How can you give yourself a gap between two molar teeth of about 1.2mm to get barbell in between?

Creating a sufficient gap between molar teeth to fit a barbell is not generally a viable or recommended procedure.

However, if you feel a specific dental or medical reason necessitate creating such a gap, consult with a professional such as an orthodontist, periodontist, or your dentist.

Keep in mind that attempting to create a gap without professional guidance can potentially damage your teeth, surrounding gum tissue or result in unintended consequences and oral health complications.