Why does my jaw stick out more when I smile since I got braces? Even though I don't have an underbite? (Photos)

My sister has maxillary deficiency class 3 which was severe she recently had surgery. I was lucky that my jaw did not turn out as bad and that braces could fix my problem well I was told. Sadly I got braces but I have noticed that when I smile my jaw sticks out more than usual. My orthodontist has not said anything and im almost done with my treatment. I'm scared that it actually got more noticeable than before but my bite has no problem.

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