Is there a way to cure mouth breathing?

Yes: Typically mouth breathing is a result of nasal obstruction. This could be from a deviated septum, enlarged or hypertrophic turbinates, concha bullosa, or nasal polyps. This should be evaluated for potency. If there are any one of these conditions they should be corrected. You should have a consult with a surgeon who can evaluate and manage these conditions.

Possible: If you are a mouth breather, then there may be a number of causes including nasal blockage, jaw deformity, etc. Have an oral and maxillofacial surgeon or ENT evaluate your nasal and facial structure.

Structural: Yes. It is usually structural. It may be due to soft tissue swelling in the nose (allergy). Intranasal steroid sprays may help. It may be due to nasal problems like deviated septum or enlarge turbinates. Occasionally due to growths in the back of the nose .Best way to find out is to see an ENT doc.