Dental lamina develops even within the mouse diastema.

: In embryos of albino mice of ICR strain, collected between days 13 and 15, the epithelial lining within the future upper maxillary diastema was studied using frontal histological sections stained with hematoxylin-eosin and PAS methods. In embryos harvested on the 12th hr of day 13 (stage 13/12), a continuous epithelial rudiment of dentition was found in the anterior extension of the epithelial anlage of the first upper molar, up to the level of the lower anterior margin of the primary choana. In this stage the rudiment acquired, in the most anterior region of the future diastema, an arrangement typical for the dental lamina. In its dorsal extension there was found a distinct tooth anlage at the transitory stage lamina bud, which further (at stage 13/24) disintegrated into several segments. Starting with the day 14 (stage 14/12), the epithelial rudiment of dentition within the future upper diastema began to regress. From the stage 14/24 on, the anlage persisted only in its posterior terminal part where it merged with the epithelial lamina extending anteriorly from the anlage of the first upper molar. The existence of the dentition rudiment within the future mouse diastema constitutes the ontogenetic evidence that the diastema originates only secondarily--by regression. In some mutant strains of mice (tabby, crooked, sleek), the regression appears incomplete. The odontogenic potency of mouse diastema tissues should be considered when interpreting the results of in vitro experiments investigating the odontogenic inductive tissue interactions in mouse.