Mind the gap: What is the appropriate time interval between sequential dentine stimuli to elicit a dentine hypersensitivity pain response in clinical studies?

Objectives:
To determine the time interval required for a tooth diagnosed with DH to recover from a stimulus (cold air-blast/tactile) and respond with a similar elicited pain response to a repeat stimulus.

Methods:
A single-centre, non-randomised, clinical study in healthy adult volunteers. Eligible participants with ≥1 tooth with either a qualifying Schiff score ≥2 following cold air-blast or tactile Yeaple score of ≤20 g were allocated to tactile or air-blast group. Following primary stimulation, the designated tooth was restimulated 10, 5, 2 min and immediately after initial pain cessation. Pain was recorded with participant VAS and investigator Schiff for air-blast.

Results:
40 participants completed the study per group. There was a significant difference in VAS scores for tactile 4 delay intervals (p < 0.001) but not air-blast stimulus, and a significant difference in mean change in VAS score from immediate to two-minute delay between stimuli (8.0 tactile vs 0.8 air-blast, p = 0.011). VAS scores in response to either stimulus showed very wide variation between participants, but changes over delay intervals within participants were relatively slight. There was a significant progressive decrease in mean Schiff score with shortening delay intervals from 10 min (2.38) to stimulation immediately after pain cessation (2.15), p = 0.018.

Conclusions:
The findings suggest healthy teeth recover after DH stimulation more quickly following an air-blast than tactile stimulus, with around 2 min allowing recovery from both. Many factors including habituation and pain measurement subjectivity need to be considered. It would be prudent for future studies to use of ≥3 min delays.

Clinical significance:
No clinical study has attempted to determine the appropriate interval between successive stimuli in DH patients. The results will impact directly on the conduct of DH trials. These findings suggest the interval could be reduced to around 2-min, but the current standard of 5-min is sufficiently long to give valid results.