Comparison of transcutaneous electrical nerve stimulation and interferential therapy for salivary stimulation in postmenopausal women: a pilot study

Abstract

The aim of this study is to compare the efficacy of Transcutaneous Electrical Nerve Stimulation (TENS) and Interferential Therapy (IFT) to enhance the salivary flow rate in post-menopausal women with oral dryness. This is a randomized pilot study design where the samples were calculated based on convenience sampling method and 15 post-menopausal women aged 45 to 70 were randomly assigned to two parallel groups and Group A received TENS therapy andGroup B received IFT and the salivary flow rate of both unstimulated and stimulated saliva was measured pre and post treatment. Statistical tests including Paired t-test, independent t-test, and two-way ANOVA were carried out which reveals that both TENS and IFT are significantly effective in salivary stimulation in post-menopausal women, however only stimulated salivary flow showed a statistically significant difference between groups, with greater values in the IFT group. The present randomized pilot study demonstrated Interferential therapy’s versatility and depth of stimulation, with consistent findings of improved comfort, function, and salivation, suggesting a potential advantage of IFT in stimulated salivary flow; however, because the study was a pilot, results should be interpreted cautiously.

Introduction

Xerostomia, defined as the subjective experience of dry mouth, may arise from numerous underlying factors¹. The most prevalent reasons include radiotherapy, several systemic illnesses, and xerogenic drugs. Additionally, elderly people and postmenopausal women are often affected by xerostomia². The available treatment for dry mouth is the same regardless of the various etiological causes of the condition, with the exception of drug-induced xerostomia, where the therapeutic approach is to stop taking the medication that is causing the dryness or replace it with one that has a less xerostomic effect³.

A decrease in saliva puts one at risk for rampant caries, increased plaque formation, opportunistic fungal infections, mucositis, difficulty swallowing, difficulty eating, malnourishment, and oral pain⁴. Palliative management of xerostomia comprises topical agents such as ice chips, and frequent sipping of water. Patient comfort and lubrication can be enhanced by saliva substitutes like formulations based on carboxymethylcellulose. In order to preserve oral health and avoid difficulties, salivary gland stimulation via massage, sugar-free lozenges, and topical fluoride treatment is crucial⁵. Other methods can include boosting water intake, applying lip balm, chewing sugar free gum, or sucking sour sugar-free lemon drops⁶.

Additional therapies for xerostomia include the use of systemic sialagogues. The cholinergic agonists pilocarpine and cevimeline work well for some patients but often have unfavourable side effects such as profuse sweating⁷. Conventional TENS is the most often used approach in dental treatment. It used 10 to 200 pulses per second high frequency and low amplitude pulsed currents. To avoid skin irritation, this can be safely used throughout the day with sporadic breaks⁸.

A non-invasive electrotherapeutic technique called interferential therapy (IFT) delivers two medium-frequency alternating currents into deeper tissues, where they converge to create a low-frequency beat current that can stimulate nerves with minimal discomfort. Because of its capacity to regulate pain and boost tissue function, it has been utilized extensively in clinical settings for analgesia, edema reduction, muscle stimulation, and improved circulation. IFT has demonstrated potential in improving glandular output by deeper parasympathetic regulation in salivary gland applications, resulting in a longer prolonged response than surface-level stimulation methods. Transcutaneous electrical nerve stimulation (TENS) stimulates the neural pathways involved in salivary production by applying low-frequency electrical impulses. In contrast, Interferential Therapy (IFT) allows for deeper tissue penetration and improved neuromodulation by using two medium-frequency currents that cross within tissues to provide a low-frequency effect. Since IFT can target deeper autonomic routes with less discomfort, it may offer more effective glandular stimulation than TENS, which mainly operates on superficial nerves⁹. The null hypothesis stated that there would be no significant difference between TENS and IFT in improving salivary flow rate in postmenopausal women.

Materials and methods

This study was designed as a randomized pilot study with parallel group trial with a 1:1 allocation ratio which was carried out to compare the efficacy of IFT with TENS in salivary stimulation in post-menopausal women with complaints of oral dryness. The study was conducted in the Department of Oral Medicine and Radiology, SRM Dental College, Ramapuram, Chennai, India. Institutional Review Board approval was obtained prior to study initiation (IRB No: 2025/PG/019) and clinical trial registry was done (CTRI/2026/03/105156). This study was conducted in accordance with CONSORT 2010 guidelines.

As this was a pilot study, a formal sample size calculation was not performed. A convenience sample of 15 participants was selected to assess feasibility and preliminary efficacy .A total of fifteen eligible participants were recruited and randomly allocated into two intervention groups: Group A received Transcutaneous Electrical Nerve Stimulation (TENS) as in Fig. 1A and Group B received Interferential Therapy (IFT) as in Fig. 1B using simple randomization generated by a computer based random number table and it was carried out by an investigator not involved in outcome assessment. The use of basic randomization in a small sample size, which can lead to imbalanced group allocation, was the cause of the participants’ uneven distribution among the groups. The variation in the final sample sizes examined was also influenced by slight attrition during follow-up.

Fig. 1.

(A) Tens Device, (B) Mini Interferential Therapy Device

It was not possible to blind participants and operators due to the nature of the interventions. Objective measures of salivary flow served as the basis for outcome evaluation.

Only post-menopausal women with xerostomia were included, while individuals with known salivary gland pathology, history of head-and-neck radiotherapy, systemic diseases affecting salivary function, use of xerogenic medications, or contraindications for electrotherapy were excluded. The absence of menstruation for a minimum of 12 consecutive months was considered post menopause. Reduced unstimulated salivary flow rate (< 0.1 mL/min) and subjective sensations of mouth dryness were used to diagnose xerostomia.

The therapeutic procedures were standardised for both groups. In Group A, TENS therapy was applied bilaterally over all three major salivary glands using low-frequency stimulation adjusted to the patient’s sensory threshold to achieve comfortable neuromodulation without inducing muscle contraction¹⁰as in Fig. 2A. In Group B, IFT was administered using a pair of intersecting medium-frequency currents positioned to stimulate all major salivary glands, enabling deeper tissue penetration and wider neural activation as in Fig. 2B.

Fig. 2.

(A) Patient receiving TENS therapy at 0–100 mA 1 k load, (B) Patient receiving IFT therapy at 50 Hz beat frequency

Each participant underwent six sessions for 15 min twice a week for 3 weeks of the assigned modality, following established protocols used in previous studies described by Hasegawa et al. (2016) on salivary stimulation in xerostomia patients. All treatments were delivered in a controlled clinical setting to minimise variability and ensure participant safety.

The patient was seated upright for five minutes while passive drooling was used to collect unstimulated salivary flow. To reduce circadian variation, collection took place between 9:00 and 11:00 in the morning. Before collection, participants were told not to eat, drink, or practice good dental hygiene for at least 90 min. Citric acid stimulation was used to produce stimulated saliva under controlled circumstances¹¹. Change in unstimulated and stimulated salivary flow rate (mL/min) before and after intervention is the primary outcome of this study.

The volume collected over a fixed time interval was measured in mL/min. These measurements allowed for both intra-group and inter-group comparison of therapeutic effect.

Statistical analysis

All data were compiled and evaluated using conventional statistical tools. Baseline salivary flow rates and demographic factors were summarized using descriptive statistics such as mean, standard deviation, and frequency distribution. Within-group comparisons of pre- and post-treatment unstimulated and stimulated salivary flow were performed using the paired t-test, while between-group comparisons of treatment outcomes for TENS and IFT were examined using the independent t-test. A p-value of < 0.05 is considered statistically significant. A two-way analysis of variance (ANOVA) was used to evaluate the main effects of treatment group (TENS vs. IFT) and age group, as well as their interaction (group × age) on changes in unstimulated and stimulated salivary flow rates. Results were provided in tabulations and graphical representations, including error bar graphs, were employed to demonstrate group differences in salivary flow response.

Results

After being evaluated for eligibility, fifteen postmenopausal women were randomized using simple randomization. Six participants were assigned to the IFT group and nine to the TENS group. Due to insufficient data, one person from each group was lost to follow-up. As a result, the final statistical analysis included five individuals from the IFT group and eight from the TENS group as shown in Fig. 3. The study participants were recruited and the trial was carried out between September 2025 to November 2025 for a period of 3 months.

Fig. 3.

CONSORT flow diagram showing the enrolment, randomization, allocation, follow-up, and analysis of study participants.

The pre-treatment salivary flow parameters and baseline demographics of the trial subjects are given in Table 1. The IFT group’s average age was 59.5 ± 8.2 years, whereas the TENS group’s was 61.0 ± 7.1 years. The two groups’ baseline unstimulated salivary flow rates were similar (0.11 ± 0.02 mL/min in the IFT group and 0.11 ± 0.03 mL/min in the TENS group). Similarly, there were no clinically significant differences between the groups in baseline stimulated salivary flow rates (0.19 ± 0.04 mL/min for TENS and 0.20 ± 0.02 mL/min for IFT), indicating that the groups were comparable at baseline prior to intervention.

Table 1.

Baseline demographic and pre-treatment salivary flow characteristics of the study groups.

Characteristic	Group A (TENS) (n = 9)	Group B (IFT) (n = 6)
Age (years), mean ± SD	61.0 ± 7.1	59.5 ± 8.2
Baseline unstimulated salivary flow (mL/min), mean ± SD	0.11 ± 0.03	0.11 ± 0.02
Baseline stimulated salivary flow (mL/min), mean ± SD	0.19 ± 0.04	0.20 ± 0.02

V2 (1 and 2 is TENS and IFT) (Stimulated)

Although salivary flow increased generally with both treatment techniques, the degree of improvement differed between the groups. There was no statistically significant post-treatment change in either unstimulated or stimulated salivary flow in Group A (TENS) (p = 0.705 and p = 0.07) as in Table 2. Although these within-group variations did not achieve significance (p = 0.369 for unstimulated; p = 0.859 for stimulated), The intra-group comparison for the IFT group is seen in Table 3, where both stimulated and unstimulated salivary flow increased after the intervention. These variations, however, did not reach statistical significance (p = 0.369 for unstimulated and p = 0.859 for stimulated salivary flow). A tendency toward improvement was noted despite the absence of statistical significance, indicating a potential therapeutic advantage of IFT that might become meaningful with a larger sample size. The two-way ANOVA analysis assessing the impact of age and treatment group on variations in salivary flow is shown in Table 4. In unstimulated salivary flow, there was no statistically significant difference between TENS and IFT (p = 0.582). Nonetheless, there was a statistically significant difference in stimulated salivary flow across the groups (p = 0.022), suggesting that IFT is more effective than TENS at increasing stimulated salivary output.

Table 2.

Pre- and post-treatment changes in unstimulated and stimulated salivary flow in Group A (TENS) shows mean difference, standard deviation, and statistical significance for unstimulated and stimulated flow before and after TENS therapy. GROUP B-IFT.

	T	Df	P	Mean diff	s.d
Diff.Unstimulated	-0.394	7	0.705	-0.090	0.22970	Not significant
Diff. Stimulated	-2.072	7	0.07	-0.025	0.123	Not significant

Table 3.

Pre- and post-treatment changes in unstimulated and stimulated salivary flow in Group B (IFT) presents mean difference, standard deviation, and p-values assessing the effect of IFT on salivary stimulation. Between Age Group and Groups (TENS AND IFT).

	T	Df	P	Mean diff	s. d
Diff.Unstimulated	0.369	4	0.369	-0.27	0.267	Not significant
Diff. Stimulated	0.189	4	0.859	0.006	0.035	Not significant

Table 4.

Comparison of treatment outcomes between TENS and IFT across age groups demonstrates intergroup and age-related effects for unstimulated and stimulated salivary flow, including interaction analysis.

Dependent variable		P VALUE	Interpretation
Diff_Unstimulated	Group (TENS vs. IFT)	0.582	Not significant
	Age Group	0.333	Not significant
	Group × Age Group	0.624	Not significant
Diff_Stimulated	Group (TENS vs. IFT)	0.022	Significant
	Age Group	0.563	Not significant
	Group × Age Group	0.330	Not significant

For both unstimulated and stimulated salivary flow, the effect of age group and the interaction between treatment group and age were not statistically significant (p > 0.05), indicating that treatment outcomes were unaffected by age differences in this investigation.

Figures 4 and 5 revealed that the mean salivary flow rates increased in both TENS and IFT, but the intra-group differences were not statistically significant. Unstimulated salivary flow did not differ significantly across the groups (p = 0.582), while stimulated salivary flow was significantly better in the IFT group than in the TENS group (p = 0.022). Because the study was a pilot and had a limited sample size, these results should be considered cautiously.

Fig. 4.

Unstimulated salivary flow difference between TENS (1) and IFT (2). The above graph displays comparative improvement in unstimulated saliva rates between groups

Fig. 5.

Stimulated salivary flow difference between TENS (1) and IFT (2). The above graph highlights the significant increase in stimulated salivary flow in the IFT group

Discussion

Saliva is crucial for maintaining dental health. Xerostomia is the impression of dry mouth and can be associated with diminution of salivary flow. A reduction of salivary flow by 40% to 50% makes the patient symptomatic and prone to develop xerostomia. Oral dryness can significantly impair quality of life and make it difficult to perform daily tasks like speaking, chewing, and swallowing¹².

Menopause is a physiological process that women experience in their fifth decade of life¹³. The reduction of partial or total synthesis of oestrogen during menopause and climacteric causes considerable decrease of salivary flow, resulting in hyposalivation and symptoms of xerostomia¹⁴ Dental caries, Dry lips, Dry mouth, Dysgeusia, Dysphagia, Halitosis, gingivitis, Mastication problems, Mucositis, candidiasis of the mouth, Poorly fitting prostheses, difficulties falling asleep, trouble speaking, Traumatic oral lesions are the clinical effects of xerostomia¹⁵.

Treatments for dry mouth concentrate on causation, prevention, and symptom alleviation through management measures⁵. While certain therapies have been utilized to alleviate xerostomia symptoms, none of them meet the needs of the patients who experience this condition. Electro-stimulation-based non-pharmacological therapies for xerostomia have been explored in recent years¹⁶. Since autonomic nervous control of salivary secretion has been recognized, similar electrostimulation of the neuronal component of salivary secretion may be therapeutically useful for increasing salivary secretion in salivary hypofunction.

Electrostimulation of neuromuscular structures has demonstrated therapeutic potential in a number of medical sciences, including pacemakers and phrenic stimulators. Therefore, applying electric impulses to one or more of the salivary glands should theoretically increase salivary production and reduce the long-term effects of hyposalivation¹⁷.

Although adverse effects including discomfort and facial twitching have been reported, transcutaneous electrical nerve stimulation (TENS) has been utilized as a non-invasive treatment for xerostomia, increasing salivary flow by 68% in healthy patients¹⁸. Interferential therapy is a non-invasive electrical stimulation technique which works by using two medium-frequency alternating currents that intersect (interfere) within the tissues to create a low-frequency “beat” current that efficiently and painlessly stimulates deeper nerves and tissues⁸ IFT therapy helps treat deep tissues since it is an alternating medium frequency current that has decreased skin resistance and causes no pain or discomfort¹⁹.

IFT is frequently used to treat a range of musculoskeletal conditions, such as neck pain, phantom limb pain, and back pain, to relieve both acute and chronic pain. However, little study has been done on how well this treatment works for orofacial pain, salivary stimulation etc²⁰.

In a study by Sinchana et al.²¹ patients with chronic or recurrent TMJ pain was split into two groups where one group received TENS therapy and other IFT therapy and concluded that there was no statistically significant difference between IFT and TENS for pain reduction or muscle tenderness. IFT shows a slightly greater improvement in mouth opening compared to TENS.

lizumi et al.²² aimed to investigate the effects of interferential current electrical stimulation (IFT) on masticatory and swallowing function in comparison with no stimulation condition and concluded that IFT may enhance swallowing and masticatory function even in healthy young adults, suggesting potential utility as a non-invasive adjunctive therapy for disorders of mastication or swallowing.

In a study by Hasegawa et al.⁹ he used interferential therapy to stimulate saliva in young adults, elderly patients and xerostomia patients where the parotid gland was stimulated and assessed for the salivary flow rate unstimulated and stimulated and the treatment was carried out in a single session for 15 min and he also additionally assessed for chromogranin A, stress biomarker and he concluded that IFT showed positive results in salivary stimulation⁸.

The goal of the current study was to evaluate the effectiveness of Interferential Therapy (IFT) and Transcutaneous Electrical Nerve Stimulation (TENS) in treating xerostomia in postmenopausal women, a group known to be at risk for hyposalivation because of hormonal changes, atrophic glandular changes, and related systemic factors. Salivary flow rate was measured both objectively and subjectively before and after treatment, and both therapeutic modalities were used according to established procedures. The results of this study demonstrate that while all modalities improved salivary flow, only the stimulated salivary flow between groups exhibited statistically significant changes. IFT’s greater neuromodulatory activity on autonomic systems and deeper tissue penetration may be responsible for the enhanced effect seen.

Additionally, participants in the IFT group reported better speech, swallowing, mastication, and reduction of oral dryness, all of which are indicative of enhanced oral function and an improvement in quality of life. The results of this study indicate that IFT may be a better non-pharmacological treatment for xerostomia in postmenopausal women, underscoring its potential as a clinically useful modality when long-term symptom control requires salivary stimulation.

Despite the positive findings of this trial, a few limitations must be acknowledged to interpret the outcomes with appropriate caution. The study is limited by small sample size, short treatment duration and follow-up period. Despite using standard clinical methods, salivary flow assessment may still vary because of physiological and patient-related factors. Future studies using sialometry or biomarker-based measures could improve reliability.

Conclusion

Both TENS and IFT demonstrated a trend toward improvement in salivary flow and patient-reported outcomes in postmenopausal women with xerostomia, within the constraints of this pilot trial. These results are preliminary and should be interpreted cautiously, even though IFT showed a relatively higher improvement in stimulated salivary flow. To validate these findings, more randomized controlled studies with bigger sample numbers are needed.

Author contributions

A” Shalini Prabha P—is the primary investigator of the study, conceptualized, collected the sample and the data, interpreted, worked on the manuscript. “B” Anuradha Ganesan—helped in framing the concept and study design. Guided throughout the study and helped in drafting the manuscript. “C” Krithika Chandrasekar Lakshmi—helped in drafting the manuscript and recruiting the samples. “D” Yesoda Aniyan—helped us with recruiting the sample and corrections in the manuscript.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Data availability

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

Declarations

Competing interests

The authors declare no competing interests.

Ethical approval and consent to participate

The researchers were committed and adhered to the principles of the Helsinki Convention and the Ethics Committee of SRM dental college ramapuram, Ethical approval was obtained from the institutional Review board of SRM Dental college (IRB No: 2025/PG/019) and clinical trial registry was done (CTRI/2026/03/105156). After providing the necessary explanations, informed consent was obtained from the patients for participation and for the publication of anonymized clinical data and images in an online open-access journal.