The cerebral representation of temporomandibular joint occlusion and its alternation by occlusal splints

Abstract

Occlusal splints are a common and effective therapy for temporomandibular joint disorder. Latest hypotheses on the impact of occlusal splints suggest an altered cerebral control on the occlusion movements after using a splint. However, the impact of using a splint during chewing on its cerebral representation is quite unknown. We used functional magnetic resonance imaging (fMRI) to investigate brain activities during occlusal function in centric occlusion on natural teeth or on occlusal splints in fifteen healthy subjects. Comparisons between conditions revealed an increased activation for the bilateral occlusion without a splint in bilateral primary and secondary sensorimotor areas, the putamen, inferior parietal and prefrontal cortex (left dorsal and bilateral orbital) and anterior insular. In contrast, using a splint increased activation in the bilateral prefrontal lobe (bilateral BA 10), bilateral temporo-parietal (BA 39), occipital and cerebellar hemispheres. An additionally applied individually based evaluation of representation sites in regions of interest demonstrated that the somatotopic representation for both conditions in the pre- and postcentral gyri did not significantly differ. Furthermore, this analysis confirmed the decreasing effect of the splint on bilateral primary and secondary motor and somatosensory cortical activation. In contrast to the decreasing effect on sensorimotor areas, an increased level of activity in the fronto-parieto-occipital and cerebellar network might be associated with the therapeutic effect of occlusal splints.

Differentiation of cerebral representation of occlusion and swallowing with fMRI

“…A significant lateralized response, as described by others for occlusion (17,37) and for swallowing (57) was absent in our study for both tasks.…”

“…Comparable to swallowing, a left hemispheric lateralization of bilateral occlusion of opercular areas to the dominant left hemisphere was reported (17,37). Overall, representational sites described during occlusion seem to be widely congruent to those described during swallowing (30).…”

“…When investigating occlusal movements in a blocked design, we found a representational map of primary and secondary motor areas, thalamus and cerebellar hemispheres, a frontoparietal network, bilateral insula, and cingulate cortex (37). Comparable to swallowing, a left hemispheric lateralization of bilateral occlusion of opercular areas to the dominant left hemisphere was reported (17,37).…”

Altered neural activation pattern during teeth clenching in temporomandibular disorders

“…Our results of normalization in the inferior temporal lobe and medial prefrontal cortex are consistent with a previous fMRI study of healthy subjects that found increased brain activity in the right and left temporal regions and prefrontal lobe related to occlusion with and without a splint (Lotze et al , ). In addition to the functional normalization in motor regions, the present results demonstrated normalized activation of the temporo‐frontal network and functional recovery of the DMN evoked by plasticity‐related changes, which may contribute to the mechanisms underlying the therapeutic effects of stabilization splints in TMDs patients.…”

“…The cerebellum plays a key role in motor coordination and learning and it is also active in mandible movements (Onozuka et al , ; Wong et al , ; Lotze et al , ). Previous studies found activation in cerebellum during jaw movements in healthy controls (Onozuka et al , ; Wong et al , ; Grabski et al , ).…”