25-Theories + Patterns of tooth eruption

Question 1

Root theory

Answer 1

Explains eruption w/root elongation

• Whilst growing ⇢ Root pushes crown towards mucous membrane
• This theory does not prove why root development occurs after tooth eruption
• There are also teeth that travel longer than root length

Question 2

Dentin growth + Pulp constriction

Answer 2

This theory is based on suggestion that:

• With apical extension of the root ⇢ pulp is apically compressed
• This creates occlusal forces
• Theory is rejected as at time of eruption ⇢ apical opening is wide

Question 3

Bone growth

Answer 3

Eruption is due to accumulation of bone beams at bottom of alveoli

• Modern experiments proven this is a consequence ⇢ not cause of breakthrough

Question 4

Phases of tooth eruption

Answer 4

Tooth eruption ⇢ when developing teeth emerge through soft tissues of jaw + from mucosa to enter oral cavity

Phases:

1. Pre-eruptive
2. Pre-functional eruptive
3. Functional eruptive

Question 5

Pre-eruptive phase

Answer 5

Movements related to tooth eruption which require adjustments relative to forming bony crypt

• Crowns move constantly in jaws ⇢ responding to positional changes + making mesial/distal movements
• Permanent anterior teeth ⇢ develop lingually to incisal level of permanent teeth
• When 1° teeth are erupted ⇢ permanent successors positioned lingually to apical ⅓ of their roots
• Permanent molars ⇢ shift from occlusal area of 1° molars⇢ to go within roots of them

Question 6

Pre-functional eruptive phase

Answer 6

• Begins w/root formation
• Ends when teeth reach occlusal contact

Question 7

Root formation

Answer 7

• Elongation of root requires space
• Proliferation of epithelial root sheath ⇢ pulp + dentin formation in root
• Causes ⇡ fibrous tissue of surrounding dental follicle

Question 8

Movement

Answer 8

• Occurs incisially + occlusally through jaw’s bony crypt to reach oral mucosa
• Results from the need of space of root
• Reduced oral epithelium ⇢ fuses w/oral epithelium = Reduced epithelilal layer around erupting crown

Question 9

Penetration

Answer 9

• enamel of crown enters oral cavity via penetration into epithelial fused layers
• Around enamel ⇢ organic developmental cuticle ⇢ replaced by pelicula dentis

Question 10

Intraoral occlusal + incisal movements

Answer 10

• Crown continues to move through oral mucosa ⇢ gradual exposure of crown + ⇡ apical shift of gingival attachment
• Exposed crown = clinical crown (Cusp tip - gingival attachment)
• Anatomical crown = cusp tip - CEJ
• Movements occur until occlusal contact w/opposite crown

Question 11

Functional eruptive phase

Answer 11

Begins when teeth are functioning + continues until teeth are present in the mouth

• Root is almost completed + alveolar processes ⇡ height
• Fundic alveolar plates resorb to form root tip apex
• Root canal narrows during root tip maturation

Primary teeth ⇢ 1 - 1.5 yrs

Permanent teeth ⇢ 2 - 3 years

Question 12

post eruptive changes

Answer 12

Attrition

Formation of compensatory cementum on apical root