Bone formation around titanium implants in the tibiae of streptozotocin- induced diabetic rats

Shin, Sang Hun; Kim, Jong Ryoul; Park, Bong Soo

Abstract

Use of osseointegrated implants for missing teeth has been widely utilized in clinical dentistry. Although the procedure has been highly successful, there have also been unavoidable failures. The success of osseointegration depends in part on the host bone and its healing capacity, and concerns have been raised about various conditions affecting its quality and quantity. Diabetes mellitus, which is a major health problem for the elderly, represents a reduction in collagen synthesis, delayed wound healing and osteoporosis. The underlying clinical problem is a deficiency of bone mass. Because age and gender are reported to be an important risk factor for diabetes mellitus, the rate of implant loss caused by failure of osseointegration may also be expected to increase correspondingly. Thus, a large population of the target population for dental implants may have a high risk for implant failure. There are, however, few histologic reports regarding tissue reaction to implants in diabetes patients. Streptozotocin is the current diabetogenic agent of choice for producing experimental diabetes mellitus. The toxic acts specifically on the alpa-cells of the pancreas and the metabolic conditions which result from the use of streptozotocin are reported to resemble those observed in humans. The purposes of this study were to histologically examine the tissue reaction to titanium implants inserted into the tibiae of streptozotocin induced diabetic rats using light microscopy and to assess over time the quantitative differences between the newly formed bone of diabetes-induced rats and controls using image processing systems and immunohistochemistry with fibronectin and CD44 antibody. Seventy adult rats of both sexes were used in this study. In thirty-five rats, streptozotocin was injected intraperitoneally to induce diabetes and the serum glucose concentration was checked to ensure the induction of diabetes prior to implant placement and at the time of sacrifice. The titanium screw implants (diameter, 2.0mm; height, 3.5mm) were inserted into left tibiae of 70 rats, 35 in the control group and 35 in the DM group. The experimental rats were sacrificed at different time interval(1st, 2nd, 3rd, 4th, 6th, 8th and 12th week) for histologic examination, histomorphomeric analysis and immunohistochemistry with fibronectin and CD44 antibody. The results obtained from this study were as follows: 1. A rapid bone formation was observed in control group compared with DM group based on histological examination. However the pattern of bone formation in both groups was similar. 2. According to the histomorphometric analysis, the control group showed significantly higher in marrow bone density, marrow bone-implant contact ratio, and total bone-implant contact ratio compared with DM group. 3. The level of fibronectin expression was the most abundant at 3 and 6 weeks, which maintained to 6 and 12 weeks in control and DM group, respectively. From 8 weeks, the level of fibronectin expression decreased gradually in control but not in DM group. 4. The level of CD44 expression was the most abundant at 4 weeks, which decreased gradually to 12 weeks in control group while high level of CD44 expression was observed with no significant change to 12 weeks in DM group. From these results, it could be stated that although the rate of bone formation was delayed in DM group, dental implant procedure was not a contraindication and longer healing period was necessary in diabetes mellitus.