Perhaps it's better to say that braces do not cause vertical growth as much as they inhibit  complementary horizontal growth during developmental stages at which vertical growth usually happens. Or, perhaps cramming the sutures together causes the bone around the suture to be broken down in an attempt to resolve the increased sutural tension across the skull.

So is mewing possible with a bonded wire lower retainer?

Mewing would be possible as long as the retainer isn't large enough to restrict tongue. As to whether or not wearing a retainer could potentially sabotage whatever you are trying to achieve, I can't see why not.

Does holding the bottom front six teeth position inhibit forward growth? How exactly does the mandible bone grow with mewing?

Posted by: Silver

.......How exactly does the mandible bone grow with mewing?

The mandible does not grow in adults, it mostly shifts position moving forward to achieve better occlusion between lower and top teeth. In children, mewing applies enough pressure on the bone to direct growth in a forward direction instead of downward in the direction of gravity.

But doesn't it expand to match the transverse growth of the palate?

Posted by: Silver

But doesn't it expand to match the transverse growth of the palate?

No, unlike the maxilla, the mandible itself does not expand in adults, the Alveolar Ridge Process is what expands. That's the soft bone ridge that the teeth insert into. Once it reaches it's limit the teeth start tipping outward. In children, however, the mandible can be directed to grow by expanding the maxilla.

Most likely braces cause vertical growth through 3 methods.

The first is through how the wire system works in the first place, and how they connect to all of the teeth at once. This usually encourages the front teeth to be pulled back and down as they get tightened against the stronger larger back molars. That's why people who use orthodontics usually have teeth that look like they are perfectly straight up and down with no natural outward flaring. I think that Damon and Invisalign avoid this issue.

The second is something Mew brought up, that how when people get fitted for braces, they stop biting with full strength because the braces are never perfectly placed on the teeth which leads to bite issues. When you stop using your full muscle to support your bite, the face will probably lengthen a bit.

The third is through the use of elastics. If elastics are placed on the teeth then the face bones will always move down and back towards the stronger and less malleable jawbone. This causes vertical growth as well.

Read more here: http://claimingpower.com/braces-damage-faces-why-all-traditional-orthodontic-treatments-suck/

I can't comment on your individual case though, gotta figure that out for yourself.