Odontogenic dysplasia in the molar teeth of Steppe lemmings (Lagurus lagurus).

In a colony of Steppe lemmings (Lagurus lagurus), of the rodent sub-family Arvicolinae, 8.6% of animals exhibited dysplastic growth of the molar teeth. Clinical findings included nodular swellings of the mandible, hypersalivation, malocclusion and emaciation. To investigate the underlying cause, two control and 10 affected animals, aged between 6 and 18 months, were examined using radiography and computed tomography and at post mortem examination. Bilaterally symmetrical masses were identified in the molar regions of the left and right mandible and maxillae. Histologically, the masses were characterised by dysplastic odontogenic epithelium, dentin, cementum, enamel and dental pulp formation that resembled odontogenic dysplasia. This tumour-like proliferative lesion has been reported in the continuously-growing incisor teeth of ageing rodents and lagomorphs but this is the first description of the clinico-pathological features of such odontogenic dysplasia of the molar teeth of Steppe lemmings.