Effects of collimated and focused low-intensity pulsed ultrasound stimulation on the mandible repair in rabbits.

Background: This study was to evaluate the effects of low-intensity collimated pulse ultrasound (LICU) and low-intensity focused-pulse ultrasound (LIFU) stimulation on the osteogenesis in the porous silicon carbide (SiC) scaffold implanted in the rabbit mandible.

Methods: Rabbits were randomly divided into LIFU group, LICU group and control group (without ultrasound treatment). The intensities of LICU and LIFU were 30 and 300 mW/cm, respectively. The subcutaneous and subperiosteal temperatures were measured continuously during the 20-min ultrasound treatment. Then, the porous SiC scaffolds were implanted into the mandible, followed by LICU or LIFU once daily, and the quantity and structure of bone were assessed by methylene blue-acid fuchsin staining and micro-CT at 3, 6 and 9 weeks after implantation.

Results: The changes in the subcutaneous and subperiosteal temperatures during LICU and LIFU were less than 1 °C. The bone mass increased and the structure of bone tissues became more mature over time. The bone mass and mean pore occupancy fraction (POF) in the LIFU group were significantly greater than in the LICU group at three time points (P<0.05). Bone ingrowth in different directions was observed, and the new bone formation in the mesial, distal, top, and lingual sides of the implants in the LIFU group was greater than in the LICU group and control group (P<0.05).

Conclusions: LIFU and LICU may effectively promote bone formation in the mandible scaffold, and LIFU significantly accelerates bone formation in both buccal side and lingual side of the scaffold.