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

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

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

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

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

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

Temporal changes in [oxy-Hb] under Tooth Loss condition as compared to Young.

<p>The values for [oxy-Hb] and under the Tooth Loss were significantly (two-way repeated measures ANOVA and Bonferroni t-test, p<0.05) decreased as compared to those in the Young group during the pre-chewing period for FPA (BA10) and OFC (BA11), during the chewing period for DLPFC (BA9, BA46), FPA (BA10), BA (BA45), and OFC (BA11), and during the post-chewing period for DLPFC (BA9, BA46), FPA (BA10), and BA (BA45). Significant differences between Tooth Loss and Young are indicated by a grey bar. All channels shown here correspond to channels that showed significant differences between the Wearing Denture and Tooth Loss presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158070#pone.0158070.g004" target="_blank">Fig 4</a>.</p

Temporal changes in [oxy-Hb] under Wearing Denture condition as compared to Young.

<p>The values for [oxy-Hb] under the Wearing were significantly (two-way repeated measures ANOVA and Bonferroni t-test, p<0.05) decreased as compared to the Young during the chewing period for DLPFC (BA9, BA46), FPA (BA10), and BA (BA45), and during the post-chewing period for DLPFC (BA46) and FPA (BA10). Significant differences between Wearing Denture and Young are indicated by a blue bar. All channels shown here correspond to channels that showed significant differences between the Wearing Denture and Tooth Loss presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0158070#pone.0158070.g004" target="_blank">Fig 4</a>.</p

Significantly different channels and corresponding brain regions presented in temporal changes of [oxy-Hb].

<p>Significantly different channels and corresponding brain regions presented in temporal changes of [oxy-Hb].</p