Oct. 27, 2015 -- The teeth on either side of a new filling might be at risk for decay, dental experts say.

New research in the Journal of Dentistry suggests the trauma caused by the initial filling may be partly to blame.

Researchers from the Nordic Institute of Dental Materials in Oslo, Norway, examined 750 tooth surfaces -- either in good shape or with decay confined to the hard outer shell (enamel) -- that were in contact with newly filled teeth.

They found that after 4.9 years on average, 34% of the neighboring tooth surfaces had decay in the enamel, and 27.2% had decay in the dentine, the soft tissue inside the tooth.

On the neighboring surfaces where the enamel was decaying at the time the person got a filling, 57.3% had decay still in the enamel, while in 42.7% it had spread into dentine.

People with fillings who took poor care of their teeth seemed more at risk for this kind of trouble over time.

Overall, the researchers found that dental treatment had a significant impact on the development of tooth decay. Dentists should be aware of this possibility and take steps to prevent it when placing fillings, and they should check on the state of neighboring teeth at every follow-up appointment, the researchers say.