A longitudinal study of tooth resorption in newly metamorphosed Xenopus laevis, with comments on tooth resorption in amphibians

Late larvae and newly metamorphosed specimens of Xenopus laevis (Daudin) were reared in such a way that their growth rates were assessed as similar. After the larvae had reached Nieuwkoop and Faber Stage 65,12 were killed each day for eight days, so that the events in resorption of the first teeth to develop could be studied histologically, and an absolute time scale applied. Resorption extended over several days and occurred in two phases, (a) erosion and (b) absorption. Erosion was a process lasting several days, and involved the destruction of a small quantity of dentine and adjacent bone at the base of a standing tooth. Osteoclasts were not seen inside the pulp, but were confined to the outer aspect of the dentine and bone, and were removing the hard tissues from without. Absorption was a rapid process lasting about 48 hours, during which the majority of the dental tissue was destroyed. Osteoclasts resorbed the dentine piecemeal from within along its full length from base to tip. As a result, the vast majority (probably all) of the calcified tissues would seem to have been available for reabsorption and recycling. It seemed that erosion occurred as a result of local mechanical factors (the growing successional tooth), but that absorption was controlled by a specific timing mechanism. It is suggested that gross internal resorption of teeth may be common in Amphibia, and that even in species where crowns are shed, extensive thinning of the dentine from its pulpal aspect is likely to have occurred beforehand.