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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 31  |  Issue : 1  |  Page : 36-39

Comparative evaluation of citric acid and TENS as means for salivary stimulation in adults: An Invivo study


1 Consultant Practitioner, A-2, M.I.G. Colony, Modern Dental College and Research Centre, Indore, Madhya Pradesh, India
2 Department of Oral Medicine and Radiology, Modern Dental College and Research Centre, Indore, Madhya Pradesh, India

Date of Submission13-Dec-2018
Date of Acceptance01-Feb-2019
Date of Web Publication23-Apr-2019

Correspondence Address:
Dr. Vanaja Reddy
Department of Oral Medicine and Radiology, Modern Dental College and Research Centre, Indore, Madhya Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiaomr.jiaomr_210_18

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   Abstract 


Introduction: Xerostomia and salivary gland hypofunction are associated with advancing age, autoimmune diseases such as Sjφgren's syndrome, head and neck radiation, smoking and recreational drug usage. Palliative management of xerostomia included topical agents such as ice chips, saliva substitutes, increasing water intake, paraffin and systemic agents like pilocarpine had been used. The above mentioned agents had side-effects and have led to find newer modalities like electrical and chemical stimulation. Aim: The present study was undertaken to evaluate the effectiveness of citric acid and transcutaneous electric nerve stimulation (TENS) as a means of stimulating salivary function in healthy adult subjects. Materials and Methods: Hundred adult subjects, 50 males and 50 females between the age group of 18-45 years, with no history of salivary gland disorder were randomly enrolled in the study. During the first visit unstimulated whole saliva was collected in a graduated tube and aafter 1 hr stimulated saliva was collected using citric acid and obtained saliva was measured and recorded. At the second visit, unstimulated whole saliva was collected in a graduated tube and after 1 hr stimulated saliva was collected with TENS and obtained saliva was measured and recorded. Results: The obtained data of unstimulated and stimulated saliva of the subjects was tabulated and subjected to statistical analysis using paired and unpaired t-test. The results showed increased salivary flow rate with both the modalities. And comparative evaluation revealed greater salivary flow rate with citric acid when compared to TENS. Conclusion: The present study substantiated the fact that citric acid as well as TENS can be used as an effective and wholesome method in stimulation of whole salivary flow rate in patients with xerostomia and salivary gland hypofunction.

Keywords: Citric acid, stimulated saliva, TENS


How to cite this article:
Pandey M, Reddy V, Wanjari PV. Comparative evaluation of citric acid and TENS as means for salivary stimulation in adults: An Invivo study. J Indian Acad Oral Med Radiol 2019;31:36-9

How to cite this URL:
Pandey M, Reddy V, Wanjari PV. Comparative evaluation of citric acid and TENS as means for salivary stimulation in adults: An Invivo study. J Indian Acad Oral Med Radiol [serial online] 2019 [cited 2019 Aug 21];31:36-9. Available from: http://www.jiaomr.in/text.asp?2019/31/1/36/256900




   Introduction Top


Saliva is a complex fluid which plays an important role in maintaining the well-being of oral cavity.[1] Saliva in human being originates from three pairs of major salivary glands (parotid, submandibular and sublingual), and 300-500 minor salivary glands. These glands produce 1.5 L of whole saliva daily, at a rate of approximately ranging from 0.25 to 0.35 ml/min. The rate of normal flow rates in unstimulated and stimulated condition ranges from 0.2-0.5 ml/min to 0.9 to 2.6 ml/min.[2]

Saliva maintains neutral pH and is essential for maintaining enamel mineralization. It not only lubricates the mouth and upper pharynx but also modulates oral flora, aids in digestion of food and facilitate speech and swallowing. Saliva also plays a role in oral immunology and possesses a number of antibacterial enzymes such as Lysozyme, peroxidase, histatins and lactoferrin.[3]

The reduction in salivary flow causes dryness of mouth, viscous sticky saliva, altered taste, a deviant sense of smell, failed speech, trouble with chewing, increased disfiguring dental caries, erosion of teeth, bad breath, esophagitis, aggravated acid reflux, burning tongue, cracked lips, and pestering yeast infections.[4]

One such condition caused due to reduced salivary stimulation is Xerostomia. Xerostomia (dry mouth), is a common clinical phenomenon and is present in about 40% of adults over the age of 50 years.[5] The major cause of xerostomia is objectively assessed salivary gland hypofunction. Xerostomia secondary to long standing salivary gland disease remains difficult to manage. While the infectious complications can be prevented or treated by conventional therapy the palliative management of xerostomia includes topical agents such as ice chips and saliva substitutes, increasing water intake, applying lip balm, chewing sugar free gum, sucking sour lemon drops, paraffin and citric acid containing lozenges and rinses;[2],[4] however, this requires patient counseling. Systemic agents like pilocarpine and cevimeline stimulate salivary flow but often have unfavorable side effects such as profuse sweating, rhinitis, dyspepsia etc.[2],[5]

The higher frequency of xerostomia thus significantly warranties significant unmet treatment needs. To ensure both short- and long-term relief, any means of stimulating salivary function should be easy to administer, reliable, and free of adverse side effects. Two such treatment modalities include electrical and acid stimulation.[2],[4]

Electrical stimulation by transcutaneous electrical nerve stimulation (TENS) is a well-known physical therapy, which is widely used to relieve various types of pain such as neurogenic pain, visceral pain postsurgical pain etc. With TENS, electrical stimulation is directed to chronic pain areas via surface electrodes, and current passed through these areas reduces or eliminates pain.[6] Acid stimulation; stimulation of saliva secretion by citric acid on the other hand results in increased saliva output and is a easy, painless, non-invasive and is more readily accepted by patients.[2]

A paucity of data and research exists in the evaluation of salivary stimulation by the use of non-invasive electrical and chemical stimulation.[2],[4] Hence, in an attempt to evaluate the effect of TENS and citric acid on whole salivary flow rate in healthy adult subjects, the present study was aimed to evaluate the clinical efficacy of these two modalities. The objectives included evaluating the effectiveness of citric acid and TENS as a means of stimulating salivary function and also to comparatively evaluate changes in flow rate between the unstimulated saliva and stimulated saliva by using above two modalities.


   Methodology Top


The present study evaluated the salivary rate flow using TENS and citric acid on 100 subjects. The study sample comprised of 50 males, and 50 females between the age groups of 18-45 years.

Study Site: The present study was conducted in Department of Oral Medicine and Radiology.

Ethical Clearance: Ethical approval to conduct the study was taken from the ethical approval committee.

Informed Consent: Written informed consent was obtained from study subjects prior to the start of study.

Study design: Cross Sectional Randomized Invivo Study.

Eligibility criteria

Inclusion Criteria- Healthy subjects, aged more than 18 years, not under any medications with noted incidence of xerostomia on its side effects profile were included in the present study.

Exclusion Criteria: Subjects with pacemakers, defibrillators and cochlear implants, subjects with systemic diseases, psychotic disorders, salivary gland pathology, history of autoimmune diseases, pregnant females and head and neck radiation were excluded from the present study.

Armamentarium

In the present study 0.25% citric acid solution was prepared by dissolving 0.25 gm of citric acid into 100 ml of distilled water. The TENS unit used in the present study was MICROSTIM GENIUS. Two graduated test tubes, funnel and test tube holder were used for saliva collection whereas the clinical assessment was carried out following standard protocol. A pretested structured proforma was used to record the demographic details and history of study subjects.

Study procedure

Demographic details as well as relevant oral findings of study subjects were entered in a structured proforma. All the participants were asked to refrain from eating, drinking, chewing gum, smoking and oral hygiene procedures like brushing and mouth rinsing for at least 1 hour prior to the appointment. Saliva sample collection was done over a period of two days in the morning session between 09.00 am – 12.00 p.m. to avoid for circadian variation of the flow rate. On day one stimulated saliva was collected using citric acid and on day two using TENS. The unstimulated saliva was collected one hour prior to the collection of stimulated saliva on both days.

Unstimulated saliva collection

Subjects were made to sit in an upright position, with head inclined forward and with minimal body and oro-facial movements. Subjects were asked to swallow saliva and stay motionless; saliva was then passively collected in the floor of the mouth. With 'low forced spitting' unstimulated saliva was collected per minute for 5 minutes. The collected saliva was measured using the micropipette and recorded in the proforma. The salivary flow rate was calculated by dividing the amount of collected saliva (volume in mL) by the duration of collection period (five minutes).

Stimulated saliva collection using acid stimulation

After half to one hour same subjects were asked to swirl freshly prepared 5 ml of citric acid (0.25%) solution in mouth for 15 seconds and stimulated saliva was then collected in a graduated test tube fitted with a funnel for 5 minutes, and collected saliva was measured and recorded.

After collection of unstimulated saliva on day 2, collection of saliva using TENS was done.

Collection of stimulated saliva with electrical stimulation (TENS)

The electrode placement was determined. The site of electrode placement was gently cleaned using an alcohol swab to remove any dirt or skin oils which might interfere in current delivery at the desired site. Surface electrode pads with electrode gel with TENS unit in off position were placed externally on the skin overlying the parotid glands angled inferiorly and the connector was then attached and locked into position.

The TENS unit was then activated, the pulse rate was fixed at 50 Hz and the amplitude was gradually increased to a maximum tolerable level of the patient. At optimal intensity (the maximum intensity that the subject still perceived to be comfortable), stimulated saliva was then collected for 5 minutes into separate graduated test tube and the flow rate was compared with unstimulated salivary flow rate.

After procedure was completed, the amplitude and frequency knobs were turned off completely, electrode leads were detached and pads were removed from the face and washed with water and mild soap gently and dried before replacing into the kit. Log of adverse effects was kept during and after experiment.

The relevant data so collected were entered in a proforma. The data gathered was tabulated and subjected to statistical analysis.

Statistical analysis

The data of the present study was initially entered into the Microsoft excel and then transferred to the statistical package MiniTab Version 17.0 for analysis. The comparison of mean saliva between un-stimulated and stimulated at Day 1, and similarly for Day 2 was done using student paired t-test and mean saliva between unstimulated at Day 1 to un-stimulated at Day 2; and stimulated at Day 1 and stimulated at Day 2 was done using student unpaired t-test. P value of ≤ 0.05 was considered statistically significant.


   Results Top


A total of 100 subjects 50 males and 50 females were included in the present study. An age wise comparison of subjects revealed that 22 (22%) subjects were in the age group of 18-25 years, 49 (49%) subjects in the age group of 26-35 years and 29 (29%) subjects were in the age group of 36-45 years.

The mean unstimulated saliva on day 1 was 1.48 ± 0.28 ml, while it was 5.52 ± 0.71 ml after citric acid application. A statistically highly significant difference was seen between unstimulated saliva and saliva production after citric acid secretion which increased significantly after using citric acid [Table 1].
Table 1: Comparison between unstimulated and stimulated salivary flow rate with citric acid

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The mean quantity of unstimulated saliva on Day 2 was 1.49 ± 0.29 ml, while it was 4.33 ± 0.77 ml after TENS application. A statistically highly significant difference was seen between unstimulated saliva and saliva production with TENS which increased significantly after TENS application [Table 2].
Table 2: Comparison between unstimulated and stimulated salivary flow rate with TENS

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When a comparatively evaluation was done a statistically highly significant difference amongst the both modalities was seen with greater stimulated saliva production after citric acid compared to TENS. Thus, stimulated saliva after citric acid is different from stimulated saliva after TENS with a higher mean of citric acid. Thus saliva production has increased more with citric acid in comparison to TENS [Table 3].
Table 3: Comparison of stimulated salivary flow rate between citric acid and TENS

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   Discussion Top


Saliva plays a critical role in maintaining oral homeostasis. Salivary secretion is normally controlled by reflex stimulation with effector nerve impulses traveling along the sympathetic as well as parasympathetic nerves to the glands. Parasympathetic stimulation produces copious saliva of low protein concentration, whereas sympathetic stimulation produces little saliva but with high protein concentration, which may give a sensation of dryness.[2],[4],[7]

Xerostomia and salivary gland hypofunction are associated with local and systemic conditions, advancing age, selected medical disorders, head and neck radiation, smoking and recreational drug usage.[2]

In the present study saliva was collected by spitting method instead of parotid saliva which is easy to perform and are useful as an indicator of general salivary performance and can be easily obtained in dental office. During the salivary assessment on day 1 unstimulated saliva was collected for 5 minutes with 'low forced spitting' method in a graduated tube. Subjects were asked to swish 5 ml of citric acid (0.25%) solution in mouth for 15 seconds after half to one hour and the saliva was measured and recorded. On Day 2, unstimulated saliva was collected for 5 minutes and after half to one hour, stimulated saliva on day 2 was collected with TENS unit for 5 min, measured and recorded. The adjustment of the pulse rate at 50 HZ and placement of electro pads on the skin overlying the parotid glands was similar to the method of Hargitai et al.,[2] taking into consideration the subject's perception to stimulus of tolerable level.

Inclusion of age group of 18-45 years in the present study was done to evaluate the efficacy of a particular method and to limit the age related variations. The age and sex wise distribution in the present study was done in accordance to the study done by Vilas SK et al.[4]

The increase in salivary rate flow before and after citric acid use was in accordance to studies done by Ekstrom et al.,[8] Femiano et al.,[9] Ben-Aryeh et al.[10] The reason is supposed to be due to the ability of citric acid to stimulate all the major and minor salivary glands together by carrying the afferent signals from anterior 1/3rd of the tongue which preferentially engage the sub-mandibular gland, lateral and posterior part of tongue preferentially engaging parotid gland. Citric acid use also seems to respond chemical stimulation leading to contraction of myo-epithelial cells which slight precedes secretion and thus helping in expulsion of saliva. Citric acid is a very potent stimulator of saliva that stimulates the gustatory receptors found mainly in the taste buds through parasympathetic pathways.[8],[9]

In a study by Femiano et al.[9] have shown that long-term use of 3% or more Citric acid can cause dental hypersensitivity and erosion, due to the demineralization of dental hard tissues from salivary pH reduction (3.5-3.0). But, in our study there is no dental erosion or dentinal hypersensitivity was found with citric acid. This could be due to less concentration (0.25%) and safe procedure of swish and spit, only for the short duration.

A highly significant increase in the salivary production was seen with TENS which is in agreement with studies done by Hargitai et al.,[2] Vilas SK,[4] Kumud et al.,[7] Agrawal et al.[11] who stated that the nerves to the salivary glands control the secretion of saliva. The possible mechanism of action of TENS is that it is believed to stimulate the auriculo-temporal nerve that supplies secretomotor drive to the parotid gland. Another reason could be the frequency and intensity settings of TENS unit i.e. nociceptive inputs reach brain via trigeminal nerve and enhance salivary reflex nuclei. Not all preganglionic parasympathetic fibers are necessarily facilitated, some may be inhibited.[2],[4],[8]

The only side effect of TENS therapy in the present study was mild twitching of the facial musculature also described by Hargitai et al.[2] The modifications suggested to avoid the side effects are manufacturing small electrodes to make electro-stimulation of the parotids more effective.

The comparative evaluation among the two modalities revealed that the stimulated salivary secretion was significantly higher with citric acid in comparison to TENS unit. The reason attributed to higher secretion of stimulated saliva is that citric acid being sour and given for swish acts as effective stimulator for secretion of all major and minor salivary gland.


   Conclusion Top


Based on the findings of the present study it can be concluded that both citric acid and TENS units were effective in increasing the salivary flow rate and salivary production; however, a comparative evaluation of the two modalities revealed greater salivary flow rate with citric acid when compared to TENS. Thus with the findings from present study it can be stated with clarity that based on patients preference any of the two modalities can be used in stimulation of whole salivary flow rate in patients with xerostomia and salivary gland hypofunction.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Tencate R, editor. Oral Histology, Development, Structure and Function. 5th ed. Missouri: Mosby Publication; 1998. p. 315-44.  Back to cited text no. 1
    
2.
Hargitai IA, Sherman RG, Strother JM. The effect of electro stimulation 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. 2
    
3.
Atkinson JC, Wu AJ. Salivary gland dysfunction: Causes, symptoms, treatment. JADA 1994;125:409-15.  Back to cited text no. 3
    
4.
Vilas SK, Shashikanth MC, Ali IM. Evaluation of the effect 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. 4
  [Full text]  
5.
Blom M, Lundbrg 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. 5
    
6.
Esposito CJ, Shay JS, Morgan B. Electronic dental anesthesia: A pilot study. Quintessence Int 1993;24:167-70.  Back to cited text no. 6
    
7.
Kumud M, Vaishali KB, Shekhar K. Evaluation of effect of TENS on salivary flow in patients with Xerostomia. Ann Dent Res 2012;2:44-50.  Back to cited text no. 7
    
8.
Ekstrom J, Khosravani N, Castagnola M, Messana I. Saliva and Control of its Secretion. Medical Radiology. Diagnostic Imaging. Springer-Verlag Berlin Heidelberg; 2012. p. 19-47.  Back to cited text no. 8
    
9.
Femiano F, Rullo R, Spirito FD, Lanza A, Festa VM, Cirillo N. A comparison of salivary substitutes versus a natural sialogogue (citric acid) in patients complaining of dry mouth as an adverse drug reaction: A clinical, randomized controlled study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;112:15-20.  Back to cited text no. 9
    
10.
Ben-Aryeh H, Miron D, Berdicevsky I, Szargel R, Gutman D. Xerostomia in the elderly: Prevalence, diagnosis, complications and treatment. Gerodontology 1985;4:77-81.  Back to cited text no. 10
    
11.
Aggarwal H, Pal-Singh M, Mathur H, Astekar S, Gulati P, Lakhani S. Evaluation of the effect of transcutaneous electrical nerve stimulation (TENS) on whole salivary flow rate. J Clin Exp Dent 2015;7:e13-7.  Back to cited text no. 11
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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