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Orofacial Structures and Tooth Development & Eruption

Contributed by:

Andrea and Cristal
SDH  PRCC, MS
  1. What 2 structures form the palate & When? Primary palate 5-6 week, Secondary plate 6-12 week.
  2. When is the palate completed? 12th week.
  3. The intermaxillary segment is a wedge shaped mass that gives rise to the primary palate? Intermaxillary segment.
  4. How is the intermaxillary segment formed? From fusion of 2 median nasal processes.
  5. What structure does the intermaxillary segment become? Floor of nasal pits.
  6. What does the primary palate form? Premaxillary portion of maxilla, anterior 1/3 of final palate, & contains maxillary incisor teeth.
  7. T/F The primary palate is the 1st & final stage of palatal development.
  8. The fusion of the 2 palatal shelves forms: secondary palate.
  9. What does the secondary palate form? Hard palate (posterior 2/3), canines, premolars, molars. Contains the uvula & soft palate.
  10.  The suture lines on anterior 1/3, on either side are rugae, line of fusion of palatal shelves: Palatine raphe.
  11. When does the oral cavity become separated from the nasal cavity? When the secondary palate meets the primary palate & they fuse together & form both hard & soft palates. Palate is completely formed.
  12. What forms palatal muscles? Mesenchyme (embryonic connective tissue).
  13. The incisive foramen is present at the junction of the primary & secondary palates, what does it become? The opening for bilateral incisive canals.
  14. What causes cleft palate? Failure of fusion of palatal shelves with primary palate or each other.
  15.  The nasal septum is formed by: fusion of medial nasal processes.
  16. Brachial arches 1-4 form: the tongue.
  17. The body of tongue develops from which brachial arch? 1st brachial arch.
  18. Brachial arches 2 3 & 4 form: the base of the tongue.
  19. The body of the tongue begins here: tuberculum impar.
  20. Where is the tuberculum impar located? On floor of primitive pharynx.
  21. What part does the copula have in formation of the base of tongue? It’s formed from fusion of mesenchyme; overgrowth of 2 arches form bas of tongue.
  22.  Inverted V shaped groove that shows the border between base of tongue and body? Sulcus terminalis.
  23.  What does the sulcus terminalis point back to? Foramen cecum.
  24. Thyroglossal duct = foramen cecum.
  25.  The tongue reaches its maximum size at what age? 13/puberty.
  26. What is a cause of ankyglossia? Short lingual frenum.
  27.  Odontogenesis: tooth development.
  28.  List the stages of tooth development & when do they occur:

Initiation Stage: 6-7 week of development.

Bud Stage: 8th week of development.

Cap stage: 9th-10th week of development.

Bell stage: 11th-12th week of development.

Apposition/ Maturation stage: varies per tooth.

  1. Matching

a. Initiation Stage

c-  bud turns concave & forms cap.

b. Bud Stage

a- induction/interaction between cells.

c. Cap Stage

d-  proliferation, differentiation, morphogenesis

d. Bell Stage

e-  Induction, Proliferation, Maturation.

e. Apposition/ Maturation

c-  proliferation, differentiation: tooth bud is becoming structurally & functionally different. Morphogenesis: takes on specific tissue characteristics. Occurs in uequal growth patterns.

 

b-  Dental lamina grows/ evolves into a bud.

 

a-  The primative mouth lined with ectoderm & leads to formation of oral epithelium & below that layer is a layer of mesenchyme. Oral epithelium layer will continue to grow & form dental lamina.

 

d-enamel organ differentiates into 4 layers.

 

e-  final stage is amelogenesis.

 

b-  prolifration/ controlled levels of cellular growth with accumulation of by products.

 

  1. Dental Lamina: gives way to formation of tooth buds.
  2. Describe developmental disturbances during the Initiation Stage: Anodontia~ absence of single or multiple teeth: max. Laterals, 3rd molars, mand. 2nd premolars.

Supernumerary teeth~ develop of 1 or more extra teeth.

  1. How many buds are in each arch? 10.
  2.  All teeth & their associated tissues originate from what embryonic tissues? Ectoderm, Mesenchyme.
  3.  Developmental disturbances during Bud Stage:

Microdontia: abnormal small tooth: peg lateral.

Macrodontia: abnormal large teeth.

  1. What makes up a tooth germ: Enamel organ, dental papilla, dental sac.
  2.  Describe enamel organ: made from ectoderm & produces enamel.
  3.  Describe dental papilla: made from mesenchyme, produces dentin & pulp tissue
  4. Describe the dental sac: made from mesenchyme, produces periodontium.
  5.  Developmental disturbances during Cap Stage:

Dens in Dente: enamel organ turns in on itself & grows into dental papilla. (tooth within tooth).

Gemination: large single rooted tooth with common pulp cavity that tried to divide.

Fusion: 2 tooth germs that unites forming a large tooth, 2 pulp cavities but some enamel & pulp.

Tubercles: teeth with extra cusps, (3rd molars).

40. Fill in the chart for the Bell Stage, the enamel organ differentiates into:

         

1st

Outer enamel epithelium

Cube shaped cells

Protective barrier to enamel organ.

2nd

Inner enamel epithelium

Tall columnar cells

Form outline of future shape of tooth crown & eventually become ameloblasts.

3rd

Stellate recticulum

Cells are star shaped

Help support production of enamel.

4th

Stratum intermedium

Flat cells

Support production of enamel.

 

  1. What are the 2 layers does the dental papilla differentiates into:

1st outer cells of papilla: which will secrete dentin become odontoblasts.

2nd centrals cells (inner) of papilla: Become pulp tissue.

  1. Amelogenesis: Lying down of enamel matrix.
  2. Ameloblasts: Enamel secreting cells.
  3.  The enamel matrix is secreted from what structure? Tome’s process.
  4.  Tome’s process: portion that’s located at apical end of each ameloblast, they develop during enamel secretion stage.
  5.  Developmental Disturbances during Apposition & Maturation Stage:

Enamel Dysplasia: Faulty development of enamel. Example: Enamel hypoplasia- reduction in quantity of enamel matrix, teeth are pitted & grooved.

Enamel Hypocalcification: reduces quality of enamel. Teeth are opaque (white spots).

Amelogenesis Imperfecta: hereditary- really thins enamel or no enamel at all.

Dentinogenesis Imperfecta: hereditary- lacking dentin.

  1. Describe root development: Cervical loop- will lengthen to form Hertwig’s root sheath- will shape the root & induce it to form root dentin, makes odontoblasts. No cells that turn into ameloblasts that’s why root has no enamel.
  2.  Epithelial rests of Malassez:  Disintegrated root sheath cells that are located in periodontal ligament & could become cystic due to chronic periapical inflammation.
  3.  Developmental Disturbances during root development:

Enamel Pearls: misplaced ameloblast that form root. May resemble calculus.

Dilaceration: root shows angular distortion of Hertwig’s root sheath due to injury or pressure.

Accessory roots: teeth with extra roots. Distortion of Hertwig’s root sheath due to injury or pressure.

 

Disclaimer: These notes were copied and pasted from files sent to me by Andrea.  They have not been reviewed for errors. You are responsible for checking out the information to verify the accuracy. This site, Amy Nieves and Andrea are not responsible for typographical errors.

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