Lateralized brain activity in response to dental nociception

Objectives: The aim of this study was to investigate whether the model of a lateral and medial pain system also applies to dental nociception.

Methods: In 23 healthy volunteers, we compared cortical activation related to electric stimulation of maxillary central incisors and canines. 40 stimuli per tooth with a constant current 150% above individual, tooth specific pain threshold were applied and corresponding online pain intensity ratings were recorded with a computerized VAS during fMRI measurements. Cortical activation was investigated by a random effects group analysis. Lateralization effects were determined by a region of interest analysis and a repeated measurement ANOVA with factors “hemisphere”, “stimulation side” and their interaction. Only interaction effects are reported.

Results: Pain was perceived with equal intensity in all stimulated teeth. Significant activation (voxel p<0.01, FWE corrected) was observed in a wide cortical network distributed across areas commonly referred to as the "pain matrix", including: postcentral and cingulate gyruses, cerebellum, thalamus, insular cortex, basal ganglia, SMA, and Brodman areas preparietalis (BA-5), supramarginalis (BA-40), subcentralis (BA-43) and frontomedialis (BA-46). Predominant contralateral activity (indicating significant interaction) was observed in the thalamus, postcentral gyrus, posterior insula as well as area preparietalis, all part of the lateral pain system.

Conclusion: Dental stimulation on both sides of the midline revealed that trigeminal nociception evokes activity in brain areas known from spinal studies as the “pain matrix”. Contralaterally activated areas indicate a cortical somatotopic organization of the human dentition. We conclude that dental pain activates a cortical pain circuitry that follows analogous pathways known from other body parts.

Acknowledgment: Supported by GlaxoSmithKline, Consumer Healthcare, Weybridge, UK, as well as the Swiss Dental Association and the Swiss Society for Endodontology.