Eruption and Shedding Flashcards
Eruption definition
The movement a tooth makes to attain and maintain its position in the jaw
T/F - Tooth movement only occurs as it is erupting
False - Tooth movement occurs throughout life
What direction(s) does a tooth move to attain and maintain its position in the jaw?
All directions, except apically
Why type of activity is involved in movements of eruption?
Cellular activity involving different cell types of the periodontal ligament (PDL)
What is the most numerous cell type of the PDL contributing to tooth movements?
Fibroblast
What are the functions of a fibroblast within the PDL?
Secrete extracellular substance (fibroblast)
Lysis extracellular substance (fibroclast)
Contracting cell (fibromyocyte)
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
What are the stages of eruption?
Preemergence
Prefunctional
Functional
When does the Preemergence occur?
Before the start of root formation
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)
What appears during the preemergence stage?
Reduced enamel epithelium
What attaches the reduced enamel epithelium to the enamel?
Basal lamina
Cervical loop
Outer and inner epithelial layers coming together to form Hertwig’s epithelial root sheath
Functions of Hertwig’s epithelial root sheath
Determines how many root canals
Determines the root-dentin outline
What about Herwig’s epithelial root sheath determines root canals?
The number of openings in Hertwig’s diaphragm
When does the prefunctional stage occur?
Begins with root dentin formation and ends when the tooth reaches the occlusal plane
What is the main tooth movement direction of the Prefunctional stage?
Occlusally
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
Epithelial rest of Malassez
Remnants of epithelial cells from Hertwig’s epithelial root sheath in the PDL
Appear during prefunctional stage of eruption
What happens to reduced enamel epithelium during the prefunctional stage?
The merged oral epithelium and reduced enamel epithelium undergo cell death
When does functional stage of eruption occur?
When the tooth reaches the occlusal plane and continues throughout life
What is the main tooth movement direction during the Functional stage?
Mesially
What happens to the PDL during the funcitonal stage?
Functional arrangement of principal fiber bundles occurs
What happens to junctional epithelium during the functional stage?
It changes position
Shedding
The physiologic elimination of primary teeth caused by the resorptive action of odontoclasts
What causes shedding
Odontoclastic activity
Odontoclasts origin
Bone marrow and goes to the site of activity via blood vessels
Odontoclasts
Resorb the 3 mineralized tissues of teeth
What stage does odontogenesis begin?
Preemergence
What stage do Ameloblasts, odontobalsts, and fibroblasts differentiate?
Preemergence
What stage does the crown dentin appear?
Preemergence
What stage does enamel formation and maturation begin?
Preemergence
What stage is the DEJ established?
Preemergence
What stage does the reduced enamel epithelium appear?
Preemergence
What stage does the pulp chamber appear?
Preemergence
What stage is Hertwig’s epithelial root sheath form?
Preemergence
What stage is the number of root canals determined?
Preemergence
What stage does the bone crypt form?
Preemergence
Bone crypt
Undergoes remodeling and becomes the alveolar process
What stage does the root dentin form?
Prefuncitonal
What stage does Hertwig’s epithelial root sheath break up?
Prefunctional
What stage does the Epithelial rest of Malassez form?
Prefunctional
What stage do cementoblasts differentiate and cementogenesis occur?
Prefunctional
What stage does the PDL and alveolar process form?
Prefuncitonal
What stage are the collagen fiber bundles of the PDL arranged obliquely?
Prefunctional
What stage does the reduced enamel epithelium merge with the oral epithelium?
Prefuncitonal
What stage does the tooth emerge into the oral cavity?
Prefunctional
What stage does the reduced enamel epithelium become the junctional epithelium of the free gingiva?
Prefunctional
What stage are the principal fiber bundles of the PDL functionally arranged?
Functional stage
What stage is the alveolar process preserved?
Functional stage
What stage is secondary and tertiary dentin formed?
Functional stage
What is the junctional epithelium movement during the functional stage?
It moves from its attachment to just enamel, to enamel and cementum, and then to just cementum
