Tooth eruption Flashcards
what is tooth eruption
- 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)
why does tooth movement vary
- vertical movement in anterior
- horizontal movement in premolars
- rotating and horizontal movements in molars
what are the 3 stages of eruption
- pre eruptive
- eruptive stage
- post eruptive
what is the pre-eruptive stage
- begins with the development of crown
- u shaped crypt of bone (socket) forms around the developing tooth
what is the eruptive stage
- 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
what is the post eruptive stage
- begins when the tooth comes into contact with opposing tooth (occlusion) until tooth is lost
- results in either passive or supra-eruption
what is a passive reaction to the eruption of a tooth (normal)
- teeth wear occlusal because of prolonged masticatory stress and wear
- slight eruption (results from continuous cellular cementum formation) to maintain tooth contact
what is the supra eruption reaction to the eruption of a tooth
- loss of opposing tooth
- causing tooth to erupt farther into space -> over eruption
- future crown/bridge, partial dentures -> difficult to reestablish normal occlusal plane
what are the 4 types of tooth movement of the permanent dentition
- occlusal movement
- horizontal movement
- rotating/horizontal movement (7’s and 8’s)
- medial drift
what is occlusal movement
- erupting teeth
- primary teeth and permanent anterior teeth
- usually perm. lingual to primary tooth
what is horizontal movement
- primary molars move vertically
- allows secondary premolars to move between roots in a horizontal movement
what is rotating/horizontal movement of the 7s and 8s
- 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
what is mesial drift
- natural tendency of teeth to move toward the midline
- occurs over time
- mastication… movement… wear contact area… teeth move mesially to keep in contact
what are diphyodonts
- during life there are 2 successive sets of teeth
- humans are an example
what is the 1st set of teeth
- 20 teeth, primary teeth
what is the 2nd set of teeth
- 32 teeth
- permanent or adult teeth
- only 20 are succedaneous
what is the significance of lost baby teeth
- spacing/malocclusion
- nutrition
- speech
- aesthetics
what is the significance of primary teeth
- 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
primary eruption rules
- 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
what is the eruption of secondary teeth like
- 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
mandible eruption
- 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
what is the process of shedding a primary tooth like
- 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
what is the function of odontoclasts
- dentinoclast (when resorbs dentin) and cementoclasts (when resorbs cementum)
what are some conditions we may see with eruption of teeth
- congenital missing tooth
- submerged primary
- alternate loose/tightening
- no resorption
- ankylosis
- ectopic teeth
how are congenitally missing teeth relevant to eruption
- no secondary tooth bud. primary roots may still resorb over time. tooth stays functional over many years
how are submerged primary teeth relevant to eruption
- eruption is prevented. tilting/drifting/crowing or adjacent teeth
how are alternate loose/tightening teeth relevant to tooth eruption
- 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
how are teeth where roots are not resorbed relevant to tooth eruption
- 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
how is ankylosis relevant to tooth eruption
- 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
how are ectopic teeth relevant to tooth eruption
- 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
what can cause ectopic teeth
- premature loss of space – drifting and unable to erupt, ankylosed primary
- growth of jaw, eruption time and size of teeth not in harmony
what is the treatment for ectopically erupted teeth
- orthodontic with gingival surgery
- remove some of primary tooth to make room
- use spacers to separate teeth
