We aimed to evaluate the acute effect of musical auditory stimulation on heart rate autonomic regulation during endodontic treatment. The study included 50 subjects from either gender between 18 and 40 years old, diagnosed with irreversible pulpitis or pulp necrosis of the upper front teeth and endodontic treatment indication. HRV was recorded 10 minutes before (T1), during (T2), and immediately (T3 and T4) after endodontic treatment. The volunteers were randomly divided into two equal groups: exposed to music (during T2, T3, and T4) or not. We found no difference regarding salivary cortisol and anxiety score. In the group with musical stimulation heart rate decreased in T3 compared to T1 and mean RR interval increased in T2 and T3 compared to T1. SDNN and TINN indices decreased in T3 compared to T4, the RMSSD and SD1 increased in T4 compared to T1, the SD2 increased compared to T3, and LF (low frequency band) increased in T4 compared to T1 and T3. In the control group, only RMSSD and SD1 increased in T3 compared to T1. Musical auditory stimulation enhanced heart rate autonomic modulation during endodontic treatment.
Dental treatment has been reported by many patients as a situation generating stress and anxiety. One of the main elements that seem to interfere with the behavior of most individuals seeking dental care is the acceptance that they will be subjected to some kind of discomfort during the treatment [
In this context, the literature has investigated alternative therapies to improve stressful situations [
Stress and anxiety are associated with the regulation of cardiac function by the autonomic nervous system (ANS), which allows us to evaluate the balance between the sympathetic and parasympathetic systems. In the heart, the ANS specifically influences heart rate and cardiac contractility. Furthermore, to increase or decrease of heart rate, ANS also regularly controls heart beats. The fluctuation of consecutive heart beats is analyzed through heart rate variability (HRV) [
Along these lines, the development of technical, scientific, and biological procedures in endodontic treatment achieves highly successful results. However, in spite of this, the treatment involves several stages ranging from anesthesia until obliteration of the root canal system. Also, the technique can be accomplished by basic technical operative steps which are prone to failure and various complications in its clinical progression [
Consequently, we believe that, during endodontic treatment, musical auditory stimulation may improve HRV. Knowledge of physiological responses involved in endodontic treatment is imperative because it provides a more appropriate treatment plan to the patient and provides greater safety clinically for the endodontist. Analysis of the ANS oscillations during endodontic procedure provides information, which can cause potential risks for cardiovascular system. Therefore, we investigated the acute effects of musical auditory stimulation on heart rate autonomic regulation during endodontic treatment.
Fifty subjects participated in this study with 13 females and 12 males in the music group and 12 females and 13 males in the control group. All participants aged between 18 and 40 years were examined. Everyone was diagnosed with irreversible pulpitis or pulp necrosis of the upper front teeth and endodontic treatment indication. The patients were divided into two equal groups: control group (patients who were submitted to standardized endodontic treatment) and music group (patients who were submitted to standardized endodontic treatment and were exposed to musical auditory stimulation). The sample was selected from endodontic treated patients undergoing the root canal procedure. All volunteers were informed about the procedures and objectives of the study and, after agreeing, they signed an informed consent form which was confidential. The study was approved by the Ethics Committee in Research of our University (Protocol number 993.350).
We considered the following as exclusion criteria: smokers; individuals with cardiorespiratory, neurological disorders and other reported impairments that prevented the subject from performing the procedures and treatment with drugs that influence cardiac autonomic regulation; patients who have undergone previous root canal treatment; women between 10–15 and 20–25 days after the first day of the menstrual cycle in order to avoid influence of luteal and follicular phase; pregnant women; and subjects who reported hearing disorders.
Prior to the endodontic treatment the following information was collected: age, gender, mass, height, and body mass index (BMI). Anthropometric measurements were obtained according to the recommendations described by Lohman [
Data collection was undertaken in a room with temperature between 21°C and 25°C and humidity between 50% and 60%. The volunteers were instructed to not ingest alcohol, caffeine, or other ANS stimulants for 24 hours before the evaluation. The volunteers were instructed to remain at rest and avoid talking during the collection.
Primarily, the blood pressure (BP) measurement was implemented. Subsequently, the saliva collection for salivary cortisol measurement was undertaken. Following this the analysis of the protocol of cardiac modulation during endodontic treatment was assumed.
Systolic (SBP) and Diastolic Blood Pressure (DBP) measurements were performed using an aneroid sphygmomanometer (Tycos®) and stethoscope (Sprague®). BP was measured before and after the endodontic treatment.
We did not induce salivation to collect saliva samples; we collected salivary cortisol samples before and after endodontic treatment between 14:00 and 17:00 by the same researcher. The volunteers were told to not eat or drink one hour before collecting saliva and wash their mouths with water. The Salivette® tubes were refrigerated until analysis of the material.
Data assembly was performed using a Salivette tube consisting of a plastic tube that contains a highly absorbent cotton roll, maintained in the mouth for about three minutes. Then, it was placed inside the collector plastic tube. After collecting all the Salivette tubes, samples were centrifuged for 20 minutes at 2800 rpm at a temperature of 4°C. During centrifugation, saliva passed the cylindrical swab medium through the cavity in the bottom of the drop tube to the clean centrifuge tube. Mucus and airborne particles were captured in the conical tip of the tube, allowing for easy decanting of clarified saliva.
Following centrifugation, the saliva was transferred to an Eppendorf type tube with lid and stored in a freezer at −20°C until the time when it was inspected. The material was cooled, ensured by the use of dry ice, Styrofoam, and a thermal bag. The samples were processed using the electrochemiluminescence method.
HRV was recorded in the first session of endodontic treatment at four intervals: 10 minutes before the beginning of root canal therapy session (T1) The initial 10 minutes after the application of local anesthetic (T2) The total duration of endodontic treatment (T3) 30 minutes after the endodontic treatment termination (T4)
After the initial assessment, we placed the heart rate receiver Polar RS800CX (Polar Electro, Finland) on the chest of the volunteers at the distal third of the sternum region and strapped at the wrist. After placing the strap and the monitor, the protocol was initiated.
The endodontic treatment was performed by the same dentist. We describe below all the steps of endodontic treatment: Inferior alveolar nerve anesthesia (2% DFL® ALPHACAINE) Decayed tissue removal and access to the pulp chamber (spherical diamond burs numbers 1012, 1014, and 1015, KG Sorensen®) compatible with the size of the pulp chamber, mounted on high speed turbine, air-cooled water, and Endo Z bur (Les Fils d’ August Mailefer SA) The operating field isolation with rubber dam Chemical-mechanical preparation of root canals (Hand files Flexofile Dentsply® and sodium hypochlorite 2.5%) Channel drying (Dentsply paper cones) Intracanal medication (SS White®) Cotton ball laying on channel input Interim sealing (IRM®)
The volunteers were randomly divided into two equal groups (
HRV analysis followed guidelines from the aforementioned Task Force [
Digital filtering was based on an algorithm in the Polar Protrainer software (Polar Electro, Finland). The algorithm intends to detect all measurement errors through analyzing median and moving average based filtering methods. The criteria adapt to the RR interval to be verified; if RR interval is very stable, relatively small peaks will be interpreted as errors. However, if RR interval includes very large variability, the criteria will be looser. Very small errors are not corrected. In the correction phase, the algorithm computes several more matching “candidates” to substitute the detected errors. The algorithm identifies the difference between previous and the next accepted RR interval and then makes the series of corrected values to follow the same differential coefficient. The special property of the error correction algorithm maintains the total time of the recording: that is, the sum of RR intervals is exactly the same as the elapsed time (
Manual filtering was performed by using Microsoft® Excel® 2013, it was based on visual inspection that detect artefacts and ectopic beats.
Only series with more than 95% sinus rhythm were included in the study; we excluded records with a percentage of artefacts higher than 5% [
The geometric indices of HRV included quantitative analysis of the Poincaré plot (SD1: standard deviation of the instantaneous variability of the beat-to-beat heart rate; SD2: standard deviation of long-term continuous RR interval variability and SD1/SD2 ratio) and time domain RRtri (triangular index) and TINN (triangular interpolation of RR intervals) indices. Significance of the abovementioned indices was previously described [
To determine the sample size a priori knowledge was needed, based on Moreno et al. [
For comparison between individuals of the same group, it was necessary to assess data normality by the Shapiro-Wilk test. When normal distribution was achieved, we applied the unpaired Student’s
After applying the normality test we checked that all distributions evaluated were parametric. In this sense, data were presented as mean and standard deviation.
Table
Age, height, mass, and BMI of volunteers.
Variable | Mean ± standard-deviation | | |
---|---|---|---|
Control | Music | ||
Age (years) (min-max) | | | 0.7628 |
Height (m) (min-max) | | | 0.6512 |
Mass (kg) (min-max) | | | 0.4704 |
BMI (kg/m2) (min-max) | | | 0.6176 |
m: meters; kg: kilograms; BMI: height and body mass index; min-max: minimum-maximum.
In the control group, we noted that RR interval was increased during endodontic treatment (T3) compared to before endodontic procedures (T1). RMSSD (root-mean square of differences between adjacent normal RR intervals) and SD1 indices were also increased during endodontic treatment (T3) compared to before endodontic procedures (T1) (Table
Mean and standard deviation of SBP, DBP, and cortisol in T1 and T4, heart rate (HR), RR interval, and linear indices in T1, T2, T3, and T4 in the volunteers without auditory stimulus.
Variable | T1 | T2 | T3 | T4 | Value |
---|---|---|---|---|---|
SAP (mmHg) | | — | — | | 0.7033 |
DAP (mmHg) | | — | — | | 0.3075 |
Cortisol (ug/dl) | | — | — | | 0.1334 |
HR (bpm) | | | | | 0.1851 |
RR (ms) | | | | | |
SDNN (ms) | | | | | 0.4717 |
RMSSD (ms) | | | | | 0.0251 |
pNN50 (ms) | | | | | 0.0620 |
RRtri (ms) | | | | | 0.1472 |
TINN (ms) | | | | | 0.0626 |
SD1 (ms) | | | | | 0.0240 |
SD2 (ms) | | | | | 0.6685 |
LF (ms2) | | | | | 0.3427 |
LF (nu) | | | | | 0.8741 |
HF (ms2) | | | | | 0.1104 |
HF (nu) | | | | | 0.4329 |
LF/HF | | | | | 0.8741 |
Regarding the groups subjected to musical auditory stimulation during the endodontic treatment, we observed that DAP increased after the procedures (T4). HR decreased while RR interval decreased during endodontic treatment (T3) compared to before treatment (T1) (Table
Mean and standard deviation of SBP, DBP, and cortisol in T1 and T4, heart rate, RR interval, and linear indices in T1, T2, T3, and T4 in subjects with auditory stimulus.
Variable | T1 | T2 | T3 | T4 | Value |
---|---|---|---|---|---|
SAP (mmHg) | | — | — | | 0.6085 |
DAP (mmHg) | | — | — | | 0.0288 |
Cortisol (ug/dl) | | — | — | | 0.0577 |
HR (bpm) | | | | | 0.0066 |
RR (ms) | | | | | 0.0014 |
SDNN (ms) | | | | | 0.0237 |
RMSSD (ms) | | | | | 0.0240 |
pNN50 (ms) | | | | | 0.1033 |
RRtri (ms) | | | | | 0.6246 |
TINN (ms) | | | | | 0.0320 |
SD1 (ms) | | | | | 0.0310 |
SD2 (ms) | | | | | 0.0336 |
LF (ms2) | | | | | 0.0004 |
LF (nu) | | | | | 0.0982 |
HF (ms2) | | | | | 0.3741 |
HF (nu) | | | | | 0.1007 |
LF/HF | | | | | 0.1391 |
Regarding HRV analysis, SDNN, TINN, and SD2 indices were weakened during endodontic treatment (T3) compared to after treatment (T4). Moreover, RMSSD and SD1 were increased after treatment (T4) compared to before treatment (T1) (Table
Regarding spectral analysis, LF in absolute units was increased after treatment (T4) compared to before (T1) and during treatment (T3) (Table
In our study, we found a decrease in the SDNN, SD2, and LF indices during endodontic treatment with musical stimulation compared to after treatment. Those indices correspond to overall HR modulation [
We also compared HRV indices between both groups at all instants. SDNN (
There was no significant difference between groups for mean RR interval, RMSSD, pNN40, SD1, LF (ms2), LF (nu), HF (ms2), and HF (nu) LF/HF ratio during T1, T2, T3, and T4.
This study assessed the acute effect of musical auditory stimulation on HRV and salivary cortisol during endodontic treatment. Accordingly, it was found that the musical auditory stimulus improved heart rate autonomic responses induced by endodontic treatment. There were no significant changes in cortisol levels, which indicates the involvement of ANS on this mechanism.
During endodontic treatment, the patient is commonly presented in a stressful condition [
Equally, we failed to find significant changes in cortisol levels after endodontic treatment in control and music group. Nevertheless, there is a trend of declination after treatment in the group exposed to musical auditory stimulation.
Regarding the effects of stress, anxiety, and depression on modulation of the ANS, Langewitz et al. [
The study of Matsumura et al. [
Moreover, Santana et al. [
In our study, we found a decrease in the SDNN, SD2, and LF indices during endodontic treatment with musical stimulation compared to after treatment. Those indices correspond to overall HR modulation [
The auditory stimulation with music influences the cardiovascular system, since there is a correlation between the noise intensity and sympathovagal balance. It is hypothesized that dopamine released in the striatal system induced by melodic and cheerful songs is involved in autonomic regulation [
Conferring to da Silva et al. [
Some studies illustrated a correlation between parasympathetic heart rate regulation (HF: high frequency band) and music [
Also, reduction of the LF index was observed in the study of da Silva et al. [
We reported that the TINN index was also decreased during endodontic treatment in the music group. Previously a study [
Founded on our data, RMSSD and SD1 indices increased after endodontic treatment compared to before treatment. Our data points to a beneficial elevation in parasympathetic heart rate regulation induced by music during endodontic treatment. Ferreira et al. [
In this study, there was deficiency of significance of salivary cortisol before and after endodontic treatment. In this context, we indicate that music operated through ANS and not via hypothalamic-pituitary axis due to the short period of endodontic treatment. Nonetheless, there was a trend (
Previously, a study stated that music has a beneficial effect in controlling anxiety to dental treatment. The authors found significant differences in salivary cortisol levels, systolic and diastolic pressure, HR, body temperature, and stimulated salivary flow for the group treated with musical treatment [
Mehr et al. [
According to our results, we reported a significant statistical increase of LF and a simultaneous decrease of SDNN between T1 and T3 during auditory stimulus; it indicated that the music induced excitatory effects on HRV. A previous study assisted us to explain this response. Roque et al. [
Some facts are worth considering. The age range was wide (18 to 40 years). Conversely, exclusion criteria helped to ensure regulatory standards regarding the sample selection. Factors such as age, gender, anthropometric characteristics, and health conditions have been shown to influence physiological reactions [
Musical auditory stimulation acutely improved heart rate autonomic regulation during endodontic treatment. Our results encourage the use of relaxant music during endodontic treatment in order to lessen cardiovascular responses.
The authors declare that there is no conflict of interests regarding the publication of this paper.
This study received financial support from FAPESP (Process 2012/01366-6).