Flashcards in Eruption and Shedding Deck (52)
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1
Eruption definition
The movement a tooth makes to attain and maintain its position in the jaw
2
T/F - Tooth movement only occurs as it is erupting
False - Tooth movement occurs throughout life
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What direction(s) does a tooth move to attain and maintain its position in the jaw?
All directions, except apically
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Why type of activity is involved in movements of eruption?
Cellular activity involving different cell types of the periodontal ligament (PDL)
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What is the most numerous cell type of the PDL contributing to tooth movements?
Fibroblast
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What are the functions of a fibroblast within the PDL?
Secrete extracellular substance (fibroblast)
Lysis extracellular substance (fibroclast)
Contracting cell (fibromyocyte)
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What is a fibromyocyte myofibroblast?
A cell connected o collagen fiber bundles that connect the tooth to the alveolar bone
When it contracts, the collagen fibers contract, moving the tooth
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What are the stages of eruption?
Preemergence
Prefunctional
Functional
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When does the Preemergence occur?
Before the start of root formation
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What is the main tooth movement direction during the Preemergence stage?
Facially (however, they move in all different directions, but the net movement is facial)
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What appears during the preemergence stage?
Reduced enamel epithelium
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What attaches the reduced enamel epithelium to the enamel?
Basal lamina
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Cervical loop
Outer and inner epithelial layers coming together to form Hertwig's epithelial root sheath
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Functions of Hertwig's epithelial root sheath
Determines how many root canals
Determines the root-dentin outline
15
What about Herwig's epithelial root sheath determines root canals?
The number of openings in Hertwig's diaphragm
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When does the prefunctional stage occur?
Begins with root dentin formation and ends when the tooth reaches the occlusal plane
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What is the main tooth movement direction of the Prefunctional stage?
Occlusally
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What happens to Hertwig's epithelial root sheath during the Prefunctional stage
The sheath covers the root dentin, the apical end continues as the diaphragm, and the sheath breaks up
19
Epithelial rest of Malassez
Remnants of epithelial cells from Hertwig's epithelial root sheath in the PDL
Appear during prefunctional stage of eruption
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What happens to reduced enamel epithelium during the prefunctional stage?
The merged oral epithelium and reduced enamel epithelium undergo cell death
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When does functional stage of eruption occur?
When the tooth reaches the occlusal plane and continues throughout life
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What is the main tooth movement direction during the Functional stage?
Mesially
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What happens to the PDL during the funcitonal stage?
Functional arrangement of principal fiber bundles occurs
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What happens to junctional epithelium during the functional stage?
It changes position
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Shedding
The physiologic elimination of primary teeth caused by the resorptive action of odontoclasts
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What causes shedding
Odontoclastic activity
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Odontoclasts origin
Bone marrow and goes to the site of activity via blood vessels
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Odontoclasts
Resorb the 3 mineralized tissues of teeth
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What stage does odontogenesis begin?
Preemergence
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