Can dental sealants be safely removed if there is decay under them without the use of a drill? if so, how will it be done?

Depends: If the decay extends into the dentin of the tooth then you will likely need to be numbed. Conventional ways of removing sealants utilize the dental drill and a bur. Other methods include air abrasion or lasers. Whatever method is used the tooth will likely need to be numbed if the decay is excessive. And it is very safe to do so.

Dental Lasers: I routinely remove leaking sealants with decay under them using the biolase waterlase iplus instead of the drill. See if you can find a local dentist doing laser dentistry. No anesthesia is generally needed with laser cavity preparation. In your situation, no needle would be needed even with preparation with the dental drill.

Hydroabrasion: Hydroabrasion can remove sealants & decay. This device uses water and aluminum oxide particles with air as the propellant. It makes no noise and does not vibrate the tooth like a drill. I use it quite often. Relatively fast and usually painless!

Yes: This is simple and easy to do. A dental laser or a dental drill can be used.

Laser: Yes they can. I use a laser. Some dentists use air abrasion.