Spatial and Temporal Effects of Capsaicin and Menthol on Intraoral Somatosensory Sensitivity

Aims: To assess the spatial and temporal sensory effects of the topical application of capsaicin and menthol on the gingiva of healthy volunteers. Methods: Capsaicin, menthol, and saline (control) were applied topically on the gingiva in the maxillary premolar area of healthy volunteers for 15 minutes. Pain intensity was rated on a 0 to 10 visual analog scale (VAS). Before, immediately after, and 30 minutes after application, three mechanical stimuli were applied at 15 gingival sites: fixed-intensity stimuli were applied by 32 mN and 512 mN von Frey filaments, and stimuli of increasing intensity were applied by an electronic von Frey (EVF, 10 g/s). The EVF was used to test the pinprick pain threshold (PiPT). The perceived pain from filament stimulation was rated on a 0-50-100 numeric rating scale (NRS). Analysis of variance for repeated measures was used to analyze the NRS scores, PiPT values, the number of hypersensitive or hyposensitive test sites, and the coordinates of the center of gravity (COG) of somatosensory sensitivity. Results: The mean ± SEM VAS score of pain intensity produced by the application of capsaicin (4.6 ± 0.5) was significantly higher than that produced by menthol (0.3 ± 0.2) and saline (0.1 ± 0.1) (P .001). Capsaicin induced local desensitization to all stimuli (P .047) , and at the application site, capsaicin induced significant desensitization to 512 mN stimuli (P = .003). Menthol did not induce significant somatosensory changes (P > .147), and saline induced slight desensitization in two sites surrounding the application site (P .023). The COG coordinates did not shift significantly over time during any condition (P > .125). Conclusion: Capsaicin but not menthol induced mechanical desensitization in the application area but not in the surrounding areas. Keywords: capsaicin, intraoral somatosensory testing, menthol, psychophysics, spatial, temporal