In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: A comprehensive examination including her medical history , panoramic radiograph , and intraoral examination revealed 19 carious lesions , which is not very common for a healthy adult .
### Output Text:
A comprehensive examination including her medical history , panoramic radiograph , and intraoral examination revealed 19 carious lesions , which is not very common for a healthy adult . 