Computerized infrared thermographic imaging and pulpal blood flow: Part 2. Rewarming of healthy human teeth following a controlled cold stimulus

Aim To investigate the rewarming pattern and rewarming rate of clinically healthy teeth following a controlled cold stimulus using TI techniques. Methodology A controlled cold stimulus was developed using an air stream at 20 degrees C, Gingival and incisal sites on 12 healthy maxillary lateral incisors in six patients were imaged under rubber dam following 20 s cooling. Images were captured at 10 s intervals during a 3-min rewarming period and the data used to construct graphs of the rewarming rate. Log transformation of the data was used to produce best fit' straight line graphs. Linear regression analysis was used to examine three variables, viz. the side of the mouth (right or left). the site of measurement (gingival or incisal) and the phase of rewarming (early 0-90 s, late 91-180 s). Results The mean temperature change (Delta t degrees C) during rewarming was 8.5 degrees C (SD 1.0 degrees C) fur gingival sites and 7.2 degrees C (SD 1.1 degrees C) for incisal sites, The slops of the 'best fit' straight line data enabled a rewarming index to be calculated for each site on each tooth, Linear regression analysis showed that the phase of rewarming was highly significant but the: other variables were not, A one-way ANOVA showed no significant differences between or within groups. Conclusions Three min is an appropriate time to record rewarming of teeth cooled for 20 s with an airstream at 20 degrees C, The side or site used to record surface temperatures using this technique is not significant. Rewarming is exponential and log transformation of the data produces a well-fitting straight line graph. The slope of this line provides a rewarming index which should enable comparison of TI and laser Doppler flowmetry in determining pulpal blood now as a measure of tooth vitality.