The effect of high temperature on the development of mouse dental enamel in vitro.

Objective: Our aim was to study the effect of high temperature (39°C) corresponding to fever on the development of enamel in cultured mouse molars.

Design: For morphological studies mandibular molar blocks from E18 mice were cultured for 11 days. After three days at 37°C the teeth were exposed to 39°C for three or five days and returned to 37°C. At the end of culture, the tooth explants were photographed. The heights of the enamel and the crown of the first molars were measured and the enamel/crown height ratio was calculated. The ratios were compared between the groups using the Mann-Whitney test. To analyze gene expression in ameloblasts and odontoblasts with RT-qPCR and in situ hybridization, part of the test explants were cultured for three days at 37°C and then five days at 39°C. Control explants were kept at 37°C for 11 or eight days.

Results: The enamel/crown height ratio of the first molars cultured for five days at 39°C was smaller than that of the unexposed (P<0.001). Tooth morphology did not differ between controls and exposed teeth. In qPCR-analysis, dentine sialophosphoprotein showed clearly decreased expression. In situ hybridization showed no dentine sialophosphoprotein expression in preameloblasts. The expressions of bone morphogenic protein 4, matrix metalloproteinase 20, dentine matrix protein 1, amelogenin and osteocalcin showed a trend of downregulation.

Conclusions: High culturing temperature interferes with enamel formation of mouse molars and alters the expression of some genes essential for normal enamel development.