D514 - Oral Histology Lecture 10: Periodontal
Ligament & Alveolar Bone | Questions with
Complete Solutions
What type of tissue are periodontal ligaments?
soft, fibrous specialized connective tissue
Where are peridontal ligaments found?
-part of periodontum
-in periodontal space b/w cementum of tooth and surround alveolar bone proper
width of periodontal ligament
ranges in width from 0.15 - 0.38 mm
thinnest portion around middle of the root
width decreases with age
4 main functions of periodontal ligament
supportive
regenerative
nutritive
sensory
supportive function of periodontal ligament
hold tooth in the socket
shock absorbers - transfer occlusal forces to alveolar bone
regenerative function of periodontal ligament
,undifferentiated mesenchymal cells when triggered can differentiate into osteoblast,
cementoblast, or fibroblast
nutritive function of periodontal ligament
vascular supply - maintain vitality of periodontum
helps to maintain cementum which is avascular
sensory function of periodontal ligament
receptor for pain and pressure
helps in proper positioning of jaws during normal function
What cells do the PDL develop from?
ectomesenchymal cells from the dental follicle/sac differentiate into fibroblasts which
lay down collagen and form PDL
Sharpey's Fibers
calcified, terminal portion of PDL fibers embedded in alveolar bone and cementum
Describe the changes in the direction of alveolar crest fibers during tooth eruption.
-Initially, these fibers slant obliquely towards the tooth root (apically)
-As the tooth continues to erupt, they become horizontal
-Once the tooth is fully erupted into the oral cavity, the alveolar crest fibers are
oriented obliquely towards the crown (coronally)
components of PDL
-cells
-extracellular matrix: fibers (collagen, elastic) & ground substance
, -vascular supply
-neural supply
PDL cells
-fibroblasts
-undifferentiated ectomesenchymal cells
-bone and cementum cells (cementoblasts, cementoclasts, osteoblasts, osteoclasts)
-cell rests of malassez (remnants of HERS)
-macrophages
-vascular and neural elements
fibroblast cells of PDL
-principal cells of PDL
-produce collagen fibers and extracellular matrix
-helps in remodeling PDL by synthesizing and degrading collagen
What can undifferentiated mesenchymal cells found in PDL differentiate into?
can differentiate into osteoblast or cementoblast or fibroblast
How do adult pulp, gingiva, and PDL change with age?
-Adult pulp, gingiva, and PDL contain undifferentiated mesenchymal cells, but the
number of these cells decreases with age
How do dentin, cementum, and enamel change over time?
-Dentin and cementum increase over time due to deposition in response to trauma,
while the pulp and PDL decrease as space becomes occupied by additional dentin and
cementum.
Ligament & Alveolar Bone | Questions with
Complete Solutions
What type of tissue are periodontal ligaments?
soft, fibrous specialized connective tissue
Where are peridontal ligaments found?
-part of periodontum
-in periodontal space b/w cementum of tooth and surround alveolar bone proper
width of periodontal ligament
ranges in width from 0.15 - 0.38 mm
thinnest portion around middle of the root
width decreases with age
4 main functions of periodontal ligament
supportive
regenerative
nutritive
sensory
supportive function of periodontal ligament
hold tooth in the socket
shock absorbers - transfer occlusal forces to alveolar bone
regenerative function of periodontal ligament
,undifferentiated mesenchymal cells when triggered can differentiate into osteoblast,
cementoblast, or fibroblast
nutritive function of periodontal ligament
vascular supply - maintain vitality of periodontum
helps to maintain cementum which is avascular
sensory function of periodontal ligament
receptor for pain and pressure
helps in proper positioning of jaws during normal function
What cells do the PDL develop from?
ectomesenchymal cells from the dental follicle/sac differentiate into fibroblasts which
lay down collagen and form PDL
Sharpey's Fibers
calcified, terminal portion of PDL fibers embedded in alveolar bone and cementum
Describe the changes in the direction of alveolar crest fibers during tooth eruption.
-Initially, these fibers slant obliquely towards the tooth root (apically)
-As the tooth continues to erupt, they become horizontal
-Once the tooth is fully erupted into the oral cavity, the alveolar crest fibers are
oriented obliquely towards the crown (coronally)
components of PDL
-cells
-extracellular matrix: fibers (collagen, elastic) & ground substance
, -vascular supply
-neural supply
PDL cells
-fibroblasts
-undifferentiated ectomesenchymal cells
-bone and cementum cells (cementoblasts, cementoclasts, osteoblasts, osteoclasts)
-cell rests of malassez (remnants of HERS)
-macrophages
-vascular and neural elements
fibroblast cells of PDL
-principal cells of PDL
-produce collagen fibers and extracellular matrix
-helps in remodeling PDL by synthesizing and degrading collagen
What can undifferentiated mesenchymal cells found in PDL differentiate into?
can differentiate into osteoblast or cementoblast or fibroblast
How do adult pulp, gingiva, and PDL change with age?
-Adult pulp, gingiva, and PDL contain undifferentiated mesenchymal cells, but the
number of these cells decreases with age
How do dentin, cementum, and enamel change over time?
-Dentin and cementum increase over time due to deposition in response to trauma,
while the pulp and PDL decrease as space becomes occupied by additional dentin and
cementum.
