Mylor Dental Practice has closed with thousands of patients left without any NHS provision.
Honor Richardson, the contract holder for the practice on Passage Hill gave notice of her intention to cease treating patients as of last Friday.
A spokesman for the Cornwall and isles of Scilly Primary Care Trust (PCT) said normally three months' notice is provided, but it is understood the early closure has been forced by personal and financial issues. "The practice was under contract to treat up to 4,000 NHS patients although it was under achieving in the number of appointments it was offering," said the spokesman.
Mrs Richardson is informing patients by letter of the closure and asking them to register on the dental waiting list while additional provision is sought in the area.
The PCT is speaking to other NHS providers in the Falmouth and Truro areas to see if any are able to take on additional patients although there are already around 1,000 people waiting for places.
Bridget Sampson, who is heading up dental commissioning for the area team of PCT successor organisation the NHS Commissioning Board, said: "We are very sorry to be losing another dentist in an area where we already have many people waiting for places with an NHS dentist.
"The PCT has ensured adequate funding is available to increase capacity but some practices simply haven't been able to offer all of the NHS appointments funded under their contracts. This is something we are addressing.
"The NHS Commissioning Board Area Team will be providing more services in the Falmouth/Helston area in the form of at least one new dental practice."
Anyone who is seeking an NHS dentist should leave their details on 01726 627990 and anyone in the area who does not have an NHS dentist and who needs emergency dental treatment should contact the Emergency Helpline on 01872 354375.