Tooth eruption

Question 1

what is tooth eruption

Answer 1

• emerging of the crown into the oral cavity
• continues in life, teeth continually move
• from beginning crown development until tooth is lost (because of continuous movement)

Question 2

why does tooth movement vary

Answer 2

• vertical movement in anterior
• horizontal movement in premolars
• rotating and horizontal movements in molars

Question 3

what are the 3 stages of eruption

Answer 3

1. pre eruptive
2. eruptive stage
3. post eruptive

Question 4

what is the pre-eruptive stage

Answer 4

• begins with the development of crown

- u shaped crypt of bone (socket) forms around the developing tooth

Question 5

what is the eruptive stage

Answer 5

• begins with the development of the root
• until it contacts opposing tooth
• develops in socket, erupts as it grows
• osteoclasts temporarily deepen the socket
• alveolar bone keeps pace with growing root
• erupts from connective tissue through oral epithelium into the oral cavity
• when REE contacts the oral epithelium: makes the junctional epithelium

Question 6

what is the post eruptive stage

Answer 6

• begins when the tooth comes into contact with opposing tooth (occlusion) until tooth is lost
• results in either passive or supra-eruption

Question 7

what is a passive reaction to the eruption of a tooth (normal)

Answer 7

• teeth wear occlusal because of prolonged masticatory stress and wear
• slight eruption (results from continuous cellular cementum formation) to maintain tooth contact

Question 8

what is the supra eruption reaction to the eruption of a tooth

Answer 8

• loss of opposing tooth
• causing tooth to erupt farther into space -> over eruption
• future crown/bridge, partial dentures -> difficult to reestablish normal occlusal plane

Question 9

what are the 4 types of tooth movement of the permanent dentition

Answer 9

1. occlusal movement
2. horizontal movement
3. rotating/horizontal movement (7’s and 8’s)
4. medial drift

Question 10

what is occlusal movement

Answer 10

• erupting teeth
• primary teeth and permanent anterior teeth
• usually perm. lingual to primary tooth

Question 11

what is horizontal movement

Answer 11

• primary molars move vertically

- allows secondary premolars to move between roots in a horizontal movement

Question 12

what is rotating/horizontal movement of the 7s and 8s

Answer 12

• max molars develop in max tuberosity in a distal orientation (the way they point)
• mand molars develop in the rams (retromolar) in a mesial orientation (the way the occlusal pit points)
• no preceding tooth guide
• erupt and move into place as jaw grows

Question 13

what is mesial drift

Answer 13

• natural tendency of teeth to move toward the midline
• occurs over time
• mastication… movement… wear contact area… teeth move mesially to keep in contact

Question 14

what are diphyodonts

Answer 14

• during life there are 2 successive sets of teeth

- humans are an example

Question 15

what is the 1st set of teeth

Answer 15

• 20 teeth, primary teeth

Question 16

what is the 2nd set of teeth

Answer 16

• 32 teeth
• permanent or adult teeth
• only 20 are succedaneous

Question 17

what is the significance of lost baby teeth

Answer 17

• spacing/malocclusion
• nutrition
• speech
• aesthetics

Question 18

what is the significance of primary teeth

Answer 18

• hold the space for developing adult teeth, facilitate the proper alignment of adult teeth and also promote jaw development
• space maintainers
• space needed for larger and more numerous secondary teeth -> preventing malocclusion
• important for nutrition, speech and aesthetics

Question 19

primary eruption rules

Answer 19

• mand > max
• A’s - 6-7 months
• B’s - 9 months
• D’s - 12 months
• C’s - 16 months
• E’s - 24 months
• sequence: a, b, d, c, e
• age 2: 20 teeth
• loss of primary teeth occurs by 12

Question 20

what is the eruption of secondary teeth like

Answer 20

• 20 succeed the primary teeth
• 12 molars develop distal to last primary molar
• anterior develop lingually to primary anteriors
• premolars develop between roots of primary molars
• molars erupt on angle and rotate into place
• eruption begins with many first molar at 6

Question 21

mandible eruption

Answer 21

• 1st molars (6): 6 yrs
• 1s - 6 yrs
• 2’s - 7 years
• 4’s - 9/10 yrs
• 3’s - 9-10 yrs
• 5’s - 11 yrs
• 7’s - 11/12 yrs
• 8’s - 17/21 yrs
  EXCEPTION: 2nd premolar (mandible – canine erupts first)
• 6, 1, 2, 4, 3, 5, 7, 8

Question 22

what is the process of shedding a primary tooth like

Answer 22

• gradual root resorption/loss of PDL attachment
• pressure from crown and growth root of secondary (beneath or lingual)
• occlusal pressure of secondary teeth on root and bone
• cells resemble osteoclasts but are called odontoclasts
• resorption of primary root - 1 year prior to exfoliation
• exfoliation - tooth falls out as root resorbs

Question 23

what is the function of odontoclasts

Answer 23

• dentinoclast (when resorbs dentin) and cementoclasts (when resorbs cementum)

Question 24

what are some conditions we may see with eruption of teeth

Answer 24

1. congenital missing tooth
2. submerged primary
3. alternate loose/tightening
4. no resorption
5. ankylosis
6. ectopic teeth

Question 25

how are congenitally missing teeth relevant to eruption

Answer 25

• no secondary tooth bud. primary roots may still resorb over time. tooth stays functional over many years

Question 26

how are submerged primary teeth relevant to eruption

Answer 26

• eruption is prevented. tilting/drifting/crowing or adjacent teeth

Question 27

how are alternate loose/tightening teeth relevant to tooth eruption

Answer 27

• may see this in children
• normal occurrence
• resorption and PDL destruction
• secondary tooth relieves (stops putting) occlusal pressure on primary tooth
• tension remains on surrounding connective issue
• this can cause temporary attachment of PDL by forming new cementum and bone, tightens the primary tooth
• tooth will eventually be lost

Question 28

how are teeth where roots are not resorbed relevant to tooth eruption

Answer 28

• crown lingual to primary
• not subject to any pressure
• root does not resorb
• primary not exfoliated
• needs to be extracted
• ex: primary mand incisors
• permanent erupt lingual, usually tongue will push in place but still may need extraction

Question 29

how is ankylosis relevant to tooth eruption

Answer 29

• union of 2 similar or dissimilar hard tissues previously detached but beside each other
• root/cementum of primary tooth to alveolar bone
• primary root can fuse to secondary crown
• secondary tooth can’t erupt, deviates its path -> ectopic
• common in the E’s

Question 30

how are ectopic teeth relevant to tooth eruption

Answer 30

• abnormal direction of tooth eruption
• occurs in 3% of children ( a genetic factor may be involved)
• more often seen in max teeth and in males
• 2/3 of the ectopic situations will erupt into normal positions without corrective treatment

Question 31

what can cause ectopic teeth

Answer 31

• premature loss of space – drifting and unable to erupt, ankylosed primary
• growth of jaw, eruption time and size of teeth not in harmony

Question 32

what is the treatment for ectopically erupted teeth

Answer 32

• orthodontic with gingival surgery
• remove some of primary tooth to make room
• use spacers to separate teeth