Teenagers in parts of Caithness and Sutherland are having to make 200 mile-long (322 km) round trips for orthodontic treatment in Inverness.
The dental care is not available on the NHS in the areas.
Campaigners claim 950 orthodontic appointments each year involved local young people, and the trips had an impact on their exam revision time.
NHS Highland said it, like other health boards, was experiencing a shortage of orthodontic consultants.
It said it was working with the North of Scotland Planning Group, which is a collaboration between it and Grampian, Orkney, Shetland, Tayside and Western Isles health boards, on finding a solution.
Campaign group Caithness Health Action Team (Chat) has begun calling for a consultant to be based in the area because of the impact it says the situation is having on young people.
Caithness has never had an orthodontist available on the NHS, according to NHS Highland.
The nearest available treatment is at Raigmore Hospital in Inverness.
Getting to the city involves a round trip of more than 200 miles from places such as Wick and Thurso in Caithness and Durness in Sutherland.
Marie Aitken, of Chat, said the long journeys were affecting young people’s schooling, with some having to attend appointments every six weeks.
She said: “They are saying that they are not achieving their best results because they are missing out on exam times and revision times.
“There is an impact on their families because they are having to take time off work, sometimes for just a five minute appointment just to get braces tightened up.”
The campaigner added: “Having to go down to Raigmore is not fair on the young people and it is not fair on their families who have an additional financial impact on their lives.”
NHS Highland said it recognised that orthodontic treatment was “one of a number of challenges facing the healthcare system in our more remote and rural areas”.
A spokeswoman said: “We have recently employed a locum on a part-time basis based in Inverness but they will not have the capacity to provide a visiting service.
“We apologise to anyone who has to travel to Inverness for treatment but, due to this national shortage, the board does not yet have the capacity to provide the outreach service that it would wish to provide and we hope that people will understand.”