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Tooth, Ameloblast - Metaplasia, Squamous

Image of normal ameloblast comparison to metaplasia, squamous in the tooth from a male B6C3F1 mouse in a chronic study
Normal ameloblasts (arrow) in a male B6C3F1 mouse from a chronic study.
Figure 1 of 4
Image of metaplasia, squamous in the tooth ameloblast from a male F344/N rat in a chronic study
Tooth, Ameloblast - Metaplasia, Squamous in a male F344/N rat from a chronic study. The ameloblasts (compare with Figure 1) have been replaced by squamous epithelium (arrow).
Figure 2 of 4
Image of normal ameloblast comparison to metaplasia, squamous in the tooth from a male B6C3F1 mouse in a chronic study
Normal ameloblasts (arrow) in a male B6C3F1 mouse from a chronic study (higher magnification of Figure 1).
Figure 3 of 4
Image of metaplasia, squamous in the tooth ameloblast from a male F344/N rat in a chronic study
Tooth, Ameloblast - Metaplasia, Squamous in a male F344/N rat from a chronic study (higher magnification of Figure 2). The ameloblasts (compare with Figure 3) have been replaced by squamous epithelium (arrow).
Figure 4 of 4
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comment:

Squamous metaplasia can be seen following injury to the ameloblasts. While atrophy is characterized by decreased cytoplasm (shortening of individual ameloblasts), squamous metaplasia is characterized by loss of the columnar layer of ameloblasts and replacement by squamous epithelium ( Figure 2image opens in a pop-up window and Figure 4image opens in a pop-up window , arrows).

recommendation:

Squamous metaplasia of the ameloblasts should be diagnosed and graded whenever present. Severity grading for squamous metaplasia is based on the extent of the lesion and the number of layers of squamous cells in the lesion.

references:

Brown HR, Hardisty JF. 1990. Oral cavity, esophagus and stomach. In: Pathology of the Fischer Rat (Boorman GA, Montgomery CA, MacKenzie WF, eds). Academic Press, San Diego, CA, 9-30.
Abstract: http://www.ncbi.nlm.nih.gov/nlmcatalog/9002563

Fletcher AM, Bregman CL, Woicke J, Salcedo TW, Zidell RH, Janke HE, Fang H, Janusz WJ, Schlze GE, Mense MG. 2010. Incisor degeneration in rats induced by vascular endothelial growth factor/fibroblast growth factor receptor tyrosine kinase inhibition. Toxicol Pathol 38:267-279.
Abstract: http://www.ncbi.nlm.nih.gov/pubmed/20100840

National Toxicology Program. 1996. NTP TR-393. Toxicology and Carcinogenesis Studies of Sodium Fluoride (CAS No. 7681-49-4) in F344/N Rats and B6C3F1 Mice (Drinking Water Studies). NTP, Research Triangle Park, NC.
Abstract: http://ntp.niehs.nih.gov/go/12237

NTP is located at the National Institute of Environmental Health Sciences, part of the National Institutes of Health.