Morphological characteristics of the depository surface of alveolar bone of diabetic mice.

Sharpey's fibers support teeth by attachment of periodontal ligament fibers to alveolar bone. The effects of diabetes mellitus on this support mechanism have not been described and were the subject of this study. Male Swiss mice were rendered diabetic by streptozotocin. Mandibles were removed 9 weeks after injections, the mineralizing front of the depository surface of the interdental septum was exposed by fracture through the periodontal ligament, rendered anorganic, and examined by scanning electron microscopy. No significant reduction in alveolar crest height was evident in diabetic as compared to control animals; however, significant changes in the a) mineralization patterns of bone depository surfaces and Sharpey's fibers, and b) number of Sharpey's fibers inserting into alveolar bone were evident in diabetics. Unmineralized fissures, characteristic of Sharpey's fibers of control, were nearly obliterated by mineralized tissue in diabetic animals. The mineralizing front of the middle and apical thirds of the diabetic alveolar wall was covered by numerous large calcified globules resembling enlarged calcospherites, which were not evident over the cervical third or control tissues. The mean Sharpey fiber density was greater in controls than in diabetics (p less than 0.001); however, there was no significant difference between their mean diameters. These observations suggest that, in early diabetes, Sharpey's fibers and depository surfaces of the middle and apical thirds of the interdental septum have morphologic evidence of aging, which precedes significant reduction in alveolar crest height. These changes may weaken the attachment of periodontal ligament fibers to bone and reduce resistance of the periodontium to intrusive forces.