A Treat to Xerotes: An Emerging Trend

Introduction

Sreenby (1988) defined xerostomia as the feeling of oral dryness and it is the result of salivary gland hypofunction. Patients with oral dryness frequently express discomfort because of glossodynia, dysgeusia and polydipsia.¹ Xerostomia can also give rise to notable incidence of carious activity, parotid enlargement, oral mucositis, sialolithiasis and halitosis.² Xerostomia can be caused by disturbance of the reflex that evokes salivation at the receptor site, the neural pathway, the peripheral ganglion or the effector site.³ In Sjogren’s syndrome, effector site gets disrupted causing destruction of glandular tissue with replacement of acinar cells with scar or fatty tissue.⁴ The mechanism in radiation therapy is contemplated to be either replacement of secretory elements as a result of high energy electron or neutron bombardment or changes in the vascular supply that cause diminution of blood flow to the gland tissue resulting in hyposalivation.⁵ Use of alcohol free mouthwashes, salivary substitutes and herbal remedies gives symptomatic aid, but there is high incidence of recurrence when treatment ends. Drugs like tacrine, pilocarpine, carbachol and muscarine promotes salivation, at the same time these drugs have adverse effects such as sweating, digestive disorders, heart burn, frequent urination, diarrhoea and vomiting.⁴ Keeping focused on the adverse effects, patient desires treatment options which have minimal or no untoward effects. Then considering patients comfort, non-pharmacological treatment modalities have come into action as recent advancements, which can give immediate response by providing constant relief from xerostomia without interfering with the normal oral function. This article aspires to review various neuroelectrostimulation devices and their effectiveness in managing xerostomia patients.

Discussion

In salivary glands, the very necessary role is played by the autonomic nervous system where cholinergic agonists acting on muscarinic and parasympathetic receptors produce saliva with high electrolytes, and sympathetic stimulation induces secretion of portion of proteins from saliva.⁶ The application of electrical stimulation to the reflex involves afferent receptors and nerves carrying impulses induced by a stimulation, the salivary nuclei and an efferent path consisting of parasympathetic and sympathetic autonomic nerve bundles that separately innervate the glands, thereby increasing salivation and indirectly decreasing the longterm effects of xerostomia. Using this concept, there have been technological advancements in xerostomia management by using salivary pacemakers.⁵

Salitron system was the first neuroelectrostimulatory device acclaimed by the US Food & Drug Administration in 1988, and in 2006 Dr. Andy Wolff introduced masterclass “saliwell” - an intraoral electrostimulation of the salivary glands to treat xerostomia in XVIII congress of the European Association for Cranio-Maxillofacial Surgery, Barcelona, Spain. In 2008-10, safety and performance evaluation of an electrostimulation mounted on an intraoral removable appliance [saliwell gen narino] for managing xerostomia was also performed.⁷

Relative contraindications of neuroelectrostimulatory devices such as, in epilepsy patients, the impulses arising from neuro electro stimulatory devices could cause seizures. Also in pregnant patients, these devices are cautiously used.

There are a few absolute contraindications regarding the use of neuroelectrostimulatory devices such as, in patients with implanted cardioverter defibrillator (ICD) they could cause ICD to malfunction.⁸

In patients undergoing head and neck surgery, using unipolar electrocautery may cause interference with the function of implanted device and may cause burns at the electrode site.⁹

Salivary Pacemakers

Salitron System [1^st Generation Device]

The outcomes of first experiment to regulate neuroelectrostimulation to bring down xerostomia was marketed in the US [ BioSonics.inc, USA]. A system which was battery powered comprising of a control module, a cord and a stimulus probes with two electrodes was introduced as salitron system. It was held daily for few minutes by user between palate and tongue.⁴ It was discovered that using such cumbersome neuroelectrostimulation device more often led to an instantaneous response and a collective long-term response in xerostomia patients. As the device gave favourable results in proof-of-principle studies and did not have any side effects, it was accepted by Food and Drug Administration in 1988. Its extensive utilisation was impeded by its heavy size, high price and lack of user friendliness. To overcome such drawbacks of this salitron system, a European commission-funded research consortium developed a miniature intraoral neuroelectrostimulator to reinforce salivation. A removable intraoral splint appliance and an osseo integrated dental implant were the two neuroelectrostimulatory devices introduced thereafter.⁵

Study done by Strietzel FP, Martin-Granizo R, Fiedele S, Lo Ruso L, Mignogna M, Reichart PA, demonstrated that neuroelectrostimulation ensues remarkable reduction in dryness of mouth, resulting in positive response from patients’ subjective condition. No notable adverse effects were recorded.¹⁰

Saliwell Gennarino [2^nd Generation Device]

A neuroelectrostimulatory intraoral splint appliance which reinforced salivation was then well known as saliwell gen narino and it has a mouthpiece and button to start and shut the device. Gen narino has a controlling circuit module completely closed between two sheets and power source which includes two 3V batteries. An electronic module connected to two electrodes made up of biocompatible material emerges from a sheet of plastic and meets the lingual side of mandibular arch.⁴ The only advantage of saliwell gen narino over salitron system is user friendliness, where patient can control the appliance by self at any given time according to his or her convenience. The positive effects were endured by the neuroelectrostimulating intraoral splint appliance for a time period of eleven months as proved by Simon D Tran, Alajbeg I and Densie P Falaco.¹¹

The device was designated only for the patients with xerostomia due to head and neck radiotherapy, Sjogren’s syndrome, diabetes, HIV infection, side effects of certain medications, chemotherapy and nerve damage from injury or surgery, and was contraindicated in patients who are allergic to the surface materials of the device such as platinum, iridium, polyurethane and poly carbonate. In patients under the age of 18 years, specific protocol needs to be followed for the clinical use of saliwell gen narino such as, in pregnant patients, device is not allowed, whereas it is rendered safe and secure with other extraoral stimulatory devices. When device battery runs out of power, it is to be replaced on a yearly basis. Gen narino can substitute drug therapy especially in severe cases. It is allowed to be used alongside sialagogues, particularly in dry eye.¹² The study by Zadik Y, Zeevi I, Luboshitz-shon N, Dakwar N, Wolff A, Shapira MY, et al, demonstrated that gen narino is innocuous in chronic graft vs. host disease in relation to oral mucosa. In addition, symptomatic relief in xerostomia patients was observed by the application of Gen narino.¹³

Saliwell Crown [3^rd Generation Device]: [Implant Supported Miniature Device]

Few individuals often require continual salivary gland stimulation. Therefore a miniature device which is neuroelectrostimulatory can be implanted forever into the oral cavity. This device was helpful over second generation device as it limits the inconvenience related to the periodic exertion and displacement of a splint appliance. Saliwell crown resembles the minimized and packaged constituents of saliwell gen narino. This device was setup on an osseointegrated implant which is commercially accessible and has a sensor embedded inside the device to determine dryness of mouth. Apart from its high price, this device is capable of fitting into the ideal best non-pharmacological way to become more appropriate and more innocuous means to treat xerostomia.⁵

Salipen

The very new advancement in neuroelectrostimulation is a device called salipen, which is very user friendly and non-invasive. Salipen has two arms which are flexible and at the tip of each arm, it has an electrode which is positioned below the tongue. No electric stimulation is experienced and the effectiveness of this practice was certified in various clinical trials in many countries. The device must be placed in the oral cavity for one or two minutes in a day for utilising it effectively in treating xerostomia.⁴ But precautionary measures should be taken before using this appliance in individuals having psychiatric and psychological disorders, cardiac pacemaker, pregnancy and other neurological disorders in the cervical region. Salipen is more advantageous compared to other devices as it is easy to use and noninvasive.¹⁴

Conclusion

Xerostomia as it is known to affect the oral cavity indirectly affects quality of life by affecting other organ systems. Using pharmacological therapeutic agents adversely affects organ system by multiple folds. The new non-pharmacological approach is efficacious in treating xerostomia and the systemic ailments arising from it while not intervening with any other systems other than increasing salivation by neuroelectric stimulation. Thus, it resolves ill effects arising from pharmacological approach of treating xerostomia and raises the standard of living of patients, both physiologically and psychologically.

Conflict of interest

None.