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ORIGINAL ARTICLE
Year : 2015  |  Volume : 11  |  Issue : 1  |  Page : 229-233

Evaluation of effect of transcutaneous electrical nerve stimulation on salivary flow rate in radiation induced xerostomia patients: A pilot study


1 Department of Oral Medicine and Radiology, Century International Institute of Dental Science and Research Centre, Poinachi, Kasaragod, Kerala, India
2 A.B. Shetty Memorial Institute of Dental Sciences, Deralakatte, India
3 Department of Radiation Oncology Division, Mangalore Institute of Oncology, Mangalore, Karnataka, India

Date of Web Publication16-Apr-2015

Correspondence Address:
Anusha Rangare Lakshman
Department of Oral Medicine and Radiology, Century International Institute of Dental Science and Research Centre, Poinachi, Kasaragod - 671 541, Kerala
India
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Source of Support: We would to like to acknowledge, Father Muller medical college and A.B. Shetty Institute of Dental Sciences for all their support and permission to conduct the study, Conflict of Interest: None


DOI: 10.4103/0973-1482.138008

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 > Abstract 

Context: Xerostomia is a common sequel in patients undergoing irradiation of malignant tumors of the head and neck. Palliative treatments of xerostomia like topical agents such as ice-chips, saliva substitutes, systemic sialogogues like pilocarpine and cevimeline work well for some patients. Electrostimulation was studied in the past and showed moderate promise but never became part of the mainstream therapy for better management of xerostomia patients.
Aims: The aim of the following study is to evaluate the effectiveness of a transcutaneous electrical nerve stimulation (TENS) unit in stimulating the whole salivary flow rate in radiation induced xerostomia patients.
Materials and Methods: A total of 40 subjects were included in the study. The study group consisted of 30 individuals and was divided into Group S1 (n = 20), which was further subdivided into Group S1A (n = 10) subjects complaining of dry mouth who were undergoing head and neck radiotherapy with TENS stimulation during the commencement of radiotherapy, on the 3 rd , 6 th week and after a month of completion of radiotherapy and Group S1B (n = 10) with TENS stimulation daily during the full course of radiotherapy and Group S2 (n = 10) subjects complaining of dry mouth who had undergone head and neck radiotherapy that ended 1 month prior to their entry into the study. The control group (n = 10) consisted of healthy individuals not complaining of dry mouth and who have not undergone head and neck radiotherapy. Whole saliva was collected without stimulation for 10 min and after electrostimulation with TENS unit for additional 10 min in a graduated test tube. The results were statistically analyzed using Mann-Whitney U-test and Kruskal-Wallis's test.
Results: The data analysis revealed that control and S1B group showed increased salivary flow rate after stimulation by TENS therapy compared with the unstimulated salivary flow, whereas in S1A and S2 group it was found to be statistically non-significant.
Conclusion: The present study gave us an insight about the effectiveness of TENS therapy in stimulating salivary flow in healthy subjects and it is very effective when used in conjunction with radiation therapy by reducing the side-effects of radiation therapy. Hence, TENS therapy can be used as an adjunctive method for the treatment of xerostomia along with other treatment modalities.

Keywords: Radiation therapy, salivary flow, transcutaneous electrical nerve stimulation


How to cite this article:
Lakshman AR, Babu G S, Rao S. Evaluation of effect of transcutaneous electrical nerve stimulation on salivary flow rate in radiation induced xerostomia patients: A pilot study. J Can Res Ther 2015;11:229-33

How to cite this URL:
Lakshman AR, Babu G S, Rao S. Evaluation of effect of transcutaneous electrical nerve stimulation on salivary flow rate in radiation induced xerostomia patients: A pilot study. J Can Res Ther [serial online] 2015 [cited 2019 Jun 16];11:229-33. Available from: http://www.cancerjournal.net/text.asp?2015/11/1/229/138008


 > Introduction Top

"You will never miss the water until the well runs dry". How true this is, especially for saliva. Saliva is the physiological fluid of the oral cavity. It is a multipurpose fluid as it keeps the mouth moist, cleanses the oral cavity, facilitates speech, lubricates food for chewing and swallowing, aids in full appreciation of taste sensation, helps in digestion, acts as a buffering agent to neutralize acid attack of bacteria, acts as an antimicrobial agent, mineralizes the teeth. [1]

Xerostomia is the symptom of oral dryness resulting from decreased salivary flow. The main causes of xerostomia are medications, radiation therapy of head and neck cancers and autoimmune disorders such as Sjogren's syndrome. [2] Because salivary glands are radiosensitive, hyposalivation is a common sequel in patients undergoing irradiation of malignant tumors of the head and neck. There is extensive evidence that the irradiation volume of the salivary glands and the total radiotherapy dose strongly influence the extent of salivary dysfunction after irradiation. [1],[2]

Palliative treatments of xerostomia include topical agents such as ice-chips and saliva substitutes, increasing water intake, applying lip balm, chewing sugar free gum, paraffin and citric acid containing lozenges and rinses. [3] Systemic sialogogues such as pilocarpine and cevimeline stimulate salivary flow, but often have unfavorable side-effects such as profuse sweating, rhinitis, dyspepsia. Acupuncture also has shown improvement in xerostomic and healthy patients. [3],[4]

Transcutaneous electrical nerve stimulation (TENS) is a well-known physical therapy, which is useful for the relief of pain. With TENS, electrical stimulation is directed to chronic pain areas via surface electrodes and current passed through these areas reduces or eliminates pain. [5] It is non-invasive, safe and easy to master and generally well-accepted by the patients. [3] It is widely used to relieve various types of conditions such as low back pain, myofascial and arthritic pain, bladder incontinence, neurogenic pain, visceral pain and post-surgical pain. [6]

Electrostimulation was studied in the past and showed moderate promise, but never became part of the mainstream therapy for better management of xerostomia patients and Sjogren's syndrome. [7] The results of preliminary investigations of non-invasive electronic stimulation of reflex salivation in xerostomic patients have been encouraging. [3],[8]

An original investigation using non-invasive electrical stimulation for treatment and prevention of radiation side-effects in patients undergoing radiotherapy for carcinoma of head and neck showed promising results. [9] Research in this area has been sparse and hence this study was undertaken to evaluate the effectiveness of a TENS unit in stimulating the whole salivary flow rate in radiation induced xerostomia patients.

The objectives of our study were as follows:

  • To evaluate the effectiveness of TENS unit in stimulating whole salivary flow rate in healthy subjects, in patients undergoing head and neck radiotherapy, in patients who have undergone head and neck radiotherapy
  • To compare the effectiveness of TENS unit in stimulating whole salivary flow rate in healthy subjects, patients undergoing head and neck radiotherapy and patients who have undergone head and neck radiotherapy.



 > Materials and methods Top


The present study was a randomized case control study conducted on patients who have been undergoing radiation therapy for head and neck cancer in Department of Radiation Oncology at Father Muller Medical College, Kankanady, Mangalore.

A total of 40 subjects were included in the study. The study group consisted of 30 individuals and were divided into Group S1 (n = 20) which was further subdivided into Group S1A (n = 10) subjects complaining of dry mouth who were undergoing head and neck radiotherapy with TENS stimulation during the commencement of radiotherapy, on the 3 rd , 6 th week and after a month of completion of radiotherapy and Group S1B (n = 10) with TENS stimulation daily during the full course of radiotherapy and Group S2 (n = 10) subjects complaining of dry mouth who had undergone head and neck radiotherapy that ended 1 month prior to their entry into the study. The control group (n = 10) consisted of healthy individuals not complaining of dry mouth and who have not undergone head and neck radiotherapy.

Ethical committee clearance and prior informed consent of all the subjects was obtained before conducting the study.

For study group S1A and S1B patient's salivary samples are collected before the commencement of head and neck radiotherapy and during radiotherapy on 3 rd and 6 th week and after 1 month of the completion of radiotherapy. For study group S2 patient's salivary samples are collected after 1 month of head and neck radiotherapy.

All the subjects are asked to refrain from eating, drinking and chewing gum, smoking or oral hygiene procedures for at least 1 h prior to the appointment. The whole saliva was collected using spit method for 10 min.

TENS unit

The apparatus used is a strong low rate conventional mode of TENS model-NS Electro pulse that generates current through AC at a continuous frequency of 500 Hz with a sweep of 0.5-2 Hz. It consists of two primary components the central control unit and electrode pads. The electrodes are placed externally on the skin overlying the parotid glands with the TENS unit in the off position [Figure 1].
Figure 1: The extraoral transcutaneous electrical nerve stimulation unit

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Then the TENS unit is activated under continuous mode and intensity control switch is adjusted for 5 min for patient's comfort. Then stimulated whole saliva is collected for 10 min in a separate glass beaker. Any increase in salivary flow with electrostimulation, per individual subjects is considered a positive finding.

Mann-Whitney U-test was applied to statistically determine significant difference within the groups and Kruskal-Wallis's test was applied to determine significant difference between the groups.


 > Results Top


When Mann-Whitney U-test was used to compare the unstimulated and stimulated salivary flow rate in each group, the values were very highly significant for the control group; for S1A group at the beginning of radiation therapy was significant and 3 rd week, 6 th week and after a month was non-significant; S1B group at the beginning of radiation therapy, 3 rd week, 6 th week and after a month was highly significant; for S2 group was non-significant. The values of mean with a standard deviation, median and range of unstimulated and stimulated salivary flow rate were calculated for all the 4 groups and are given in [Table 1] and [Graph 1 [Additional file 1]].
Table 1: Comparison between unstimulated and stimulated salivary flow rate in each group

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Comparison of unstimulated and stimulated salivary flow rate between the study group S1A and S1B at the beginning of radiotherapy was found to be non-significant, 3 rd week was found to be significant, 6 th week was significant and after a month was very highly significant [Table 2] and [Graph 2 [Additional file 2]].
Table 2: Comparison of unstimulated and stimulated salivary flow rate between the study Group S1A and S1B

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Kruskal-Wallis's test was applied to determine significant difference between the groups, which was found to be non-significant when comparison of unstimulated and stimulated salivary flow rate between the control and study groups (S1 and S2) [Table 3] and [Graph 3 [Additional file 3]].
Table 3: Comparison of unstimulated and stimulated salivary flow rate between the groups

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 > Discussion Top


In the present study, the control group showed increased salivary flow rate after stimulation by TENS therapy compared to the unstimulated salivary flow which was in agreement with study by Hargitai et al. [3] in which 15 (out of 22) healthy subjects demonstrated a significant increase in the parotid salivary flow and the maximum increase was 8.75 fold greater than the baseline.

In a study by Saraf et al. [10] showed that 85 of hundred healthy subjects demonstrated increased salivary flow when stimulated via the TENS unit. And also in a study by Weiss et al. [8] who reported the use of an electronic stimulator as a method for increasing salivary production. Following a visual examination of the oral cavity as well as a gloved finger test to determine the presence of moisture (any reflection was considered a sign of wetness), patients were administered a 3-min stimulus to the tongue and roof of the mouth with the probe (electrodes) of the hand-held stimulator.

In patients who were undergoing radiotherapy with weekly TENS therapy (0 th week, 3 rd week, 6 th week and after a month) and after a month of radiation therapy, it was found to be non-significant. However, in a study by Damingo et al., [11] 6 of the 18 post-radiation head and neck cancer patients demonstrated a significant increase in saliva flow during TENS application, which is in contrary to our study.

The possible explanation could be that TENS, by itself, is less likely to be effective in cases where there is no baseline saliva flow such as in high-dose radiation therapy where complete destruction of the salivary gland unit has occurred. In the previous study by Hargitai et al. [3] had observed that TENS was unable to stimulate the parotid saliva and it was interpreted that TENS may act more efficiently as an accelerator of salivary flow rather than an initiator.

Therefore, it is likely to be more effective in cases of decreased salivary gland function rather than absolute absence of function and other possible explanation may be because of the smaller sample size taken in this study.

However, TENS therapy was found to be effective when used along the full course of radiation therapy as a concurrent treatment modality which is in agreement with the study by Nathalie and William [9] which concluded that electrical stimulation and radiation therapy are two modalities which seem to complement each other and electrostimulation enhances the healing process, thereby reducing the side-effects produced by radiation.

The mechanism by which the TENS unit worked on the parotid gland may be by directly stimulating the auriculotemporal nerve that supplies secretomotor drive to the parotid gland. It is believed that afferent nerves carry such impulses to the salivary nuclei (salivation center) in the medulla oblongata which in turn directs signals to the efferent part of the reflex leading to initiation of salivation [Figure 2]. [10]
Figure 2: The probable mechanism of action of transcutaneous electrical nerve stimulation in stimulating saliva

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In order to electrically stimulate sympathetic salivation, higher frequencies and longer pulse duration is required. On the other hand, electric stimulation of parasympathetic nerves of salivary glands produces copious amounts of watery saliva of the parotid gland at lower frequencies and it is this voluminous serous saliva which would be clinically most useful for management of xerostomia. [ 7]


 > Conclusion Top


Based on the above study it can be concluded that, the TENS therapy is effective in stimulating whole salivary flow in healthy individuals and it is effective when used in conjunction with radiation therapy by reducing the side-effects of radiation therapy. TENS is an effective extraoral device having minimal side-effects, which are transient. TENS therapy can be used as an adjunctive method for the treatment of xerostomia along with other treatment modalities.


 > Acknowlegment Top


We would to like to acknowledge, Father Muller medical college and A.B. Shetty Institute of Dental Sciences for all their support and permission to conduct the study.

 
 > References Top

1.
Crisius MM, Fox PC. Salivary gland diseases. In: Greenberg MS, Glick M, editors. Burket′s Oral Medicine, Diagnosis and Treatment. 10 th ed. Ontario: BC Decker Inc. Elsevier; 2003. p. 236-43, 259-60.  Back to cited text no. 1
    
2.
Porter SR, Scully C, Hegarty AM. An update of the etiology and management of xerostomia. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2004;97:28-46.  Back to cited text no. 2
    
3.
Hargitai IA, Sherman RG, Strother JM. The effects of electrostimulation on parotid saliva flow: A pilot study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005;99:316-20.  Back to cited text no. 3
    
4.
Blom M, Lundeberg T. Long-term follow-up of patients treated with acupuncture for xerostomia and the influence of additional treatment. Oral Dis 2000;6:15-24.  Back to cited text no. 4
    
5.
Esposito CJ, Shay JS, Morgan B. Electronic dental anesthesia: A pilot study. Quintessence Int 1993;24:167-70.  Back to cited text no. 5
    
6.
Yap AU, Ong G. An introduction to dental electronic anesthesia. Quintessence Int 1996;27:325-31.  Back to cited text no. 6
    
7.
Steller M, Chou L, Daniels TE. Electrical stimulation of salivary flow in patients with Sjögren′s syndrome. J Dent Res 1988;67:1334-7.  Back to cited text no. 7
    
8.
Weiss WW Jr, Brenman HS, Katz P, Bennett JA. Use of an electronic stimulator for the treatment of dry mouth. J Oral Maxillofac Surg 1986;44:845-50.  Back to cited text no. 8
    
9.
Nathalie SB, William B. Noninvasive electrical stimulation for the treatment of radiotherapy side-effects. Am J Electromedicine 1985;1.  Back to cited text no. 9
    
10.
Saraf KV, Shashikant MC, Ali IM. Evaluation of the effects of transcutaneous electrical nerve stimulation on whole saliva flow: A clinical study. J Indian Acad Oral Med Radiol 2009;21:7-11.  Back to cited text no. 10
    
11.
Damingo DL. The effects of electrostimulation on saliva production in postradiation head and neck cancer patients. Oral Surg Oral Med Oral Pathol 2004;95:464.  Back to cited text no. 11
    


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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