Catastrophizing is Associated with Dental Pain in a Stressful Context-Jan

Pain is associated with anxiety in a dental setting. It has remained unclear how cognitive-affective factors modulate pain and anxiety in a stressful context, such as receiving dental procedures. We hypothesized that both the situational factor (unpredictability about painful stimuli) and the trait factor (pain catastrophizing, i.e., the tendency to interpret pain in negative orientation) account for dental pain. Fifteen healthy participants were recruited to perform an associative learning task. They were asked to learn the pairing between visual cues and the intensity of incoming painful stimuli delivered at the right upper central incisor. Brain activation associated with pain was recorded by functional magnetic resonance imaging (fMRI). The participants reported increased anxiety and pain in the stressful context, where stimuli intensity was not predicted by the preceding cue. The score of the Pain Catastrophizing Scale was positively correlated with the increased pain modulated by unpredictability. Brain activation at the right posterior hippocampus, a region critically related to associative learning of aversive stimuli and context, was correlated with the individual catastrophizing level. Our findings suggest that both the situational factor (unpredictability) and the trait factor (catastrophizing) influence dental pain, highlighting the role of cognitive-affective factors in pain control of dental patients. KEY WOrDs: anxiety, dental care, functional MRI, hippocampus, pain catastrophizing, pain management. IntrODuctIOn Pain is modulated by complex cognitive and affective factors (Tracey and Mantyh, 2007). In a clinical setting, highly anxious patients anticipate and perceive worse pain when receiving stressful dental procedures (e.g., root canal treatment or extraction) (Klages et al., 2004; van Wijk and Hoogstraten, 2009), and dental fear leads to avoidance of treatment and poor oral health (Armfield et al., 2007). The etiology of dental pain could be misdiagnosed when patients were highly anxious (Eli, 1993), and patient satisfaction with treatment would decline due to unsuccessful relief of pain and anxiety (Ståhlnacke et al., 2007). Patients’ subjective experience of pain fluctuates in a stressful context of dental pain and dental procedures, yet its psychological and neurological mechanisms are largely unknown. Feeling uncertain about an imminent threat is stressful (Asmundson et al., 2007). Receiving aversive stimuli with unpredictable occurrence or intensity would evoke sustained anxiety (Shankman et al., 2011). Nociceptive stimuli with unpredictable intensity would be perceived as more painful, even though the physical intensity of stimuli did not change (Ploghaus et al., 2001; Brown et al., 2008). The findings suggest that, on the one hand, the situational factor, such as unpredictability about pain, critically modulates our pain experience (Armfield, 2010). On the other hand, trait factors regarding the cognitiveaffective processing of threat may contribute to individual vulnerability to develop anxiety and pain (Asmundson et al., 2007). A critical trait of this kind is pain catastrophizing, the tendency to anticipate pain and interpret experienced pain in a negative orientation (Quartana et al., 2009). This trait can be assessed by the pain catastrophizing scale (PCS) from 3 subcategories: rumination (regarding attentional engagement to pain-related experience), magnification (regarding the tendency to exaggerate pain-related threat), and helplessness (regarding the inability to cope with pain effectively) (Sullivan et al., 1995). People with a higher PCS score showed biased cognitive-affective processing regarding pain-related information (e.g., heightened attentional engagement with the cues predicting incoming pain) (Van Damme et al., 2002, 2004). In the dental setting, patients with higher PCS scores reported more dental anxiety and pain during dental procedures (Sullivan and Neish, 1998, 2000). Therefore, pain catastrophizing may contribute to individual pain experience in a stressful setting, in which the subjects need to learn the dynamic association between pain and the pain-related context. However, the underlying psychological and brain mechanisms remained unclear. We hypothesized that individual variation in pain catastrophizing would account for participants’ exacerbated pain experience in the stressful context regarding dental pain (e.g., receiving painful pulpal stimulation). We adopted Pain catastrophizing is Associated with Dental Pain in a stressful context at National Yang-Ming University on July 10, 2013 For personal use only. No other uses without permission. jdr.sagepub. com Downloaded from © 2012 International & American Associations for Dental Research 2 Lin et al. J Dent Res X(X) XXXX an associative learning paradigm to compare the self-reported pain intensity and pain-related anxiety in the condition where stimulating intensity was predictable vs. unpredictable (Ploghaus et al., 2001). We hypothesized that the PCS score predicts pain exacerbated by increased unpredictability, but not pain evoked by increased stimulating intensity. We reasoned that catastrophizers experience such unpredictabile-modulated pain because they tended to associate pain with the stressful context in negative orientation (e.g., through ruminating and magnifying painrelated information). We hypothesized that such a biased cognitive/affective processing of pain relates to functions of the hippocampus, a brain region critically related to acquisition of the association between aversive stimuli and the context (Fanselow and Dong, 2010; Goosens, 2011). To test the working hypothesis, we applied functional magnetic resonance imaging (fMRI) to investigate the correlation between hippocampal activation and the PCS score, when the participants received painful pulpal stimulation in a stressful context.