Ultrastructurally abnormal bone and dentin produced by microphthalmic mice.

An ultrastructural study of the jaws of osteopetrotic microphthalmic mice (mi/mi) showed that both bone matrix and dentin were abnormal. In 5 days old mice, the number of osteoblasts was increased: in 15 days old mice, the number of osteocytes was decreased and many of the cells were dead or dying. Mutant osteocytes lacked osmiophilic laminae, calcospherites were irregular in size and density and collagen fibres were scarce and abnormally distributed. In mi/mi mice, the predentin layer of the incisor tooth was abnormally wide, the predentin-dentin junction irregular and patches of hypocalcified or uncalcified dentin were present.