Dentinal Hypersensitivity: Evidence for a "No Treatment" Effect

OBJECTIVE: This study was undertaken to assess the variability in untreated pain-response over a 24-week period in a population typical of that recruited for desensitization studies. METHODS: Subjects, who qualified based on pre-determined medical and dental criteria, had at least 4 air-sensitive and 2 tactile-sensitive teeth. At Screening, Baseline and every 4th week post-baseline, subjects completed an experimental Pain Scale Calibration (PSC) exercise, and every clinically evaluable tooth was stimulated by Yeaple Probe (YP), air and ice. Response was assessed by threshold (YP, g), subject-completed 100mm Visual Analogue Scale (VAS) (air, ice, subjective, PSC) and Examiner's Assessment (EA, 0-3 verbal descriptor scale) (air). RESULTS: Sixteen (6 male, 10 female) subjects qualified and 13 completed the study. At baseline, subjects had 8.88±5.24 (mean±sd) tactile-sensitive (threshold ≤30g) and 9.44±4.07 air-sensitive (VAS ≥30mm) teeth. Over 24 weeks, this decreased by 1.53 (p=0.0004) and 1.94 (p<0.0001) teeth, respectively (repeated measures ANOVA). The baseline tactile threshold (23.25±5.83g) decreased by 2.93g (p=0.023). The baseline air-response (44.08±18.15mm) decreased by 4.60mm (p=0.004). The baseline ice-response (54.82±17.63mm) decreased by 2.82mm (p=0.095). The baseline EA (2.22±0.46) decreased by 0.32 (p<0.001). The PSC "moderate" response (54.34±22.57mm) remained unchanged (+0.36mm, p>0.5) and the PSC "mild" response (34.47±25.31mm) increased (9.15mm, p=0.002). CONCLUSION: Over 24 weeks, hypersensitivity response decreased significantly, as measured by three different stimuli and three different evaluation scales, under conditions where the subjects knew that they were not being treated. The results do not support self-healing (reparative dentin formation), cyclical hypersensitivity in different teeth or internal pain-scale variability. The most likely explanation is a decrease in the affective component of the pain response as the result of increased familiarly with the study procedures. The size of this "no treatment" effect represents a significant portion of the typically reported placebo effect. Supported by a grant from GlaxoSmithKline Consumer Health.