The effect of hypoxia on the formation of mouse incisor enamel.
OBJECTIVE
The permanently growing mouse incisors exhibit all stages of tooth development along their inciso-apical axis at any time. Any disturbance or injury of the ameloblasts during enamel formation or maturation may result in permanent defects in the finished enamel since the enamel does not undergo repair or remodeling after formation. In order to increase our understanding of how hypoxia affects enamel formation, we induced severe acute hypoxia in adult mice and observed its effects on the enamel in incisors.


METHODS
Incisors from hypoxic mice were obtained 5 and 49 days after the hypoxic insult. Hypoxic and control incisors were dissected out and observed by scanning electron microscopy (SEM). Incisors were subsequently ground longitudinally or transversely, etched, and observed again by SEM. The nature and position of defects were considered in relation to the configuration and dynamics of the incisors.


RESULTS
The effect of hypoxia varied considerably, among mice, among incisors, and among ameloblasts. Affected enamel showed hypoplasia with hypomineralization or hypomineralization without hypoplasia. Vascular endothelial growth factor (VEGF) showed considerably stronger labeling in hypoxic compared to control ameloblasts.


CONCLUSIONS
The present study demonstrates quantitative and qualitative defects in the enamel reflecting the vulnerability of ameloblasts toward severe acute hypoxia in mouse incisors.
Department of Biomaterials, Faculty of Dentistry, University of Oslo, Norway. Electronic address: rivan.sidaly@odont.uio.no.
Rivan
R
Sidaly
Department of Oral Biology, Faculty of Dentistry, University of Oslo, Norway.
Steinar
S
Risnes
Department of Oral Biology, Faculty of Dentistry, University of Oslo, Norway.
Qalb-E-Saleem
QE
Khan
Department of Neonatology, Oslo University Hospital, Norway.
Tom
T
Stiris
Department of Oral Biology, Faculty of Dentistry, University of Oslo, Norway.
Amer
A
Sehic
D000565:Ameloblasts / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D000566:Amelogenesis / Q000502:physiology; D000818:Animals; D003743:Dental Enamel / Q000378:metabolism / Q000473:pathology*; D003744:Dental Enamel Hypoplasia / Q000378:metabolism / Q000473:pathology; D005260:Female; D000860:Hypoxia / Q000378:metabolism / Q000473:pathology*; D007150:Immunohistochemistry; D007180:Incisor / Q000254:growth & development / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D008855:Microscopy, Electron, Scanning; D017001:Tooth Demineralization; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D042461:Vascular Endothelial Growth Factor A
Ameloblasts; Dental enamel; Hypoxia; Mouse; Scanning electron microscopy