Extra Qs/ theme III

Question 1

How are palatal cysts formed

Answer 1

The medial epithelial seam established during fusion of the palatal shelves must be removed by apoptosis to generate a continuous layer of mesenchymal cells. If not completely removed, they could receive inductive differentiation signals and begin to secrete extracellular matrix or other material resulting in the formation of palatal cysts. Palatal cysts are benign and usually do not need treatment, but they could be obstructive if fitting a denture, for example.

Question 2

The main difference of a foetal TMJ to an adult’s

Answer 2

Flat articular eminence in early development as TMJ not in use.
The articular eminence only becomes prominent after tooth eruption as the mandibular fossa adapts in response to masticatory forces.

Question 3

What does a bite-jumping orthodontic device do. When is it most effective in life

Answer 3

it pulls the mandible forward, inducing growth of the condyle. Dormant progenitor cells start to proliferate, differentiate into chondrocytes, and condylar growth by endochondral ossification.
-However, condylar growth induced in adults is limited, so orthodontic treatment is usually performed in younger patients who still grow.

Question 4

How synchondrosis differs from an epiphyseal plate in a developing long bone and what is its functional advantage

Answer 4

chondrocytes in long bone are in columns. Growth in 1 direction.
-Synchondroses [cartilaginous growth plates that join 2 endochondrally ossifying bones] Mirror image of the growth plate compared to long bones. Grows from the middle outwards in 2 directions.

Question 5

endochondral ossification steps

Answer 5

-Mesechymal cells differentiate into resting chondrocytes
-Then proliferating chondrocytes produce collagen 2 and divide rapidly, forming the basis for the increase in size and growth of the skull bones.
-Terminal differentiation is initiated in pre-hypertrophic chondrocytes which start to produce collagen 10 and begin to swell.
-Hypertrophic chondrocytes are fully differentiated
and produce abundant cartilage matrix.
-Eventually they undergo apoptosis and the deposited
cartilage matrix is replaced by bone
- Osteoblasts have migrated into the area of mineralisation and deposit bone matrix onto the cartilage template.

Question 6

When the metopic suture closes

Answer 6

2-14 months (average of 8 months)

Question 7

When does mandibular symphysis close

Answer 7

1-2 years

Question 8

what sutures unite the parietal and temporal, and temporal and occipital

Answer 8

Parietal-Temporal: Squamosal suture

Temporal-Occipital: Occipitomastoid suture

Question 9

the 2 mechanisms that cranial vault grows

Answer 9

• displacement at sutures

- remodelling at internal and external surfaces (deposition and resorption)

Question 10

Bones that make up the cranial vault and the base.

Answer 10

BASE: Ethmoid, Sphenoid, Temporal (petrous part), Occipital (basioccipital and exoccipital parts

VAULT: Frontal, Parietal, Temporal (squamous part), Occipital (interparietal and supraoccipital = squamous part)

Question 11

ossification of the 2 main synchondrosis in the cranial base. When does the inter-sphenoidal ossify

Answer 11

Spheno-ethmoidal synchondrosis: Ossifies at ~7 years of age.
Spheno-occipital synchondrosis: Ossifies at ~13-15 years (females) and ~15-17 years (males)

inter = 7 months in utero

Question 12

how the maxilla increases in height, width and length

Answer 12

1. Height:
   • deposition at the zygomatic and frontal sutures
   • remodelling at alveolar processes (vertical tooth drift)
   • remodelling of hard palate (deposition on inferior surface and resorption at floor of the nose and maxillary sinuses.
2. width:
   • Growth at mid-palatal suture
   • Some external bone remodelling.
3. length:
   • Growth at posterior surface of maxillary tuberosities (forward displacement results in backward growth of the maxilla)
   • Bone remodelling in area above maxillary incisors

Question 13

How the mandible grows forward and down, and laterally

Answer 13

a)“Forward and downward” growth (in relation to cranial base) by:
• Growth of the condylar cartilage
• Bone remodelling of the ramus (bone deposition along posterior margin, resorption along the anterior of the ramus)
b) Lateral growth:
• Complex remodelling along lateral and lingual surfaces of the condyle, coronoid, ramus, and angle.

Question 14

where do you find these points: sella , nasion, orbitale, A, ANS, PNS, basion, Menton, gonion

Answer 14

• sella= midpoint of sella turcica
• nasion= where frontal and nasal bones meet
• orbitale= base or orbit
• A= deepest indent of maxilla
• ANS= anterior nasal spine. Tip of anterior maxilla
• PNS= tip of posterior maxilla
• basion= deepest indent of mandible
• menton= lowermost point of mandibular symphysis
• gonion= most posterior-inferior point on angle of mandible

Question 15

Amelogenins and non-amelogenins differences (hydrophobic. hydrophilic, %, which made first, function)

Answer 15

• Amelogenins: 90%. Hydrophobic. Form nanosphres around crystals. Regulates growth and thickness of crystals
• Enamelin, ameloblastin: 10%. Hydrophilic. Acidic. Made first. Role in Ca and PO4 concentration and promote crystal formation.

Question 16

What stage of tooth development does amelogensis and dentogensis occur

Answer 16

late bell in histogenesis

Question 17

what are contained in dentine matrix vesicles

Answer 17

phosphoporyns that bind Ca

Alkaline phosphatase that increase PO4

Question 18

difference between mantle and circumpulpal dentine

Answer 18

• Mantle: outer layer. Fast globular calcification by matrix vesicles. Made first
• Circumpulpal: linear and globular calcification

Question 19

What are spindles, lamella and tufts

Answer 19

• Spindles - short. Odontoblast between amelbolasts
• Tufts - branched. 2/3 into enamel. Tuftulin that hasn’t been removed. Hypomineralised.
• Lamella - through the whole enamel. Hypomineralised

Question 20

What are the different incremental growth lines in enamel, dentine and cementum

Answer 20

-Cementum = lines of salter

-Enamel: short= cross striations
long = striae of retzus (perikymata)
secondary= Wilson lines

-Dentine: short= von Ebner
long =Anderson lines
secondary = contour lines of Owen

Question 21

3 features that prevent cracks prorating into deeper areas of enamel

Answer 21

• gnarled enamel near pits
• decussation of rods
• keyhole structure

Question 22

what % of pulp is water

Answer 22

75

Question 23

what shape are coronal and root odontoblasts

Answer 23

coronal = columnar
root = cuboidal

Question 24

what % of PDL is ECM -What its made of.
What type of fibres (% and function)
What collagen is only present after eruption

Answer 24

1-60% - glycosaminoglycans (hyaluronic acid), proteoglycans, glycoproteins. Bind water and ions for shock absorbance.

2-10% Elastic fibres. Perpendicular to collagen. Regulates blood flow

3-90% collagen fibres. -90% = type I. Make fibre bundles
-10%= type III (same collagen ratios in dentine) Support vessels when compressed.

-after eruption = type XII

Question 25

what collagen type is in gingiva. its function

Answer 25

type I. Tensile strength to rest shearing forces

Question 26

what is the most common missing teeth for MXS1 and PAX9 mutations

Answer 26

• MSX1 = premolars

- PAX9= permanent molars

Question 27

what happens at smooth and ruffle ends during amelogenesis

Answer 27

• smooth= proteins and water exit

- ruffle = Ca enter enamel

Question 28

difference between reversible and irreversible pulpits. What dentine sensitivity feel like and stimuli

Answer 28

• Reversible= short- lived pain. Vital pulp
• Irreversible = longer, persist when stimulus taken away (mins-hrs) Induced by cold. Pulp cannot be preserved

-Short sharp pain in response to thermal, osmotic, evaporative, tactile, chemical stimuli

Question 29

function of OEE, stellate reticulum, stratum intermedium

Answer 29

• OEE= maintains tooth shape. Nutrient exchange with follicle
• reticulum= glycosaminoglycans and desmosomes. Cushioning
• intermedium=Alkaline phosphatase. nourishment to ameloblasts

Question 30

formation of enamel pearls, lateral canals

Answer 30

• pearls: rests of malassez attach to predentine which induce ameloblast differentiation. OR differentiation caused by reticulum/ intermedium becoming trapped in rest cells.
• Lateral: capillaries interrupt HERS, interfering with formation of odontoblasts.

Question 31

how are primary and secondary curvatures caused in dentine

Answer 31

Primary = sigmoid shaped due to overcrowding pushing odontoblasts apically 
Secondary = odontoblast processes bent in stressful events (Owen during birth)

Question 32

Where is granular tomes layer and how is it caused. Interglobular dentine

Answer 32

• In root dentine, between hyaline layer and root dentine
• caused by incomplete fusion of calcospherites or backward looping of odontoblast processes
• Interglobular = upper 3rd of coronal dentine. Also caused by incomplete fusion of calcospherites

Question 33

what 2 things make up nasmyth’s membrane

Answer 33

• primary enamel cuticle and REE remnants

- it attaches the junctional epithelium to the enamel

Question 34

name things that are orthokeratanised, para or non. Their differences

Answer 34

• ortho= gingiva under high abrasion, medial hard palate, tongue. [No nuclei]
• para = gingiva, lips. [Nuclei]
• non = junctional and sulcular epithelium, lining mucosa. [Live cells]

Question 35

what are the cell layers in the oral epithelium. Name non-keratinocytes. What layers are below epithelium. Why rate pegs are there

Answer 35

• keratinised layer, granular layer, prickle, and basal
• lamina propria and submucosa
• melanocytes, merkel cells (touch), Langerhans cells(dendritic) lymphocytes
• rete pegs between epithelium and propria to improve attachment and stability, important in areas under abrasion

Question 36

what tongue papilla is used for mastication. Atrophy of this type causes what tongue disorders

Answer 36

filiform

black hairy tongue and geography tongue

Question 37

4 main steps of oral mucosa wound healing. what added step is involved in repair from extraction

Answer 37

1. Haemostasis - deposition of fibrin
2. Inflammatory response = clearance of cell debris
3. Epithelial tissue repair = epithelial cell sheet formation
4. Connective tissue repair =deposition of collagen

osteogenic precursor cells to absorb bone

Question 38

what cytokines induce MMP secretion from fibroblasts

Answer 38

IL 6, TNF-a

Question 39

what is the dent-ginigval epithelium made of and what is the junctional epithelium

Answer 39

• REE and oral epithelium

- REE

Question 40

what doe the 4 pharyngeal pouches make

Answer 40

1- middle ear, auditory tube
2- supratonsillar fossa
3- thymus, inferior parathyroid gland
4- superior parathyroid gland

Question 41

at what week does tongue development occur

Answer 41

week 8

Question 42

main mandibular growth processes from week 6 to brith

Answer 42

6= merkel's cartilage develops to support the mandible during growth 
7= ossification of mandible begins. Trough shape enclosing the incisive nerve, Merkel and tooth germ
10= symphyseal cartilage develops
12= articular disc develops

Question 43

the structures associated with the TMJ

Answer 43

• Articular disc= anterior band, intermediate zone, posterior band, bilaminar zone
• Synovial cavity
• Mandibular fossa, articular eminence
• Condyle
• Lateral pterygoid muscle for protrusion and side to side

Question 44

what a damaged articular disc looks like. Difference between with reduction and without reduction

Answer 44

-anterior displacement of the posterior band. Bilaminar zone is stretched
1-with reduction =disc is able to slip back to normal position. POPPING OR CLICKING
2-without reduction= cannot return. GRINDING SOUND as bone against bone