Early Tooth Development (Larsen 2) Flashcards
Two tissues required by odontogenesis
- Oral ectoderm (epithelium)
- Ectomesenchyme (dental mesenchyme) (connective tissue)
Oral ectoderm
Oral epithelium that forms enamel organ
Ectomesenchyme (dental mesenchyme)
- Connective tissue
- Neural crest origin
- Forms dentin and pulp of both crown and root
Life cycle of a tooth
- Growth (Initiation, Proliferation, Morphodifferentiation, Histodifferentiation, Apposition [adjacent but different, like enamel and dentin])
- Calcification/Mineralization
- Eruption
- Attrition
Initiation: ______ is the first sign of tooth development, is a horseshoe-shaped thickening of the oral epithelium, and develops around 6 weeks in utero.
Dental lamina
Initiation: The _____ is an epithelial thickening that forms along ten specific points called ______ on both the mandibular and maxillary arches.
- Tooth bud
- Dental placode (becomes specific teeth)
Tooth bud stage: oral epithelium grows down into the _____.
Ectomesenchyme
Tooth bud stage: growth of oral epithelium becomes bulbous and resembles a ____.
Boot
Tooth bud stage: mitosis takes place on _____ and _____ causing a ______.
- Superior surface
- Distal tip
- Concavity
Tooth bud stage: oral epithelium will form _____.
Enamel
Tooth bud stage: Ectomesenchyme in cavity will become ______.
Dental papilla
Steps from dental lamina to tooth bud
- Dental lamina
- Elongation
- Tooth bud
In the cap stage, cells become ____ and ____ different.
- Functionally
- Morphologically
Outer Layer of the Enamel Organin Cap Stage (Outer enamel epithelium)
Single layer of cuboidal epithelium along the convexity of the cap
Inner Layer of the Enamel Organ Cap Stage (Inner enamel epithelium)
Single layer of low columnar cells along the concavity of the cap
Middle Layer of the Enamel Organ Cap Stage (Stellate reticulum)
Stellate shaped cells separated by glycosaminoglycans
Dental Papilla in Cap Stage: _______ in the concavity underneath the ______.
- Ectomesenchyme
- Inner enamel epithelium
Dental Papilla in Cap Stage: Forms the _____ and ____ of the crown
- Dentin
- Pulp
Dental Sac or Follicle in Cap Stage: ______ surrounding the developing enamel organ and dental papilla
Ectomesenchyme
Dental Sac or Follicle in Cap Stage: Will form ______, ______, and ______.
- Cementum
- Periodontal ligament
- Alveolar process
Cervical Loop in Cap Stage: ______ rim of the enamel organ formed by ______.
- Outer
- Outer and inner enamel epithelium
Cervical Loop in Cap Stage: Is later involved in ______ formation.
Root
Cap Stage Summary: Proliferation of growth by mitosis of ______ cells resulting in _____ morphology.
- Epithelial
- Concave
Cap Stage Summary: Three layers in the enamel organ
- Outer enamel epithelium
- Inner enamel epithelium
- Stellate reticulum
Cap Stage Summary: _______ at the outer rim of the enamel organ
Cervical loop
Cap Stage Summary: Ectomesenchyme forms _______.
Dental papilla
Cap Stage Summary: ______ surrounds enamel organ and dental papilla
Dental sac
Shaping of the tooth such as incisor or molar
Morphodifferentiation
Differentiation of ameloblasts from the inner enamel epithelium
Histodifferentiation
Differentiation begins at the ______ and moves ______.
- Cuspal tip
- Cervically
Differentiation of odontoblasts from the dental papilla
Histodifferentiation
Name and describe the inner layer of the bell stage enamel organ
Inner enamel epithelium - columnar cells that form ameloblasts
The ______ is a cluster of non-dividing epithelial cells that orchestrates cuspal morphogenesis.
Enamel knot
Name and describe the outer layer of the bell stage enamel organ
Outer enamel epithelium - Avascular (fed by blood vessels in follicle)
Name the new layer of the bell stage enamel organ
Stratum intermedium
The ______ is composed of two to three layers of cells on the surface of the inner enamel epithelium and is the nutritional layer needed for the formation of enamel.
Stratum intermedium
Name and describe the middle layer of the bell stage enamel organ
Stellate reticulum - continued secretion of GAGs to allow growth of the crown
Dental papilla in bell stage
- Odontoblasts
- Dental Pulp
Describe odontoblasts of dental papilla in bell stage
Terminally differentiated cell; cells next to the basement membrane start secreting the organic matrix of mantle dentin
Describe the dental pulp of dental papilla in bell stage
The central portion of the connective tissue also contains the blood vessels and nerves
The bell stage dental sac or follicle is composed of _______ of neural crest origin and forms ____, _____, and ____.
-Ectomesenchyme
-Periodontal ligament
-Cementum
Alveolar process
The bell stage ______ is where the inner enamel epithelium and the outer enamel epithelium meet.
Cervical loop
The _____ will be involved in the formation of the root after the crown has fully formed.
Cervical loop
In the bell stage, the cells of the ______ continue to divide.
Cervical loop
Crown Formation: the inner enamel epithelium is constrained between the ______ and _____.
- Cervical loop
- Cusp tip
Crown Formation: ______ forms as a result of cell proliferation
Cuspal outline
Crown Formation: Future cusp is pushed up toward the _______.
Outer enamel epithelium
Bell Stage Summary: Four layers of the enamel organ
- Outer enamel epithelium
- Inner enamel epithelium, ameloblasts
- Stellate reticulum
- Stratum intermedium (NEW)
Bell Stage Summary: Two layers of dental pulp
- Dental papilla
2. Odontoblasts (NEW)
Bell Stage Summary: Cell surrounding enamel organ and pulp
Dental sac or dental follicle
______ is a thickening of oral epithelium lateral to dental lamina in which cells grow downward into the connective tissue and degenerate forming a cavity.
Vestibular lamina
______ is an extension of the dental lamina lingual to the primary tooth and forms ___ of the permanent teeth.
- Successional lamina
- 20
Parent dental lamina
Remains of the original lamina
Lateral lamina
Connects developing primary tooth to parent lamina
Permanent molars are derived directly from the distal portion of the _______ without a primary tooth precursor.
Dental lamina
Successional lamina is _____ to primary tooth.
Lingual
Degeneration of the Parent Dental Lamina: During the bell stage the enamel organ loses contact with the ________ when the parent (general) lamina degenerates, which may leave islands of epithelial cells in the connective tissue.
Oral epithelium
