Abstract
The purpose of this study was to elucidate the effects of wearing a denture on prefrontal activity during chewing performance. We specifically examined that activity in 12 elderly edentulous subjects [63.1±6.1 years old (mean ± SD)] and 12 young healthy controls (22.1±2.3 years old) using functional near-infrared spectroscopy (fNIRS) in order to evaluate the quality of prefrontal functionality during chewing performance under the conditions of wearing a denture and tooth loss, and then compared the findings with those of young healthy controls. fNIRS and electromyography were used simultaneously to detect prefrontal and masticatory muscle activities during chewing, while occlusal force and masticatory score were also examined by use of a food intake questionnaire. A significant increase in prefrontal activity was observed during chewing while wearing a denture, which was accompanied by increased masticatory muscle activity, occlusal force, and masticatory score, as compared with the tooth loss condition. Prefrontal activation during chewing while wearing a denture in the elderly subjects was not much different from that in the young controls. In contrast, tooth loss in the elderly group resulted in marked prefrontal deactivation, accompanied by decreased masticatory muscle activity, occlusal force, and masticatory score, as compared with the young controls. We concluded that intrinsic prefrontal activation during chewing with a denture may prevent prefrontal depression induced by tooth loss in elderly edentulous patients.
Highlights
Previous investigations have found that wearing a denture activates the prefrontal cortex while chewing as compared to a tooth loss condition, which is accompanied by improved masticatory muscle activity and occlusal contact status in partially edentulous individuals [28, 32]
We considered that the effects of wearing a denture on chewing efficacy could be determined from the viewpoint of cognitive functioning and related oral structural environment in partially edentulous elderly subjects by evaluating prefrontal and chewing activities while chewing with and without wearing a denture, and comparing the results with those of young healthy subjects
We investigated dorsal prefrontal deactivation during the periods of preparation and execution of chewing performance under a tooth loss condition in partially edentulous elderly individuals (Fig 3A and Table 5-1), and compared our results with those obtained while wearing a denture (Fig 4 and Table 6-1) as well as in young healthy control subjects (Fig 6 and Table 6-2)
Summary
Tooth loss may induce neurodegenerative cognitive decline [1, 2], which has been speculated to be a major risk factor for cognitive impairment [3,4,5,6,7], dementia [4, 8, 9], and Alzheimer’s disease [9, 10], while chewing disability has been reported to have effects on cognitive decline [11,12,13,14,15,16], activities of daily living [17, 18], quality of life [19,20,21,22], physical functions [11, 12], and PLOS ONE | DOI:10.1371/journal.pone.0158070 June 30, 2016Improved Prefrontal Activity and Chewing Performance by Wearing Denture mortality rate [23,24,25]. Previous investigations have found that wearing a denture activates the prefrontal cortex while chewing as compared to a tooth loss condition, which is accompanied by improved masticatory muscle activity and occlusal contact status in partially edentulous individuals [28, 32]. We considered that the effects of wearing a denture on chewing efficacy could be determined from the viewpoint of cognitive functioning and related oral structural environment in partially edentulous elderly subjects by evaluating prefrontal and chewing activities while chewing with and without wearing a denture, and comparing the results with those of young healthy subjects. The present study was conducted to investigate masticatory muscle and prefrontal activities during chewing, as well as occlusal force and masticatory score under the conditions of wearing a denture and tooth loss
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