Comparison of radiographic and histological assessment of peri-implant bone around oral implants.

OBJECTIVES: The aim of this study was to compare the radiographic bone mineral density and the histological assessment of relative volume density of bone and bone-to-implant contact (BIC) of single implants placed in the posterior mandible of monkeys. MATERIALS AND METHODS: Five mature, male cynomolgus monkeys (Macaca fascicularis) with a total of 20 implants inserted 3-6 months previously were available for investigation. Digital intra-oral radiographs were obtained with two different sensors and one phosphor plate system. The marginal bone level was measured on both sides of the implant on digital radiographs. Furthermore, bone density was evaluated using histogram analysis of the grey shades in a distance of 1 mm from the implant surface. The radiographic assessments were compared to histomorphometric analyses. RESULTS: The marginal bone level, the distance from the margin of the implant to the most coronal bone in direct contact with the implant evaluated histologically, was on average 1.4 mm, whereas this distance was significantly shorter (0.3 mm) on the digital radiographs. Still, a statistical significant correlation between the two bone level measurements was observed. The average radiographic bone density evaluated with the three different systems varied considerably. The histologic bone density was statistically significantly lower than the radiographic bone density measured with all the three techniques for acquiring digital radiographic images. Furthermore, the histologic bone density was statistically significantly correlated with the radiographic bone density only when measured with one of the sensors. On the other hand, the histologic BIC was statistically significantly correlated with the radiographic bone density obtained with all three techniques for acquiring digital radiographic images. CONCLUSIONS: The distance from the margin of the implant to the most coronal bone in direct contact with the implant showed lower values on digital intra-oral radiographs than histologically. Furthermore, the bone density assessed on intra-oral radiographs reflected to some extend the amount of bone at or near the implant surfaces evaluated histologically.

Quantitative histological assessment of hepatic ischemia-reperfusion injuries following ischemic pre- and post-conditioning in the rat liver.

BACKGROUND: Ischemic preconditioning (IPC) has been shown to protect the liver against ischemia-reperfusion (I/R) injuries. However, ischemic post-conditioning has received little attention. The aim of the present study was to quantify and compare the hepato-protective properties of IPC and IPO, for the first time, using unbiased design-based stereological methods. METHODS: We divided 67 rats into four groups: sham, liver ischemia (LI), IPC, and IPO. Rats were subjected to 60 min LI, followed by 4- or 24-h reperfusion. We performed quantification of (NVR) and apoptotic cell profile number. RESULTS: We observed no significant differences in NVR between ischemic groups after 4 h. After 24-h reperfusion, NVR had increased to 70% in the LI group, compared with 51% (P = 0.02) and 49% (P = 0.01) in the IPC and IPO groups, respectively. After 4-h reperfusion, the apoptotic cell number was significantly higher in all ischemic groups than in the sham group; we detected no difference between ischemic groups. After 24-h reperfusion, we detected a significantly lower number of apoptotic cell profiles in the IPC group than in the LI group (P = 0.02). The mean number of apoptotic cell profiles decreased insignificantly in the IPO group (P = 0.06). Liver parameters were at all time comparable between groups. CONCLUSIONS: After I/R, IPC and IPO reduce the degree of hepatocellular injury. Both methods are equally efficient at preventing hepatocellular necrosis. Furthermore, apoptosis is significantly lower after IPC.