The primary purpose of Sodium Hydroxide (NaOH) as a toothpaste ingredient is to adjust the pH of the paste by making it more basic. It can neutralize the acidic ingredients in toothpaste so that it can be safe to brush with.
Of course that means it isn't necessary in every toothpaste because not all of them have an acidic pH. Usually if you see it as an ingredient, it means the paste is probably acidic without NaOH.
Sodium hydroxide in toothpaste overview:
Description: White odorless solid aka caustic soda or lye.
Benefits: Neutralize acids in toothpaste.
Side effects: Highly corrosive upon contact.
Safety: Relatively safe in toothpaste, no observed adverse effects.
What is sodium hydroxide in toothpaste?
Sodium hydroxide is a common ingredient in various cleaners and soaps with the molecular formula NaOH. It is also known as caustic soda or lye.
Appearance: At room temperature it is a white odorless solid. In liquid form it is colorless and also odorless.
Common uses:
To make bagels and pretzel dough shiny.
Bar soap
Detergents
Drain cleaner
Oven cleaner
Rayon - artificial textiles
Water deacidification
Manufacture of paper
If you're a New Yorker, you've definitely had a bagel or pretzel before and therefore should have eaten sodium hydroxide at least once in your life!
Benefits/function in toothpaste
The reason for adding sodium hydroxide to toothpaste is to make it less acidic so that it becomes safer to brush with. That is why it is often known as a pH adjuster in oral care products.
For instance, some ingredients such as cocamidopropyl betaine can acidify the toothpaste with its 5.5 pH and that can harm the enamel via demineralization. However, adding NaoH can help neutralize the acidity and rebalance the pH back to neutral thus making it safer.
Toothpastes with NaOH:
Pronamel Intensive Enamel Repair
Pronamel Gentle Whitening
Pronamel Active Shield
Pronamel Daily Protection
Also based on my observations, if a toothpaste is not acidic, you will not find NaOH as one of the ingredients. An example would be a SLS based toothpaste which often has a pH of 7-9.5 thus rendering NaOH to be unnecessary.
Acid neutralisation mechanism
When sodium hydroxide reacts with an acid, it forms water and salt.
What you should take away from this is that it is safe to use for buffering acids. The end products are literally plain water and salt. In a later section, I will explain how this ingredient can also be used for deacidifying drinking water so that it is safe to drink.
Side effects
No side effects have been reported from using toothpastes with sodium hydroxide in it. This is because the concentration used in dentifrices are so low that its typically uneventful. It's usually one of the last ingredients on the label.
However, high concentrations of NaoH in other products do have severe adverse reactions which you do need to be cautious of.
Strongly irritating and corrosive. It can cause severe tissue burns that may result in permanent damage.
Inhalation results in swelling. Laryngeal swelling and fluid accumulation in the lungs.
Gastrointestinal symptoms. Stridor, vomiting, drooling, abdominal pain, shock and perforation of the GI tract.
Note: If you google image search "sodium hydroxide burns" you'll quickly understand the severity of its corrosive nature.
Although surprisingly, it does not produce any systemic toxicity since most of the adverse effects are from its corrosive nature. In other words, the side effects are due to bodily tissues coming into direct contact with NaOH.
Safety
Sodium hydroxide is relatively safe to use in toothpaste despite the potential severe side effects from high concentrations. It is FDA approved and listed as, "direct food substances affirmed as generally recognized as safe."
Perhaps its safety can be better understood once you realize that NaOH is also used in making bar soap and also deacidification of drinking water.
Deacidify drinking water
The normal pH range of drinking water is between 6-8.5 but a neutral pH is the most ideal. However, if the water source is too acidic, sodium hydroxide can be injected into the water supply to neutralize the acid and raise the pH.
The benefits of neutral pH drinking water is that it is safer and it doesn't corrode the pipes. Yes, acidic water running through our plumbing system can corrode it.
Makes bar soap
All bar soaps are made using sodium hydroxide via a process called saponification, which converts esters into soap. Yes, the same type of soap that you use to clean your body and hands with.
Mechanism of making soap:
Oil (non-charged) + sodium hydroxide.
Results in glycerol (non-charged) + fatty acid salt (anion).
The fatty acid salt has a hydrophobic tail and hydrophilic head.
Ultimately it is due to the dual hydrophilicity of the soap molecule which gives it the ability to be attracted to both dirt/oil and water at the same time.
Drain openers
You may be interested to know that a lot of drain openers or uncloggers often use sodium hydroxide to do so. A prime example would be Drano.
As you can see, NaOH is an ingredient in it and the way it unclogs your kitchen/bathroom pipes is via saponification. That's right, when you pour Drano down your pipes, it turns all of that fat/grease into soap which can then get washed down with water.
If you recall the instructions for these products, you pour it down the drain and then wait X amount of time. Then you run hot water to wash it through!
Verdict
In my opinion, I think sodium hydroxide is a useful toothpaste ingredient because it can help make the paste less acidic and thus safer to brush with.
It is an ingredient that I would consider using in my own personal toothpaste formulation especially if I were to forego sodium lauryl sulfate. A popular substitute would be cocamidopropyl betaine which is more acidic thus necessitating the inclusion of NaOH. Overall it serves its purpose in preventative dentistry.
This article by your favorite dentist in Long Island City, NY.
