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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?

1. Phosphophoryn
2. Sialprotein
3. AG1


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
1. Osteoporosis
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+
F-: OH-
CO32-: PO43-


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
Enzyme cofactors


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
5. Unconsciousness


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?

1. Dose
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


Why is rectification important in radiography?

Convert AC to DC current
Current always on (when pressed) thus less dose to patient as more photons produced