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What are the clinical implications of PDL in terms of orthodontics?

Tension: inc. PDL space w/ inc. CT and osteoid deposition
Pressure: red. PDL, inc. resorption


Define ideal occlusion and normal occlusion

Ideal: based on morphology of unworn teeth
Normal: satisfies functional and aesthetic requirements but may have minor irregularities in individual teeth


What are the 3 features of OC at birth?

1. Dental arches represented by gum pads
2. Upper gum pad longer and wider than lower
3. Segmented elevations: represent in-erupted teeth


Describe the development of deciduous dentition? Commence, calcification, complete

Commence w/ eruption of LAs @ 6/12 +/- 6/12
Teeth present at birth called neonatal teeth

Calcification begins 4-6/12 in utero

Complete 2.5 yrs


What are the 3 features of deciduous dentition?

1. Incisors spaced
2. Primate spacing: M to UCs, D to LCs; allows space for permanent dentition
3. Flush terminal plane: Es in straight line


What is the general function of deciduous dentition? Apart from mastication

Hold space for permanent teeth
If removed may cause permanent to not erupt or be impacted


Describe the eruption of permanent dentition

Commences w/ L6s @ 6yrs +/- 18/12

6: L6,1s, U6s
7: U1s, L2s
8: U2s

11: L3,4s, U4s
12: U3s, U+L5s, U+L7s


Where do the permanent incisors develop?

Palatal/lingual to deciduous incisors


What 3 features accommodate for the inc. width of permanent incisors?

1. Pre-existing space: primate spacing
2. Proclination: erupt inclined giving more space
3. Growth: inc. inter-canine space


Describe the ugly duckling stage of development

Erupting 3s impact on roots of 2+1s cause crowns to spread out distally
As 3s clinically erupt influence crowns of 2+1s pushing them back to straight


Define Leeway space

Difference between the mesio-buccal distance of C,D,Es compared to 3,4,5s


What is the purpose of the leeway space?

Allows 6s to drift forward (after Es exfoliate) and form class I molar relation


Quantify the leeway space

Mandible: 2mm/quadrant
Maxilla: 1mm/quadrant


Define class I molar relation

Mesio-buccal cusp of U6 occludes w/ mid-buccal groove of L6


Define class I incisor relation

L incisal edge occludes w/ cingulum plateau of U incisors


How are the permanent molars guided into place?

By flush terminal plane of Es


What is biomineralisation?

Process by which inorganic crystal growth and formation is controlled by organic molecules (proteins)


Describe the growth of crystals and why control is required

Crystals grow in all directions thus proteins required to control rate in some directions or completely stop


What is minimal intervention dentistry?

Approach by which dentists base patient care on disease risk assessment, earliest diagnosis and minimal invasive treatment


Describe amelogenin

Forms 90% developing enamel ECM
Highly species conservative
Unique to enamel
High in proline and glutamate


Describe the structure of amelogenin

N: TRAP, hydrophobic, 44-45AAs
Core: hydrophobic, proline, leucine repeats, 100-130AAs
C: hydrophilic, acidic, 15AAs; charged region binds to HA


Describe the regional and molecular structure of amelogenin

Regional: secondary
Molecular: tertiary

Poorly defined
Beta sheets detected by NMR; could act as Ca2+ channels


What post-translational modification occurs in amelogenin?

No glycosylation
Some phosphorylation: serines to phosphoserines


Describe the supramolecular structure of amelogenin

1. Bipolar
2. Self-assembly into nano-spheres
3. 100 monomer units
4. C-terminus on exterior


Describe the primary and secondary functions of amelogenin

Primary: myocells bind to lat. aspects of growing HA crystals, prevent/slow lat. growth, crystals grow sup. forming v long crystals

Secondary: proteins lost, crystals grow lat.


Describe enamelin

5-10% enamel matrix
AA sequence unknown: high in glycine and proline
pI 4-6.5
Bind to HA
Known to retard seeded growth


Describe tuftelin

Secreted before amelogenin
Mainly located @ DEJ
Has Ca binding domain
Associated w/ regulation of HA crystal nucleation


What are another 3 examples of non-amelogenin matrix proteins?

Serum albumins: don't bind crystals
Proline-rich: in un-erupted enamel
Enzymes: proteases, serine proteases


What is the clinical relevance of proteins of enamel biomineralisation?

When process disturbed can lead to conditions such as AI


What is AI?

Inherited condition causing disfigured enamel: smooth, thin, creamy or yellow, localised pits etc.

4 types: hypocalcified, hypomatured, hypoplastic, X-linked
Hypocalcified prone to caries and fracturing

Only 50-53% mineral, enamel usually >90% mineral
More protein: 4-5% rather than 0.06-0.75%

Proposed that TRAP region protein is not removed preventing maturation