Timaru and Oamaru will be miss out on annual free dental days this year.

Smile NZ's free dental days, an incentive of the New Zealand Dental Association and Southern Cross Health Trust, will take place from September 10 to September 22.

Although the offer is across the country, at this stage, Timaru and Oamaru, are among the centres likely to miss out.

New Zealand Dental Association spokesperson Deepa Hughes said there would be a number of reasons as to why.

"The dental services are offering this voluntarily. One of the practices that offered it last year is undergoing renovations so is too busy to offer it."

"There is no government subsidy, this is fully funded privately by the NZDA dentists volunteering and Southern Cross Health Trust.

"We are trying to do our best to help as many as we can but any funding to help high needs groups at larger scale has to supported by the government."

Hughes said they hoped to service up to 900 patients nationwide.

"Anyone with a community service card is eligible for one basic (simple fillings and extractions) free care. Due to the nature of this programme (once a year) we don't have a waiting list. We don't want people to wait with toothache or decay for a another year as it is better to get it treated early than later."

"The Southern Cross Health Trust provides recompense to participating dental practices for the use of their premises, equipment and dental assistants. Dentists donate their time."

The free dental days will take place in Alexandra, Ashburton, Auckland, North Shore, Christchurch, Cromwell, Dunedin, Feilding, Gore, Hamilton, Invercargill, Lower Hutt, Masterton, Matamata, Mosgiel, Motueka, Nelson, Palmerston North, Paraparaumu, Stratford, Takaka, Upper Hutt, Wairoa and Wanganui.