Tissues surrounding teeth PERIODONTIUM

Includes structures and tissues that surround and support the teeth

Alveolar Process Gingiva Periodontal Ligament/Membrane Cementum

Cementum Characteristics:

Covers root of tooth – forms a thin layer around the root

Has same density as bone 55% inorganic Contains fibers that attach tooth to the

alveolar bone

Cementum Cementum is a tissue of the tooth

and an important part of the supporting structure

Function: attachment of the tooth in its socket

Cementum Clinical concerns:

May be exposed with recession of gingiva

Removal of some of cementum could expose dentin

Extreme sensitivity is experienced by patients with exposed cementum and dentin

Cementum Clinical concerns:

Cemental spurs may form at C E J• Calculus is easy to remove, spurs are not

Hypercementosis – occurs at apex in response to trauma

Alveolar Bone Structure:

Bones in the maxilla and mandible are formed by osteoblasts

Extended areas of bone that hold the teeth are referred to as the alveolar process

Alveolar bone/process Lamina dura – outside layer of bone

surrounding the periodontal ligament

Lamina dura – ‘hard layer’ (like the crust of bread)

Cortical bone – compact or dense layer of bone

Alveolar bone/process Cancellous bone – inner or central

part of alveolar bone Cancellous bones is also referred to

as trabecular bone Spongy or porous in appearance

Alveolar bone/process Function:

Supports the tooth

Stabilizes the root

Alveolar bone Clinical concerns:

Periodontal disease can cause loss of bone

Bone is stimulated from chewing and speech – if teeth are removed this stimulation is lost and bone resorbs

Alveolar Process

Lamina dura, cortical, spongy

Periodontal Ligament Surrounds the root of the tooth Composed of fibers, or ligaments,

that support and suspend the tooth in the socket

Fibers are arranged in bundles Forms a ‘shock-absorber’ for the

tooth in the socket

Periodontal ligament Contains fibers for attachment Contains nerves, blood vessels and

lymph vessels

Periodontal ligament FUNCTIONS: Supportive – maintains tooth in socket Sensory – nerves supply ‘sense of touch Formative – fibroblasts, cementoblasts Protective- cushion-like action from shock Nutritive– blood vessels provide nutrients

Periodontal fiber groups Alveolar crest fibers-extend from cervical

area of tooth to alveolar crest Horizontal group – run at right angles Oblique group – slants into alveolar bone Apical group – extend from apex Interradicular –only in multi-rooted teeth Transseptal – from one tooth to another

PDL Fibers

Periodontal fiber groups Most important fibers:

Oblique – largest group – resist vertical (up and down) force• Work like shock absorbers

Transseptal or interdental – support interdental gingiva

Gingival fiber group Found above the alveolar bone crest

and below the epithelium Dentogingival fibers Circular ligament fibers Alveologingival fibers Dentoperiosteal fibers

Periodontal ligament Clinical considerations:

Occlusal trauma does not cause periodontal disease but can accelerate an existing condition

Chronic periodontal disease causes the fiber groups to become disorganized and lose attachment due to resorption

Gingiva Only portion of periodontium visible

in oral cavity Made up of epithelial tissue covered

with mucosa Surrounds cervix of tooth Fills interproximal spaces

Gingiva Free Gingiva – movable – fits snugly

around the crown just above the cervix of tooth

Attached Gingiva – non-movable – extends from the base of the sulcus to the mucogingival junction Attached directly to the cementum and

alveolar process

Gingiva

Gingiva Characteristics of normal tissue:

1) adapts tightly to tooth and bone 2) firm and resistant 3) surrounds tooth in collar-like fashion 4) color varies from pink to coral 5) surface is stippled

• Stippling – like surface of an orange

Gingiva Alveolar mucosa – appears thin and

loosely attached Attached gingiva – part that is stippled Gingival sulcus – space between the

unattached gingiva and the tooth Normal depth is about 2 mm

Gingival papilla – interdental extension of free gingiva (between teeth)

Mucosa -- differences

Masticatory mucosa – dense covering in the mouth Withstands activity of mastication (chewing) Covers gingiva and hard palate

Lining mucosa – covers the oral soft tissues that are not covered by masticatory mucosa Covers insides of cheeks, soft palate, floor of

mouth; tears and injures easily

Gingiva Clinical considerations:

Certain drugs can affect the gingiva and cause gingival hyperplasia, (over growth of tissue)

Tissue can become inflamed to fight infection – appearing swollen and red, bleeds easily, and looses its stippling

Gingival description Healthy gingiva is pink and stippled

on the attached portion. Normal gingiva is firm and resilient;

it follows the contour of the bone and fills the interproximal spaces, forming a sharp, knifelike triangular point at the contact area.

Gingival description Attached gingiva adheres tightly to

the bone and is pale, compared to the smooth shiny alveolar mucosa, which contains many blood vessels and thus appears more red in color.

Review: Periodontium – supporting structure

of the tooth – composed of:

Cementum Periodontal ligament Gingiva Alveolar process

Review: Healthy gingiva: Fits tightly around tooth and bone Surrounds like a collar Color varies with ethnicity Surface is stippled

Review: Two types of gingiva: Free gingiva Attached gingiva

Review: Function of periodontal ligament Most important function is

supportive – maintains the tooth in the socket by fiber attachment

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