDL
Types V and VI	Present in small amounts
Types IV and VII	Found only in traces

Types I and III are classified as fibrous collagens and are the most abundant.

Key Feature - Rapid Turnover:

The rate of collagen turnover (breakdown and replacement) in PDL is faster than in any other connective tissue in the body.
Type III collagen is associated with this rapid turnover.
Turnover rate varies within the same tooth - it is highest at the root apex.

Principal Fibre Bundles

Collagen fibres in the PDL are about 5 µm in diameter.
They are arranged in bundles running from tooth to bone.
These bundles are called the principal fibre bundles of the PDL.

Sharpey's Fibres

The terminal (end) portions of the principal fibres that are embedded (inserted) into the cementum and alveolar bone are called Sharpey's fibres.
At the cementum end, Sharpey's fibres are smaller.
At the alveolar bone end, they are larger.

Mineralization of Sharpey's Fibres:

Location	Degree of Mineralization
Acellular cementum	Fully mineralized
Cellular cementum	Partially mineralized
Alveolar bone	Partially mineralized

The mineralization occurs at approximately 90° (perpendicular) to the long axis of the fibre.

Five Groups of Principal Fibres

The principal fibres of the PDL are arranged into five groups based on their orientation and location (the passage references Table 40.1 and Figure 40.4 for the detailed list). These groups form in a developmental sequence as covered in the previous section (alveolar crest, horizontal, oblique, apical, and interradicular groups).

Interstitial Spaces

Between each principal fibre bundle, there are interstitial spaces. These spaces are important as they house the blood vessels, nerves, and loose connective tissue that support the PDL.

Oxytalan Fibres

Oxytalan fibres are a form of immature elastin fibres. Key features:

Made up of bundles of microfibrils
Diameter: 0.5 to 2.5 µm
Comprise approximately 3% of the total extracellular fibre composition
Appear to contain type IV collagen and elastin components

Orientation:

Run longitudinally from the cementum into the PDL proper
Run parallel to the root surface
Run almost perpendicular to the oblique group of principal fibres
Their ends terminate in the apical complex of vascular and neural components

Functions:

Not completely understood
Thought to be involved in regulating vascular flow within the PDL
Found to be thicker in areas of heavy masticatory (chewing) loads and areas under orthodontic forces - suggesting they respond to and help manage mechanical stress

Elaunin Fibres

Another form of immature elastin fibre, called elaunin, is possibly present within the PDL.
Less well characterized than oxytalan fibres.

Indifferent Fibre Plexus

Apart from the principal collagen fibres and oxytalan fibres, the PDL also contains:

Smaller collagen fibres that are associated with the larger principal collagen fibres
These smaller fibres run in multiple different directions, forming a plexus (a network)
This network is called the indifferent fibre plexus
They do not follow the organized directional pattern of the principal fibres

Summary Overview of PDL Fibre Components

Fibre	Type	Proportion	Key Role
Principal collagen fibres	Type I and III collagen	~90%	Anchor tooth to bone
Oxytalan fibres	Immature elastin	~3%	Vascular flow regulation
Elaunin fibres	Immature elastin	Trace	Not fully characterized
Reticulin fibres	Fine collagen	Small amount	Structural support
Indifferent fibre plexus	Small collagen fibres	Distributed	Multi-directional network

In summary, the PDL's extracellular matrix is a highly organized, biochemically active framework. Collagen - especially types I and III - dominates its fibre content, with the unique feature of very rapid turnover. Sharpey's fibres anchor everything firmly into bone and cementum, while oxytalan fibres and the indifferent plexus add supplementary structural and functional support.

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