Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Effect of Correction of Bilateral Differences in Masseter Muscle Functional Pressure on the Mandible of Growing Rats

Shuhei Mizuno
,
Satoru Matsunaga
* ORCID logo ,
Norio Kasahara
ORCID logo ,
Masaaki Kasahara
,
Yoshiaki Shimoo
,
Shinichi Abe
ORCID logo ,
Takayoshi Nakano
ORCID logo ,
Takuya Ishimoto
,
Atsuhiko Hikita
,
Kunihiko Nojima
,
Yasushi Nishii
ORCID logo
Version 1 : Received: 19 July 2023 / Approved: 20 July 2023 / Online: 20 July 2023 (05:14:59 CEST)

A peer-reviewed article of this Preprint also exists.

Mizuno, S.; Matsunaga, S.; Kasahara, N.; Kasahara, M.; Shimoo, Y.; Abe, S.; Nakano, T.; Ishimoto, T.; Hikita, A.; Nojima, K.; Nishii, Y. Effect of the Correction of Bilateral Differences in Masseter Muscle Functional Pressure on the Mandible of Growing Rats. J. Funct. Biomater. 2023, 14, 435. Mizuno, S.; Matsunaga, S.; Kasahara, N.; Kasahara, M.; Shimoo, Y.; Abe, S.; Nakano, T.; Ishimoto, T.; Hikita, A.; Nojima, K.; Nishii, Y. Effect of the Correction of Bilateral Differences in Masseter Muscle Functional Pressure on the Mandible of Growing Rats. J. Funct. Biomater. 2023, 14, 435.

Abstract

The objective of this study is to clarify the effect of restoring the lowered masticatory muscle functional pressure and correcting the imbalance of bilateral masticatory muscle functional pressure on jawbone growth during growth and development with quantitative evaluation of the changes in micro/nanostructural characteristics of entheses. Male Wistar rats aged 4 weeks were divided into an experimental group injected with a botulinum toxin serotype A (BoNT/A) formulation to reduce muscle function (BTX group) and a control group (CTRL group). They were euthanized after 6, 8, 10, 12, and 16 weeks after measuring the difference between the midline of the upper and lower incisors. The mandibles were harvested for histological examination, second harmonic generation imaging, and quantitative evaluation of biological apatite (BAp) crystal alignment. The midline difference decreased with age in weeks. In rats from 6 weeks after BoNT/A administration to 12 weeks after administration, collagen fibre bundle diameter was significantly smaller in the BTX group; the difference between the two groups decreased with increasing age. BAp crystal alignment was significantly different on the X-axis and the Y-axis on the BTX group from 6 weeks after BoNT/A administration to 10 weeks after administration. Asymmetry of mandibular bone formation caused by load imbalance during growth could be corrected by adjustment of the function of the masseter muscle on either side.

Keywords

bone quality; collagen fiber; biological apatite crystallite; microbeam X-ray diffraction; second harmonic generation imaging

Subject

Medicine and Pharmacology, Pharmacology and Toxicology

Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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