Extra Qs/ theme III Flashcards
How are palatal cysts formed
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.
The main difference of a foetal TMJ to an adult’s
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.
What does a bite-jumping orthodontic device do. When is it most effective in life
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.
How synchondrosis differs from an epiphyseal plate in a developing long bone and what is its functional advantage
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.
endochondral ossification steps
-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.
When the metopic suture closes
2-14 months (average of 8 months)
When does mandibular symphysis close
1-2 years
what sutures unite the parietal and temporal, and temporal and occipital
-Parietal-Temporal: Squamosal suture
-occipitomastoid suture
Temporal-Occipital: Occipitomastoid suture
the 2 mechanisms that cranial vault grows
- displacement at sutures
-remodelling (bone deposition and resorption) of the shape to change locally the curvature
- remodelling at internal and external surfaces (deposition and resorption)
Bones that make up the cranial vault and the base.
BASE: Ethmoid, Sphenoid, Temporal (petrous part), Occipital (basioccipital and exoccipital parts
VAULT: Frontal, Parietal, Temporal (squamous part), Occipital (interparietal and supraoccipital = squamous part)
ossification of the 2 main synchondrosis in the cranial base. When does the inter-sphenoidal ossify
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
how the maxilla increases in height, width and length
- 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. - width:
-Growth at mid-palatal suture
-Some external bone remodelling. - length:
-Growth at posterior surface of maxillary tuberosities (forward displacement results in backward growth of the maxilla)
-Bone remodelling in area above maxillary incisors
How the mandible grows a) forward and down, and b) laterally, in relation to cranial base
a) Growth of the condylar cartilage
-Bone remodelling of the ramus (bone deposition along posterior margin, resorption along the anterior of the ramus)
b) Complex remodelling along lateral and lingual surfaces of the condyle, coronoid, ramus, and angle.
where do you find these points: sella, nasion, orbitale, A, ANS, PNS, basion, Menton, gonion
- sella= midpoint of sella turcica
- nasion= where frontal and nasal bones meet
- orbitale= base or orbit
- A= deepest concave of maxilla
- ANS= anterior nasal spine. Tip of anterior maxilla
- PNS= tip of posterior maxilla
- basion= deepest concave of mandible
- menton= lowermost point of mandibular symphysis -under chin
- gonion= most posterior-inferior point on angle of mandible
Amelogenins and non-amelogenins differences (hydrophobic. hydrophilic, %, which made first, function)
- 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.
What stage of tooth development does amelogensis and dentogensis occur
late bell in histogenesis
what are contained in dentine matrix vesicles
phosphoporyns that bind Ca
Alkaline phosphatase that increase PO4
difference between mantle and circumpulpal dentine
- Mantle: outer layer. Fast globular calcification by matrix vesicles. Made first
- Circumpulpal: linear and globular calcification
What are spindles, lamella and tufts
- Spindles - short. Odontoblast between amelbolasts
- Tufts - branched. 2/3 into enamel. Tuftulin that hasn’t been removed. Hypomineralised.
- Lamella - through the whole enamel. Hypomineralised
What are the different incremental growth lines in enamel, dentine and cementum
-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
3 features that prevent cracks prorating into deeper areas of enamel
- gnarled enamel near pits
- decussation of rods
- keyhole structure
what % of pulp is water
75
what shape are coronal and root odontoblasts
coronal = columnar
root = cuboidal
what % of PDL is ECM -What its made of.
What type of fibres (% and function)
What collagen is only present after eruption
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
what collagen type is in gingiva. its function
type I. Tensile strength to rest shearing forces
what happens at smooth and ruffle ends during amelogenesis
- smooth= proteins and water exit
- ruffle = Ca enter enamel
function of OEE, stellate reticulum, stratum intermedium
- OEE= maintains tooth shape. Nutrient exchange with follicle
- reticulum= glycosaminoglycans and desmosomes. Cushioning
- intermedium=Alkaline phosphatase. nourishment to ameloblasts
formation of enamel pearls, lateral canals
- 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.
how are primary and secondary curvatures caused in dentine
Primary = sigmoid shaped due to overcrowding pushing odontoblasts apically
Secondary = odontoblast processes bent in stressful events (Owen during birth)
Where is granular tomes layer and how is it caused. Interglobular dentine
- 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
what 2 things make up nasmyth’s membrane
- primary enamel cuticle and REE remnants
- it attaches the junctional epithelium to the enamel
name things that are orthokeratanised, para or non. Their differences
- ortho= gingiva under high abrasion, medial hard palate, tongue. [No nuclei]
- para = gingiva, lips. [Nuclei]
- non = junctional and sulcular epithelium, lining mucosa. [Live cells]
what are the cell layers in the oral epithelium. Name non-keratinocytes. What layers are below epithelium. Why rate pegs are there
- 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
4 main steps of oral mucosa wound healing. what added step is involved in repair from extraction
- Haemostasis - deposition of fibrin
- Inflammatory response = clearance of cell debris
- Epithelial tissue repair = epithelial cell sheet formation
- Connective tissue repair =deposition of collagen
osteogenic precursor cells to absorb bone
what cytokines induce MMP secretion from fibroblasts
IL 6, TNF-a
what is the dent-ginigval epithelium made of and what is the junctional epithelium
- REE and oral epithelium
- REE
what doe the 4 pharyngeal pouches make
1- middle ear, auditory tube
2- supratonsillar fossa
3- thymus, inferior parathyroid gland
4- superior parathyroid gland
at what week does tongue development occur
week 8
main mandibular growth processes from week 6 to birth
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
the structures associated with the TMJ
- 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
what a damaged articular disc looks like. Difference between with reduction and without reduction
-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
