[Research on periodontal changes on the compression side during rapid tooth movement into newly distracted bone]

To investigate periodontal remodeling mechanism on the compression side during early tooth movement into newly distracted bone.

Ten male Beagle dogs were selected. Distraction osteogenesis was performed on randomized side as experimental group, while the fourth premolars were extracted on the other side as control group. Then the third premolars were distalized with 30g orthodontic force instantly after the cessation of distraction or extraction. The distance of the tooth movement was measured with a sliding caliper every week. Each distance was measured 3 times and the mean value was recorded. The measurement data were analysed with paired t test by SPSS 18.0 software package. Beagle dogs were killed in the first, second, fourth week after tooth movement. Slices were obtained for HE staining and TRAP staining to observe the periodontal tissue on the compression side.

The average moving velocity of the teeth in the distracted bone was (1.055±0.054)mm per week, which was significantly faster than that in the control group(P<0.05).There was no apparent lag period in the experimental group. In addition, there was no hyalinization observed on the compression side of the periodontal tissue in the experimental group, while the amount and area of distribution of the TRAP-positive cells on the compression side was significantly larger and strongly expressed.

The moving velocity of the teeth in the newly distracted bone was significantly faster, and no apparent lag period, which may be related to no hyalinization and more early-appeared, vigorous and wide-distributed osteoclasts on the compression side of the periodontal tissue.