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Questions and Answers
What is the primary function of the alveolar crest group fibers?
What is the primary function of the alveolar crest group fibers?
Which group of fibers is primarily responsible for resisting vertical masticatory forces?
Which group of fibers is primarily responsible for resisting vertical masticatory forces?
What characteristic defines interradicular group fibers?
What characteristic defines interradicular group fibers?
Over time, which of the following changes occur within the periodontal ligament (PDL) as individuals age?
Over time, which of the following changes occur within the periodontal ligament (PDL) as individuals age?
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Which group of fibers connects neighboring teeth and helps resist rotational forces?
Which group of fibers connects neighboring teeth and helps resist rotational forces?
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What is the primary function of the periodontal ligament?
What is the primary function of the periodontal ligament?
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How does the periodontal ligament develop?
How does the periodontal ligament develop?
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Which statement accurately describes the blood supply to the periodontal ligament?
Which statement accurately describes the blood supply to the periodontal ligament?
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What is one of the principal fibres of the periodontal ligament?
What is one of the principal fibres of the periodontal ligament?
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What type of connective tissue is the periodontal ligament classified as?
What type of connective tissue is the periodontal ligament classified as?
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Where does the periodontal ligament merge with the dental pulp?
Where does the periodontal ligament merge with the dental pulp?
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Which of the following best describes the relationship between the periodontal ligament and the gingiva?
Which of the following best describes the relationship between the periodontal ligament and the gingiva?
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Which statement about the sensory properties of the periodontal ligament is true?
Which statement about the sensory properties of the periodontal ligament is true?
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Which of the following types of vessels are responsible for linking the periodontal ligament to the gingiva?
Which of the following types of vessels are responsible for linking the periodontal ligament to the gingiva?
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What is the primary component of the fibers in the periodontal ligament?
What is the primary component of the fibers in the periodontal ligament?
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What is the main function of the principal fibers of the periodontal ligament?
What is the main function of the principal fibers of the periodontal ligament?
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Which nerve types are present in the periodontal ligament?
Which nerve types are present in the periodontal ligament?
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How does smoking affect the periodontal ligament?
How does smoking affect the periodontal ligament?
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Which group is NOT one of the principal fiber groups of the periodontal ligament?
Which group is NOT one of the principal fiber groups of the periodontal ligament?
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What is the significance of Sharpey's fibers in the periodontal ligament?
What is the significance of Sharpey's fibers in the periodontal ligament?
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Which feature characterizes the width of the periodontal ligament?
Which feature characterizes the width of the periodontal ligament?
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What type of blood supply is essential for the periodontal ligament's high turnover rate?
What type of blood supply is essential for the periodontal ligament's high turnover rate?
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Which branches are involved in supplying nerve fibers to the periodontal ligament?
Which branches are involved in supplying nerve fibers to the periodontal ligament?
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What is the primary function of fibroblasts in the periodontal ligament?
What is the primary function of fibroblasts in the periodontal ligament?
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During tooth eruption, which type of fibers appears first in the periodontal ligament?
During tooth eruption, which type of fibers appears first in the periodontal ligament?
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What role do progenitor cells play in the periodontal ligament?
What role do progenitor cells play in the periodontal ligament?
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Which cells are primarily responsible for breaking down bone in the periodontal ligament?
Which cells are primarily responsible for breaking down bone in the periodontal ligament?
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What is the primary blood supply to the periodontal ligament?
What is the primary blood supply to the periodontal ligament?
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How do alveolar fibers contribute during occlusal function?
How do alveolar fibers contribute during occlusal function?
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Which of the following is a remnant of Hertwig's epithelial root sheath found in the periodontal ligament?
Which of the following is a remnant of Hertwig's epithelial root sheath found in the periodontal ligament?
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What is a key characteristic of Sharpey’s fibers in bone compared to those in cementum?
What is a key characteristic of Sharpey’s fibers in bone compared to those in cementum?
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What type of cell is responsible for the synthetic function in the periodontal ligament?
What type of cell is responsible for the synthetic function in the periodontal ligament?
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What happens to collagen fibers as periodontal ligament fibers develop during tooth eruption?
What happens to collagen fibers as periodontal ligament fibers develop during tooth eruption?
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What is the average width of the periodontal ligament (PDL)?
What is the average width of the periodontal ligament (PDL)?
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What role does the sensory function of the periodontal ligament primarily serve?
What role does the sensory function of the periodontal ligament primarily serve?
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How does the width of the PDL change under heavy loading conditions near the crest of the alveolus?
How does the width of the PDL change under heavy loading conditions near the crest of the alveolus?
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What is the primary role of the nutritive function of the periodontal ligament?
What is the primary role of the nutritive function of the periodontal ligament?
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In which area of the alveolus is the PDL typically narrower?
In which area of the alveolus is the PDL typically narrower?
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Which cellular activity is primarily associated with the formative and resorptive functions of the periodontal ligament?
Which cellular activity is primarily associated with the formative and resorptive functions of the periodontal ligament?
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The periodontal ligament adapts to loading conditions by becoming:
The periodontal ligament adapts to loading conditions by becoming:
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What is the appearance of the PDL on radiographs?
What is the appearance of the PDL on radiographs?
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How does the PDL's structural adaptation occur in response to occlusal forces?
How does the PDL's structural adaptation occur in response to occlusal forces?
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The development of the PDL starts after what process begins?
The development of the PDL starts after what process begins?
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Study Notes
Periodontal Ligament (PDL)
- Connective tissue surrounding the tooth root and connecting it to the alveolar bone
- Continuous with the gingiva and marrow spaces through vascular channels in bone
- Merges with the dental pulp at the root apex
PDL Functions
- Sensory: Rich nerve supply; senses touch, pressure, temperature, and pain
- Physical: Attaches tooth to bone, maintains tooth position, shock absorber, transmits occlusal forces
- Nutritive: Rich blood supply provides nutrition to the tooth
- Formative & Resorptive: High cell turnover; can both build and resorb tissue
PDL Width & Loading Conditions
- Average width: 0.2 mm (range: 0.15 mm to 0.38 mm)
- Heavy loaded: 0.35 mm (near crest), 0.28 mm (middle), 0.30 mm (near fundus)
- Normally loaded: 0.14 mm (near crest), 0.10 mm (middle), 0.12 mm (near fundus)
- Functionless: 0.10 mm (near crest), 0.06 mm (middle), 0.06 mm (near fundus)
PDL and Radiographs
- Appears as radiolucent periodontal space between the lamina dura of alveolar bone and radiopaque cementum
- Wider at the top (near the crown) and bottom (near the apex), narrower in the middle
PDL Development
- Forms from the dental follicle shortly after root development begins
- Fibroblasts in follicle become active producing collagen
- Early fibres lack organization but become oblique to the tooth
- First fibres form apical to the CEJ and give rise to gingivodental fibers
- More fibres develop as the tooth erupts, attaching to new cementum and bone
PDL Components
-
Cells:
- Formative: Osteoblasts (bone), fibroblasts (collagen), cementoblasts (cementum)
- Resorptive: Osteoclasts, cementoclasts, fibroblasts
- Progenitor: Undifferentiated mesenchymal cells; act as stem cells
- Defense: Mast cells, macrophages
- Epithelial Rests of Malassez: Epithelial cells near the cemental side of the PDL; remnants of Hertwig's epithelial root sheath
-
Extracellular Substance:
- Fibers: Collagen
- Ground Substance: Water, collagen, tissue fluid (high pressure)
PDL Blood Supply
- Primarily from the superior and inferior alveolar arteries
- Three types of vessels:
- Apical
- Penetrating (from alveolar bone)
- Anastomosing (from the gingiva)
- Rich blood supply crucial for its high turnover rate
- Smoking can impact blood supply and accelerate periodontal disease
PDL Nerve Supply
- Two types of nerves:
- Sensory: Touch, pressure, pain
- Autonomic: Associated with blood vessels of PDL
- Branches of the second and third divisions of the 5th cranial nerve (trigeminal nerve)
PDL Principal Fiber Groups
- Alveolar Crest Group: Just beneath junctional epithelium; runs downward and outward, prevents tooth extrusion
- Horizontal Group: First 1/4 of the PDL; runs at right angles to the tooth, resists tipping forces
- Oblique Group: 2/3 of the PDL; runs obliquely in a coronal direction, resists vertical masticatory forces
- Apical Group: At the root tip; fans out irregularly, resists vertical, luxative, and twisting forces
- Interradicular Group: Found in multi-rooted teeth; connects cementum to the interradicular septum, prevents lateral movement
Additional Fibers
- Interdental/Transseptal Fibers: Connect neighboring teeth through the gingival mucosa; resist rotational forces
- Gingival Fiber Group: Separate groups in the marginal gingiva
PDL Age Changes
- Decrease in cells
- Increase in fibrous tissue
- Decrease in vascularity and mitotic activity
- Narrowing of PDL width
- Scalloping seen on calcified tissues (bone, cementum)
Clinical Considerations of the PDL
- The PDL's structure, function, and changes with age are critical for understanding periodontal disease and treatment planning.
- PDL involvement is a significant indicator of disease severity.
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Description
This quiz explores the structure and function of the periodontal ligament (PDL), including its sensory, physical, nutritive, formative, and resorptive roles. You'll also learn about the width of the PDL under different loading conditions and its appearance in radiographs. Test your knowledge on this essential component of dental anatomy!
