Chapter 1: Periodontium: The Tooth-supporting Structures

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What is periodontium?

The functional system of tissues that surrounds the teeth and attaches them to the jaw bone

What is the periodontium also called?

"Supporting tissues of the teeth" and "the attachment apparatus"

What do the tissues of the periodontium include?

Gingiva, periodontal ligaments (PDL), cementum, and alveolar bone

What is the gingiva?

Tissue that covers the cervical portions of the teeth and the alveolar processes of the jaws

What is the periodontal ligament (PDL)?

Fibers that surround the root of the tooth

What does the PDL attach to?

the bone socket on one side and the cementum of the root on the other

What is the cementum?

Thin layer of mineralized tissue that covers the root of the mouth

What is alveolar bone?

Bone that surrounds the roots of the teeth

What does the alveolar bone form that support and protect the roots of the teeth?

Bony sockets

What does the bony sockets help do?

Support and protect the roots of the teeth

What is the function of a periodontal ligament?

Suspends and maintains the tooth in its socket

What is the function of the cementum?

Anchors the ends of the periodontal ligament fibers to the tooth so that the tooth stays in its socket

What is the function of the alveolar bone?

Surrounds and supports the roots of the tooth

Knowledge of the periodontal tissues in health is a necessary foundation for understanding the concepts of what?

Normal function of the periodontium, disease prevention, and periodontal disease process

Where does the gingiva end?

Coronal to the cementoenamel junction (CEJ) of each tooth

How does the gingiva attach to the tooth?

By a specialized type of epithelial tissue called the junctional epithelium

What is the specialized type of epithelial tissue that attaches the gingiva to the tooth called?

Junctional epithelium

What is the gingiva composed of?

A thin outer layer of epithelium and an underlying core of connective tissue

What are the four anatomical areas of the gingiva?

Free gingiva, gingival sulcus, interdental gingiva, and attached gingiva

What is the function of the gingiva?

Protects the underlying tooth supporting structures of the periodontium from the oral environment

What is the oral environment exposed to?

A wide range of temperatures in food and drink, mechanical forces, and a large number of oral bacteria

What are some of the defense mechanisms of the gingiva?

Saliva and immune system defense mechanism

What is the coronal boundary of the gingiva?

Gingival margin

What is the apical boundary of the gingiva?

Alveolar mucosa

How is the alveolar mucosa distinguished from the gingiva?

By its dark red color and smooth shiny surface

What is the free gingival groove?

A shallow linear depression that separates the free and attached gingiva

What is the mucogingival junction?

The clinically visible boundary where the pink attached gingiva meets the red shiny alveolar mucosa

What is the free gingiva?

Unattached portion of the gingiva that surrounds the tooth in the region of the CEJ

What is the free gingiva also known as?

The unattached gingiva or the marginal gingiva

Where is the free gingiva located?

Coronal to the CEJ and surrounds the tooth in a cufflike manner

What does the free gingiva attach to the tooth by means of?

A specialized epithelium called the junctional epithelium

What is the specialized epithelium that attached the free gingiva to the tooth?

Junctional epithelium

Is the free gingiva directly attached to the tooth?

No, it fits closely

What can be used to stretch the unattached gingiva away from the tooth surface with a periodontal probe?

A periodontal probe

What does the free gingiva form the soft tissue wall of?

The gingival sulcus

The tissue of the free gingiva meets the tooth where?

In an edge called the gingival margin

What does the gingival margin look like?

A thin rounded edge or knife edge like

What does the gingival margin follow?

The contours of the teeth

What sort of outline does the gingival margin create?

A scalloped wavy outline

What is the attached gingiva?

The part of the gingiva that is tightly connected to the cementum on the cervical third of the root and to the periosteum of the alveolar bone

Where is the attached gingiva?

Between the free gingiva and the alveolar mucosa

Where is the attached gingiva widest?

In the incisor and molar regions

What is the range of the attached gingiva in the mandible?

3.3 to 3.9 mm on the mandible

What is the range of the attached gingiva in the maxilla?

3.5 to 4.5 mm on the maxilla

Where is the attached gingiva narrowest?

In premolar regions

What is the measurement of the attached gingiva in the narrowest regions?

1.8 mm in the mandible and 1.9 in the maxilla

Where is the width of the attached gingiva not measured?

On the palate

Why is the width of the attached gingiva not measured on the palate?

Because it is clinically not possible to determine where the attached gingiva ends and the palatal mucosa begins

What concept was once believed but no longer accepted today?

A minimum of 2 mm width of the attached gingiva is necessary to maintain the health of periodontium

What is the color of the attached gingiva?

Pale or coral pink

When does pigmentation occur frequently in the attached gingiva?

Dark skinned individuals

What color is the pigmented areas of the attached gingiva?

can range from light brown to black

What is the texture of the attached gingiva?

A dimpled appearance similar to the skin of an orange peel

What is the dimple appearance similar to the skin of an orange peel known as?

Stippling

Stippling appears in what percent of adults?

40%

Does stippling occur in healthy tissue?

It may or may not occur, varies from individual to individual

What does attached gingiva allow for?

The gingival tissue to withstand the mechanical forces created during activities such as mastication, speaking, and toothbrushing

What does the attached gingiva prevent from happening?

The free gingiva being pulled away from the tooth when tension is applied to the alveolar mucosa

What allows the gingival tissue to withstand the mechanical forces created during activities such as mastication, speaking, and toothbrushing?

The attached gingiva

What prevents the free gingiva from being pulled away from the tooth when tension is applied to the alveolar mucosa?

Attached gingiva

What is the interdental gingiva?

The portion of the gingiva that fills the interdental embrasure between two adjacent teeth apical to the contact area

What does the interdental gingiva consists of what?

Two interdental papillae

What are the two interdental papillae of the interdental gingiva?

One facial papilla and one lingual papilla

What are the lateral borders and tip of an interdental papillae formed by?

The free gingiva from the adjacent teeth

What is the center portion of the interdental papilla formed by?

The attached gingva

What is the col?

A valleylike depression in the portion of the interdental gingiva that lies directly apical to the contact area

Where is the col located?

Directly apical to the contact area

When is the col not present?

If the adjacent teeth are not in contact or if the gingiva has receded

What is the function of the intergingival gingiva?

Prevents food from becoming packed between the teeth during mastification

What is the gingival sulcus?

The space between the free gingiva and the tooth surface

What is the shape of the gingival sulcus?

V-shaped, shallow space around the tooth

What is the depth of a clinically normal gingival sulcus?

1 to 3 mm as measured using a periodontal probe

What is the base of the gingival sulcus formed by?

The junctional epithelium

What is a junctional epithelium?

A specialized type of epithelium that attaches to the tooth surface

What is the gingival crevicular fluid?

A fluid that seeps from the underlying connective tissue into the sulcular space

What is another name for the gingival crevicular fluid?

Gingival sulcular fluid

How much fluid is found in the healthy gingival sulcus?

Little or no fluid

When does fluid flow increase in the gingival sulcus?

In the presence of dental plaque biofilm and the resulting gingival inflammation; in response to toothbrushing, mastication, or other stimulation of the gingiva; flow is greatly increased when the gingiva are inflamed

What does a filter strip do when inserted into the gingival sulcus?

It absorbs the fluid in the sulcus

What can the filter strip measure?

The amount of gingival crevicular fluid can be measured and used as an index of gingival inflammation

What is a Periotron?

Used to measure how much fluid was on filter strip to indicate inflammation

What is a periodontal ligament?

A layer of soft connective tissue that covers the root of the tooth and attaches it to the bone of the tooth socket

What is the periodontal ligament composed mainly of?

Dense fibrous connective tissue

Where do the fibers of periodontal ligament attach?

On one side of the root cementum and on the other side to the alveolar bone of the tooth socket

How does the periodontal ligament protect the tooth in its socket?

The periodontal ligament not only connects the tooth to the alveolar process but also supports the tooth in the socket and absorbs mechanical loads placed on the tooth, thus protecting the tooth in its socket

What are the five functions of the periodontal ligament in the periodontium?

1. Supportive function
2. Sensory function
3. Nutritive function
4. Formative function
5. Resorptive function

What is the supportive function of the periodontal ligament in the periodontium?

Suspends and maintains the tooth in its socket

What is the sensory function of the periodontal ligament in the periodontium?

Provides sensory feeling to the tooth, such as pressure and pain sensations

What is the nutritive function of the periodontal ligament in the periodontium?

Provides nutrients to the cementum and bone

What is the formative function of the periodontal ligament in the periodontium?

Builds and maintains cementum and the alveolar bone of the tooth socket

What is the resorptive function of the periodontal ligament in the periodontium?

Can remodel the alveolar bone in response to pressure, such as that applied during orthodontic treatment

What is proprioception?

Sensitive to pressure or touch

What is cementum?

A thin layer of hard, mineralized connective tissue that covers the surface of the tooth root

What is cementum attached to?

Cementum overlies and is attached to the dentin of the root

What color is cementum?

Light yellow in color and softer than dentin or enamel

What is an important characteristic of cementum?

Resistance to resorption (loss of substance) is an important characteristic of cementum that makes it possible for the teeth to be moved during orthodontic treatment

What does the high resistance of cementum to resorption allows for?

The pressure applied during orthodontics to cause resorption of the alveolar bone, for tooth movement, without resulting in root resorption

What are the types of cementum?

Acellular and cellular

How does cementum receive nutrients?

Cementum does not have its own blood or nutrient supply; it receives its nutrients from the periodontal ligament

Why is conservation of cementum a goal of periodontal instrumentation?

Because cementum performs several important roles in the periodontium

What is the primary function of cementum?

To give attachment to the collagen fibers of the periodontal instrumentation

What does cementum anchor to the tooth?

The ends of the periodontal ligament fibers

What happens if there is no cementum?

The tooth would fall out of its socket

What is the function of the outer layer of cementum?

Protects the underlying dentin and seals the ends of the open dentinal tubules

What does cementum formation compensate for?

Tooth wear at the occlusal or incisal surface due to attrition

Cementum is formed at the apical area of the root to compensate for what?

Occlusal attrition

What is another name for alveolar process?

Alveolar bone

What is alveolar process?

The bone of the upper or lower jaw that surrounds and supports the roots of the teeth

What is alveolar bone composed of?

Mineralized connective tissue and consists, by weight, of about 60% inorganic material, 25% organic material, and about 15% water

What is the existence of the alveolar bone is dependent on?

The presence of teeth

What happens when teeth are extracted?

Alveolar bone resorbs

What happens if teeth do not develop?

Alveolar bone does not develop

What is the function of alveolar bone in the periodontium?

Alveolar bone forms the bony socket that provide support and protection for the roots of the teeth

What tissues is the alveolar process composed of?

Three layers of hard tissue and covered by a thin layer of connective tissue

What is the alveolar bone proper?

The thin layer of bone that lines the socket to surround the root of the tooth

What is another term for alveolar bone proper?

Cribriform plate, lamina dura in radiographs

What is the alveolus?

The bony socket, a cavity in the alveolar bone that houses the root of a tooth

What do the numerous holes in the alveolar bone proper allow for?

Blood vessels from the cancellous bone to connect with the vessels of the periodontal ligament space

What is embedded in the alveolar bone proper?

Ends of the periodontal ligament fibers

What is the cortical bone?

A layer of compact bone that forms the hard, outside wall of the mandible and maxilla on the facial and lingual aspects

What does the cortical bone surround?

The alveolar bone proper and gives support to the socket

Where is the buccal cortical bone thin?

In the incisor, canine, and premolar regions

Where is the cortical bone thick?

In molar regions

Why won't the cortical plate appear in radiograph?

Because it is only on the lingual and facial sides of the jaw

Which bones can be seen in a radiograph?

cancellous bone and alveolar bone proper

What is the most coronal portion of the alveolar process?

Alveolar crest

In health, where is the alveolar crest located?

1 to 2 mm apical to the CEJ of the teeth

When viewed from the facial or lingual aspect, how does the alveolar crest appear?

The alveolar crest meets the teeth in a scalloped/wavy line that follows the contours of the CEJs

What is another name for cancellous bone?

Spongy bone

What is cancellous bone?

The latticelike bone that fills the anterior portion of the alveolar process

Where is the cancellous bone oriented?

Around the tooth to form support for alveolar bone proper

What is the function of cancellous bone?

To form support for alveolar bone proper

What is periosteum?

A layer of connective soft tissue covering the outer surface of bone

What does the periosteum consist of?

An outer layer of collagenous tissue and an inner layer of fine elastic fiber

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