LO 6 - Eruption & Shedding

Question 1

What are the 3 phases of tooth eruption?

Answer 1

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

Question 2

Describe the pre-eruptive phase

Answer 2

1. Movement of primary & permanent tooth crowns within the forming bony crypt
2. From the early initiation to crown completion
3. Ends with early initiation of root formation

Question 3

During the pre-eruptive phase, the movement of primary and permanent developing crowns is due to what changes?

Answer 3

1. Size and shape of developing mandible & maxilla
2. Position and development of adjacent teeth
3. Permanent teeth movement in relationship to resorptive roots of primary teeth and remodeling of alveolar processes
4. All movement BEFORE root formation

Question 4

Describe the pre-eruptive phase for incisors

Answer 4

1. Permanent anteriors develop lingual to the incisal level of the forming primary teeth
2. Later development, as the primary teeth erupt: permanent successors are lingual to the apical third of the primary tooth

Question 5

Describe the pre-eruptive phase for premolars

Answer 5

1. Permanent premolars shift from location near occlusal area of primary molars to location enclosed within roots of the primary molars
2. This change in position is result of increased height of the alveolar bone

Question 6

Describe the pre-eruptive phase for permanent molars

Answer 6

1. Permanent molars have NO primary predecessors, therefore develop without relationship to primary teeth
2. Maxillary molars develop with occlusal slanted distally
3. Mandibular molars develop with occlusal slanted mesially

Question 7

Describe the steps of the Prefunctional Eruptive Phase

Answer 7

1. Root formation - With increase in root length, the tooth begins eruptive movements providing space for further root lengthening
2. Movement
3. Penetration through epithelial layers
4. Intraoral movement

Question 8

What are the causative factors of eruption?

Answer 8

1. Root growth
2. Changes in vascularity
3. Increased cellular activity around forming tooth
4. Endocrine factors (growth hormone)
5. Enzyme activity

Question 9

Describe structures of movement in the Prefunctional Eruptive Phase: Movement

Answer 9

1. Dental follicle (area of mesenchymal cells and fibers that surround the dental papilla and the enamel organ of the developing teeth) forms a pathway for eruption
2. Gubernacular cord (A fibrous tissue band connecting the tooth sac with the alveolar mucosa)
3. Bone and connective tissue resorbed to allow movement OCCLUSALLY
4. Reduced enamel epithelium (REE – layers of the epithelial enamel organ compacted and remaining on the surface of enamel after its formation is complete) contacts and fuses with oral epithelium
5. Breakdown of oral epithelium from enzymes within REE (reduced enamel epithelium)

Question 10

Describe the Penetration of the Epithelium during the Prefunctional Eruptive Phase

Answer 10

1. The tooth’s crown penetrates through the fused epithelial layers
2. Fused epithelial layers become the first epithelial attachment: junctional epithelium

Question 11

List the stages of tooth eruption

Answer 11

1. Tooth crown approaching oral epithelium in preeruptive stage
2. Contact of REE including the developmental cuticle fusing with oral epithelium
3. Fusion of REE including the developmental cuticle and oral epithelium
4. Thinning of the fused epithelium
5. Rupture of oral epithelium, formation of the attached gingiva and emergence.
6. Clinical crown appearance into the oral cavity (prefunctional stage_
7. Tooth erupting into functional occlusion - Tooth continues to erupt until in clinical contact with opposing tooth

Question 12

Describe Nasmyth’s Membrane

Answer 12

1. Fused tissue of the REE (Reduced Enamel Epithelium)/ Oral epithelium
2. Primary cuticle (a thin film on the enamel surface of an unerupted tooth. Product of the degenerating ameloblasts)
3. Easily stains with food debris, causing staining of the newly erupted primary teeth

Question 13

Describe formation of Periodontal ligament fibers during the Prefunctional eruptive phase

Answer 13

1. First fibers to form are cervical
2. With eruption: fibers grow along the elongating root

Question 14

What structural changes occur during the Functional eruptive phase due to function

Answer 14

1. Completion of the apex of the tooth root
2. Rapid formation of cementum
3. Formation of Apical periodontal ligament fibers
4. Thickening and final orientation of all PDL fibers
5. Alveolar bone density increases

Question 15

What are the parameters of the Functional Eruptive Phase

Answer 15

1. Occurs after the teeth are in functional occlusion
2. And continues until teeth are lost or death

Question 16

Describe the Functional eruptive phase

Answer 16

1. Balance in arches accommodating to the continued growth of maxilla and mandible
2. Eruption balances occlusion during continued growth
3. functional attrition with occlusal/incisal wear - eruption maintains teeth in contact
4. slight interproximal wear - mesial eruptive force to keep teeth in contact

Question 17

Describe what happens in the case of losing a permanent tooth

Answer 17

1. Over eruption of opposing tooth (teeth): supraeruption
2. unbalanced normal occlusal plane - leads to Temporomandibular joint malfunction
3. Reduced vertical dimension