Objective:
Earlier studies on crevicular fluid flow and gingival blood flow indicated increased gingival blood flow after smoking. In this study, we measured gingival blood flow following heated tobacco smoking.

Methods:
We used a laser Doppler flowmeter (LDF) with different optic-fiber separations of 0.3 mm (LDF-0.3) and 0.7 mm (LDF-0.7). We have confirmed that the LDF-0.3 and difference between LDF-0.7 and LDF-0.3 (LDF-d) represented gingival blood flow in superficial fraction and deeper fraction, respectively. Eight heated-tobacco smokers consuming 4-25 daily volunteered and were asked not to smoke at least 5 h before the experiment. Gingival blood flow of upper papillary gingiva of frontal teeth was measured before and after smoking. Subjects smoked heated tobacco for about 5 min.

Results:
Changes in LDF-0.3 and LDF-d after smoking were not statistically significant. However, LDF-0.7 significantly decreased after smoking (P<0.05). Five subjects showed a decrease in LDF-0.3 immediately after smoking, while smoking in 5 subjects caused a relative increase in LDF-d after smoking. Decreases in gingival blood flow in both fractions of gingiva after smoking were found only in one subject.

Conclusions:
These results suggest that heated tobacco smoking may decrease gingival blood flow particularly in superficial layer of gingival.