Assessment of bone surrounding implants in goats: ex vivo measurements by dual X-ray absorptiometry.

The aim of the present study is to determine the possibility of measuring the bone mineral density (BMD) around implants by dual energy X-ray absorptiometry (DEXA). Therefore, the trabecular BMD was measured close to 127-600 microns and at a distance from various uncoated and Ca-P-coated implants inserted into the femoral condyle of goals. The implants were left in situ for 12 weeks. In addition, the bone-implant interface was evaluated histologically. For comparative reasons the BMD of non-implanted lateral and medial femoral condyles was also measured. The reproducibility of the measurements, expressed as a coefficient of variation, was found to be 0.44%. Moreover, the regions closest to the implants exhibited a higher BMD than all other regions, and the regions located in the medial condyle showed a higher BMD than the lateral condylar regions. Although the histological sections of the implants in the medial condyle demonstrated more bone contact with the coated than with the uncoated implants, a higher density was measured around the uncoated implants. The results regarding the non-implanted condyles indicated a higher density in the medial than in the lateral condyle. In view of these results, we conclude that BMD around dental implants depends on the location of the implant and that DEXA appears to be an excellent tool for analysing bone-implant reactions.

[Osteoporosis and jaw bone reduction]. / Osteoporose en kaakbotreductie.

The relationship between osteoporosis and residual ridge reduction has been investigated in many studies. As a result it can be concluded that it is not easy to measure the extent of osteoporosis of the jaws. Several studies have shown that individuals with general signs of osteoporosis do not necessary have an osteoporotic mandible or maxilla. The same applies to the relationship between osteoporosis and residual ridge reduction in edentulous patients and osteoporosis and bone loss in patients with periodontal diseases. Taken into account the positive effect of healthy food intake and functional loading in the prevention and treatment of osteoporosis, it can be expected that they also influence the bone quality of the jaws. Preservation of strategic teeth or roots under the overdenture as well as the insertion of implants have a positive effect on the bone of the jaws.

Measurement of mandibular bone density ex vivo and in vivo by dual-energy X-ray absorptiometry.

Severe bone resorption is a vexing clinical problem, especially in patients without teeth. To study resorption in vivo, measurements of bone mineral density (BMD) of the mandible of both patients with and without teeth are needed. Using a Hologic QDR-1000 bone densitometer designed to measure lumbar spine and hips, ex vivo and in vivo measurements were made in selected areas of the mandible. The mandible was positioned such that the X-ray beam was perpendicular to its sagittal plane. In this way the beam hits first one half of the mandible and then the other. The reproducibility--expressed as coefficient of variation--of the ex vivo measurements was 0.5%. For in vivo measurements this coefficient was 3%. The method used for mandibular BMD would make it possible to define an average BMD in several categories of the normal population and of patients, and to compare bone density in the mandible with that in the axial and perpendicular skeleton. Improvement may be obtained by repeating the measurement. The entrance dose per scan is low, equalling that of one bitewing/radiograph.