Anxiety and Endodontic Treatment

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Anxiety and Endodontic Treatment

Dental treatment is often stressful for patients and can evoke dental fear or dental anxiety (DA). Dental fear occurs as a normal reaction to a threat or hazard that the individual perceives.1Cianetti S, Lombardo G, Lupatelli E, Salvato R. Dental fear/anxiety among children and adolescents. A systematic review. Eur J Paediatr Dent 2017;18:121-30. DA is a state of apprehension in which the individual senses that something unpleasant is going to happen in association with treatment.1Cianetti S, Lombardo G, Lupatelli E, Salvato R. Dental fear/anxiety among children and adolescents. A systematic review. Eur J Paediatr Dent 2017;18:121-30. Dental phobia is an anxiety disorder with an intense, unreasonable fear or dread of dental visits and treatment. DA and dental fear are used interchangeably in the literature.2Klingberg G, Broberg AG. Dental fear/anxiety and dental behaviour management problems in children and adolescents: a review of prevalence and concomitant psychological factors. Int J Paediatr Dent 2007;17:391-406. The need for endodontic treatment (ET) is recognized as being particularly stressful for patients, and frequently evokes DA.3Georgelin-Gurgel M, Diemer F, Nicolas E, Hennequin M. Surgical and nonsurgical endodontic treatment-induced stress. J Endod 2009;35(1):19-22. The identification of patients with DA and its management are important components of care for patients receiving ET.

The need for endodontic treatment (ET) is recognized as being particularly stressful for patients.

Prevalence of DA

Reports from several countries indicate a prevalence of high levels of DA ranging from 10% to 42%.4Carter A, Carter G, Boschen M, AlShwaimi E, George R. Pathways of fear and anxiety in dentistry: A review. World J Clin Cases 2014;2(11):642-53. However, DA is particularly problematic for ET. In one study, patients who had never received ET experienced high levels of DA and considered ET to be more unpleasant than oral surgery.5Wong M, Lytle WR. A comparison of anxiety levels associated with root canal therapy and oral surgery treatment. J Endod 1991:17:461-5. In a second study, significantly higher levels of DA were reported for ET than for direct restorations, scaling or extractions.6Udoye CI, Oginni AO, Oginni FO. Dental anxiety among patients undergoing various dental treatments in a Nigerian teaching hospital. J Cont Dent Pract 2005;6(2):1-8. These findings are supported in other studies, and women experience greater levels of DA than men.4Carter A, Carter G, Boschen M, AlShwaimi E, George R. Pathways of fear and anxiety in dentistry: A review. World J Clin Cases 2014;2(11):642-53.,7Peretz B and Moshonov J. Dental anxiety among patients undergoing endodontic treatment. J Endod 1998;24:435‐7.,8Wali A, Siddiqui TM, Gul A, Khan A. Analysis of level of anxiety and fear before and after endodontic treatment. J Dent Oral Health 2016;2(3):036.,9Hussein HM, Saeed NA, Al-Zaka IM. Pathways of endodontic fear in different age groups for Iraqi endodontic patients. Iraqi Dent J 2017;39(1):27-33.
A recent study examined DA in Chinese patients with irreversible pulpitis.10Dou L, Vanschaayk MM, Zhang Y, Fu X, Ji P, Yang D. The prevalence of dental anxiety and its association with pain and other variables among adult patients with irreversible pulpitis. BMC Oral Health 2018;18(1):101. Patients completed questionnaires to evaluate their levels of stress, including the Chinese version of the Modified Dental Anxiety Scale (MDAS). Their dentists evaluated patients’ stress levels using the clinical anxiety rating scale (CARS). Both MDAS and CARS use a 5-point scale, with 1 representing no anxiety and 5 representing extreme/very severe anxiety. Sixty-seven percent of patients reported moderate anxiety associated with ET, while 17% experienced intense anxiety. From the providers’ perspectives, more than one-third of patients exhibited anxiety at a moderate-to-severe level. Higher levels of stress were found in patients reporting a negative experience at their most recent visit (p<0.05). Experiencing pain during the previous visit (p<0.01) or prior to the current visit (p<0.05) were most closely associated with DA.10Dou L, Vanschaayk MM, Zhang Y, Fu X, Ji P, Yang D. The prevalence of dental anxiety and its association with pain and other variables among adult patients with irreversible pulpitis. BMC Oral Health 2018;18(1):101.

Origins of DA

DA is the result of direct and/or indirect conditioning. Direct conditioning occurs in association with a prior negative/traumatic experience, such as pain.4Carter A, Carter G, Boschen M, AlShwaimi E, George R. Pathways of fear and anxiety in dentistry: A review. World J Clin Cases 2014;2(11):642-53.,9Hussein HM, Saeed NA, Al-Zaka IM. Pathways of endodontic fear in different age groups for Iraqi endodontic patients. Iraqi Dent J 2017;39(1):27-33.,10Dou L, Vanschaayk MM, Zhang Y, Fu X, Ji P, Yang D. The prevalence of dental anxiety and its association with pain and other variables among adult patients with irreversible pulpitis. BMC Oral Health 2018;18(1):101. Indirect conditioning has several pathways. These include information learned from parents (parental indirect conditioning), second-hand reports/learning (informative), being threatened with a visit to the dentist for bad behavior (verbal threat) and assimilating negative visual images in the media (visual vicarious).4Carter A, Carter G, Boschen M, AlShwaimi E, George R. Pathways of fear and anxiety in dentistry: A review. World J Clin Cases 2014;2(11):642-53. (Table 1) In one study with almost 600 patients receiving or treatment planned for ET, direct conditioning and parental indirect conditioning were the main causes of DA.11Carter AE, Carter G, George R. Pathways of fear and anxiety in endodontic patients. Int Endod J 2015;48(6):528-32. Indirect conditioning was a greater factor for females than males.

Table 1. Pathways by which DA can occur
Direct Conditioning: occurs in association with a negative experience
Indirect Conditioning
Parental: information learned from parents
Informative: second-hand learning
Verbal threat: threatened with a visit to the dentist
Visual vicarious: assimilation of negative visual images

In a second study, direct conditioning and parental indirect conditioning were most relevant for female patients (p<0.001 and p=0.002, respectively).12Carter AE, Carter G, Boschen M. Ethnicity and pathways of fear in endodontics. J Endod 2015;41(9):1437-40. The most common pathways in a third study were direct conditioning, and parental and informative indirect conditioning, and were reported by 32.9%, 29% and 25% of patients, respectively.9Hussein HM, Saeed NA, Al-Zaka IM. Pathways of endodontic fear in different age groups for Iraqi endodontic patients. Iraqi Dent J 2017;39(1):27-33. Verbal threats and visual vicarious pathways were reported by 6.7% and 6.4%, respectively. (Figure 1) Not surprisingly, direct conditioning became more relevant in older patients. Just as negative direct conditioning increases DA, positive direct conditioning reduces DA.5Wong M, Lytle WR. A comparison of anxiety levels associated with root canal therapy and oral surgery treatment. J Endod 1991:17:461-5.,13LeClaire AJ, Skidmore AE, Griffin JA. Endodontic fear survey. J Endod 1988;14(11):560-4. In one study, approximately 44% of patients who had never received ET experienced less DA after favorable experiences during treatment.13LeClaire AJ, Skidmore AE, Griffin JA. Endodontic fear survey. J Endod 1988;14(11):560-4.

Figure 1. Reported occurrence of direct and indirect conditioning pathways9Hussein HM, Saeed NA, Al-Zaka IM. Pathways of endodontic fear in different age groups for Iraqi endodontic patients. Iraqi Dent J 2017;39(1):27-33.


Anticipated pain has been found to influence DA,10Dou L, Vanschaayk MM, Zhang Y, Fu X, Ji P, Yang D. The prevalence of dental anxiety and its association with pain and other variables among adult patients with irreversible pulpitis. BMC Oral Health 2018;18(1):101. and younger patients in one study anticipated and experienced higher levels of pain than older patients.14Watkins CA, Logan HL, Kirchner HL. Anticipated and experienced pain associated with endodontic therapy. J Am Dent Assoc 2002;133(1):45-54. The issue of anticipated versus experienced pain is also complicated by individuals’ pain sensitivity. While anticipated pain was generally reported to be greater than experienced pain in one study, in patients with high pain sensitivity in addition to high levels of DA, self-reported anticipated and experienced pain were similar.15Klages U, Ulusoy O, Kianifard S, Wehrbein H. Dental trait anxiety and pain sensitivity as predictors of expected and experienced pain in stressful dental procedures. Eur J Oral Sci 2004;112(6):477-83. Personality traits, genetic susceptibility, vulnerability to negative emotions and ethnicity may also play a role in DA.4Carter A, Carter G, Boschen M, AlShwaimi E, George R. Pathways of fear and anxiety in dentistry: A review. World J Clin Cases 2014;2(11):642-53.,10Dou L, Vanschaayk MM, Zhang Y, Fu X, Ji P, Yang D. The prevalence of dental anxiety and its association with pain and other variables among adult patients with irreversible pulpitis. BMC Oral Health 2018;18(1):101.,12Carter AE, Carter G, Boschen M. Ethnicity and pathways of fear in endodontics. J Endod 2015;41(9):1437-40. Conflicting results have been reported for the potential influence of education level/socioeconomic status.4,7Peretz B and Moshonov J. Dental anxiety among patients undergoing endodontic treatment. J Endod 1998;24:435‐7.,10Dou L, Vanschaayk MM, Zhang Y, Fu X, Ji P, Yang D. The prevalence of dental anxiety and its association with pain and other variables among adult patients with irreversible pulpitis. BMC Oral Health 2018;18(1):101.,16Arslan S, Erta E, Ülker M. The relationship between dental fear and sociodemographic variables. Erciyes Med J 2011;33:295-300.

Physiologic response to DA

ET creates a stressful situation for anxious patients and results in a physiologic response involving the autonomic nervous system.3Georgelin-Gurgel M, Diemer F, Nicolas E, Hennequin M. Surgical and nonsurgical endodontic treatment-induced stress. J Endod 2009;35(1):19-22.,8Wali A, Siddiqui TM, Gul A, Khan A. Analysis of level of anxiety and fear before and after endodontic treatment. J Dent Oral Health 2016;2(3):036.,17Santana MDR, Martiniano EC, Monteiro LRL, Valenti VE, Garner DM, Sorpreso ICE, de Abreu LC. Musical auditory stimulation influences heart rate autonomic responses to endodontic treatment. Evid-Based Complem Alt Med 2017;Article ID 4847869. An important addition to the body of literature on DA is a study that examined stress before and after non-surgical/surgical ET.3Georgelin-Gurgel M, Diemer F, Nicolas E, Hennequin M. Surgical and nonsurgical endodontic treatment-induced stress. J Endod 2009;35(1):19-22. Patients self-reported their stress levels prior to ET, and their heart rates, systolic and diastolic blood pressures were measured before, during and after treatment. A correlation was found for pre-treatment DA and the level of physiologic stress. In addition, stress levels decreased during the appointment.3Georgelin-Gurgel M, Diemer F, Nicolas E, Hennequin M. Surgical and nonsurgical endodontic treatment-induced stress. J Endod 2009;35(1):19-22. In another study, patients’ heart rate variability (HRV) increased prior to ET, as a result of stress.18Santana MD, Pita Neto IC, Martiniano EC, Monteiro LR, Ramos JL, Garner DM, Valenti VE, Abreu LC. Non-linear indices of heart rate variability during endodontic treatment. Braz Oral Res 2016;30.

ET creates a stressful situation for anxious patients and results in a physiologic response involving the autonomic nervous system.

Outcomes of DA

Outcomes of DA include avoidance and postponement of dental visits.19Hmud R, Walsh LJ. Dental anxiety: Causes, complications and management approaches. J Minim Interv Dent 2009;2(1):67-78. In one study, 18% of patients reported postponing ET.9Hussein HM, Saeed NA, Al-Zaka IM. Pathways of endodontic fear in different age groups for Iraqi endodontic patients. Iraqi Dent J 2017;39(1):27-33. Not surprisingly, patients with high levels of DA/dental fear attend irregularly or only when in pain, and tend to have poor oral health.4Carter A, Carter G, Boschen M, AlShwaimi E, George R. Pathways of fear and anxiety in dentistry: A review. World J Clin Cases 2014;2(11):642-53.,9Hussein HM, Saeed NA, Al-Zaka IM. Pathways of endodontic fear in different age groups for Iraqi endodontic patients. Iraqi Dent J 2017;39(1):27-33.,10Dou L, Vanschaayk MM, Zhang Y, Fu X, Ji P, Yang D. The prevalence of dental anxiety and its association with pain and other variables among adult patients with irreversible pulpitis. BMC Oral Health 2018;18(1):101. As a result, DA is also predictive of attendance only to treat a serious problem, thereby creating a vicious circle. In one study, this applied to approximately 39% of patients with moderate/high DA.20Armfield JM. What goes around comes around: Revisiting the hypothesized vicious cycle of dental fear and avoidance. Community Dent Oral Epidemiol 2013;41(3):279-87. Treating patients with DA can require extra time and be more difficult.9Hussein HM, Saeed NA, Al-Zaka IM. Pathways of endodontic fear in different age groups for Iraqi endodontic patients. Iraqi Dent J 2017;39(1):27-33. DA may also impact the type and treatment provided, thereby creating a barrier to the provision of quality care.21Malamed S. Anxiety and fear in the endodontic patients. In: Ingle's Endodontics, 2008:737-48.,22Newton T, Asimakopoulou K, Daly B, Scambler S, Scott S. The management of dental anxiety: time for a sense of proportion? Br Dent J 2012;213(6):271-4. Further, DA can negatively impact quality of life, including social interactions.4Carter A, Carter G, Boschen M, AlShwaimi E, George R. Pathways of fear and anxiety in dentistry: A review. World J Clin Cases 2014;2(11):642-53.,22Newton T, Asimakopoulou K, Daly B, Scambler S, Scott S. The management of dental anxiety: time for a sense of proportion? Br Dent J 2012;213(6):271-4.

DA is predictive of dental visits only to treat a serious problem, thereby creating a vicious circle.

Managing patients with DA

Interventions to manage DA are warranted. These should be tailored to the patient’s level of DA, requiring that patients first be evaluated.9Hussein HM, Saeed NA, Al-Zaka IM. Pathways of endodontic fear in different age groups for Iraqi endodontic patients. Iraqi Dent J 2017;39(1):27-33.,10Dou L, Vanschaayk MM, Zhang Y, Fu X, Ji P, Yang D. The prevalence of dental anxiety and its association with pain and other variables among adult patients with irreversible pulpitis. BMC Oral Health 2018;18(1):101. Several evaluation tools are available for patient and clinician assessment of DA, including MDAS and CARS. An innovative tool with just one question and multiple-choice answers is also available,23Jaakkola S, Rautava P, Alanen P, Aromaa M, Pienihäkkinen K, Räihä H, Vahlberg T, Mattila M-L, Sillanpää M. Dental fear: One single clinical question for measurement. Open Dent J 2009;3:161-6. and may simplify assessment of DA in the dental office.

For patients with relatively low levels of DA, nonpharmacological options such as pleasant scents, rapport building, giving the patient a sense of control during treatment and cognitive distraction are available.4Carter A, Carter G, Boschen M, AlShwaimi E, George R. Pathways of fear and anxiety in dentistry: A review. World J Clin Cases 2014;2(11):642-53.,22Newton T, Asimakopoulou K, Daly B, Scambler S, Scott S. The management of dental anxiety: time for a sense of proportion? Br Dent J 2012;213(6):271-4. For patients with moderate levels of DA, also providing more information about ET and what they will experience can reduce DA and fear of pain.22Newton T, Asimakopoulou K, Daly B, Scambler S, Scott S. The management of dental anxiety: time for a sense of proportion? Br Dent J 2012;213(6):271-4.,24Van Wijk AJ, Hoogstraten J. Reducing fear of pain associated with endodontic therapy. Int Endod J 2006;39(5):384-8. Additional interventions can be utilized as indicated for patients with moderate/severe DA, including cognitive behavioral therapy.4Carter A, Carter G, Boschen M, AlShwaimi E, George R. Pathways of fear and anxiety in dentistry: A review. World J Clin Cases 2014;2(11):642-53.,22Newton T, Asimakopoulou K, Daly B, Scambler S, Scott S. The management of dental anxiety: time for a sense of proportion? Br Dent J 2012;213(6):271-4. (Table 2)

Table 2. Nonpharmacological options for the management of DA
Pleasing scents
Rapport building
Giving patients a sense of control
Distraction – visual and/or aural
Increased information about procedures
Increased information on the experience
Cognitive behavioral therapy
Systematic desensitization
Computer-assisted relaxation learning
Behavioral change
Hypnosis
Relaxation therapy

Nonpharmacological interventions include relaxation therapy, systematic desensitization through exposure to stressful situations to decrease DA, computer-assisted relaxation learning to change behaviors, hypnosis, and distraction.4Carter A, Carter G, Boschen M, AlShwaimi E, George R. Pathways of fear and anxiety in dentistry: A review. World J Clin Cases 2014;2(11):642-53.,22Newton T, Asimakopoulou K, Daly B, Scambler S, Scott S. The management of dental anxiety: time for a sense of proportion? Br Dent J 2012;213(6):271-4. (Table 2) In a systematic review of 29 trials with almost 3,000 patients, hypnosis was found to be effective in reducing stress.25Burghardt S, Koranyi S, Magnucki G, Strauss B, Rosendahl J. Non-pharmacological interventions for reducing mental distress in patients undergoing dental procedures: Systematic review and meta-analysis. J Dent 2018;69:22-31. Distraction may consist of visual distraction, audiovisual tools such as virtual reality headsets, or music.4Carter A, Carter G, Boschen M, AlShwaimi E, George R. Pathways of fear and anxiety in dentistry: A review. World J Clin Cases 2014;2(11):642-53.,22Newton T, Asimakopoulou K, Daly B, Scambler S, Scott S. The management of dental anxiety: time for a sense of proportion? Br Dent J 2012;213(6):271-4.,26Lai HL, Hwang MJ, Chen CJ, Chang KF, Peng TC, Chang FM. Randomized controlled trial of music on state anxiety and physiological indices in patients undergoing root canal treatment. J Clin Nurs 2008;17:2654‐60. In a recent randomized, controlled study, music decreased diastolic and systolic blood pressure and heart rate in patients undergoing ET, signifying lowered levels of both stress and DA.27Di Nasso L, Nizzardo A, Pace R. Influences of 432 Hz music on the perception of anxiety during endodontic treatment: A randomized controlled clinical trial. J Endod 2016;42(9):1338-43. In a second study, music also was found to reduce salivary levels of cortisol.16Arslan S, Erta E, Ülker M. The relationship between dental fear and sociodemographic variables. Erciyes Med J 2011;33:295-300. In addition, psychological interventions have been shown to increase dental visit attendance, with one systematic review finding that more than three quarters of patients were regular attenders for at least four years after the intervention.22Newton T, Asimakopoulou K, Daly B, Scambler S, Scott S. The management of dental anxiety: time for a sense of proportion? Br Dent J 2012;213(6):271-4.

Psychological interventions have been shown to increase dental visit attendance.

Pharmacological interventions include oral premedication with anxiolytics (e.g., benzodiazepines), conscious sedation and general anesthesia. With respect to pharmacological interventions, their relative efficacy, mechanisms of action, side effects and contraindications must be considered, and directions for use adhered to. In addition, regulations and recommendations relevant to your location and dental license must be followed. Interprofessional collaboration and referral for medical management may be required in the treatment of patients who experience dental phobia.

Conclusions

DA is a well-recognized problem for patients and clinicians, particularly in relation to ET, and impacts oral health and ultimately quality of life. Nonpharmacological and pharmacological interventions are available to reduce DA in patients receiving ET, as well as dental treatment in general. Patients should be evaluated for DA prior to treatment visits to enable appropriate intervention to reduce DA and thereby enhance oral health and the provision of care. In addition, more research is required on the relative benefits of different interventions for DA.25Burghardt S, Koranyi S, Magnucki G, Strauss B, Rosendahl J. Non-pharmacological interventions for reducing mental distress in patients undergoing dental procedures: Systematic review and meta-analysis. J Dent 2018;69:22-31.

References

  • 1.Cianetti S, Lombardo G, Lupatelli E, Salvato R. Dental fear/anxiety among children and adolescents. A systematic review. Eur J Paediatr Dent 2017;18:121-30.
  • 2.Klingberg G, Broberg AG. Dental fear/anxiety and dental behaviour management problems in children and adolescents: a review of prevalence and concomitant psychological factors. Int J Paediatr Dent 2007;17:391-406.
  • 3.Georgelin-Gurgel M, Diemer F, Nicolas E, Hennequin M. Surgical and nonsurgical endodontic treatment-induced stress. J Endod 2009;35(1):19-22.
  • 4.Carter A, Carter G, Boschen M, AlShwaimi E, George R. Pathways of fear and anxiety in dentistry: A review. World J Clin Cases 2014;2(11):642-53.
  • 5.Wong M, Lytle WR. A comparison of anxiety levels associated with root canal therapy and oral surgery treatment. J Endod 1991:17:461-5.
  • 6.Udoye CI, Oginni AO, Oginni FO. Dental anxiety among patients undergoing various dental treatments in a Nigerian teaching hospital. J Cont Dent Pract 2005;6(2):1-8.
  • 7.Peretz B and Moshonov J. Dental anxiety among patients undergoing endodontic treatment. J Endod 1998;24:435‐7.
  • 8.Wali A, Siddiqui TM, Gul A, Khan A. Analysis of level of anxiety and fear before and after endodontic treatment. J Dent Oral Health 2016;2(3):036.
  • 9.Hussein HM, Saeed NA, Al-Zaka IM. Pathways of endodontic fear in different age groups for Iraqi endodontic patients. Iraqi Dent J 2017;39(1):27-33.
  • 10.Dou L, Vanschaayk MM, Zhang Y, Fu X, Ji P, Yang D. The prevalence of dental anxiety and its association with pain and other variables among adult patients with irreversible pulpitis. BMC Oral Health 2018;18(1):101.
  • 11.Carter AE, Carter G, George R. Pathways of fear and anxiety in endodontic patients. Int Endod J 2015;48(6):528-32.
  • 12.Carter AE, Carter G, Boschen M. Ethnicity and pathways of fear in endodontics. J Endod 2015;41(9):1437-40.
  • 13.LeClaire AJ, Skidmore AE, Griffin JA. Endodontic fear survey. J Endod 1988;14(11):560-4.
  • 14.Watkins CA, Logan HL, Kirchner HL. Anticipated and experienced pain associated with endodontic therapy. J Am Dent Assoc 2002;133(1):45-54.
  • 15.Klages U, Ulusoy O, Kianifard S, Wehrbein H. Dental trait anxiety and pain sensitivity as predictors of expected and experienced pain in stressful dental procedures. Eur J Oral Sci 2004;112(6):477-83.
  • 16.Arslan S, Erta E, Ülker M. The relationship between dental fear and sociodemographic variables. Erciyes Med J 2011;33:295-300.
  • 17.Santana MDR, Martiniano EC, Monteiro LRL, Valenti VE, Garner DM, Sorpreso ICE, de Abreu LC. Musical auditory stimulation influences heart rate autonomic responses to endodontic treatment. Evid-Based Complem Alt Med 2017;Article ID 4847869.
  • 18.Santana MD, Pita Neto IC, Martiniano EC, Monteiro LR, Ramos JL, Garner DM, Valenti VE, Abreu LC. Non-linear indices of heart rate variability during endodontic treatment. Braz Oral Res 2016;30.
  • 19.Hmud R, Walsh LJ. Dental anxiety: Causes, complications and management approaches. J Minim Interv Dent 2009;2(1):67-78.
  • 20.Armfield JM. What goes around comes around: Revisiting the hypothesized vicious cycle of dental fear and avoidance. Community Dent Oral Epidemiol 2013;41(3):279-87.
  • 21.Malamed S. Anxiety and fear in the endodontic patients. In: Ingle's Endodontics, 2008:737-48.
  • 22.Newton T, Asimakopoulou K, Daly B, Scambler S, Scott S. The management of dental anxiety: time for a sense of proportion? Br Dent J 2012;213(6):271-4.
  • 23.Jaakkola S, Rautava P, Alanen P, Aromaa M, Pienihäkkinen K, Räihä H, Vahlberg T, Mattila M-L, Sillanpää M. Dental fear: One single clinical question for measurement. Open Dent J 2009;3:161-6.
  • 24.Van Wijk AJ, Hoogstraten J. Reducing fear of pain associated with endodontic therapy. Int Endod J 2006;39(5):384-8.
  • 25.Burghardt S, Koranyi S, Magnucki G, Strauss B, Rosendahl J. Non-pharmacological interventions for reducing mental distress in patients undergoing dental procedures: Systematic review and meta-analysis. J Dent 2018;69:22-31.
  • 26.Lai HL, Hwang MJ, Chen CJ, Chang KF, Peng TC, Chang FM. Randomized controlled trial of music on state anxiety and physiological indices in patients undergoing root canal treatment. J Clin Nurs 2008;17:2654‐60.
  • 27.Di Nasso L, Nizzardo A, Pace R. Influences of 432 Hz music on the perception of anxiety during endodontic treatment: A randomized controlled clinical trial. J Endod 2016;42(9):1338-43.