SummaryThe series consisted of sixty subjects selected from the patients who attended the prosthetic or restorative departments of the Institute of Dentistry at the University of Kuopio in 1978–82. All the patients had had a mutilated or reduced dental arch in the upper or lower jaw for at least 1 year. They had received no prosthetic treatment and little restorative treatment.Helkimo's indices were registered in the first examination. After the first examination the pre‐prosthetic treatment was performed on all the patients. The second examination was after 18 months. Then Helkimo's indices were registered again. The prosthetic treatment had then been performed on thirty‐nine patients (group A). The control group consisted of nineteen patients without prosthetic treatment (group B).The changes in Helkimo's indices were analysed statistically (Mann‐WhitneyU‐test). The changes in the anamnestic index were not significant in either group while the changes in the dysfunction and occlusal index were highly significant in both groups