My dentist used cotton wool for my tooth filling
It is highly unlikely that your dentist used cotton wool to fill your tooth. It could be he/she placed some cotton wool against your cheek to separate your cheek from your tooth something we all do he/she would then have removed it at the end. The silver metal is probably amalgam a standard filling used for many years. The materials used to treat teeth are wide ranging and depend on the condition of your tooth and of course your budget. If a filling is very deep it can be close to the nerve (root canal) of your tooth over time the tooth can breakdown further and need root canal treatment.
I hope this helps you
Dr Riten Patel
18 Ashley Road, Walton on Thames Surrey, KT12 1HS
Web: www.mulberrydental.co.uk Tel: 01932 223 479