I found this a while ago. u might be interested.

Question :
I have a bad case of acne. After several medications were unsuccessful, my dermatologist suggested that I schedule a dental exam. He said cavities may fuel my acne infection. How can this be?

Answer :
An abscessed or decayed tooth may contribute to acne. Dermatologists described a patient who had acne outbreaks that did not respond to traditional medications (Boyd et al. 1999). However, the acne disappeared after the patient had an abscessed tooth removed. This cycle of acne outbreak, tooth decay diagnosis, dental treatment and acne cure was repeated on several separate occasions.

Acne vulgaris triggers the immune system to produce antibodies against Propionibacterium acnes, the bacteria found in acne lesions. This bacteria is also commonly found in the mouth and throat. The authors concluded, "We believe that the presence of our patient's dental infections provoked a follicular inflammatory response resulting in his recalcitrant acne."

This limited anecdotal evidence does not prove that tooth decay contributes to stubborn cases of acne vulgaris. Most people with tooth decay do not have acne. Alternatively, most people with acne do not have tooth decay. However, if your acne does not improve with benzoyl peroxide, tetracycline, or other medications, perhaps it is time to visit your dentist!

Reference:

Boyd et al., "Recalcitrant acne vulgaris secondary to dental abscess" Cutis (1999) 64(2):116-118.