Pleasantness and unpleasantness in somatosensory investigation.

ABSTRACT

BACKGROUND: 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. OBJECTIVES: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.