Reliability of pulpal blood-flow measurements utilizing laser Doppler flowmetry

Pulpal blood flow can now be measured non-invasively in the clinic utilizing laser Doppler flowmetry. The purpose of our study was to test (1) whether the position of the measurement probe on the tooth affects blood-flow measurements and (2) whether measurements from identical locations vary over time. Blood flow of one maxillary central incisor was measured in each of 13 volunteers. Measurements were recorded at five different locations on the labial surface of each tooth. Four measurement sessions were performed, and two sets of measurements were recorded at each session. Custom-made splints ensured accurate and reproducible positioning of the measurement probe at each session. Spatial position of the probe had a clear effect on the pulpal blood-flow measurements (p less than 0.0001). Measurements made at incisal and gingival locations were less and greater (p less than 0.05), respectively, than those made at central locations. Measurements from various mesio-distal locations did not differ (p greater than 0.05) when made at the same height on the tooth. Pulpal blood-flow measurements recorded at a given site were not consistent across all of the testing sessions (p less than 0.0001). Our data suggest that reliable interpretation of longitudinal measurements of pulpal blood flow obtained with laser Doppler flowmetry requires accurate repositioning of the measurement probe. In addition, an adequate control condition should be included to account for bias due to temporal variation.