Method: Capsaicin, menthol, or saline were applied topically on the gingiva of 15 healthy subjects for 15 minutes. During application, the subjects rated pain intensity on a 0 to 10 electronic visual analogue scale. A standardized intraoral QST protocol was performed before and immediately after application. Ten atypical odontalgia (AO) patients and 11 healthy controls were also recruited and examined with the intraoral QST protocol. Data before- and after- application were compared with paired-t tests and QST profiles of healthy subjects after application and AO patients were made after Z-transformation.
Result: Application of capsaicin caused moderate to severe levels of pain (VASpeak=6.0±0.7), menthol produced mild to moderate levels of pain (VASpeak=1.8±0.6)(P<0.001). Capsaicin induced changes in sensitivity to warmth, heat pain, cold pain and mechanical stimuli (P<0.05). Menthol changed sensitivity to cold, warm and pressure stimuli (P<0.05). Analyses of Z-scores demonstrated sensory gains regarding warmth detection and heat pain after capsaicin. Highly individual profiles were observed in AO patients.
Conclusion: A standardized battery of QST showed somatosensory changes after application of capsaicin, menthol and saline to the gingiva. The present QST protocol is applicable in clinical intraoral pain conditions. Based on the sensory profiles, AO appears to be a heterogenous group with several different pain mechanisms involved.