Dentistry: Cementum Characteristics

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Questions and Answers

What is the main function of cementum in relation to the periodontal fibers?

It provides a medium for the incorporation of the principal periodontal fibers (correct)

It aids in the resorption of the root

It helps to remove plaque and tartar

It acts as an anchor for the tooth in the alveolar bone

What is the thickness of cellular mixed cementum?

100-1000 μm (correct)

30-230 μm

1000-1500 μm

1-15 μm

What is cementum?

A specialized calcified mesenchymal tissue that covers the root (correct)

A type of dentin

A type of enamel

A type of bone tissue

Where is the cellular intrinsic cementum typically found?

Apical third of roots and furcation areas Signup and view all the answers

What is the characteristic of intact cementoenamel junction?

An edge-to-edge butt joint exists Signup and view all the answers

What is the hardness of cementum compared to dentin?

Less than that of dentin Signup and view all the answers

What is the function of cementum in case of root fracture or resorption?

It serves as a reparative tissue Signup and view all the answers

What is the color of cementum?

Light yellow Signup and view all the answers

What is unique about the composition of cementum?

High fluoride content Signup and view all the answers

What is the characteristic of overlapping cementoenamel junction?

Cementum overlaps the enamel Signup and view all the answers

What is the function of cementoblasts?

Forming cementum during tooth formation Signup and view all the answers

What is the function of cementum in relation to functional adaptation?

It restores the integrity of the attachment apparatus Signup and view all the answers

What is the percentage of intact cementoenamel junction?

30% Signup and view all the answers

Where is the thickness of cementum greatest?

In the apical third Signup and view all the answers

What is the characteristic of acellular cementum?

It is highly calcified Signup and view all the answers

What is the characteristic of cellular cementum?

It is less calcified Signup and view all the answers

What is the alveolar process primarily responsible for?

Supporting and forming the tooth socket Signup and view all the answers

What is the outermost layer of the alveolar bone composed of?

External plate of cortical bone Signup and view all the answers

What is the term given to the bone adjacent to the periodontal ligament?

Bundle bone Signup and view all the answers

During which process is the alveolar bone formed?

Intramembranous ossification Signup and view all the answers

What is the primary component of the inorganic matter in bone?

Hydroxyapatite crystals Signup and view all the answers

What is the primary function of the alveolar bone?

To support the tooth roots Signup and view all the answers

What is the function of Sharpey's fibers?

To attach the periodontal ligament Signup and view all the answers

What is the result of bone remodeling in the alveolar bone?

Changes in shape, resistance to forces, repair of wounds, and calcium and phosphate homeostasis Signup and view all the answers

What is the purpose of excessive formation of cementum on the apical root surface?

To restore normal occlusion after occlusal and incisal wear Signup and view all the answers

Which of the following is a local condition that can cause cementum resorption?

Orthodontic movement Signup and view all the answers

What is hypercementosis?

An abnormal thickening of cementum Signup and view all the answers

What is the term for the overgrowth of cementum that improves the functional qualities of the cementum?

Cementum hypertrophy Signup and view all the answers

What is the term for the union of tooth and bone with no intervening connective tissue?

Ankylosis Signup and view all the answers

What is the term for the irregular and calcified epithelial rests found in localized areas of hyperplastic cementum?

Excementosis Signup and view all the answers

Which of the following can cause ankylosis?

All of the above Signup and view all the answers

What is the term for the abnormal thickening of cementum that occurs in non-functional teeth?

Cementum hyperplasia Signup and view all the answers

Study Notes

Cementum

Definition: Specialized calcified mesenchymal tissue that covers the root and is part of the hard tissue component of the periodontium.
Characteristics:
- Hardness is less than that of dentin.
- Light yellow in color.
- Semi-permeable to a variety of materials.
- Contains inorganic substances, organic material, and water.
- Highest fluoride content of all mineralized tissues.
Composition:
- Organic: 30% (collagen: Type I 90%, Type III 5%)
- Inorganic: 70% (hydroxyapatite: Ca10(PO4)6(OH)2)
Structure:
- Cellular: cementocytes (form cementum during tooth formation) and cementoblasts (found in lacuni, form cementum in resorption foci)
- Fibrillar: extrinsic and intrinsic fibers
- Ground substance
Thickness:
- Varies: 16-60um (coronal), 120-200um (apical)
- Thicker in distal surfaces than in mesial surfaces
Types:
- Acellular: Sharpey's fibers make up most of its structure, thickness 30-230 μm
- Cellular: less calcified, formed after tooth reaches occlusal plane, irregular and contains cells (cementocytes)

Cementum Classification

Acellular Afibrillar: product of cementoblasts, most coronal, thickness 1-15 μm
Acellular Extrinsic Fibrillar: product of fibroblasts and cementoblasts, composed of densely packed bundles of Sharpey's fibers, cervical third of roots, thickness 30-230 μm
Cellular Mixed: composed of extrinsic and intrinsic fibers, may contain cells, co-product of cementoblasts and fibroblasts, apical third of roots, thickness 100-1000 μm
Cellular Intrinsic: contains cells but no extrinsic collagen fibers, formed by cementoblasts, fills resorption lacunae
Intermediate: poorly defined zone near the cementodentinal junction, contains cellular remnants of Hertwig's sheath embedded in calcified ground substance

Cementoenamel Junction (CEJ)

Borderline between cementum and enamel
Three types of relationships:
- Intact: 30%, edge-to-edge butt joint exists
- Deficient: 5-10%, enamel and cementum fail to contact
- Overlapping: 60-65%, cementum overlaps the enamel

Functions of Cementum

Furnishes a medium for the incorporation of the principal periodontal fibers, securing the binding of the tooth root to the alveolar bone
Serves as a reparative tissue in case of root fracture or resorption
Functional adaptation: restores the integrity of the attachment apparatus, excessive formation of cementum on the apical root surface to compensate for occlusal and incisal wear

Cementum Resorption and Repair

Causes: local or systemic, idiopathic, trauma from occlusion, orthodontic movement, pressure from malaligned erupting teeth, cysts, tumors, etc.
Abnormalities:
- Hypercementosis: abnormal thickening of cementum, diffuse or circumscribed
- Ankylosis: union of tooth and bone with no intervening connective tissue, develops after chronic periapical inflammation, tooth replantation, and occlusal trauma
- Excementosis: embedded calcified round bodies in localized areas of hyperplastic cementum

Alveolar Bone

Definition: part of the jaw that forms and supports the teeth socket
Formation: forms when the teeth erupt to provide the osseous attachment to the forming PDL
Disappearance: disappears gradually after the tooth is lost
Components:
- External plate of cortical bone: formed by Haversian bone and compact bone lamellae
- Alveolar bone proper: inner socket wall formed of thin, compact bone and bundle bone
- Cancellous trabeculae: lie between the two compact bone, acts as support for the alveolar bone

Socket Wall

Consists of dense, lamellated bone, some of which is arranged in haversian systems, and bundle bone
Bundle bone: bone adjacent to the periodontal ligament that contains a great number of Sharpey's fibers

Functions of Alveolar Bone

Protection: forms and protects the sockets for the teeth
Attachment: gives the attachment to the periodontal ligament fibers
Support: supports the tooth roots on the facial and on the palatal/lingual sides
Shock-absorber: helps absorb the forces placed upon the tooth by disseminating the force to underlying tissues

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Description

This quiz covers the characteristics of cementum, a calcified tissue that covers the root and is part of the periodontium. Learn about its hardness, color, and composition.