Effects of bleaching on laser Doppler blood-flow signals recorded from human teeth in vitro

Objective: To determine if bleaching a tooth affects significantly laser Doppler recordings of pulpal blood flow that are made through the treated enamel and dentine. Design: Recordings of blood flow (flux) were made with a laser-Doppler flow meter from the crowns of 14, recently extracted, human premolars while diluted blood was pumped at three different rates through a cannula that was inserted into the pulp cavity with its tip in the coronal pulp chamber. The recordings of flux were made before and after bleaching the crown with 38% hydrogen peroxide for 30 min. The colour changes produced by bleaching were also measured with a digital spectrophotometer in 15 teeth. The effects of bleaching on both blood flow recordings and tooth colour were studied in 11 of the teeth. Results: Both before and after bleaching, there was a linear relationship between blood perfusion rate and flux. After bleaching, the flux readings increased by an average of 46%, and were significantly increased in every tooth (P < 0.001, Wilcoxon Signed Rank Test). There was no significant correlation between the changes in flux and the changes in tooth colour. Conclusion: A laser Doppler flow meter cannot be used to determine the effect of bleaching on pulpal blood flow in intact teeth. (C) 2015 Elsevier Ltd. All rights reserved.