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: CLINICAL SIGNIFICANCE : This clinical case showing oral manifestations of meth mouth was presented to help dental practitioners recognize and manage patients who may be abusing methamphetamines .
### Output Text:
CLINICAL SIGNIFICANCE : This clinical case showing oral manifestations of meth mouth was presented to help dental practitioners recognize and manage patients who may be abusing <span class="chemical">methamphetamines</span> . 