AsianScientist (Jun. 17, 2019) – In a study published in Scientific Reports, researchers in Japan found that chewing force has an impact on jawbone structure.
Throughout an animal’s lifespan, bone tissue in the skeleton is continuously restructured in response to changes in applied force, such as those associated with exercise and locomotion. Examining how the structure of the jawbone varies with the intensity of chewing force, or masticatory force, may illuminate the mechanisms that lead to the reconstruction of bone tissue.
In the present study, researchers led by Professors Masamu Inoue and Takehito Ono of Tokyo Medical and Dental University, Japan, have uncovered how and under what circumstances jawbone reconstruction takes place. Based on computer simulations, they predicted that increased chewing directly leads to changes in jawbone structure.
The team then created a mouse model of increased mastication in which mice were fed harder foods (hard diet: HD) to increase their chewing force. Histological and gene expression analyses revealed that the mechanical loading onto the jawbone changes cytokine expression of the osteocytes in the bone, resulting in enhanced bone formation.
The researchers found that the width of the masseter muscle, which is critical for mastication, increased in the HD-fed mice. The HD led to more activation in the primary motor cortex of the brain, which controls the masticatory muscles. Thus, the HD increased chewing and the amount of force applied to the jawbone.
In vivo micro-computed tomography analysis further showed that mechanical load onto the jawbone by the HD affected the jawbone’s shape, validating the results of the computer simulation. The simulation also indicated that these morphological changes redistributed the mechanical stress generated in the bone by the HD, indicating that the jawbone is able to adapt its shape to changes in mechanical force.
Additionally, the researchers found that increasing the force applied to the jawbone stimulated osteocytes to produce more IGF-1, one of main growth factors that promotes bone formation. This alteration led to bone formation, resulting in morphological changes in the jawbone.
“Our data indicate that masticatory force can prompt changes in facial structure by modulating the function of cells that regulate bone reconstruction,” said the authors. “This discovery—that increased chewing itself can directly change the shape of the jawbone—could facilitate the development of treatments for skeletal abnormalities, such as jaw deformities.”
The article can be found at: Inoue et al. (2019) Forceful Mastication Activates Osteocytes and Builds a Stout Jawbone.
Source: Tokyo Medical and Dental University; Photo: Pixabay.
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