Mechanism and control of tooth eruption: overview and clinical implications.
OBJECTIVE
To review pre- and post-emergent eruption, with particular emphasis on distinguishing isolated molar ankylosis from primary failure of eruption (PFE) and genetic considerations in eruption problems.


METHODS
Radiographic review of eruption failure patients; animal and human experiments; high precision observations of movements of erupting teeth.


RESULTS
In pre-emergent tooth eruption, the controlling element is the rate of resorption of overlying structures. A path is cleared, and then the erupting tooth moves along it. This has clinical importance in recognizing the cause of eruption problems, particularly PFE, in which all teeth distal to the most mesial involved tooth do not erupt or respond to orthodontics. In our study of by far the largest sample of PFE cases yet reported, familial cases of PFE accounted for approximately (1/4) of all cases examined. Candidate genes now are being evaluated. In post-emergent eruption, control seems to be light forces of long duration that oppose eruption, rather than heavy forces of short duration such as those during mastication. Studies of human premolars in their passage from gingival emergence to the occlusal plane show that in this phase eruption occurs only during a few hours in the early evening. The critical hours for eruption parallel the time that growth hormone levels are highest in a growing child. In this stage intermittent force does not affect the rate of eruption, but changes in periodontal blood flow do affect it.
Proffit
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WR
Department of Orthodontics, University of North Carolina School of Dentistry, Chapel Hill, NC 27599-7450, USA. William_Proffit@dentistry.unc.edu
Frazier-Bowers
S A
SA
D000539:Alveolar Process / Q000503:physiopathology; D000818:Animals; D001696:Biomechanical Phenomena; D001862:Bone Resorption / Q000503:physiopathology; D002940:Circadian Rhythm / Q000502:physiology; D006801:Humans; D009805:Odontogenesis / Q000502:physiology; D014076:Tooth Diseases / Q000503:physiopathology; D014078:Tooth Eruption / Q000235:genetics / Q000502:physiology*; D014087:Tooth Movement Techniques