Correlation of perceptive temperature threshold of oral mucosa and sympathetic skin response

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Objectives: To explore the critical values of temperature perception in various mucosa sites of oral cavity and to draw the perceptive temperature threshold maps in healthy volunteers. To observe the interrelationship between subjective cognitive perception and sympathetic skin response (SSR) under various levels of thermal stimuli. Methods: Forty-two healthy volunteers (recruited from the students of Tianjin Medical University, 16 females and 26 males) were enrolled in the present study. The whole oral mucosa of each subject was divided into multiple partitions according to the mucosa type as well as tooth position. Peltier patch (commodity name) semiconductor chip was placed in the central part of each subarea of the mucosa. The stimulus was increased or decreased at 1 ℃ each time from a baseline temperature of 37 ℃. Warm (WT) and cold (CT) perception thresholds were measured thereafter respectively. A topographic temperature map of the oral mucosa for each subject was drew. Furthermore, the SSR was elicited and recorded at three temperature levels of 50 ℃, 55 ℃, 60 ℃ respectively. Analog test with visual analogue scale (VAS) and McGill scales were also performed. Data were statistically analyzed with variance and generalized estimation equation. Results: The tip of the tongue was the most sensitive area with both WT [(38.8±2.1) ℃, P<0.05] and CT [(23.5±4.2) ℃, P<0.05]. The highest heat threshold of gingival mucosa was in the left lower posterior teeth area [(49.9±3.7) ℃, P<0.05], and the highest cold threshold of gingival mucosa was in the left upper posterior teeth area [(15.9±5.5) ℃, P<0.05]. The perceptive temperature threshold increased gradually from the midline to both left and right sides were observed symmetrically and bilaterally. There was no statistically significant differences in temperature perception threshold between males and females [WT, male (44.8±3.1) ℃, female (44.8±3.2) ℃, OR=1.100, P=0.930; CT, Male (18.4±4.9) ℃, female (20.8±4.8) ℃, OR=0.157, P=0.210]. The SSR amplitude at sites of the tongue tip and the lower lip were increased with the rise of temperature [tongue tip (4.58±4.04) mv, P<0.05, lower lip (2.89±3.01) mv, P<0.05]. However, SSR amplitude values had no significant differences between males and females [tongue tip, male (2.00±2.16) mv, female (1.89±1.20) mv, P=0.890; lower lip, male (0.94±0.82) mv, female (0.85±0.68) mv, P=0.887]. Nevertheless, the amplitude of SSR and the VAS score of subjects showed a similar trend. Conclusions: The temperature perception levels were different amongst sites of lip, buccal mucosa, tongue dorsal mucosa and gingival mucosa. SSR amplitude values could reflect the responses of the mouth to the thermal stimuli.