26 April 2023

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Electrodermal activity in pulp diagnosis and assessment of odontogenic pain

Lara Figini

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At present there is still no quantitative measurement or objective method for the assessment of dental pain. Pulp diagnostic tests, which include cold testing and electrical testing (EPT), are also based solely on patient responses. 

The cold test causes tubular fluid to flow outward from the dentin and stimulates the nerve fibers. EPT works by conducting a current through the tooth to stimulate nerve fibers. However, both tests are not 100% accurate in determining pulpal status. In addition, despite high sensitivity and specificity, these tests are often inconsistent or inconclusive in patients who are unable to communicate, such as young children, and in patients with intellectual disabilities or a language barrier. 

An automated record of patient responses to pulp vitality tests remains an unmet need in endodontic diagnosis. Electrodermal activity (EDA) can be a physiomarker for testing pain before and after the administration of local anesthesia in dentistry and for making pulpal diagnosis. 

EDA, known as galvanic skin response (GSR), is a measurement of changes in the electrical conductance of the skin, highly associated with sweat gland activity modulated by the sympathetic nervous system (SNS). 

Multiple indices can be used to evaluate EDA, including skin conductance level (SCL), nonspecific skin conductance responses (NS.SCR), time-varying index of sympathetic activity (TVSymp), modified time-varying index of the EDA (MTVSymp) and others. 

Specifically, TVSimp quantifies the phasic response of the EDA and is calculated using a high pass filter (0.01 Hz), demodulation of the variable frequency complex and the Hilbert transform. TVSymp is a reconstructed EDA signal with EDA frequency bandwidth associated with sympathetic tone (0.04–0.25Hz) and is one of the most sensitive indices with high consistency compared to other EDA indices.

Materials and methods

In a study published online in November 2022 in the International Endodontic Journal, the authors investigated whether EDA could serve as a complementary tool for pulpal diagnosis and as an objective tool for assessing dental pain before and after anesthesia. local. A total of 53 subjects (189 teeth) and 14 subjects (14 teeth) were recruited for pulpal diagnosis and dental pain assessment before and after local anesthesia, respectively. 

EDA was recorded using commercially available devices such as the PowerLab and Galvanic Skin Response Amplifier, in addition to cold and electrical pulp tests (EPT). 

Participants rated their level of pain or sensation via the visual analog scale (VAS) from 0 to 10 after each test. EPT-stimulated EDA activity before and after administration of local anesthesia was recorded for participants who required root canal treatment (RCT for pulpitis). Raw data were converted to the variable index sympathetic activity, a sensitive and specific parameter of EDA over time. Statistical analysis was performed using Python 3.6 and its Scikit-post hoc library.

Results

Electrodermal activity was upregulated by cold stimuli and EPT tests in normal pulp. TVSymp signals were significantly increased in viable pulp compared to necrotic pulp by both cold test and EPT. 

Teeth showing intense cold sensitivity with or without persistent pain had higher peak TVSymp numbers than teeth with mild cold sensation. EDA activity and VAS scores were recorded in patients with pre- and post anesthesia painful pulpitis.

Post-anesthesia EDA signals were significantly lower than pre-anesthesia levels. Approximately 71% of patients (10 out of 14 patients) experienced no pain during treatment and reported a VAS score of 0 or 1. Most patients (10 out of 14) showed a reduction in TVSymp following the administration of anesthesia. Two out of three patients who experienced increased pain during root canal treatment RCT (post-treatment VAS > pre-treatment VAS) showed a post-anesthesia TVSymp increase.

Conclusions

From the data of this study, researchers concluded that the use of EDA in pulpal diagnosis and for the evaluation of dental pain can offer promising results. The authors said that while testing was limited to subjects who had adequate communication skills, the team’s future goal is to be able to use this technology to aid in the endodontic diagnosis of patients who have limited communication ability.

Hanh T. Tran, Youngsun Kong, Ankur Talati, Hugo Posada-Quintero, Ki H. Chon, I-Ping Chen. “The use of electrodermal activity in pulpal diagnosis and dental pain assessment.” Int Endod J. March 2023; 56:356–368. https://doi.org/10.1111/iej.13868