Instant assessment of pulpal blood flow after orthodontic force application

The purpose of the present investigation was to measure the effect of tooth intrusion and extrusion on pulpal blood flow in man. The flow changes were measured in 10 lateral incisors (6 subjects) by means of laser Doppler flowmetry (Perimed, Sweden) applied on the buccal surface through metal tubes bonded to the teeth. Brackets were bonded onto teeth 13 and 23, and intrusive and extrusive forces of 2 N were applied in random order to the experimental tooth for 5 min before unloading. The contralateral tooth served as a control. Extrusion of the teeth gave no significant changes in pulpal blood flow during loading or unloading. However, intrusion of the teeth reduced the pulpal blood flow by 20% during the first minute after force application. The pulpal blood flow gradually increased towards the preloading flow values for the next 4 min, and was returned to the prestimulus level 3 min after unloading. In conclusion orthodontic intrusion of teeth with a 2 N force evoked a temporary reduction in the pulpal blood flow, whereas extrusion had no effect on the pulpal blood flow.