Salivary pH: More Than Just a Number

As discussed in-depth in this blog post, saliva is made up of several different biological factors that contribute to the overall health status of the human body, and it can be used via non-invasive screening protocols – both in-office and at home – to identify early disease processes occurring in both the mouth and systemically.

In addition to the microbial framework of saliva, there are a few other factors that are highly important to oral health that we will discuss in this blog post — salivary pH and salivary buffering capacity.

Keep reading to learn why salivary pH is more than just a simple number!

Salivary pH

At a foundational level, salivary pH is influenced by activities of daily living such as eating, drinking, and oral homecare routines. The process that brings salivary pH levels back to an optimal range after changes initiated by these habits is known as the salivary buffering capacity.

Both the pH level and the buffering capacity of an individual’s saliva contribute to the formation of oral diseases such as dental caries (i.e. cavities) and/or periodontal diseases such as gingivitis and periodontitis, and the process by which this occurs is more complex than you may think.

The Basics of pH

Before we can get into the nerdy side of how cavities and gum disease are influenced by salivary pH levels, we first have to understand what pH is at a basic level (pun intended).

The acronym pH stands for potential hydrogen [8].

It was first defined by S.P.L Sørensen in 1909 [6], and it refers to the degree of alkalinity or acidity of a water solution — remember, saliva is 99% water — and is based on the concentration of hydrogen (H+) ions [11].

More specifically, the term pH is based on a negative logarithm of the hydrogen ion concentration of aqueous solutions [11], meaning there is an inverse relationship between pH and [H+]: the greater the [H+], the lower the pH [5].

The pH of a solution is measured on a scale of 0 to 14 with 7.0 being the midpoint and indicating neutrality, which means a solution is neither acidic nor basic (alkaline) [14].

[14]

As a logarithmic scale, moving one unit either way results in a 10-fold increase in the degree of acidity or alkalinity [14].

Salivary pH and Oral Health

Saliva is one of the most important aspects of oral health as it contributes significantly to the environment of the oral cavity, and oral pH levels have been proven by years of research to impact various states of disease.

Salivary pH is maintained near neutrality with a normal

range of 6.2 - 7.6 and an average reading of 6.7 [2].

Although we are discussing only one feature of saliva — its pH level — it’s important to understand that salivary pH levels actually change based on other characteristics of saliva itself that contribute to the maintenance of pH levels.

Essentially, there are two specific mechanisms of action by which saliva is able to maintain its own pH levels [2]

Salivary flow eliminates the food source for oral bacteria, such as carbohydrates, as well as the acids the bacteria produce by metabolizing said food sources
The process of salivary buffering neutralizes pH levels of saliva after exposure to acidic drinks and food and bacterial byproducts

Some studies have suggested that oral disease severity is correlated with salivary pH levels with more alkaline pH seen in patients with gingivitis and more acidic pH seen with generalized chronic periodontitis [2].

Oral pH and Dental Caries

One of the major oral diseases associated with sub-optimal oral pH levels is dental caries or cavities.

The food and drinks we consume throughout our days (and nights) have a major impact on salivary pH levels. This happens through a process by which the microbes in the oral cavity break down foods we consume and subsequently release acids.

For example, microbes break down carbohydrates and release lactic acid, butyric acid, and aspartic acid [8], thus altering oral pH levels

The constant changes in pH levels associated with food and drink consumption have been explained via the Stephan Curve, which identifies a pH of 5.5 as the critical pH level where demineralization of teeth begins and thus increases caries risk.

[15]

To better understand the Stephan Curve, let’s review the two sample charts below.

[15]

The healthy Stephan Curve (above, left image) depicts an initial pH drop with food and drink intake during breakfast. Over the next hour, pH returns to neutral via the salivary buffering capacity, which we will discuss more below.

The chart then shows a mid-morning snack, lunch, mid-afternoon snack, and dinner
Between all of these meals, the oral pH levels return to an ideal pH level, which is important for prevention of caries.

Conversely, the less healthy Stephan Curve (above, right image) shows what happens to oral pH levels when acidic beverages such as coffee are sipped on throughout the day.

The oral pH levels remain more acidic for longer periods of time, which increases caries risk
Teeth are bathed in saliva below the optimal 5.5 pH level needed for demineralization to begin more frequently and for a longer period of time throughout the day

[13]

This second example of a less healthy Stephan Curve shows how pH levels remain below the optimal level for caries prevention in an individual who sips on a sugary, acidic beverage all morning long. As you can see, this is a habit that should be avoided at all costs to prevent breakdown of tooth structure.

Salivary Neutralization

With constant exposure to different foods, drinks, medications, and other substances, salivary pH levels fluctuate non-stop. Thus, the return to a more neutral pH is essential in caries prevention and overall optimal oral health. Let’s take a look at how this happens.

There are three main ways in which salivary pH returns to the optimal range

Salivary clearance – the process by which substances are removed through swallowing, thus eliminating acids within the oral cavity [4]
Salivary flow rate – allows for the dilution of acids within saliva [4] with a greater flow rate returning oral pH levels to an optimal range more quickly
Salivary buffering capacity — refers to saliva’s ability to resist changes in pH

Salivary Buffering Capacity

In simple terms, buffering helps to neutralize acids and maintain a stable pH in the mouth. A group of three buffering systems can be found in saliva and contribute to salivary buffering mechanisms of action.

Carbonic acid / bicarbonate buffer
Phosphate buffer
Protein buffer

When pH levels change, the buffering systems act to neutralize saliva

and return pH levels to the optimal range of 6.7 pH.

It has been noted that the bicarbonate buffering system is the primary component responsible for buffering saliva as it does the most for returning saliva to an optimal pH level. Conversely, the phosphate system allows for the maintenance of tooth mineral integrity and thus prevents demineralization and carious lesions [4].

As mentioned above, once the pH reaches a critical level (below pH 5.5), enamel demineralization exceeds remineralization [10]
If the acidic conditions persist or are repeated frequently without sufficient time for remineralization, then a caries lesion can develop [10]

The phosphate buffering system pulls phosphate ions from enamel with a salivary pH below 5.5 in an attempt to restore pH balance, which contributes to demineralization of tooth structure and increased caries risk [9].

On the other end, when salivary pH levels reach more alkaline levels, it may contribute to the formation of dental calculus.

Oral pH must elevate above 7.6 to grow dental plaque that plays into the development of periodontal diseases [7].

It’s important to note that the concentration of buffering systems (mainly bicarbonate) grows with the rate of saliva secretion, and the buffering capacity can be ineffective in the case of low flow of unstimulated saliva [3], also known as xerostomia (dry mouth).

Overall, salivary pH levels play a critical role in the maintenance of various factors of oral health, which we know also supports optimal systemic health as well.

Oral pH and Periodontal Disease

In addition to dental caries formation, oral pH levels play a critical role in the development of periodontal disease.

The state of saliva plays a pivotal role in preventing or accelerating gum disease.

Periodontal disease is an inflammatory condition caused by a bacterial infection that affects the supporting structures of teeth, including the bone and ligaments that anchor teeth in place. The disease progresses in stages, from gingivitis (mild inflammation) to periodontitis (severe damage), and if untreated, it can lead to tooth loss.

As mentioned above, the level of severity of periodontal disease is often correlated with salivary pH levels. Essentially, pH first becomes more alkaline indicating gingivitis before it transitions to a more acidic pH as the disease state progresses and bacterial loads change from aerobic to anaerobic.

Overall, changes to salivary pH levels ultimately alter the dynamics of the oral environment that are essential for health, thus increasing the pathogenicity of microbial communities, which initiates and promotes oral diseases.

Supporting the Oral Environment

Research has shown that individuals with reduced salivary flow or those with poor-quality saliva are at greater risk of developing dental caries and more severe forms of gum disease.

Causes of Unbalanced Oral pH

Generally speaking, there are several conditions and habits that reduce the production of saliva or alter its composition, which promotes disease formation.

Below is a list of several factors that should be taken into consideration when determining an individual’s risk for sub-optimal salivary parameters and thus oral diseases.

Xerostomia
- Without enough saliva, plaque buildup increases, and the mouth becomes more prone to bacterial infections, leading to gum inflammation and periodontal disease
Smoking, including e-cigarettes & Cannabis
- Smoking reduces saliva flow and changes its composition, making it less effective in neutralizing acids and fighting bacteria
- Smokers are at a higher risk for gum disease due to reduced salivary defense and the harmful chemicals in tobacco that can directly irritate and damage gum tissue
Medications
- Medications that lower saliva flow can impair the mouth's natural ability to neutralize acids, flush away bacteria, and repair gum tissue, which may result in an increased risk of periodontal infections
Diet
- Foods and beverages that are high in sugar or acidity, such as sodas, citrus fruits, and candy, can lower the pH of saliva, making it more acidic and prone to enamel erosion
Hydration
- Dehydration can reduce saliva flow, diminishing its ability to buffer acids and maintain pH balance
Age
- As people age, the production of saliva tends to decrease, which may impair the mouth's ability to buffer acids
Systemic health conditions
- Medical conditions such as diabetes, Sjögren’s syndrome, and gastroesophageal reflux disease (GERD) can alter the pH and buffering capacity of saliva

Symptoms of Unbalanced Oral pH [12]

Maintaining a balanced pH in saliva is crucial for optimal oral health and overall well-being.

Below is a list of symptoms often associated with unbalanced oral pH levels.

Increase in cavities
Dry mouth
Enamel erosion
Altered taste
Slow wound healing
Periodontal disease

Keep in mind that these symptoms are not only indicators of unbalanced pH but can be warning signs of other oral diseases as well. Make sure you see a dental professional regularly to monitor symptoms!

How to Prevent Unbalanced Oral pH

Individuals with healthy saliva flow and composition are better equipped to prevent the onset of periodontal disease and to maintain strong, healthy teeth over time.

Below is a list of beneficial habits that help maintain optimal salivary pH and buffering capacity mechanisms.

Practice good oral hygiene
- Regular brushing, flossing, and tongue scraping help remove food particles and bacterial plaque that can contribute to acid production in the mouth
- Regular checkups with a dentist can help identify early signs of tooth decay and oral health issues, allowing for timely intervention
Stay hydrated
- Drinking plenty of water helps maintain a healthy saliva flow and supports its cleansing and buffering functions
- Aim to drink water consistently throughout the day, especially if you suffer from dry mouth
Limit sugary and acidic foods
- Reducing the consumption of sugary snacks and acidic beverages can prevent excessive acid buildup and help maintain a more neutral pH
- Alkaline foods like vegetables and dairy products can help maintain a more neutral or slightly alkaline pH
Chew sugar-free gum
- Chewing gum stimulates saliva production, increasing the mouth’s buffering capacity and reducing the impact of acids

BONUS — chewing gum with xylitol limits the proliferation of cariogenic bacteria and reduces biofilm formation!

Avoid smoking and limit alcohol consumption
- Both smoking and alcohol use can dry out the mouth and reduce the effectiveness of saliva
- Quitting smoking and limiting alcohol consumption can drastically improve both salivary and periodontal health
Avoid antimicrobial mouthwash
- Look for mouthwashes that promote moisture, support commensal (i.e. beneficial) bacteria growth, and help balance the pH in your mouth

Research has shown that frequent use of antimicrobial mouthwashes containing alcohol and/or essential oils kills commensal bacteria within the oral cavity, reduces nitric oxide levels (which increases blood pressure), and contributes to more acidic salivary pH levels (increasing risk for dental caries and periodontal disease).

Consider Medication Adjustments
- If you notice xerostomia as a side effect of a medication, talk with your prescribing doctor about a possible alternative medication or ways to manage symptoms

For patients with xerostomia and/or high caries risk, I highly recommend OraBio’s Periovance Dry Mouth Gel to support oral moisture and pH levels during the daytime and while sleeping.

For dental healthcare providers looking to incorporate chairside assessment of salivary pH levels, use of GC America's Saliva-Check Buffer system is easy to implement and provides point-of-care results that can be discussed with patients during their visit.

GC America saliva-check buffer — GC America Saliva-Check BUFFER In Vitro Test for pH & Saliva Buffering Capacity

Use of this system allows providers to discuss individualized care plans with patients based on their personal risk levels. Because it tests for salivary pH and buffering capacity, it is a great indicator of a patient’s risk of dental caries and can identify a shift toward parameters associated with periodontal disease.

As you can see, saliva is much more than just a fluid in the mouth—it is an essential defense mechanism for maintaining oral health. Understanding the role of salivary pH and buffering capacity is crucial for recognizing how they protect the teeth and soft tissues from the harmful effects of acids and bacteria. By maintaining a healthy lifestyle, staying hydrated, and practicing good oral hygiene, we can support our saliva’s natural functions and keep our smiles bright and healthy.

Talk soon,

Liz Laney, BSDH, RDH

Oral-Systemic RDH & Educator

Have questions about periodontal disease and systemic health or want to know more? Check out the forum and start a conversation!

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