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Classic Lit Fall 2021 > Tooth/Periodontal Development and myth of enamel matrix derivatives (EMD) on periodontal regeneration > Flashcards

Tooth/Periodontal Development and myth of enamel matrix derivatives (EMD) on periodontal regeneration Flashcards

1
Q

Where are the Maxilla and Mandible derived from and by what process do they ossify?

A

Derived from the first branchial arch
Intramembranous Ossification

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2
Q

In which week of development does the first branchial arch from?

A

4th week

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3
Q

What is the difference between branchial (Pharyngeal) arches, clefts, and pouches?

A

Arches are bulges around the neck region of the embryo
Clefts separate arches externally
Pouches separate arches internally - opposing clefts

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4
Q

How many Branchial arches are there?

A

6

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5
Q

What structures form from the 1st Branchial Arch?

A

I Smelt My Many Mcdonalds Muffins.. Mm.. Smell!

Incus, Sphenomalleolar ligament, Mandible, Maxilla, Merkles cartlidge, Malleus, MUSCLES OF MASTICATION, Sphenomandibular ligament

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6
Q

What structures form from the 1st Branchial Groove?

A

External Auditory Meatus

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7
Q

What structures form from the 1st Branchial Pouch?

A

Tympanic membrane, Tympanic cavity, Mastoid antrum, Eustachian tube

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8
Q

What structures form from the 2nd Branchial Arch?

A

Styloid and facial associated things

Reichert’s cartilage: Styloid process of temporal bone, Stylohyoid ligament, Lesser horns of the hyoid, Upper part of the body of the hyoid, Stapes
STAPEDIAL ARTERY, MUSCLES OF FACIAL EXPRESSION

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9
Q

What structures form from the 2nd Branchial Groove?

A

The second groove is obliterated by the down-growth of the 2nd Arch

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10
Q

What structures form from the 2nd Branchial Pouch?

A

It’s mostly obliterated but CONTRIBUTES TO THE PALATINE TONSILS

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11
Q

What structures form from the 3rd Branchial Arch?

A

Lower part of the body of the hyoid, Greater horns of Hyoid

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12
Q

What structures form from the 3rd Branchial Groove?

A

nothing

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13
Q

What structures form from the 3rd Branchial Pouch?

A

INFERIOR PARATHYROID GLAND, Thymus

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14
Q

What structures form from the 4th Branchial Arch?

A

Cartilages of the Larynx

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15
Q

What structures form from the 4th Branchial Groove?

A

nothing

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16
Q

What structures form from the 4th Branchial Pouch?

A

SUPERIOR PARATHYROID GLAND, Ultimobranchial body, Thyroid gland

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17
Q

What structures are formed by the 5th and 6ths arches/clefts/pouches?

A

They are transient and do not form structures

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18
Q

How do cleft palates form?

A

failure of fusion between the palatine processes and the maxillary process

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19
Q

How do cleft lips form?

A

failure of fusion between the maxillary process and the median nasal process

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20
Q

When does the timeline of human tooth development begin? What happens on this day?

A

Day 26 - Primitive oral cavity formation (epithelium from ectoderm and endoderm line oral cavity)

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21
Q

What day of fetal development do the initial stage, bud stage, cap stage, and bell stage for deciduous teeth occur? Permanent teeth?

A

Deciduous:
42-48: Initial stage - Dental lamina formation (6.5 WEEKS)
55-56: Bud stage - incisors, canines, and molars
~8-14wks: Cap stage
14wks: Bell stage
18wks: Dentin and functional ameloblasts

Succedaneous teeth:

14wks: Bud stage
32wks: Dentin and functional ameloblasts

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22
Q

When do the following structures form?
Specialized cells of the tongue?
Oral vestibule?
Palatal shelf fusion?

A

7-10wks
10-14wks
8-11 wks (12 weeks complete)

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23
Q

What determines cell fate during tooth development?

A

sequential and reciprical interactions between the dental mesenchyme and oral epithelium

Note: Pax 9 is found in locations that a tooth will form - BMPs inhibit Pax9 and guide tooth location
Shh induces local cell proliferation

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24
Q

Why is Wnt important?

A

it is the most upstream signal and inducer of tooth initiation

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25
Q

Describe the initial stage of tooth development

A

Day 42-48 (6.5wks) - the Primary Epithelial Band forms in the presumed locations of the maxillary and mandibular arches in the 1st Branchial Arch
the PEB splits into 2 segments (dental and vestibular lamina)

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26
Q

WHAT ARE REMNANTS OF THE DENTAL LAMINA CALLED?

A

SERRES PEARLS

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27
Q

What are the 2 hypothetical models for patterning of dentition?

A

The Odontogenic (Homeobox Code) Model

The Clone Model

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28
Q

What is the Odontogenic (Homeobox) Code Model? Describe it.

A

A hypothetical model for dentition patterning
It postulates that tooth shape is determined by the mesenchyme - where different homeobox genes are expressed in the regions of Incisors/premolars/molars

29
Q

What is the Clone Model? Describe it

A

A hypothetical model for dentition patterning - It postulates that each tooth class is produced by a “clone” of mesenchymal cells that were PROGRAMED BY EPITHELIAL CELLS to produce teeth of specific patterns.

Epithelium induces mesenchymal clone, clone progresses posteriorly and induces similar teeth buds.

30
Q

Which model of tooth patterning could be correct?

A

Both!

31
Q

Describe the Bud stage

A

Characterized by proliferation of epithelial cells and local condensation of ectomesenchymal cells

First epithelial incursion into the ectomesenchyme of the jaw

32
Q

Describe the Cap Stage

A

Characterized by an epithelial outgrown that forms a cap of epithelium (the dental (or enamel) organ) overlying a ball of ectomesenchyme (the dental papilla) all surrounded by a condensation of ectomesenchymal cells (the dental follicle)

33
Q

What structures are formed from the different parts of the dental organ?

A
34
Q

What is Histodifferentiation and Morphodifferentiation?

When does it occur? What forms as a result?

A

A process by which similar epithelial cells transform themselves into morphologically and functionally distince components

Late cap - Early bell

Outer Enamel Epithelium, Stellate Reticulum, Stratum Intermedium, Inner Enamel Epithelium, Cervical loop…

35
Q

How do cells of the stellate reticulum form?

A

During hisodifferentiation, cells within the enamel organ begin to secrete glycosaminoglycans. This attracts water into the enamel organ and their extracellular spaces, while they maintain their desmosomal contacts - forming star shaped cells.

36
Q

Describe the Bell Stage

A

Histo and Morphodifferentiation continue - form the OEE, Stellate R, Stratum I, IEE, CL… Form the shape of a bell

Dental lamina degenerates and separates the developing tooth from the oral epithelium

37
Q

What process forms the hard tissues of the tooth?

A

Reciprocal Induction

38
Q

What is Reciprocal Induction?

A

At the site of future cusp tips, mitotic activity ceases

Local IEE is induced to differentiate (reverse their polarity so nuclei are adjacent to stratum and Golgi face dental papilla - and elongate) into Pre-Ameloblasts

Pre-ameloblasts secrete enamel matrix proteins that induce outer ectomesenchyme to differentiate into Pre-Odontoblasts

Pre-Odontoblasts secrete Mantle Dentin

Mantle Dentin causes Pre-Ameloblasts to differentiate into Ameloblasts

Ameloblasts secrete organic matrix that immediately mineralizes to enamel

39
Q

Which comes first - amelogenesis, or dentinogenesis?

A

Dentinogenesis

40
Q

What is HERS and when/how does it form?

A

Hertwig’s Epithelial Root Sheath

Once the crown formation is complete, the IEE and OEE proliferate at the cercical loop and form a double cell layer (HERS)

41
Q

What is the rim of HERS called? What does it enclose?

A

the Epithelial Diaphram

The primary apical foramen

42
Q

How does the root form?

A

As HERS encloses the dental papilla, it induces peripheral cells of the papilla to differentiate into odontoblasts. HERS disintegrates except at the advanceing epithelial diaphram. Exposed dentin that contacts the Dental Follicle cells induce differentiation into Cementoblasts

43
Q

How does root separation occur during multi root formation?

A

The epithelial cells of the epithelial diaphram grown towards each other and divide a single apical foramen into 2-3 apical foramina corresponding to the number of roots.

44
Q

What structurs/pathology can HERS contribute to?

What are remnants of HERS referred to as?

A

Failure of HERS to detach can lead to Enamel Pearls or Cervical Enamel Projections

Invagination of HERS forms Palatogingival Grooves

Remnants of HERS = Epithelial Rests of Malassez - can form Dental Cysts

45
Q

What is the origen of Masicatory Mucosa?

A

Ectoderm

46
Q

How does Junctional Epithelium form?

A

JE forms during tooth eruption when oral epithelium and reduced enamel epithelium fuse

47
Q

What is the origen of the PDL? What cell type forms the PDL?

A

Ectomesenchymal cells of the Dental Follicle differentiating into Fibroblasts

48
Q

What is the average width of the PDL? What happens to it as we age?

A

0.15 - 0.38mm

It decreases in width

49
Q

What is the origen of the Cementum?

A

Ectomesenchymal cells of the Dental Follicle induced by Enamel Matrix Proteins secreted by HERS differentiate into cementoblasts

or

HERS differentiate into Cementoblasts

50
Q

What is the origen of the Alveolar Bone

A

Ectomesenchymal cells of the Dental Follicle differentiating into Osteoblasts

51
Q

What is Bundle Bone?

A

The alveolar bone lining the socket that has Sharpey’s Fibers embedded in it

52
Q

What are Sharpey’s Fibers?

A

The terminal portion of PDL fibers that are embedded in Bundle Bone and Cementum

53
Q

What are the Principal Fiber Groups of the PDL

A

Transseptal Fibers

Alveolar Crest Fibers

Horizontal Fibers

Oblique Fibers

Apical Fibers

Interradicular Fibers

54
Q

What are Transseptal Fibers? Location? Response to perio?

A

Fibers that connect two adjacent teeth

located above the alveolar crest

Always present, even after destruction from periodontal disease

55
Q

What are Alveolar Crest Fibers responsible for? Location? Orientation?

A

Responsible for resisting tooth extrusion and lateral movement.

Located below the JE and running obliquely from cementum to alveolar crest

56
Q

What are Horizotal Fibers responsible for? Location? Orientation?

A

Responsible for resisting lateral tooth movement.

Located in the Cervical Third

Oriented perpendicular from cementum to bone

57
Q

What are Oblique Fibers responsible for? Location? Orientation?

A

Responsible for resisting occlusal forces/shock absorption.

Located in the Middle Third (most abundant fiber) Oriented obliquely from bone to cementum

58
Q

What are Apical Fibers responsible for? Location? Orientation

A

Oriented in an irregular pattern around the apex

59
Q

Where are Interradicular fibers located?

A

Fan out from the fcementum of the tooth at furcation areas of multirooted teeth.

60
Q

What is EMD? When is it expressed? What is it composed of?

A

Enamel Matrix Derivatives

Expressed transiently during early root formation (by HERS)

Induces cementoblast or odontoblast formation

Composed of: 90% Amelogenin 10% proline rich non-amelogenins, tuftelin, tuft protein, serum protein, etc.

61
Q

What is EMD developed from?

A

Porcine unerupted tooth-buds

62
Q

Sculean et al. 2006

A

Aim: to determine the effect of root conditioning on the healing of intrabony defects treated with EMD

Results: NSSD in groups treated with or without PrefGel (24% EDTA)

63
Q

How is PrefGel supposed to be used

A

Applied to the root surface for 2min, after the bleeding from the pocket has stopped, followed by copious irrigation with saline.

64
Q

How does EMD help with Non-Surgical therapy?

A

No additional benefit to SRP alone for pocket depth reduction and CAL gain. However, may enhance early soft tissue healing (lower GI, less BOP, less post-op discomfort)

Wennstrom and Lindhe 2002

65
Q

How does EMD help with Intrabony defects?

A

Systematic review and meta analysis comparing flap alone vs GTR, EMD, GTR+EMD found that no regenerative procedure was significantly better than the others in either CAL or PD reduction.

Tsai et al. 2020

66
Q

How does EMD help with Class II furcation defects?

A

RCT

EMD vs Membrane

45pts with 90 defects

EMD>Membrane in Horizontal depth reduction, less pain/swellling, recession reduction, resorption

Jepsen 2004

67
Q

How do minimally invasive therapies compare when using EMD?

A

Entire Papilla Preservation technique showed equal gain in patients with EPP+EMD+DBBS vs EPP alone

Aslan et al. 2020

68
Q

How does EMD help with root coverage procedures?

A

Mixed reviews

Clinically insignifiant differences

Histologically significant

69
Q
A

Classic Lit Fall 2021 (29 decks)

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