(Finals) OHE Laboratory: Periodontium

Cementum

What hard, avascular tissue covers the roots of teeth?

Root apex and in interradicular areas of multirooted teeth

Where is the thickest part of the cementum?

Bone

The composition of the cementum closely resembles ______.

Cementum

What is both a part of the tooth and the periodontium?

• Light yellow

• Not as hard as dentin

• Permeable

What are the physical properties of Cementum?

45-50% - Calcium hydroxyapatite crystals

What is the chemical composition of Cementum - Inorganic Material?

50-55% - Water, proteins, and Type I collagen

What is the chemical composition of Cementum - Organic Material?

Support

Function of Cementum that: Provides attachment for teeth

Protection

Function of Cementum that: Helps prevent root resorption during tooth movement

Formative

Function of Cementum that: Continual apical cementum deposition accounts for continual tooth eruption and movement

Cellular and Acellular Cementum

Classification of Cementum - By Cellularity

• Intrinsic Fibers

• Extrinsic Fibers

• Mixed Fibers

Classification of Cementum - By Collagen Fibers

Primary and Secondary Cementum

Classification of Cementum - By Formation

Cellular Cementum

• Contains cementocytes, cementoblasts, and cementoclasts.

• Most commonly found in apical areas of cementum.

• Provides attachment for the tooth.

Acellular Cementum

• Devoid of cells.

• Most commonly found in coronal areas of cementum.

• Adaptive role in response to tooth wear.

• Movement and is associated with repair of periodontal tissues.

Intrinsic Fibers

• Produced by cementoblasts;

• Arranged parallel to the tooth surface

Extrinsic Fibers

• Produced by the PDL; arranged perpendicular to the tooth surface ― as they become trapped in the cementum.

• They are known as Sharpey’s fibers (fiber attached to cementum on one side and attached to the alveolar bone proper on the other side).

Mixed Fibers

Intrinsic + Extrinsic Fibers

Primary Cementum

• First formed cementum;

• Covers coronal cementum, is acellular, and

• Consists of extrinsic collagen fibers.

Secondary Cementum

• Overlies primary cementum.

• Covers apical cementum, may be acellular or cellular, and consists of mixed collagen fibers.

Acellular Afibrillar Cementum

no cells, no fibers

Acellular Extrinsic Fiber Cementum

no cells, with fibers; primary cementum

Cellular Mixed Fiber Cementum

with cells, and both intrinsic and extrinsic fibers; present in apical 3rd of the root, with lacunae

Cellular Intrinsic Fiber Cementum

with cells, and intrinsic fibers; secondary cementum

Intermediate Cementum

first layer, seals the tubules

Clinical Implications (Cementum)

enables orthodontic tooth movement because it is more resistant to resorption of alveolar bone

Periodontal Ligament

What is the soft connective tissue located between the tooth and alveolar bone?

Periodontal Ligament

PDL is approximately ______ wide but varies with tooth function and age.

Organic material: 100% - Collagen Type I (mostly) & III

What is the chemical composition of PDL?

Support

Function of PDL that: Provides attachment of the tooth to the alveolar bone.

Formative

Function of PDL that: Contains cells responsible for formation of the periodontium.

Nutritive

Function of PDL that: Contains a vascular network providing nutrients to its cells.

Sensory

Function of PDL that: Contains afferent nerve fibers responsible for pain, pressure, and proprioception.

Remodeling

Function of PDL that: Contains cells responsible for _______ of the periodontium.

Fibroblasts

Most common cells of the PDL.

Ground Substance

From PDL: Proteoglycans, glycosaminoglycans, glycoproteins, and water (70%).

Epithelial Rests of Malassez

• Remnants of HERS.

• Found closer to cementum than alveolar bone.

Cementicles

Calcified masses either attached or unattached to root surfaces.

Transseptal fibers

• Extend interproximally over the alveolar crest from the cementum of one tooth to that of an adjacent tooth.

• Resist mesial and distal forces

Alveolar crest fibers

• Extend obliquely from cementum just apical to the junctional epithelium to the alveolar crest.

• Resist vertical (intrusive/extrusive) forces.

Horizontal fibers

• Extend at right angles from cementum to alveolar bone.

• Resist lateral (tipping) and rotational forces.

Oblique fibers

• Extend obliquely from cementum to alveolar bone.

• They are the most abundant principal fibers.

• Main resistance to masticatory (intrusive and rotational) forces.

Apical fibers

• Extend from cementum to alveolar bone at root apices.

• Resist vertical (extrusive) forces.

Interradicular fibers

• Extend from radicular cementum to interradicular alveolar bone.

• Only present in multirooted teeth.

• Resist vertical (intrusive/extrusive) and lateral (tipping) forces.

• Transseptal fibers

• Alveolar crest fibers

• Horizontal fibers

• Oblique fibers

• Apical fibers

• Interradicular fibers

What are the principal collagen fibers?

Oxytalan fibers

• Elastic-like fibers that run parallel to the tooth surface and bend to attach to cementum.

• They are largely associated with blood vessels.

Clinical Implications (PDL)

When there is an increase in load or mechanical stress (for example, during chewing or orthodontic tooth movement),

There is an increase in the number and density of PDL fibers, including oxytalan fibers, to strengthen the ligament and adapt to the new stress.

Alveolar Bone

What is a general term to describe the bone in the maxilla and mandible which houses the teeth?

Alveolar Bone

What forms the eruption of tooth to provide osseous attachment to forming PDL?

Alveolar Bone

What disappears with loss of tooth?

Interalveolar Septum

The bony projection separating two alveoli.

Interradicular Septum

Alveolar bone between the roots of multi-rooted teeth.

Differentiated ectomesenchymal cells of the dental follicle.

What is the origin of the Alveolar Bone?

• Alveolar Bone Proper

• Supporting Alveolar Bone

  • Cortical bone

  • Cancellous bone

What are the components of the Alveolar Bone?

Alveolar Bone Proper

• The thin layer of cortical bone that immediately surrounds the teeth and into which PDL fibers (Sharpey’s fibers) are embedded.

• AKA bundle bone, lamina dura, or cribriform plate.

Supporting Alveolar Bone

The part of the alveolus that surrounds the alveolar bone proper. It consists of the ff:

• Cortical Bone

• Cancellous Bone

Cortical Bone (cortical plate)

• Forms the buccal and lingual outer surfaces of the maxilla and mandible.

• It is generally thicker in the mandible and in posterior (molar) regions.

Cancellous Bone (spongy bone, trabecular bone)

• Fills the area between the cortical plates.

• It makes up the majority of alveolar bone.

lamina dura

The radiographic appearance of the _______ is determined as much by the x-ray beam angulation as it is by its integrity.

TRUE

The radiographic presence (or absence) of the crestal lamina dura has no correlation with periodontal attachment loss.