Emotional responses evoked by dental odors: an evaluation from autonomic parameters

Among the factors which could explain avoidance behavior toward dental care, the typical clinging odor of the dental office, due to eugenol, is investigated in this study. The hypothesis is supported by the well-known effects of odorants which may influence cognition, emotion, and behavior. The association between the odor of eugenol and dental fear and anxiety could be explained by the fact that eugenates (eugenol-containing cements) are often used in potentially painful restorative dentistry on vital teeth. The emotional impact of the odors of eugenol and two other dental products (menthol and methyl methacrylate) was evaluated on volunteer subjects through autonomic nervous system (ANS) analysis by recording the variations of six ANS parameters (two electrodermal, two thermovascular, and two cardiorespiratory) induced by the inhalation of the odorants. After the experiment, subjects were asked to fill out an 11-point hedonic scale to rate the pleasantness vs. unpleasantness for each odorant. Results were compared between two groups of subjects divided according to their own dental experience (fearful and non-fearful dental-care subjects). These showed that, in both groups, menthol was rated as pleasant and methyl methacrylate as very unpleasant, whereas eugenol was judged pleasant by non-fearful subjects but unpleasant by fearful subjects. Concerning autonomic analysis, only eugenol induced significantly different patterns of ANS responses between the two groups, with stronger variations for dentally fearful subjects, mainly observed through the electrodermal channel. These results suggest that eugenol can be responsible for different emotional states, depending on the unpleasantness of the subjects' dental experience. This seems to confirm the role of odors as elicitors of emotional memories and to support the possible influence of eugenol odor on the avoidance behavior of some subjects toward dental care.