Noriyuki Tani D.D.S., Shigeyuki Tanaka, Masaru Ono and Yoshihiro Yagyu First Department of Prosthodontics Meikai University School of Dentistry 1-1, Keyakidai, Sakado-shi, Saitama Prefecture


The Bi-Digital O-Ring test (O-ring test) developed in 1978 by Y. Omura as a new diagnostic approach has gained a wide-spread recognition in many countries of the world as a clinically useful test. In spite of and contrary to the simplicity of its procedure, its mechanism has remained largely unknown. It is especially obscure what cerebro-physiological changes are induced or how sensitive the cerebral recognition level is. In other words, since a stimulant applied in the O-ring test or given by a chemical substance produces very feeble stimulation, it still remains unknown whether the reaction occurring in the O-ring test is identical to the conventionally-defined cerebral evoked response or whether the reaction is induced through a completely different response mechanism.

To determine the mechanism on a cerebro-physiologial level, it is necessary to define the potentiality of this test as a human cerebral sensor as so described in 1965 by Tsunoda and in 1986 by Kikuchi et al. Our presentation at the Third International Symposium on Acupuncture and Elerctro-Therapeutics has confirmed the potentiality of the O-ring test as a human cerebral sensor, because the reaction could be recognized as a cerebral response to weak light of 80 luxs. This study was undertaken to further confirm our previous results. Experiment was carried out using the same experimental system as in our previous study presented at the symposium to confirm the existence of cerebral responses to non-contact stimulation with chemical substances delivered at a distance of 1 or 15cm from the stimulation points at the regions of the oral cavity and stomach in 10 subjects. The chemical substances used as stimuli consisted of potassium cyanide, arsenic, paraformaldehyde, methyl methacrylate monomer, vitamin C and toothpaste. The following results were obtained:

1. When stimulated by a conventional manner of stimulation, cerebral evoked potential tended to appear acutely at stimulation. In the O-ring test with chemical substances, the appearance of the response (integration of 10-second values )tended to be suppressed.

2. The cerebral responses produced by stimulation of the oral cavity and stomach in a resting state with closed eyes were not symmetrical over both sides. Especially at the d, ?, a and ß1 regions, the responses were dominant on the right temporal and left occipital areas. This finding does not agree with the earlier described symmetry of the cerebral response.

3. The characteristic finding in this experiment was the left-hemispheric dominance at the ß2 region unlike the right-hemispheric dominance at other regions.

4. A distinct difference was found between the responses by stimulation with harmful substances and those by stimulation with harmless substances. However, there were no substance-related differences between the group of harmful substances and that of harmless substances.

5. Distance-related differences were demonstrated in the intensity of cerebral responses. Stimulation at a distance of 1cm frontally to the oral cavity induced strong cerebral responses to methyl methacrylate monomer, vitamin C and toothpaste.

6. In stimulation with potassium cyanide, arsenic and paraformaldehyde, the difference in distance produced no differences in the intensity of responses. It is considered that since the both substance groups induced cerebral responses at either distance as described in 4, potassium cyanide, arsenic and paraformaldehyde induced cerebral responses to almost the same degree at either distance, which accounts for the lack of significant differences.