Can I take bactrim for an abcess tooth?

It is not recommended for the treatment of abscess tooth, the various ailments it is used for are:

Bactrim® (sulfamethoxazole/trimethoprim) is an antibiotic used to treat a variety of different infections.

Urinary tract infections (UTIs), such as bladder infections; Ear infections; Acute worsening of chronic bronchitis; Shigellosis (a form of dysentery);
Traveler's diarrhea; A certain type of pneumonia known as Pneumocystis carinii pneumonia.

Bactrim is also approved to prevent Pneumocystis carinii pneumonia in people with weakened immune systems at risk for the infection (such as people with HIV or AIDS).

However it would be best to check with your doc./pharmacist for more details, hope this helps?