Figure 1 - A facial sinus associated with a severe periapical abscess on the upper canine.

From the following article

Verifiable CPD Paper: 
Endodontics: Part 2 Diagnosis and treatment planning

P Carrotte

British Dental Journal 197, 231 - 238 (2004) Published online: 11 September 2004

doi:10.1038/sj.bdj.4811612