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: Dental patients abusing methamphetamine can present with poor oral hygiene , xerostomia , rampant caries ( " meth mouth " ) , and excessive tooth wear .
### Output Text:
Dental patients abusing <span class="chemical">methamphetamine</span> can present with poor oral hygiene , xerostomia , rampant caries ( " meth mouth " ) , and excessive tooth wear . 