Chapter 1: Periodontium: The Tooth-supporting Structures
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?
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?
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?
What is the apical boundary of the gingiva?
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?
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 appears in what percent of adults?
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?
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?
What is another name for alveolar process?
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?
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?
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