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= Artificial saliva =

Artificial saliva refers to synthetically produced liquid that mimics the natural secretion of saliva, composed of electrolytes such as calcium, potassium, sodium and enzymes which helps digestion and protect oral health. It is primarily used to alleviate the symptoms of xerostomia, a condition that depletes moisture in the oral cavity, arising from various causes such as Sjögren's syndrome, neuropathies and side effects of radiation therapy in cancer treatment. Artificial saliva serves its purpose by mitigating difficulties in speaking, chewing, and swallowing and compensating for the protective effects against oral infections and dental decay.

As an over the counter product, artificial saliva is available in various forms such as sprays, gels, lozenges, and mouthwashes. Artificial saliva products are designed for ease of use and targets a variety of preferences and needs. While it does not cure the underlying causes of dry mouth, it serves as a symptomatic relief tool to improve comfort and oral health of individuals affected by xerostomia. To expand artificial saliva’s functionality, current research focuses on improving formulations to more closely replicate the complex biological nature of natural saliva. This includes efforts to incorporate substances that can stimulate the natural production of saliva in patients whose salivary glands retain partial functionality, with the goal to restore normal saliva-producing ability.

The use of artificial saliva may present challenges and limitations despite its benefits, including variability in effectiveness among different users and the potential need for frequent application. In extreme cases, artificial saliva could also elicit severe allergic responses. In the long run, there are also uncertainties over the impact of artificial saliva on microbiota balance in the oral cavity, which is crucial in maintaining both the dental and gastrointestinal health.

Composition
Artificial saliva comprises an array of constituents designed to mimic the natural functions of human saliva. The composition typically includes buffering agents, cellulose derivatives, and flavouring agents as core components. Each plays a pivotal role in the efficacy and palatability of the product.

Buffering agents
Buffering agents in artificial saliva maintain the pH levels, ensuring the oral environment remains within the optimal range for enamel protection and microbial balance. A stable pH is essential for preventing dental caries and maintaining oral health. These buffering agents neutralise acidic substances in the oral cavity, thereby safeguarding tooth enamel and soft tissues from acid-related damage.

Cellulose derivatives
Cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose are used as rheological modifiers. These compounds are responsible for the viscosity and texture of artificial saliva, enabling it to adhere to oral tissues and provide a protective, lubricating film. This viscosity is necessary for individuals with dry mouth conditions, as it aids in speaking, swallowing, and general comfort by simulating the sticky consistency of natural saliva.

Flavouring agents
Flavouring agents are added to enhance the taste and acceptability of artificial saliva. These agents can mask any unpleasant flavours inherent in the other components and make the user's experience of using artificial saliva more pleasant. Flavouring agents encourage the user's compliance with the treatment regimen, mainly when long-term use is necessary.

Mechanism of action
Artificial saliva functions through chemical and physical processes that simulate human saliva's natural properties and activities. The mechanism involves moisture restoration, lubrication, and protection of the oral mucosa, as well as enzymatic activity that aids digestion and oral hygiene.

Moisture restoration
The primary function of artificial saliva is to restore moisture in the oral cavity, which is often lacking in individuals with hyposalivation or xerostomia. Water, a central component of these products, provides moisture, relieving dry mouth symptoms.

Lubrication
Lubrication is achieved by including viscosity-enhancing agents such as cellulose derivatives. These agents increase the thickness of the artificial saliva, allowing it to coat the oral tissues effectively. This coating action replicates the lubricating film that natural saliva provides, enabling essential functions like speaking, swallowing and maintaining comfort for the user.

Protection of oral health
Artificial saliva serves to protect oral health management through two primary mechanisms: chemical and physical. The chemical aspect involves the regulation of the oral cavity's pH, which is achieved by including buffering agents in the artificial saliva formulation. These agents are critical in neutralising acids in the mouth, helping prevent dental caries and maintaining a healthy microbial environment. The physical aspect relates to coating oral tissues with a lubricating layer. This layer is formed due to the viscosity of artificial saliva, which is adjusted through various rheological modifiers. The lubricating film aids in the protection of oral mucosa from dryness and abrasions, ensuring comfort during daily activities such as speaking and swallowing.

Enzymatic Activity
While not all artificial saliva products contain enzymes, those that do include components such as lysozyme, lactoferrin, or peroxidase, which mimic the antimicrobial and digestive functions of natural saliva, these enzymes contribute to the breakdown of food particles and inhibit the growth of harmful bacteria, thereby improving oral health and assisting in the digestive process. Binding to Mucous Membranes

The artificial saliva's viscosity facilitates the binding to mucous membranes and ensures adherence to the oral tissues. This interaction allows for sustained lubrication and protection, which is beneficial for individuals requiring long-term management of dry mouth symptoms. The interaction with mucous membranes also aids in the retention of the product within the oral cavity, preventing rapid clearance and prolonging the moisturising and protective effects.

Available products
Artificial saliva is available in various forms, including liquids, sprays, gels, oils, mouthwash and toothpaste. The products vary in chemical-physical properties, including viscosity, pH, buffering capacity, superficial tension, density, and spinnbarkeit.

Liquids
Artificial saliva in liquid form is the most prevalent type available on the market. It is designed to closely replicate the rheological properties of natural saliva, including its viscosity and density, which are essential for lubricating and protecting oral tissues. These properties are evaluated using specific measurements such as kinematic and dynamic viscosity, which help determine the liquid's flow characteristics and its ability to coat and adhere to the oral mucosa.

Sprays
Artificial saliva sprays are a convenient and targeted delivery method for individuals who require immediate relief from dry mouth symptoms. These sprays distribute a fine mist, which can directly coat the oral mucosa and rapidly alleviate discomfort. The chemical-physical properties of sprays, including their pH and superficial tension, are formulated to ensure that the product spreads evenly across affected areas, providing a swift and effective reduction in dryness and irritation.

Gels
Gels represent a more viscous option for artificial saliva. Their higher viscosity ensures a prolonged retention time on oral tissues, making them particularly suitable for overnight use or for individuals with severe dry mouth conditions. Including cellulose derivatives in gels gives them their characteristic thickness, which creates a sustained, moisturising barrier. Gels are often assessed for their spinnbarkeit, a measure of their ability to stretch and form threads, simulating the stringy nature of natural saliva, which is fundamental for creating a cohesive and lubricating oral film.

Oils
Artificial saliva oils are a less common form. These oils can provide a durable lubricating layer on oral tissues, which water-based products may not offer. Oils differ from aqueous solutions in density and viscosity, and their interaction with the oral mucosa can result in a distinct sensation for the user. While less widely studied or available, oils may be suitable for specific cases where a more tenacious lubricating effect is desired.

Mouthwash
Mouthwashes formulated as artificial saliva can moisten the mouth and provide cleansing. They often contain antibacterial agents, fluoride, and primary moisturising components. The rheological properties of mouthwashes, such as viscosity and surface tension, are tailored to allow the liquid to flow freely around the oral cavity, ensuring even distribution and contact with all oral surfaces. This type of artificial saliva is typically used as an adjunct to daily oral hygiene practices.

Toothpaste
Toothpaste formulated with artificial saliva components provides moisture while promoting oral hygiene. Including cellulose derivatives and other agents helps maintain a moist environment in the mouth, which is particularly important for individuals with dry mouths who may be more susceptible to tooth decay and gum disease. The consistency of these kinds of toothpaste can clean the teeth and coat the oral mucosa.

Allergic reactions
Side effects of artificial saliva are relatively uncommon, but still exists with varying severity. Minor side effects might not necessitate medical attention and typically diminish as the body adjusts to the treatment. However, in certain instances, users may experience symptoms indicative of an allergic reaction, such as rash, hives, itching, and swelling of the mouth, face, lips, tongue, or throat. Difficulty in breathing, swallowing, or speaking, and unusual hoarseness or chest tightness, are severe side effects requiring immediate medical attention.

Restoring microbiota
On the other hand, the effect long term usage of artificial saliva on the oral microbiota is uncertain. Xerostomia associated hypo-salivation is found to be linked to shifts in the oral microbiome causing higher abundances of Candida spp. (C. albicans), Staphylococcus spp. and cariogenic species, which leads to formation of dental plaques and candidiasis of oral mucosa increasing the risk of lung formation. However, research has shown that commercially available artificially saliva has not shown significant impact on reducing the adhesion of these bacteria on biomaterial mimicking the oral mucosa, suggesting potential ineffectiveness of artificial saliva in restoring balance in microbiota hence protecting oral health.