On cantilever loading of vital and non-vital teeth. An experimental clinical study

Three healthy subjects with neighboring or contralateral vital and root-filled teeth requiring crown therapy were selected as test persons. All teeth had optimal alveolar bone support. The root-filled teeth were furnished with individual cast posts and cores, and veneer crowns were made on both the vital and non-vital teeth. Buccal extension bars were then soldered to the occlusal surfaces of these crowns, and weights were applied in different positions along the bars until the test persons experienced pain. The experiments were repeated under local anesthesia. The results showed that non-vital teeth had mean pain threshold levels that, on cantilever loading, were more than twice as high as those of their neighboring or contralateral vital teeth. The positions of the centers of rotational deformations of the loaded teeth, which were assumed to be mainly rotational, were calculated and found to be located inside the peripheries of the crowns for the vital teeth but extracoronally in markedly more peripheral positions for the non-vital teeth.