Mechanisms of Acupuncture Analgesia on Experimental Dental Pain - A Psychophysical Study (Phase1) (MAC-DENT1)

Mechanisms of Acupuncture Analgesia on Experimental Dental Pain - A Randomized, Single Blinded, Sham-controlled Psychophysical Study (Phase1)

First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, Charite University, Berlin, Germany

The investigators will assess the effects of manual acupuncture on experimental dental pain in 36 healthy subjects by means of subjective pain intensity ratings and pain-specific autonomic nervous system (ANS) reactions.

This psychophysical and -physiological study is the first part of a two-phase project which pursues to explore how acupuncture-induced pain modulation interacts with pain-specific brain processing patterns by means of functional magnetic resonance imaging (fMRI) and by using an experimental dental pain model. In this preceding study, the characterization of manual acupuncture effects on the experimental dental pain model will be tested under laboratory conditions and without restrictions of an fMRI-measurement in order to provide a sound foundation for the following fMRI-experiment. Pain modulating effects of the manual acupuncture intervention (4 points: needle manipulation of bilateral large-intestine 4 (LI4), stomach 6 and 7 (ST6, ST7) ipsilateral to the stimulated tooth) will be compared to sham-acupuncture (insertion and manipulation of 4 non-acupuncture points) and a control intervention (no acupuncture) which will each be performed at 3 different days in a randomized order. Intervention effects on experimental dental pain will be assessed by testing of 36 healthy volunteers by means of subjective pain intensity ratings and pain-specific ANS reactions such as electrodermal activity and heart rate/respiratory changes. Besides laying the groundwork for the following fMRI experiment, this study could provide valuable basic insights into the dynamics of the tested manual acupuncture effects and further provide important knowledge for the planning of future clinical studies encompassing dental conditions and development of acupuncture treatments.

Manual acupuncture, Experimental dental pain, Psychophysics, Autonomic nervous system, Subjective pain ratings

All subjects participate at 3 experimental conditions (Acupuncture, Sham-Acupuncture and No Acupuncture) at 3 different days in a randomized order.

Comparison of the - mean post-pre acupuncture intervention pain intensity rating differences - and mean post-pre control intervention (no acupuncture) rating differences

Comparison of the - mean post-pre acupuncture intervention pain intensity rating differences - and mean post-pre sham-acupuncture rating differences

In case of a significant effect in outcome 1, outcome 2 will be tested using a hierarchical procedure in order to avoid multiple testing.

Besides the pre-post intervention comparisons (primary outcome), 2 additional timepoints (Total: pre-intervention, post-intervention, 15 min post-intervention, 30 min post-intervention) will be examined to test differences in temporal dynamics between the 3 intervention effects on subjective pain intensity.

Besides the pre-post intervention comparisons (primary outcome), 2 additional timepoints (Total: pre-intervention, post-intervention, 15 min post-intervention, 30 min post-intervention) will be examined to test differences in temporal dynamics between the 3 intervention effects on pain-specific heart rate alterations.

Besides the pre-post intervention comparisons (primary outcome), 2 additional timepoints (Total: pre-intervention, post-intervention, 15 min post-intervention, 30 min post-intervention) will be examined to test differences in temporal dynamics between the 3 intervention effects on pain-specific skin conductance alterations.

Besides the pre-post intervention comparisons (primary outcome), 2 additional timepoints (Total: pre-intervention, post-intervention, 15 min post-intervention, 30 min post-intervention) will be examined to test differences in temporal dynamics between the 3 intervention effects on pain-specific changes in respiratory frequency.

Changes in skin conductance during the three intervention types (acupuncture, sham-Acupuncture, no acupuncture).

Comparison of changes in the skin conductance measured during the acupuncture/sham-acupuncture and no acupuncture

Changes in heart rate variability (HRV) during the three intervention types (acupuncture, sham-Acupuncture, no acupuncture).

Changes in respiratory frequency during the three intervention types (acupuncture, sham-Acupuncture, no acupuncture).

Comparison of changes in respiratory frequency measured during the acupuncture/sham-acupuncture and no acupuncture.

Acupuncture expectation will be assessed using an acupuncture expectation questionnaire developed by the Institut for Complementary and Integrative Medicine, University Hospital Zurich

For the assessment of anxiety levels, the State-Trait Anxiety Inventory(STAI)(Bieling et al., 1998) questionnaire will be applied.

Inclusion Criteria: right-handed Written informed consent Fluent in German language Sufficient dental sensitivity for the tooth stimulation No acupuncture treatment in the previous 12 months No medical knowledge about acupuncure Exclusion Criteria: Alcohol, drug, and analgesics consumption within the last 24 hours Complaints of diseases of the oral cavity Pre-existing neurological and(or psychiatric conditions History of severe dental pain Regular intake of pain medication History of brain injuries Alcohol and drug abuse Chronic diseases that require a permanent intake of drugs

Clinic of Masticatory Disorders, Removable Prosthodontics, Geriatric and Special Care Dentistry Center of Dental Medicine University of Zurich

Bieling PJ, Antony MM, Swinson RP. The State-Trait Anxiety Inventory, Trait version: structure and content re-examined. Behav Res Ther. 1998 Jul-Aug;36(7-8):777-88. doi: 10.1016/s0005-7967(98)00023-0.

de Matos NMP, Pach D, Xing JJ, Barth J, Beyer LE, Shi X, Kern A, Lukic N, Ettlin DA, Brugger M, Witt CM. Evaluating the Effects of Acupuncture Using a Dental Pain Model in Healthy Subjects - A Randomized, Cross-Over Trial. J Pain. 2020 Mar-Apr;21(3-4):440-454. doi: 10.1016/j.jpain.2019.08.013. Epub 2019 Sep 12.