In the dentist's chair

Version 1

Trigger is in_dent_chair

Other useful keywords for prompts:

Dentists_chair

Dentists surgery

White_coat - for your dentist

Open_wide, especially if used with gums and teeth gives a wider mouth than just open mouth on its own

Also trained with mouth_pull, for that uncomfortable sensation of having your cheek pulled to one side by fingers in another's mouth, dental_mirror or dental_instrument (these last two a bit undertrained, but will give you something metallic being held/inserted)