Tooth Eruption and Exfoliation Flashcards
How do the primary and permanent dentitions develop in relation to one another?
at the same time
How many teeth can the jaw of an infant fit?
20 teeth
How many teeth can the jaw of a 4-5 year old accomadate?
20 erupted teeth and 28 developing teeth
When is the mixed dentition stage?
8-12 years
What is involved with the mixed dentition stage?
simultanous exfoliation of decidious teeth and eruption of permanent teet
What is tooth eruption ?
the movement of a tooth from its site of development within the alveolar process to its functional position in the oral cavity
What are the three stage of tooth eruption?
-pre-eruptive stage
-pre-functional eruptive phase
-functional phase (post-eruptive phase)
What causes the movement of teeth in the pre-eruptive stage?
-growth of jaws
-growth of tooth buds
-remodeling of the walls in the bony crypt
(mesial migration results when there is resorption of the mesial wall with the concomitnant apposition of bone on the distal wall
In which directions does the jaw increase in size?
-length of jaw (antero-posterior)
-width of jaw (coronal plane)
-alveolar ridge height
-buccal-lingual width of alveolus
Which grows faster, teeth or the jaw?
teeth
-individual tooth germ grows rapidly and due to the jaw length ,they become crowded
As the jaw increases in size, which way do the teeth move?
outward (facially) and toward the oral cavity (either upward or downward)
Which way do the permanent molars grow in?
angled inclination prior to and during eruption and achieve vertical alignment only when the jaw length is sufficient to allow it
What are the five theories of tooth eruption?
-root growth
-vascular pressure
-selective bone deposition and resorption
-pulpal pressure
-periodontal and gingival fiber ligaments
What is the root growth theory of tooth eruption?
elongation of the roots in relation to stability of the fundus of the pocket
What is the vascular pressure theory of tooth eruption?
increased hydrostatic pressures in the apical dental sac or periodontal ligament
What is the selective bone deposition and resorption theory of tooth eruption?
coronal bone resorption concomitant with bone apposition in the fundus area
What is the pulpal pressure theory of tooth eruption?
-tissue pressure differential in the pulp compared to the PDL
-decrease in pressure inside, PDL exerts pressure on the tooth and it moves up
What is the periodontal and gingival fiber ligament theory of eruption?
cells (myofibroblasts) exert traction on the tooth through the collagen network and cell to cell contacts
-contacts help to push the tooth up
What are the most frequently accepted theories of tooth eruption?
root growth, alveolar bone remodeling, and periodontal ligament formation
What other factors influence tooth eruption?
-parathyroid hormone (influence mineralization and resorption of roots)
-MMPs produced by fibroblasts, osteoclasts, macrophages
What is a gubernacular canal?
strand of connective tissue that contains remnants of dental lamina epithelium (derived from previous lamina)
What is the best description of rate of eruption?
“burst of eruption” that averages about 3 mm every 3 months
What is occlusal surface wear?
oblique fibers of PDL continue to pull tooth into occlusion as enamel is abraded
What is a compensatory eruptive mechanism to continued occlusal abrasion?
apical cementum deposition
