*(See disclaimer below)
It's pretty easy to put a new mouth or new teeth into an image using Photoshop. You can simply select it, and use Photoshop's generative AI fill. It will give three variations. Choose one that fits best, or generate again until you find an acceptable fix.
However, it's worth noting that most modelling agencies will likely just reject heavily manipulated images, especially those changing actual facial features. Many also request that models don't use excessive makeup either in photographs. They want to see what you actually look like - which is the whole point of sending images in the hope that someone will employ you as a model.
As an example, take an online modelling agency such as Models Direct: on this page, they have a guide for submitting photographs
Here's the relevant quote from them.
Avoid photoshopping
Filters and wacky tricks using photography apps are fabulous, creative
and a whole lot of fun but should be avoided when sending over images
to us. We know it’s tempting but Models Direct would prefer you to
avoid any apps to edit features just because we want to see the real
you.
*Disclaimer - Although entirely possible, I would strongly discourage editing your modelling photos like this. You will be found out as soon as you turn up for a photoshoot/interview, because it won't actually be a true representation of what you actually look like.