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What are cusps of Carabelli?

Extra cusp on palatial surface of palatal cusp on upper molars


What are the main distinguishing factors between deciduous and permanent dentition?

5 teeth in each quadrant vs 8
ABCs markedly smaller than permanent 123s
DEs larger than 45s that replace them
Deciduous crows more bulbous
Deciduous less mineralised; crown more susceptible to wear
Roots smaller, thinner; D, Es divergent allowing space for premolars to grow


Which deciduous teeth have 1 root?



Which deciduous teeth have 2 roots?

L: DEs


Which deciduous teeth have 3 roots?

U: DEs


What are the main differences between permanent and deciduous teeth?

Number: 20vs32
Size: smaller, narrower, shorter
Structure: thinner enamel
Crown shape: molars less complex
Root shape: robust, spindly, divergent
Pulp size, shape: relatively larger, prominent horns


What are the 4 theories of tooth eruption?

1. Root growth
2. Bone remodelling
3. Dental follicle
4. Periodontal ligament


What are the 4 processes of tooth development and eruption?

1. Pre-eruptive movement
2. Intra-issues, tooth in alveolar bone
3. Mucosal penetration: clinical emergence
4. Post-occlusal movement: passive eruption


What are the 4 stages of dentition?

1. Edentulous: before any teeth erupted
2. Deciduous: 6m-5y
3. Mixed: 6-12y
4. Permanent: 12y+


Outline the timeline of deciduous eruption

6-12m: LABs, UABs
14m: Ds
18m: Cs
24m: Es


Outline the timeline of permanent dentition

Phase 1: 6-8y: [16] 2
Phase 2: 10-12y: [467] 3
Phase 3: 17-20y+: 8


What are the 2 stages of tooth development?

1. Tissue differentiation
2. Hard tissue formation: enamel, cementum, dentine


What is the tooth germ derived from?

ectodermal mesenchyme
Dental lamina grows down from oral epithelium and grows bud which gives rise to tooth germ - each develops a tooth


What are the 3 sections of the tooth germ?

1. Enamel organ
2. Dental papilla
3. Dental follicle


Where is the enamel organ derived from and what does it differentiate to?

Derived from ectodermal oral epithelium
Tissue differentiates to ameloblasts - secretes enamel, dictates shape of crown


Where is dental papilla derived from and what does it differentiate to?

Derived from mesenchyme neural crest cells
Tissue differentiates into odontoblasts and develops into pulp


Where is the dental follicle derived from and what does it differentiate into?

Derived from mesenchyme neural crest cells
Differentiates into cementoblasts, osteoblasts, fibroblasts


What are the 6 stages of tooth development and when do they occur?

1. Initiation: 6/7w
2. Bud: 8w
3. Cap: 9/10w
4. Bell: 11/12w
5. Apposition: m-yrs
6. Maturation: m-yrs


What happens in the bud stage?

Mesenchyme condenses around ectodermal bud from oral epithelium


What happens in cap stage?

Enamel organ forms 'cap' above dental papilla


What 3 things happen in bell stage?

1. Enamel organ folds into shape of crown
2. Differentiation of enamel organ tissue (pre-ameloblasts) and dental papilla tissue (odontoblasts) begins at cusp tip
3. Dentine secretion by odontoblasts stimulates ameloblasts


What happens in the appositional stage?

Hard tissues secreted as partially calcified matrix starting at cusp tip
Crown: mineralised crown tissue deposition first
Root: after crown formation, roots grow, tooth erupts


What happens in maturation stage?

Mineralisation completes, enamel matures
Ameloblasts die, odontoblasts line pulp


What is the alveolar bone?

Part of the maxilla/mandible that supports and protects teeth


What is the boundary of the alveolar bone?

Arbitrary but apices of roots


Describe the morphology of the alveolar bone

Finer towards margins (ventral and dorsal), thickest at apices
Dense facial and lingual cortical plates: thinnest at mandibular incisors, thickest at mandibular molars
Maxilla: thicker P>B
Mandible: 1-5 thicker L>B, 6-8 thicker B>L
Radiographically: radio opaque line (lamina dura) lining alveolar socket


What are the 4 functions of the alveolar bone?

1. Distribute and absorb forces (mastication)
2. Serve as attachment site for tooth apparatus: PDL, muscles
3. Framework for bone marrow
4. Ion reservoir


What does the biological property of plasticity allow the alveolar bone to do?

Remodel according to functional demand


What is the possible damage when doing extractions regarding the alveolar bone?

At thinnest parts (mandibular incisor) remove alveolar bone w/ tooth


What is the dependency of the alveolar bone?

Dependent on tooth
Following extraction will atrophy