Improved Prefrontal Activity and Chewing Performance as Function of Wearing Denture in Partially Edentulous Elderly Individuals: Functional Near-Infrared Spectroscopy Study

<div><p>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.</p></div

Masticatory scores for Tooth Loss, Wearing Denture, and Young.

<p>Masticatory scores for Tooth Loss, Wearing Denture, and Young.</p

Numbers of residual, lost, and prosthetic teeth in 12 elderly edentulous subjects.

<p>Numbers of residual, lost, and prosthetic teeth in 12 elderly edentulous subjects.</p

Occlusal force (N) for Tooth Loss, Wearing Denture, and Young.

<p>Occlusal force (N) for Tooth Loss, Wearing Denture, and Young.</p

Temporal changes under Tooth Loss and Wearing Denture conditions.

<p>The values for [oxy-Hb] during the pre-chewing period for Wearing Denture were significantly (two-way repeated measures ANOVA and Bonferroni t-test, p<0.05) increased for DLPFC (BA46), and FPA (BA10), and during the chewing period for DLPFC (BA9, BA46), FPA (BA10), BA (BA45), and OFC (BA11), and remained increased during the post-chewing period for DLPFC (BA9, BA46), FPA (BA10), BA (BA45), and OFC (BA11) as compared to Tooth Loss. Significant differences between the conditions are indicated by a blue bar.</p

Masticatory muscle EMG activities for Tooth Loss, Wearing Denture, and Young.

<p>Masticatory muscle EMG activities for Tooth Loss, Wearing Denture, and Young.</p

Median of the reaction time in the psychomotor vigilance test.

<p>Median of the reaction time in the psychomotor vigilance test.</p

Sleep architecture in the PER+Nap and NoPER+Nap conditions.

<p>Sleep architecture in the PER+Nap and NoPER+Nap conditions.</p

Dental state of 12 partially edentulous subjects.

<p>Shown is the dental state of each of the present 12 partially edentulous subjects (A to L). Using Eichner’s tooth loss classification, subjects A-F were classified as B2, G-I were classified as B3, and J-L were classified as B4. The mean numbers of residual, lost, and prosthetic teeth in those groups were 18.8±3.16, 9.2±3.16, and 8.8±3.3, respectively. Residual teeth are indicated in black and prosthetic teeth in red.</p

Design of the experiment.

<p>Three experimental conditions were carried out: (1) perturbation and nap (PER+Nap), (2) no-perturbation and nap (NoPER+Nap), and (3) perturbation and rest (PER+Rest). In the PER+Nap condition, participants conducted the visuomotor task with perturbation caused by the axis rotation of the mouse. After the task, participants took a 90 min nap. In the NoPER+Nap condition, participants conducted the visuomotor task without perturbation and then took a nap. In the PER+Rest condition, they conducted the perturbation task and instead of a nap they took a 90 min break.</p