Influence of changing the vertical dimension on the occlusal tooth contact patterns

Changing the vertical dimension (VD) in occlusal reconstruction has many problems of serious concern. In the present study, to study the influence of changing the VD on the masticatory system, the occlusal tooth contact patterns were investigated using a new radiotelemetry system. Occlusal resin splints or resin crowns covering all maxillary teeth were used continuously for periods up to 7 days to change the VD. The frequency and the duration of tooth contact in the habitual jaw closing position were measured during these periods of different activities such as when awake (resting, working, swallowing) and sleeping. It was found that the frequency and the duration of tooth contact when awake increased to a great extent immediately after the VD was raised except when swallowing and that, on the contrary, they diminished by reducing the VD. However, 3 or 7 days after, they returned to nearly the same level as before in both cases when raising and reducing the VD. On the other hand, the tooth contact patterns during sleeping varied little even though the VD was changed. Thus it is suggested that, in the masticatory system, the process of adaptation to the altered VD is different when awake and when sleeping.