Of mice and mutations: Phenotypic effects of the diabetic db/db and ob/ob mutations on the skull and teeth of mice

Aim: To compare the phenotypic appearance of the skull bones and teeth of wild type C57BL/6J mice with that of diabetic leptin-deficient (ob/ob) and diabetic leptin receptor-deficient (db/db) mice used as models for diabetes. Study design and methods: Skulls were extracted from the carcasses of mice belonging to wild-type C57B/6J mice, db/db mice on a C57BLKS/J background, and ob/ob mice on a C57B/6J background. After removal of overlying tissue, the skulls and mandibles were then left to dehydrate and examined for phenotypic variations in structure and wear. Results: Bone surfaces of the skulls of wild type mice had a whiter and smoother surface compared with a yellowish colour with a grainy texture in the two mutant strains. The frontal, parietal and occipital bones were translucent in the two mutant strains. Breakages of the zygomatic arches and mandibles were more common in the ob/ob and db/db mice than in the wild type mice. Half of the teeth of the db/db mice and 90% teeth of the ob/ob mice showed considerable wear compared with marginal wear in the wild type mice. Conclusions: These observations suggested that the teeth of the two diabetic mutant strains are exhibiting considerable signs of hypomineralization with increased fragility and decreased bone thickness.