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Tissue responses to titanium implantation with two different surface conditions in our established implantation model in rat maxillae were investigated by light and transmission electron microscopy and by histochemistry for tartrate-resistant acid phosphatase (TRAPase) activity. Here we used two types of implants with different surface qualities: titanium implants sandblasted with Al2O3 (SA-group) and implants coated with hydroxyapatite (HA-group). In both groups, bone formation had begun by 5 days postimplantation when the inflammatory reaction had almost disappeared in the prepared bone cavity. In the SA-group, however, the bone formation process in the bone cavity was almost identical to that shown in our previous report using smooth surfaced implants (Futami et al. 2000): new bone formation, which occurred from the pre-existing bone toward the implant, was preceded by active bone resorption in the lateral area with a narrow gap, but not so in the base area with a wide gap. In the HA-group, direct bone formation from the implant toward the pre-existing bone was recognizable in both lateral and base areas. Many TRAPase-reactive cells were found near the implant surface. On the pre-existing bone, new bone formation occurred with bone resorption by typical osteoclasts. Osseointegration around the implants was achieved by postoperative day 28 in both SA- and HA-groups except for the lateral area, where the implant had been installed close to the cavity margin. These findings indicate that ossification around the titanium implants progresses in different patterns, probably dependent on surface properties and quality.

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Purpose While optical frequency domain imaging (OFDI) can delineate calcium modification and fracture, the capability of high-definition intravascular ultrasound (HD-IVUS) for detecting these remains unclear. This study evaluated the diagnostic accuracy of HD-IVUS for assessing calcium modification and fracture as compared to OFDI. Methods HD-IVUS and OFDI were used during orbital or rotational atherectomy procedures conducted for 21 heavily calcified coronary lesions in 19 patients. With OFDI assessment used as the gold standard, diagnostic accuracies of HD-IVUS for calcium modification and fracture were compared every 1 mm to the matched pre-stenting images (n=1,129). Calcium modification, as assessed by OFDI, was defined as polished and concave-shaped calcium. For HD-IVUS, calcium modification was defined as the presence of reverberation with concave-shaped calcium. In both assessments, the definition of calcium fracture was defined as a slit or complete break in the calcium plate. Results Calcified plaque was found in 86.4% of analyzed OFDI images. Calcium modification and fracture were detected in 20.6% and 11.0% of detected calcified plaques. Sensitivity, specificity, positive and negative predictive values of HD-IVUS detection for calcium modification and fracture were 54.4%, 97.8%, 86.7%, 89.1% and 86.0%, 94.5%, 58.2%, 96.8%, respectively. Discordance cases between both assessments demonstrated that heterogeneous calcium visualized by OFDI, separated calcium and guide wire artifact can be misdiagnosed. Conclusion Diagnostic accuracies of HD-IVUS for assessing calcium modification and fracture were modest as compared to OFDI. These results suggest that OFDI guidance is more feasible during treatment of heavily calcified coronary lesions versus HD-IVUS guidance.

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