NHS Highland says it is "vigorously" seeking a full-time dentist for the Isle of Mull.
The dentist in the post is due to retire leaving the island covered on a part-time basis.
NHS Highland has advertised the vacancy on a number of occasions, but has so far been unsuccessful in attracting any applicants.
Local councillor Mary Jean Devon said delays getting an appointment could harm islanders' dental health.
The dentist retiring runs a mobile service.
Ms Devon said some islanders could be put off keeping appointments because of long journeys to reach the remaining dentist.
A spokesman for NHS Highland's Argyll and Bute Health and Social Care Partnership, said: "We have been actively seeking a dentist for this post and despite advertising the vacancy on a number of occasions we have been unsuccessful in attracting any applicants.
"We will continue to vigorously seek a dentist for this vacancy and the remaining dentist on Mull has agreed to temporarily increase their hours in order to ensure that we can keep any waits to a minimum.
"Until we are able to recruit a replacement dentist those patients who are seeking appointments for day-to-day dental treatment may have to wait longer to be seen as we will have to focus on priority groups, children and those seeking emergency dental care."