Influence of Test Site and Baseline Temperature on Orofacial Thermal Thresholds

Aims: To investigate thermal thresholds of selected orofacial sites, determine if there is a relationship between thermal thresholds at each site, and analyze the influence of two different baseline temperatures on thermal thresholds at the tongue tip. Methods: Thirty healthy men (mean age, 26 years) participated. Cold detection (CDT), warm detection (WDT), cold pain (CPT), and heat pain (HPT) thresholds were measured bilaterally at five orofacial sites (mentum, lower lip, cheek, forehead, and tongue tip). Relations between thermal thresholds at each test site were assessed. Thermal sensitivity of the tongue tip was compared at two different baseline temperatures (32˚C and 36˚C). One-way ANOVA, Turkey post-hoc test, paired t test and Pearson's correlation were used for statistical analyses. Results: There was a significant difference for CDT, WDT, and HPT between test sites (ANOVA, P .001) but no significant difference for CPT (P = .634). Subjects sensitive to cooling were sensitive to warming at the mentum (r = 0.379), tongue tip (r = 0.610), and cheek (r = 0.431) but not at the other test sites. There was a strong negative correlation between CPT and HPT at all test sites. There was no significant difference for CDT and WDT at the baseline temperature of 36˚C (paired t test, P =.660), but there was a significant difference at the baseline temperature of 32˚C (P .001). There were no significant differences between CPTs at the two different baseline temperatures (P =.773), while a significant difference existed between HPTs (P = .034). Conclusion: Thermal thresholds varied between the orofacial test sites, and baseline temperature affected thermal sensitivity of the tongue. Subjects who were relatively sensitive to cold tended to be more sensitive to heat. Keywords: baseline temperature, orofacial, quantitative sensory testing, thermal thresholds, trigeminal site