Conclusion
There isn’t research to support that chewing gum helps define your jawline. While it isn’t likely to cause any major health issues. Too much of it can lead to strain and discomfort. If you are looking to improve your jawline, there are other proven ways to do it. You should discuss with a medical professional about what your options are.
References;
[1] https://teachmeanatomy.info/head/muscles/mastication/
[2] https://www.webmd.com/oral-health/guide/temporomandibular-disorders-tmd
[3] https://www.healthline.com/health/enamel-erosion
[4] https://www.toothiq.com/dental-diagnosis/tooth-enamel-demineralization/
[5] https://www.who.int/news-room/fact-sheets/detail/healthy-diet
[6] https://www.healthline.com/health/kybella