My own homemade Scolds Bridle, with mouth cover taken from an old version where the straps were too long for a woman to wear. Inside is a 3" penis gag to ensure her compliance and silence.

That is more of a quick and nasty punishment. Much more than 12 hours and your jaw would be in severe discomfort and you would probably be very dehydrated too unless an alternative method of keeping you hydrated could be found.

I do have a muzzle that can be used for long term restriction. It was made for me by Top-To-Bottom-Leathers in the UK, after some misgivings on their part about the safety aspect of the item if someone should have something placed behind the muzzle while it was locked on. Such activity would be fraught with risk. I will only lock it on somebody when their mouth is empty. If I wish to use a inflatable gag, which fits nicely, the muzzle remains unlocked and other measures taken to prevent her from removing it herself, such as padded mittens.

The longest that I have had someone locked in it is 24 hours, at her own request, and she found it far more challenging than she imagined. She could take on fluids and even liquidated food via a straw through the 10mm hole placed in front of her lips. There is no chance of solid foods being taken in, however, medical wisdom suggests that it is possible to survive on liquidated food for up to seven weeks without side effects. Those who have had their jaws wired after being fractured would be fed this way and websites dedicated to recipes to cater for such patients exist.

Whilst the muzzle doesn't prevent speech, it does muffle it significantly and makes comprehension difficult. The greatest challenge for her, however, was the way that the jaw cup was connected to the collar. It prevented her from moving her head from side to side by more than a few degrees of arc and also stopped her from looking down, which prevented her from performing many of the tasks that she had planned to pass the time. The nine padlocks that combine to lock it also provide a constant reminder as they jingle in her ear with each movement of her head.

Incidently the young lady in the photo was also fitted with a nose clamp made by Aaxmar. It was connected to the ceiling preventing her from sitting down, which was part of the challenge, since she was fitted with ballet boots at the time.