Flashcards in Oral Cavity Deck (310)
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
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
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
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
Beta sheets detected by NMR; could act as Ca2+ channels
What post-translational modification occurs in amelogenin?
Some phosphorylation: serines to phosphoserines
Describe the supramolecular structure of amelogenin
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.
5-10% enamel matrix
AA sequence unknown: high in glycine and proline
Bind to HA
Known to retard seeded growth
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