Your mouth and throat will get dry when you breathe through your mouth. Drink lots and use cough lozenges.
The sun can burn your lower lip badly. Using a zinc sun screen will help to protect it.
Visit the dentist before you travel. Painful teeth for days (or weeks) could ruin your trip.
All problems with teeth can be prevented. Poor hygiene can trigger the wisdom teeth problems which younger people often get. The cold air at altitude will upset un-treated broken fillings and cavities.
Too much sugar may make a decayed cavity so painful that it needs root treatment or extraction which is, in most cases, impossible on an expedition.
Most teeth and gum infections can be helped for a short time with Amoxycillin and Metronidazole. You can also take ibuprofen to cut down swelling.
Drink lots to moisten mouth, lips and throat.
Protect lips with zinc cream.
Take antibiotics and ibuprofen for dental swellings and severe pain.
Dental check with x-rays at least 6 weeks before you travel.
Buy zinc glacier cream for lips.
Buy a chap stick.
Buy cough lozenges.
In one month at Namche Bazaar dental clinic the author of this page treated climbers from seven expeditions whose summit hopes on Everest, Lhotse, Nuptse, Ama Dablam and Pumori were ended by serious dental symptoms. None had dental checks before leaving home.