Mandibular prognathism attenuates brain blood flow induced by chewing

Hiroyuki Kanzaki,Masumi Murakami,Yuko Yamada,Erika Ozawa,Shun Akaike,Takuya Seko,Tomomi Sudo,Masao Kumazawa,Satoshi Wada,Satoshi Okumura,Hiroshi Tomonari,Takashi Oikawa,Yoshiki Nakamura

doi:10.1038/s41598-019-55553-5

Hiroyuki Kanzaki, Masumi Murakami + Show 11 more

Open Access

https://doi.org/10.1038/s41598-019-55553-5

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Journal: Scientific Reports	Publication Date: Dec 1, 2019
Citations: 4	License type: open-access

Affiliation: Tsurumi University

Abstract

Mastication is closely related to brain function. Animal experiments have revealed that tooth loss has a negative influence on brain function. Clinical studies also suggest that normal occlusion is an essential factor for favorable brain function. Mandibular prognathism (MP) usually results in occlusal dysfunction. However, the relationship between MP and brain function remains unclear. In the present study, we examined the relationship between MP and brain function by measuring brain blood flow (BBF). Seventeen subjects with normal occlusion (NORM) and 25 patients with MP participated in this study. The number of occlusal contacts were counted. Electromyography of the masseter muscles during clenching was also recorded. BBF was measured with non-invasive functional near-infrared spectroscopy during calculation task and chewing task. The number of the occlusal contacts and masseter muscle activity were lower in MP compared with NORM. The calculation task increased BBF in both groups. The chewing task also increased BBF in the inferior frontal gyrus in both groups, although the increase in MP was smaller than in NORM. We discovered that patients with MP exhibited a smaller increase in BBF at the inferior frontal gyrus during chewing as compared with NORM. As such, MP would negatively affect brain function.

Highlights

Mastication is closely related to brain function
The number of the occlusal contacts in mandibular prognathism (MP) was smaller than that observed in normal occlusion (NORM) (Table 1), signifying MP has a negative influence on occlusal function
The chewing-induced increase in brain blood flow (BBF) at the other part of brain, such as right and left central parts, exhibited no statistical difference between the groups (Fig. 2C). These results suggest that the chewing task increased BBF at the inferior frontal gyrus, and that this induction was higher in NORM compared with MP

Summary

Introduction

Mastication is closely related to brain function. Animal experiments have revealed that tooth loss has a negative influence on brain function. We examined the relationship between MP and brain function by measuring brain blood flow (BBF). The number of the occlusal contacts and masseter muscle activity were lower in MP compared with NORM. The chewing task increased BBF in the inferior frontal gyrus in both groups, the increase in MP was smaller than in NORM. We discovered that patients with MP exhibited a smaller increase in BBF at the inferior frontal gyrus during chewing as compared with NORM. A study investigating the interaction between mastication and brain blood flow (BBF) with positron-emission tomography revealed that chewing activates widespread regions of the brain[11]. We examined BBF to investigate the relationship between MP and brain function using functional near-infrared spectroscopy (fNIRS)

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Conclusion