Blood flow changes in permanent maxillary canines during retraction

The influence of external load on the blood flow of permanent maxillary canine teeth was assessed by laser Doppler flowmetry (LDF). Blood flow readings were obtained from 10 maxillary canines and compared with the contralateral teeth simultaneously. Readings were obtained from the teeth before, during, and after the application of a 50 g force (gf) which was applied using a removable appliance. The probe for LDF measurement was held in place by a splint constructed of a silicone impression material designed to allow movement of the tooth, but prevent instability of the probe. LDF demonstrated a reading from the canine teeth consistent with recordings of blood flow, i.e. the traces were similar to the pulsatile nature of pulse pressure recordings taken from the subjects' ear-lobes. After loading the effect on the canine was (1) a decrease in blood flow as measured with LDF followed by (2) an increase in flow after 32.3 minutes (SD 4.74). These changes were statistically significant (P < 0.05) using Student's t-test. The increase in blood flow was still present after 24 and 48 hours, but returned to preload values within 72 hours. In two cases it was found that the decrease in blood flow remained as long as the load was applied. The response appeared similar to reactive hyperaemia found following placement of a tourniquet. However, the response time was substantially longer for the hyperaemic phase.