Introduction

Saliva plays an important role in preserving oral health. Saliva cleans food particles and bacteria, reducing the chances of plaque. It also protects from dental caries (tooth decay). Overall, the properties of saliva make it a vital component in maintaining dental health.¹

Brief overview of tooth decay

Bacteria in the mouth feed on sugars and produce acids that weaken the enamel and cause tooth decay, leading to dental cavities or caries.¹ If the decay reaches deeper layers of the teeth, it can affect the nerves and roots, resulting in tooth sensitivity, particularly when consuming cold or sweet foods and beverages. Severe tooth decay may require tooth replacement options, such as bridges. Such damage to your teeth leads to significant discomfort, even tooth loss, which is a possibility. Tooth decay has become less common compared to previous decades, largely attributed to improved oral hygiene practices and the widespread use of fluoride toothpaste.²

Importance of saliva in oral health

Human salivary glands generate approximately 0.5 to 1.5 litres of saliva within 24 hours. Saliva comprises electrolytes, and proteins from both salivary glands and serum, along with small organic molecules, metabolites, and residue from microorganisms.³ It plays multiple roles within the oral cavity especially protecting against dental caries (tooth decay). The buffering quality of saliva maintains the pH balance in the mouth and helps prevent acidic conditions that contribute to enamel erosion. Saliva also cleans food particles and bacteria, reducing the chances of plaque. Additionally, saliva contains antibacterial components that prevent the growth of harmful bacteria. Overall, the properties of saliva make it a vital component in maintaining dental health¹.

Composition of saliva

Majorly, we have three salivary glands namely, the parotid, submandibular, and sublingual, along with numerous minor glands. These different types of glands produce serous, mucous, or seromucous secretions, which contain proteins and many key compounds. Health conditions and physiological requirements play important roles in the composition of saliva.⁴ Saliva consists of over 99% water- containing a wide range of electrolytes like sodium, potassium, calcium, magnesium, bicarbonate, and phosphates. Additionally, saliva contains immunoglobulins, proteins, enzymes, mucins, and nitrogenous compounds.⁵

Role of saliva in combating tooth decay 

The terms "whole saliva," "mixed saliva," or "oral fluid" refer to the fluids found within the oral cavity, and comprise a complex blend of proteins and various molecules with multiple origins. These components interact with  related functions in the following general areas:⁵

• Bicarbonates, phosphates, and urea act to modulate pH and the buffering capacity of saliva
• Macromolecule proteins and mucins serve to cleanse, aggregate, and/or attach oral microorganisms and contribute to dental plaque metabolism 
• Calcium, phosphate, and proteins work together as an anti-solubility factor and modulate demineralization and remineralization; and 
• Immunoglobulins, proteins, and enzymes provide antibacterial action

Saliva's consistent delivery of fluoride to the tooth surface underscores the significance of salivary fluoride in protecting against cavities, primarily by fostering remineralization and minimizing demineralization.⁶

Factors affecting saliva's role

A dry mouth stands out as a significant factor contributing to an elevated risk of tooth decay.⁷ Reduced saliva secretion and a decreased buffer capacity result in ineffective removal of microorganisms and food particles, inadequate neutralization of acids, and reduced potential for remineralization of initial enamel. Different factors, like diseases and medications, have an impact on salivary secretion through various mechanisms, which result in dysfunction of the salivary glands and cause oral issues such as xerostomia, dental caries, and fungal infections.⁸

• Diseases: Salivary gland function is affected by some diseases like Sjögren's syndrome, diabetes, HIV/AIDS, autoimmune disorders, and neurological disorders
  • Sjögren's syndrome is an autoimmune disorder that primarily impacts the salivary glands, which reduce saliva production and dry mouth (xerostomia)
  • Neurological disorders like Parkinson's disease can interfere with the neural signals that reduce saliva production by the salivary gland
• Medications: Medications such as antihistamines, antidepressants, diuretics, and antihypertensive drugs decrease the production of saliva as a side effect. These medications may interfere with the normal functioning of the salivary glands or affect the nerves that control saliva production. Additionally, chemotherapy and radiation therapy used in cancer treatment can damage the salivary glands, leading to decreased saliva production and associated oral problems
• Consequences: Reduced saliva production can lead to
  • Xerostomia is characterized by a dry mouth and difficulty chewing, swallowing, and speaking 
  • Inadequate saliva flow also increases the risk of dental caries (tooth decay) and periodontal (gum) disease due to decreased buffering capacity and impaired remineralization of teeth 
  • Furthermore, the lack of saliva can create an environment conducive to fungal infections, such as oral thrush (caused by Candida albicans), due to the decreased antimicrobial properties of saliva⁸

Tips to enhance saliva's role

Your healthcare provider will assess your different parameters, like medication intake, and medical background, and conduct oral examinations to understand the reason behind your dry mouth. In some cases, blood tests, imaging scans of your salivary glands, or saliva production tests may be necessary. If Sjogren syndrome is suspected, a biopsy, involving a small sample of cells from your lip's salivary glands may be conducted for further analysis. These are some tips to increase saliva production practically:⁹

1. Chew sugar-free gum or sucking on sugar-free hard candies are good options to stimulate saliva flow. However, excessive consumption of xylitol, commonly found in these products, may lead to diarrhoea
2. Reduce caffeine intake as it can enhance dry mouth symptoms
3. Avoid mouthwashes containing alcohol, as they can lead to dryness
4. Stop using tobacco, including smoking or chewing tobacco
5. Regularly sip water and stay hydrated
6. Use a mouthwash specifically formulated for dry mouth, preferably containing xylitol, such as Biotene Dry Mouth Oral Rinse, bio Xtra Dry Mouth Ultra Mild Mouthrinse, or ACT Dry Mouth Mouthwash
7. Practice nasal breathing rather than mouth breathing
8. Increase nighttime air moisture by using a room humidifier

Summary

Various attributes and functions of saliva significantly contribute to dental erosion. Salivary clearance aids in gradually removing acids by swallowing, while saliva's buffering capacity helps neutralize and counteract dietary acids. Salivary flow enables the acids to be diluted effectively. Moreover, saliva contains an abundance of tooth mineral constituents such as calcium, phosphate, and fluoride, which are essential for remineralization.

Take care of your saliva to prevent tooth decay! Hydrate with water, chew sugar-free gum, and skip caffeine. Avoid alcohol mouthwashes and tobacco. Try saliva substitutes and specialized mouthwashes. Stay away from drying medications and breathe through your nose. Boost nighttime moisture with a humidifier. Your saliva is your smile's best friend. 

FAQs

Can saliva have an impact on dental decay?

The preservation of general health depends on saliva. Saliva acts as a defence mechanism against oral infections and tooth decay. The antibacterial qualities of saliva fight harmful microorganisms that cause illnesses while also coating the teeth and acting as a buffer against them

How does saliva shield the mouth cavity?

The four main ways that saliva protects teeth against cavities are through the following mechanisms: 

• buffering ability
• dilution and elimination of carbohydrates 
• other chemicals, balancing demineralization and remineralization 
•  its antibacterial qualities

Does saliva combat plaque?

Saliva is necessary to maintain dental health. One of its most important functions is to regulate dental plaque. The bacterial film sticks to teeth and can lead to gum disease and tooth damage

How acidic is the saliva?

A healthy mouth typically has saliva at a pH of 7.4, with a goal range of 7.0 to 7.5. A pH dip to the 6.25 to 6.75 range raises concerns. Slight lifestyle adjustments within this range can help mitigate the negative consequences of an unbalanced salivary pH

Is saliva affected by toothpaste?

The amount of toothpaste applied and the technique used to rinse it off are thought to not have an effect on the salivary flow rate

What is the quantity of enzymes found in saliva?

List of the enzymes that are mostly found in saliva is as follows: Enterokinase, chymotrypsin, aminopeptidase, pepsin, lactase, rennin, nuclease, nucleosidase, maltase, and sucrase are among the enzymes

Which hormones do salivary glands release?

Salivary peptide hormones such as:

• Transforming growth factor-alpha (TGF-alpha) 
• Epidermal growth factor (EGF)
• Amines like melatonin