All toothpastes have abrasives in them. Some whitening toothpastes have larger particles to 'clean' your teath more (or wear them away!). Other whiteners have bleach in them, look at the ingredients, for instance peroxide is a bleach
Many toothpastes contain Benzoyl Peroxide (BPO). This bleaches quite aggressively. If you ever had a treatment for acne it may well have contained BPO, especially if you remember white towels and bed sheets!. Alot of models apply toothpaste to any spots they feel coming on to attempt to treat them!