A series of studies on the relationship between the condition of the stomatognathic system and the systemic condition has been conducted, it has been found that they both influence the somatic nervous system. In this series, the usefulness of the digital plethysmogram, which is simple, noninvasive, quick, and quantitative among autonomic function tests, was evaluated. Experimental occlusal interference was applied to the lower first molar teeth on the primary mastication side in 5 healthy subjects with natural teeth, and changes in the height of the digital plethysmogram were examined after interference. The following conclusions were drawn concerning the usefulness of the test.
1. The height of the digital plethysmogram was reduced 24 hours after occlusal interference, and its base line was unstable in many subjects. It tended to return to the level before interference one week after discontinuation of interference.
2. These findings suggest that plethysmography is useful for evaluation of the effect of occlusal interference as an abnormality of the stomatognathic system on autonomic activity.