Pleasantness and unpleasantness in somatosensory investigation.

Abstract

Qualitative sensory testing (QualST) is a simple, standardised, chairside method for evaluating somatosensory function; however, testing focuses on detection of cold, touch and pain with no recognition of perceptions of pleasantness and unpleasantness. The study aimed to utilise the stimuli in QualST, with the addition of a soft brush, to investigate stimulus-evoked perceptions of pleasantness and unpleasantness on the facial skin and if any side-to-side differences. Additional aims were to determine the inter- and intra-rater reliability using the modified QualST protocol and in the side-to-side differences. Thirty healthy adult female participants underwent three sessions of sensitivity testing as per the modified QualST protocol. Stimuli were applied bilaterally to the facial skin, and participants provided separate yes/no responses for presence of stimulus-evoked pleasantness, unpleasantness and/or differences between sides. The stimuli were able to evoke sensations of pleasantness and unpleasantness with little differences in responses between the Q-tip and goat hair brush for the perceptions. Side-to-side differences in evoked perceptions were observed and greatest, when evaluating for pinprick-evoked unpleasantness (range between sessions = 18-19 participants). Acceptable percentage (≥90%) and excellent Cohen's Kappa (≥0.762) inter- and intra-rater agreements were identified for one or more positive responses for each stimulus modality and the targeted perception. The modified QualST protocol provides a simple, reproducible method for the investigation of perceptions of pleasantness and unpleasantness, with readily accessible instrumentation to dental professionals and allowing for a more holistic approach in somatosensory testing.