Flashcards in Oral Cavity Deck (310)
Describe the composition of alveolar bone in terms of wet weight and volume
What makes up the majority of the organic material in alveolar bone?
What makes up the rest of the organic material in alveolar bone?
Proteins in small amounts
Describe the differences between internal and external compact bone of alveolar bone
Internal: thin layer lines socket, gives attachment to some PDL fibres
External: thicker layers form external and internal alveolar plates
What is meant by cribriform plate and bundle bone in alveolar bone?
Cribriform: sieve-like appearance of bone produced by vascular canals
Bundle: bundles of Sharpey's fibres bass into bone from PDL
What are the 5 types of cell in bone?
1. Osteoblast: bone secreting
2. Osteoclast: bone resorbing
3. Osteoclast: bone monitoring, osteoblast entombed in bone
4. Osteoprogenitor cells: mesenchymal cell that differentiates into osteoblast
5. Bone-lining: flattened, undifferentiated inactive osteoblast
What is the link between osteoblast and osteoclast activity?
Osteoblasts secrete RANK ligand when forming bone which binds to pre-osteoclasts resulting in differentiation to osteoclasts and becomes activated
What is the difference between caries and erosion?
Caries: bacterial acids
Erosion: non-bacterial acids
What are the 3 ways in which demineralisation can occur by wear?
What is calcium hydroxyapatite?
Synthetic material analogous to calcium phosphate in bone and teeth
Is bioactive and biocompatible
Is a bioresorbable implant material
What are the 3 main properties of calcium hydroxyapatite?
2. Insoluble: will react w/ acid
3. Chemically complex
Compare the solubility of hydroxyapatite and fluoroapatite
HA less soluble than FA
Why fluoride is added to toothpastes, water etc.
Describe the conditions that favour remineralisation and those that favour demineralisation
Demineralisation: low pH, low Ca2+ conc.
Remineralisation: high pH, high Ca2+ conc.
Compare mature enamel to CaHA
Ca ions replaced by other ions; F, CO2
Enamel more soluble than HA
Where is carbonate most concentrated in enamel?
What is the effect of carbonate on CaHA?
Makes it more soluble thus demineralisation/dissolving is more likely to occur
What is the effect of fluoride on CaHA?
Reduces solubility thus less likely to demineralise/dissolve
What is a Stephan curve?
Graph showing effect of acid attack on pH of oral cavity
What is dentine?
Mineralised tissue that forms bulk of tooth
Small, parallel tubules in mineralised matrix
What 4 things do dentine tubules contain?
1. Odontoblastic processes
2. Dentinal fluid
3. Nerve endings
4. Antigen presenting cells
When does formation of dentine begin and stop?
Begins during bell stage
Continues throughout life
Describe the physical properties of dentine
Harder than bone and cementum, softer than enamel
Compare the composition of dentine in weight and volume
Weight: inorganic 70%; organic 20%; water 10%
Volume: inorganic 50%; organic 30%; water 20%
Where are the CaHA crystals found in dentine and how do they compare to enamel crystals?
Crystals found between collagen fibrils
Much smaller than enamel crystals
What are the 6 components of dentine organic matrix?
1. Collagen fibrils
5. Growth factors
What are dentinal tubules?
Tube through which odontoblastic processes project through dentine to EDJ
Why do dentinal tubules follow a S shape?
Due to crowding of odontoblasts as they are squeezed into smaller space within pulp cavity i.e. shape of tooth
Known as primary curve
What do subtle changes in direction of dentine during formation result in?
Wavy dentinal tubules
Can from Contour lines of Owen if coincide w/ adjacent tubules, will appear as line across dentine
Where do secondary curves usually occur?
At junction between primary and secondary dentine due to all odontoblasts taking similar and simultaneous change in direction