Answered by Shaykh Yusuf Weltch
Question: Assalamu alaykum
What is the ruling regarding the validity of ghusl if one has a retainer in their mouth?
Answer: In the Name of Allah, the Most Merciful and Compassionate
It is permissible to keep the retainer in your mouth. Especially if there is direct need in doing so. [Ibn Abidin, Radd al-Muhtar]
If the retainer can be taken out without undue hardship or any perceived harm, it should be removed for the sake of ghusl. However, if it is not removable or removing it will cause difficulty, it is not necessary to remove, and the ghusl is valid. [Ibn Abidin, Radd al-Muhtar]
Hope this helps
[Shaykh] Yusuf Weltch
Shaykh Yusuf Weltch is a graduate from Tarim; student of Habib Umar and other luminaries; and authorized teachers of Qur’an and the Islamic sciences.