Om the German board, a linkwas posted to a document from an orthodontist. It reads:
"Wir wünschen uns mit Ihnen, zu einem guten Ergebnis kommen zu können. Dazu benötigen wir Ihr Verständnis als auch zuverlässige Mitarbeit. Nur so können wir vermeiden, das Headgear im Extremfall so befestigen zu müssen, daß der Patient es selber nicht entfernen kann."
With my relatively bad German knowledge, I believe this translates to:
"We want to help you to success. Therefore we need your understanding and cooperation. Only in this way can we avoid in having to fix the headgear extreme cases so the patient can't remove it."
(See
https://dereferer.me/?https://dereferer.me/?http://www.orthodont-toll.de/headgear.pdf)
Haven't seen anything about this anywhere else, and I believe it is mainly a threat directed towards disobedient patiens (who are plenty, not least when it comes to headgear). I mean, fixing the HG seriously inflicts with the rest of the patient's life with respect to eating, drinking, doing sports etc., and I do not believe othodontists are willing to do that.
Perhaps it was different earlier when braces were not as developed as today. Perhaps some orthodontists even bond them for a couple of days to get the patient to wear them in public. But I can't imagine it would be more.