Periodontium I Flashcards
What is the periodontium?
What 3 structures make it up?
Tissues that invest and support the tooth
- Alveolar process
- Cementum
- PDL
When does the periodontium develop?
Series of complex interactions of mesenchymal, HERS, and dental follicle
What are the gomphoses?
Fibrous peg-in-socket joint
What is the fx of teeth?
Survive cycling loading over time
What are the origins of the periodontium?
Osteoblasts - Surrounding mesenchymal (NOT ECTOMESENCHYME) tissues
Cementoblasts - HERS/follicle cells - Ectomesenchymal cells
PDL fibroblasts - Follicle cells/ectomesenchymal cells
Odontoblasts - Form dentin part of the cemento-dental junction, dental papilla
T/F - The periodontium contains 3 out of the 4 types of mineralized tissues found in the oral cavity.
TRUE
Bone, dentin, cementum
—NOT ENAMEL
What is avulsion?
Traumatic removal of teeth
The alveolar process is formed by what?
Intramembranous ossification
-Mesenchyme direct to bone - NO CARTILAGE INTERMEDIATE
When does the alveolar process form?
8th week of uterine life
- Tooth germs contained in horseshoe-shaped grooves of the mandible and maxilla
- Crypts develop around tooth germs, such that they eventually form the sockets
T/F - The alveolar process develops substantially during tooth eruption, under the influence of the dental follicle.
TRUE
-Remodeled thru-out life
What is an anodontic individual?
Alveolar process development impaired
What are the differences b/t alveolar bone proper and supporting alveolar bone?
Alveolar bone proper (right around tooth)
-Compact bone
—Cribiform plate, lamina dura
Supporting alveolar bone (supports the compact bone around the tooth)
-Compact and trabecular bone
—Compact: Cortical plates
—Trabecular: Central spongiosa
What are the 3 parts of the alveolar bone proper and describe them?
Cribriform plate - Volkmann’s canals running thru it
Lamina dura - Area of PDL attachment
Bundle bone - Sharpey’s fibers (PDL) embedded in bone
T/F - W/o the dental follicle, a tooth will NOT erupt.
TRUE
Tell me about the inner part of the alveolar bone proper.
Remodeling rate my be high due to constant adaptation to tooth movements
—Consists of woven bone, but some lamellar bone is present
—Smooth surface in young individuals, but comes rougher with age
Tell me about the outer portion of the alveolar bone proper.
Lamellar bone, continuous with supporting alveolar bone
Tell me about the cortical plate of the supporting alveolar bone.
Inner - Lingual and palatal surface
Outer - Labial and buccal surface
What is the alveolar crest?
Junction of cortical plate and alveolar bone proper
-Thinner in maxilla, thicker in premolars and molar region of mandible
Tell me about the central spongiosa.
Trabecular bone supporting alveolar bone proper and cortical plate
Marrow - Red (hemopoietic in young, yellow in aged
T/F - Spongiosa is more prevalent than mandible.
TRUE
T/F - Spongiosa is often absent/diminished in anterior region of both jaws.
TRUE
Tell me about the two parts of the bone septa.
Interradicular septum
-Bony septum b/t roots of a single tooth
Interalveolar septum
-Bony septum b/t adj teeth
What are 4 functions of alveolar bone?
Protection and structure of the socket for the tooth to rest in
Attachment of Sharpey’s fibers of the PDL which are embedded in bone
Support of tooth roots, esp facial and lingual
Distribution of loading from the tooth and PDL to the surrounding bone
Ectomesenchymal cells from the _________ _________ differentiate into fibroblasts which produce and organize collagen fibers, generally in an oblique orientation.
Dental follicle
T/F - PDL fiber orientation changes with eruption.
TRUE
In what direction does the PDL form?
From the CEJ apically
-Orientation is changed during eruption, based on the relative positions of the tooth and alveolar crest
T/F - Remodeling of the PDL occurs throughout life.
TRUE
T/F - Developing cells of the PDL may also prevent mineralization, preventing ankylosis.
TRUE
What is the PDL composed of? 7 things.
Fibroblasts
Mesenchymal cells
Epithelial cells
Macrophages
Osteoblasts
Osteoclasts
Cementoblasts
What is the width range of the PDL?
- 15 mm to 0.38 mm
* Decreases in width with age
Primarily, the PDL is ________ fibers, supported by a non-collagenous protein matrix.
Collagen
*Types I, III, sometimes IV and XII
**Arranged in fibers, which are grouped into bundles
T/F - Individual fibers can be remodeled while the overall bundle is not changes, making a very dynamic environment.
TRUE
What is the main elastic fiber of the PDL?
OXYTALAN
Not mature elastin
PDL fiber run _________ from cementum to the tooth apex, terminating in the neurovascular complex.
VERTICALLY
The ground substance is ___% water.
70%
What does the ground substance do?
Sequesters water via proteoglycans
Increased hydrostatic pressure, and increases its ability to absorb loads
T/F - PDL is well vascularized.
TRUE
What penetrates the cribriform plate?
Arterioles
Posterior teeth have more of them and they are more prevalent in the mandible as opposed to the maxilla
Arteries occupy loose connective tissue bays in the PDL called what?
Interstitial areas
*Blood is critical for tissue healing/regeneration
Where do nerves come from to the PDL?
Apically and thru the cribriform plate
The nerves run _____ in relation to the tooth.
Axially
Where is the greatest concentration of nerve endings?
At the apex
*Except at the upper incisors
What are the 4 types of nerve endings?
Free - most prevalent - reach to cementum - nociceptive/mechanoreceptive
Ruffini’s corpuscles - Bulbous dendritic endings - associated with collagen fibers - mechanoreceptive
Coiled - Unknown fx
Spindle - Unknown fx
What are the 5 PDL fiber orientations?
Alveolar crest - Attach just at the CEJ and run outward to attach into the alveolar socket rim
Horizontal - From cementum at a right angle to the tooth into the socket
Oblique - MOST NUMEROUS, oblique angle from cementum down to the root
Apical - Root apex to the underlying bone
Interradicular - Multi-rooted teeth - attach to interradicular septum
What are the 5 types of gingival ligaments?
Transseptal - From cementum under the junctional epi, over the alveolar crest, and into cementum of an adj tooth - CAUSE OF ORTHO RELAPSE
Dentogingival - MOST NUMEROUS - Cervical cementum to lamina propria of free and attached gingiva
Alveologingival - Run from the alveolar crest to lamina propria of free and attached gingiva
Circular - Around the neck of tooth - attaches to other fibers
Dentoperiosteal - Apically from cementum to the periosteum of the outer cortical plate
