Intraoral temperature detection and pain thresholds. Reliability, influence of time and size of stimulation area.

Aim To investigate the reliability and influence of time and size of the stimulation area on cold detection, warm detection, and painful heat thresholds. Methods Thirty healthy individuals (15 females and 15 males, mean age 24.9 years, range 20–31 years) participated in the study. The subjects were recruited among Malmö University students. Thresholds for warm detection (WDT), cool detection (CDT), and heat pain (HPT) were measured using a thermotester (MSA - Modular Sensory Analyzer, Somedic®). The intraoral thermode was custom-made with a 9 x 9-mm square surface (0.81cm2). Four acrylic tips that could be attached to the top of the thermode were made (tip areas: 0.50 cm2, 0.28 cm2, 0.125 cm2, and 0.00 cm2). Baseline temperature was set at 37.0°C, and the temperature change rate at 1.0°C/s. Patients were instructed to push a stop-button when the threshold was reached. The average of three measurements was recorded. The stimuli were repeated at 4–6-s intervals. Participants were examined on three occasions: at baseline, after 2 weeks (2w), and after 6 weeks (6w). Measurements were made on the tip of the tongue. Two operators who had been calibrated in the investigation method made the measurements. Results Reliability: Acceptable to excellent reliability (test-retest) was found for cool detection thresholds (ICC 0.51), warm detection thresholds (ICC 0.48), and heat pain thresholds (ICC 0.88). Influence of time: Significant differences were found for some measurements made at 2- and 6-week intervals. For cold detection thresholds, measurement differences between baseline and the 2- and 6-week follow-ups were significant (p<0.05); for warm detection thresholds, differences between baseline and the 6-week follow-up were significant (p<0.05); for heat pain thresholds, differences between baseline and the 2- and (p<0.05) and 6-week (p