Flashcards in Oral Cavity Deck (310)
Describe the composition of dentine
20% organic; predentine almost completely organic
90% collagen: structural and associated w/ mineralisation
T1: high proline triple helix, Pro rings stick out
Glycine every 3rd residue
Stabilised by interchain H bonding
What are 3 main proteins found in dentine?
Phosphoproteins: Ca binding
Osteocalcin: mainly found in bone; Ca binding
Osteonectin: bind HA and collagen
What are the 3 dentine specific non-collagenous proteins?
What is dentinogenesis imperfecta?
Genetic condition characterised by malformed dentine
Opalescent teeth that have malformed, unmineralised dentine
Obliterated pulp chambers and shorted roots w/ bulbous centres
Abnormally soft dentine, undergoes rapid and severe functional attrition
Why are apatites important?
Loss of bone/tooth mineral basis of
2. Tooth decay and caries
3. Acid erosion
4. Periodontal disease
In non-stoichiometric solid solutions formed what are magnesium, manganese, fluoride, carbonate each substituted by?
Mg2+, Mn2+: Ca2+
Compare the degree of crystallinity in enamel and bone and dentine
Enamel apatite: sharp diffraction lines; higher conc. F- probably favours more ordered crystal structure
Bone/dentine: diffusion diffraction pattern
What is tooth decay?
Caused by bacteria in plaque and carious lesions producing acids which dissolve tooth mineral
Also produce enzymes which hydrolyse protein component of tooth
What is erosion?
Acid dissolution of mineral
Natural acids: no bacteria involved
What is the significance of the hexagonal lattice structure of HA?
OH slightly too large to fit perfectly into hexagonal lattice thus disoriented/monoclinic structure
F- smaller and fits much better thus readily exchanged for OH in enamel surface
FA chemically and thermodynamically more stable: more resistant to dissolution
Why is fluoride toothpaste important but what does it lack?
F substitutes OH to form FA: more stable, withstand dissolution
To remineralise require Ca2+ and PO43-
What is fluorosis?
Mottling of teeth of children associated w/ fluoride
What may mottling also be a result of?
Disrupted enamel mineralisation resulting from viral disease
Why can fluoride be toxic?
Form complexes with elements in
Electron transport system
What are the 5 effects of fluoride poisoning?
1. Nausea, epigastric pain, vomiting
2. Limb spasms, tetany, convulsions
3. BP, pulse rate fall
4. Respiration depressed
Why is solid state NMR important for apatite?
Only good way to distinguish between HA and FA
What is the water fluoridation level in the UK?
Beneficial as withstand acid dissolution
What DM is fluoride releasing?
GIC, can also release other ions: strontium
Can also uptake and re-release F: act as F battery
Why are bioactive glass toothpastes good?
Release Ca2+, PO43- and raise pH
Forms hydroxycarbonated apatite
Binds directly to bone/tooth
What is NovaMin and what are its disadvantages?
Bioactive glass toothpaste: forms hydroxycarbonated apatite that binds to tooth surface and blocks dentinal tubules where it releases Ca, PO
FA is better
Not quick to form apatite
Glass is harder than enamel, will wear enamel
What are bitewings?
Check up X-rays
Show crowns of premolars and molars
Used for caries risk assessment and bone loss
What are peri-apical X-rays?
Can be of posterior or anterior teeth
Show crown and root
Used for RCT, extraction, bone loss and caries assessment
What is a pan-occlusal X-ray?
X-ray of occlusal view
Useful for un-erupted teeth
What is a panoramic X-ray?
X-ray from condyle to condyle
Can see sinuses, orbits, nose and soft tissue spaces
Useful for orthodontics
What are the 2 most important factors when taking X-rays and how do they relate?
2. Image quality
For safety need lowest dose as reasonably practical
Describe the process of X-ray production in an X-ray tube
Leaded glass vacuum to prevent radiation leaking
Tungsten cathode and copper anode w/ tungsten target
Current applied to cathode, heat generated and electron cloud formed
Potential difference applied, electrons accelerate towards anode
Release energy in X-ray photon (1%) others produce heat (reason for copper block)
Surrounded in oil to dissipate heat
What is the function of aluminium filters in X-rays?
Remove the lower energy photons that would be absorbed by body tissues and potentially cause problems
Describe the effect of inc. voltage in the generation of X-rays
Inc. energy of photos, inc. penetrating power
If too high, non will be absorbed produce grey image
If too low, all absorbed produced light image
How does inc. time current is applied for alter X-rays?
Inc. no. photons produced
Potential for more to be absorbed creating darker image