Quantitative scanning acoustic microscopy compared to microradiography for assessment of new bone formation.

Recently, it has been shown that quantitative scanning acoustic microscopy (SAM) is a powerful tool to image the acoustic impedance of even inhomogeneous materials like bone. Therefore, the aim of our study was to compare SAM to conventional microradiography with respect to histomorphometrical assessment of undecalcified sections of newly formed bone. Forty specimens were harvested 12 weeks after implantation of either autogenous cancellous bone graft or 5.0 mg of Osteogenic Protein-1 (BMP-7) in a critical-sized defect model in sheep. Undecalcified transverse bone sections of 500 microm thickness were investigated with conventional microradiography and SAM. Linear regression analysis was carried out to compare the measurements of the area of new bone formation within the defect sites. Both methods allowed for good discrimination between newly formed bone and cortical bone at the edges of the former defect. Images obtained with SAM revealed a better resolution and sharpness compared to that of microradiographs since SAM imaging unlike microradiography does not depend on the thickness of bone sections. The results of quantitative histomorphometric analysis obtained by both methods showed no significant differences, and it was possible to predict 90% of the variability of each method (coefficient of determination r2 = 0.90; P < 0.0001). In conclusion, SAM offers comparable quantitative histomorphometric information with a better spatial resolution than conventional microradiography. Thus, SAM is a promising new micro-visualizing technique for basic bone research.

In vivo animal trials with a scanning CO2 laser osteotome.

BACKGROUND AND OBJECTIVES: We report first results of animal trials using an improved laser osteotomy technique. This technique allows effective bone cutting without the usual thermal tissue damage. STUDY DESIGN/MATERIALS AND METHODS: A comparative in vivo study on mandibles of seven canines was done with a mechanical saw and a CO(2) laser based osteotome with a pulse duration of 80 microseconds. The laser incisions were performed in a multipass mode using a PC-controlled galvanic beam scanner and an assisting water spray. RESULTS: A complete healing through a whole bony rearrangement of the osteotomy gap with newly build lamellar Haversian bone was observed 22 days after the laser operations under optimal irradiation conditions. CONCLUSIONS: An effective CO(2) laser osteotomy without aggravating thermal side effects and healing delay is possible using the described irradiation technique. It allows an arbitrary cut geometry and may result in new advantageous bone surgery procedures.