sites (i.e. pathways labelled in blue and red) are investigated primarily via animal models. Notably, the circuitries within the brain (i.e. the intracortical pathways labelled in black) have not been fully elucidated.
Source: Avivi‐Arber and Sessle (2018). Reproduced with permission of John Wiley and Sons.
Table 1.2 Selected findings (since 2010)a of neuroimaging research, which are related to the issues of the ‘landmark discoveries or concepts’ of oral neuroscience (Iwata and Sessle 2019), as quoted in field (A) to (G).
Source: Field (A) to (G) based on Iwata and Sessle (2019).
| Source | Participants | Methods | Major findings |
|---|---|---|---|
| (A) ‘Presentation of the gate control theory of pain’ | |||
| Brügger et al. (2012) | Healthy adults | fMRI | ‘Cerebral toothache intensity coding on a group level can thus be attributed to specific subregions within the cortical pain network’. |
| Gustin et al. (2011) | TNP and TMD patients | sMRI, MRS | ‘…neuropathic pain conditions that result from peripheral injuries may be generated and/or maintained by structural changes in regions such as the thalamus’ |
| (B) ‘… the multidimensionality and biopsychosocial aspects of pain and their application to improved diagnosis and management of orofacial pain conditions’ | |||
| Youssef et al. (2014) | Painful TN and TMD patients | ASL‐MRI | ‘… non‐neuropathic pain was associated with significant CBF increases in regions commonly associated with higher‐order cognitive and emotional functions …’ |
| Weissman‐Fogel et al. (2011) | Patients with nontraumatic TMD | fMRI | ‘… the slow behavioural responses in idiopathic TMD may be due to attenuated, slower and/or unsynchronized recruitment of attention/cognition processing areas’. |
| (C) ‘Discovery of trigeminal nociceptive afferents and their modulation by processes within orofacial tissues …’/‘Discovery of the plasticity of the nociceptive neurons …’ | |||
| Gustin et al. (2012) | Patients with painful TN and painful TMD | fMRI, ASL‐MRI | ‘… while human patients with neuropathic pain displayed cortical reorganization and changes in somatosensory cortex activity, patients with non‐neuropathic chronic pain did not’. |
| Moayedi et al. (2012) | TMD patients | DTI | ‘… novel evidence for CNV microstructural abnormalities that may be caused by increased nociceptive activity, accompanied by abnormalities along central WM pathways in TMD’. |
| (D) ‘Discovery of nociceptive neurons in the brain and their modulation by intrinsic CNS circuits and endogenous mediators…’ | |||
| Desouza et al. (2013) | Patients with idiopathic trigeminal neuralgia | sMRI | ‘These findings may reflect increased nociceptive input to the brain, an impaired descending modulation system that does not adequately inhibit pain …’ |
| Abrahamsen et al. (2010) | TMD patients | fMRI | ‘… hypnotic hypoalgesia is associated with a pronounced suppression of cortical activity …’ |
| (E) ‘Definition of the central pattern generators for chewing and swallowing’ | |||
| Lowell et al. (2012) | Healthy adults | fMRI | ‘The greater connectivity from the left hemisphere insula to brain regions within and across hemispheres suggests that the insula is a primary integrative region for volitional swallowing in humans’. |
| Quintero et al. (2013) | Healthy adults | fMRI | ‘… demonstrated that brain activation patterns may dynamically change over the course of chewing sequences’. |
| (F) ‘… discovery of the plasticity of sensorimotor cortex and other CNS regions in relation to orofacial sensorimotor control, learning and adaptation to injury and other changes in orofacial tissues’ | |||
| Kimoto et al. (2011) | Edentulous patients wearing a CD and an IOD | fMRI | ‘…differential neural activity in the frontal pole within the prefrontal cortex between the two prosthodontic therapies – mandibular CD and IOD’. |
| Luraschi et al. (2013) | Edentulous patients wearing a CD | fMRI | ‘Changes in brain activity occurred in the adaptation to replacement dentures …’ |
| (G) ‘Delineation of peripheral processes and CNS circuits underlying touch, temperature, taste and salivation, including the discovery of a fifth taste, umami’ | |||
| Trulsson et al. (2010) | Healthy adults | fMRI | ‘… PDLMs, and SA II‐type receptors in general, may be involved in one aspect of the feeling of body ownership’. |
| Nakamura et al. (2011) | Healthy adults | fMRI | ‘The peaks of the activated areas in the middle insular cortex by umami were very close to another prototypical taste quality (salty)’. |
ASL‐MRI: arterial spin labelling magnetic resonance imaging; CBF: cerebral blood flow; CD: complete denture; CNV: the trigeminal nerve; DTI: diffusion tensor imaging; fMRI: functional magnetic resonance imaging; sMRI: structural magnetic resonance imaging; IOD: implant‐supported denture; MRS: magnetic resonance spectroscopy; PDLM: periodontal ligament mechanoreceptor; SA: slowly adapting; TMD: temporomandibular disorders; TN: trigeminal neuropathy; TNP: trigeminal neuropathic pain; WM: white matter.
a The survey is performed using Google Scholar, with the date of publication ranged from 1 January 2010 to 30 May 2021.
Table 1.3 Selected findings (since 2010) of brain imaging research related to the clinical disciplines of dentistrya.