It's a dental tool, as I recall, giving the person easy access to all of the teeth and gums.
Some triggers that may help are ...
dental cheek spreader,
lip retractor,
mouth spreader,
along with ethnicity's, and various adult ages, including wrinkles.
There are certainly other terms that will send similar noise to be interpreted, like a hotdog will be turned into something else if you add specific characteristics and Krea 2 is not that much different so, while "metal thingy in her mouth" is not part of the training data, it's likely to trigger noise related to the intent.
If using a partial term, like "retractor" and you get no hits then say where it is, what it's applied to, but this is typical prompting for Krea 2, for instance "she has a metal spreader in her mouth".
There's a variety of attachments: on head, under chin, strap.
If there's too much cum, or it shows up when you don't want it, you'll likely need to lower the weight, this can operate at 0.20 and a value of 0.40 will give you a nice variety of these and those, keeping the same basic concept if given a more generic prompt like "The mouth is spread open by a metal object attached to leather straps".
A variety of colors were baked in so that the model didn't stick to a single path, which has the side effect of being able to add most colors, even those that were not in the dataset, so some characteristics that can be applied with most colors are ...
brushed aluminum
wood material
metal
opaque plastic
There's a variety of cum terms were captioned and in the dataset. For instance, these augmentations can be used...
cum strings,
cum on face,
cum on cheek,
cum in mouth,
cum on chin,
in addition to a few more potential characteristics, your vary may mileage...
strap,
head support,
chin support,
upper face support,
face support on nose,
breathing tube
.
Your supporting filter bypass LoRA will have a major impact on what's shown, especially ejaculate, so adjust that accordingly. Bypass filters will also affect things like color and material, so if you want a metal retractor you may need to adjust one or more of your filters or realism LoRA.