The effect of pulsed ultrasound on mandibular distraction.

This study evaluated the effect of pulsed ultrasound on tissue repair and bone growth during mandibular osteodistraction. Twenty-one rabbits were divided into three groups of 7. The distraction started 72 h after surgically severing both sides of the mandible and proceeded at a rate of 1.5 mm/12 h for 5 days. Group I received pulsed ultrasound (nominally 200 micros pulse of 1.5 MHz at a 1.1 kHz pulse repetition frequency, 30 mW/cm2) for 20 min on both sides of the mandible every other day (alternating sides). Group 2 received the same pulsed ultrasound treatment on one side of the mandible every day for 20 min. Group 3 did not receive any ultrasound treatment. Bone formation at the distraction site was assessed by photodensitometry on head radiographs, a vibratory coherence test across the distraction site, a postmortem three-point bending mechanical stiffness test, and a postmortem histological examination. Statistical analyses performed using analysis of variance revealed that pulsed ultrasound enhanced bone formation at the distraction site with a high level of significance when assessed by the increase in new bone photodensity (p = 0.001), vibratory coherence (p = 0.001), mechanical stiffness (p = 0.003), and qualitative histological studies, especially when the pulsed ultrasound treatment was directly applied daily.