Short answer: Yes, you may clean your teeth during Ekasana, but do it in the Jain way so the vow is not disturbed.

Simple Jain achar (discipline):

• Use only plain, boiled-and-cooled, filtered water. Do not swallow even a drop.
• Prefer no toothpaste or mouthwash (they have rasa/taste). Use a soft brush, tooth‑powder without taste, or a datun. Spit thoroughly.
• Best time: early morning, before sunrise; or just before your Ekasana meal. Avoid brushing at night (especially if you keep chauvihar).
• If you are observing a very strict Ekasana where water is only with the meal, then rinse and clean at the meal time and not outside it.

Tradition notes:

• Shwetambar: Generally allow careful brushing with plain water in the morning, avoiding taste and swallowing.
• Digambar (Ekabhukta is the close equivalent): Often stricter—keep brushing minimal, with plain water only, and many prefer doing it at the permitted water time (usually tied to the meal).

Essence: Keep saiyam. No rasa, no swallowing, minimal himsa, and no water use after sunset.

Helpful references:

• Brushing during fasting
• Water rules in Ekasana
• Water timing in Ekasana