Physical Flashcards
Morphogenetic fields
- A group of cells able to respond to discrete, localised biochemical signals leading to the development of specific morphological structures or organs
- Spatial and temporal extent of the embryonic fields are dynamic, and within the field is a collection of interacting cells out of which a particular organ is formed
- Cells within a given morphogenetic field are constrained
- Specific cellular programming of individual cells in a field is flexible
Paracrine and autocrine secretions
paracrine = nearby
autocrine = self
influence activity of adjacent or self-cells (act locally, generally don’t enter bloodstream
e.g., mast cells = paracrine, histamine released and act on adjacent blood vessels; increase vasodilation and permeability
Neurohormones
Secreted by specialised neurons (neurosecretory/ neuroendocrine cells rather than glandular epithelial cells) into blood.
Meet definition of hormone as they diffuse into bloodstream and act on target cells.
May also serve as a neurotransmitter or as autocrine/ paracrine messengers
e.g., ADH
Hormones
Released from endocrine cells.
Chemical messengers that regulate activity of target cells
Endocrine cells
- Secrete hormones into the blood stream that caries them to target cells often distant from the endocrine cells
- Single scattered cells or clumped into glands
- Target cells have the appropriate receptors for endocrine signals making them specificC
Characteristics of root caries
- Follows gingival recession
- Often starts over a large area of exposed root
- Is ‘circumferential’: cannot distinguish between proximal, B and L
- Most often seen in older people and those with a dry mouth
- Can spread coronally to undermine enamel
- Teeth at increased risk of fracture
Clinical appearance of root caries
If active: soft, yellowish/ light brown
If slow progressing: harder and more darkly stained
If arrested: darkly stained, often almost black
Titratable acid
No. of H+ ions available to react related to the chelating effect (calcium brought out and bound to things like juices)
Hypersensitivity to heat
- Heat gradient: expansion/ contraction of dentinal fluid in tubules
- Pressure gradient
- Fluid movement
- Movement stimulates nerve endings
- Action potential (transduction)
- Nerve fibres to CNS
- Pain
Types of fissure sealants
Resin-based: good retention, up to 70% survival rate, moisture sensitive if contaminated
GIC/ RMGIC: ‘poorer’ retention = chemical bond to tooth surface, advantageous in moist areas, fluoride release
Aprismatic enamel
- Not as highly crystallised structure
- Modified technique for etching: longer
- Often in pits and fissures
Diagnosing gingivitis
Local: 10-30% BOP
Generalised: >30% BOP
Less than 10% BOP = periodontal health
GIC setting reaction
(acid-base reaction contributes to the setting process)
1. Polyacid attacks glass particles (20-30% glass breaks-down), calcium, strontium, aluminium and fluoride ions are released
2. Precipitation of salts = ‘gelation’ and hardening
3. Maturation phase = acid/ base reaction, continues for a few days
Composition of GICs
Glass powder (silicate glass), or glass powder + dried polyacrylic acid
Liquid: polyacrylic acid, water
Other additives: maleic acid (improves shelf life), tartaric acid (helps working time)
Unfilled resin on primer
- Chases/ bonds the hydrophobic end of the primer
- Partly enters. the collagen framework and forms a layer on top
- Creates resin tags in dentinal tubules
- Micro mechanical retention with CR on top
- fluid will still come up from tubules: ‘weak zone’
