Tooth Decay – Guide

Written & Reviewed by Dr David Chen

This is your complete guide to tooth decay (cavities) which encompasses everything that you need to know about it and what to do if you get it.

tooth filling joke with canoli


Tooth decay is a dental condition in which the bacteria in your mouth cause holes in your teeth. The bacteria accomplishes this by consuming the sugar and carbohydrates that we eat and produce acid as a byproduct. This acid will erode through the enamel and form an actual hole which we call a cavity. The very definition of a cavity is a hole.

It is important to note that it is impossible to eliminate the bacteria from our mouths and they will always be there. However, depending on our lifestyle choices they may go through periods of high activity and inactivity. For that reason there is no cure for tooth decay but it can at least be managed like any other disease, hypertension and diabetes.

The layperson may call it a cavity but dentists call it dental caries, signifying that it is an oral disease that needs to be managed.


According to the National Institute of Dental and Craniofacial Research (NIDCR), dental caries is very common and it becomes more prevalent as we age.

Age (years)% with tooth decay
Tooth Decay Statistic by Age


The early stages of tooth decay are typically asymptomatic and very difficult to detect. However as it progresses and gets bigger, certain signs and symptoms start to appear.

Signs and symptoms of decay:

  • Brown or Black discoloration. Cavities often have a distinct brown/black color to them.
  • Cavitation. If you can visually see a hole in the tooth. Pitting in the enamel is also valid.
  • Chewing pain. It hurts when you bite down or chew.
  • Fractured tooth. Advanced stage decay will weaken the tooth to the point where pieces start to break off on their own.
  • Malodor. Cavitated lesions will trap food and that can cause bad breath or taste.
  • Toothache. Tooth pain that may occur spontaneously or when provoked such as while eating or drinking.
  • Sensitivity. Dentition feels sensitive when you eat hot, cold, sweet, sour, spicy, or acidic foods and beverages.
  • Swelling. When left untreated for an extended period of time it can turn into an abscess.
  • White spots. Patches or splotches of opaque white on your enamel is a sign of demineralization. That is what is known as a pre-cavity.
  • Part of tooth fell out. If parts of your decayed tooth are falling out, it is an indication of later stages of a cavity.

When to see a dentist

If you suspect that you have any of the associated symptoms, we highly recommend scheduling a dental check up or consultation. It will need a proper diagnosis and a treatment plan. The advanced stages are often untreatable with home remedies.

Even if you’re not feeling any symptoms we still recommend going in for a check up especially if it has been more than 6 months. As a reminder, the early and beginning stages of cavities are often asymptomatic. You want to catch them early so that you can treat them conservatively.


Cavities are caused by oral bacteria in plaque that produce acid whenever we eat sugars/carbohydrates. Since plaque sticks to the surfaces of the enamel, the acid byproducts will directly erode the enamel and form a hole in it.

Bacteria and sugar are an over simplified explanation of how tooth decay forms. From a broader conceptual understanding, the entire decay mechanism can be summed up by net pH over time.

Essentially when your mouth stays below the critical pH level of 5.5 for an extended period of time, you will end up with a cavity. Therefore the risk factors that influences the formation of tooth decay are lifestyle habits that either decrease or increase the pH in the mouth.

pH increasing activities:

  • Brushing
  • Flossing
  • Mouth rinsing
  • Drinking water throughout day
  • Minimizing carbohydrates/sugars
  • Decrease snacking
  • Fluoride or nano-hydroxyapatite

pH decreasing activities:

  • Frequent meals or snacking
  • Sweet foods
  • Spicy foods
  • Sour foods
  • Acidic foods
  • Smoking
  • Alcohol
  • Poor oral hygiene habits

Progression of cavities

Dental caries will progress through the stages of tooth decay sequentially without fail when left untreated.

  1. Demineralization. It starts with the tooth weakening by losing minerals in the enamel.
  2. Enamel decay. If the enamel demineralizes enough, it will form a cavity.
  3. Dentin decay. Untreated enamel decay will grow large enough and penetrate the dentin.
  4. Pulp decay. Untreated decay in the dentin will eventually reach the pulp.
  5. Abscess. Once the pulp is infected, the infection can travel down to the tip of the root and form an abscess.

It is important to understand that the entire progression of dental caries all begins with demineralization. If you eat or drink acidic foods/beverages, the enamel will start losing minerals. You do it enough times and a hole will form.

demineralization remineralization of teeth
Credit: Sangi Co

The good news is that if you brush with fluoride or hydoxyapatite toothpastes, you can reverse the process and remineralize the teeth. However the reversal process can only happen while the lesion is still located in the enamel. Once it reaches the dentin, it will become irreversible.

Types of cavities

Decay can form on any surface of your tooth. If it is exposed to the oral environment and plaque can attach to it, it is fair game. We can broadly categorize them into three groups.

  • Pit and fissure. These occur in the grooves of your teeth. They are at the highest risk for decay especially if the grooves (pits and fissures) happen to be deeper than usual.
  • Smooth surface. This is decay that happens outside of the pits and fissures. The most common one would be in between the teeth where you floss, which we call kissing cavities.
  • Root surface. As its name implies, this is a cavity that is on the surface of your tooth root. You typically won’t get these unless you have gum recession, which exposes the root to the oral environment.
Type of CavityAffected tooth surfaces
Pit and fissureOcclusal (chewing surface); Buccal (cheek facing)
Smooth surfaceMesial and Distal (in between teeth); Lingual and Buccal (tongue/cheek)
Root surfaceAnywhere on the root
The cavities and where surfaces they occur


You may use the symptoms we listed above as a guideline for whether or not you should go in for a dental consultation. However, just because you’re experiencing one or more of the signs/symptoms it is not definitive that you’ve a cavity until it is diagnosed by a dentist.

How cavities are diagnosed:

  • Clinical examination. Using a combination of what your tooth clinically looks like and a dental explorer, your dentist will be able to tell. The explorer is a metal instrument with a sharp end that can detect caries via tactile sensation. The tooth surface will feel soft when you prod it with the explorer. Non-decayed teeth will feel rock solid.
  • Dental x-rays. As good as your dentist may be with the clinical exam, they can’t see in between your teeth. The purpose for taking bitewing x-rays is to allow them to see cavities that are in between your teeth.
  • Caries detection tool. Recently, there has been certain lasers which have been marketed as being able to detect cavities. It looks like a wand or pen which you shine over the tooth and it will tell you if you have something or not.

There are many brands of the caries detection tool but the video above shows the DIAGNOdent pen. It demonstrates how it is able to detect things that a clinician’s eye may miss.

However we must say that despite the technology being around for awhile, it hasn’t received mass adoption. Most dentists find it more than adequate just using a clinical exam with x-rays.


Treatment for tooth decay will differ depending on the severity of the cavity and which stage it is currently at. If you catch it early you can treat it conservatively but if you catch it late, it will become more complex.

Treatment for demineralization

Demineralized enamel can be remineralized by using a remineralizing agent such as fluoride or nano-hydroxyapatite. These can often be found in toothpaste and other oral care products.

It is a very conservative treatment approach since it requires zero drilling from your dentist. For this process to be successful you must stay on top of your oral hygiene and have it re-evaluated by your dentist every six months.

Treatment for enamel and dentin decay

  • Dental filling. For smaller sized lesions, a conservative tooth filling will be adequate. Typically if the decay is less than 50% of the tooth, this method should work.
  • Crown. If the lesion encompasses more than 50% of the entire tooth, the filling would be inadequate. You would need a much stronger restoration like a dental crown that can protect the entire tooth.

Treatment for pulp decay and abscess

  • Root canal. Lesions that have reached the pulp or formed an abscess, the bare minimum would require a root canal. This procedure removes the infected nerve from the tooth. Sometimes if there is facial swelling present, you may need it drained as well.
  • Extraction. Tooth decay can mostly be treated but if it becomes too severe, the tooth may be deemed hopeless. For severe cavities, a tooth removal may be the only option. Afterwards you would need to replace the missing tooth with an implant.


Caries is a disease but it can be managed. When you practice good habits the cavity causing bacteria will become less active and less likely to cause tooth damage.

Oral hygiene tips for prevention:

  • Brushing after every meal. You may find it a bit excessive but if you can brush for two minutes after every meal, you’d be surprised at what it can do. To make it more effective you should use a remineralizing toothpaste.
  • Mouth rinsing. Periodic rinses can help bring the pH in your mouth back to neutral. If your condition is severe enough, you can get prescribed an antibacterial rinse.
  • Regular dental check ups. Seeing your dentist every 6 months for a cleaning can help keep your teeth and gums healthy.
  • Dental sealants. For children, tooth sealants can help prevent pit and fissure cavities. Adults typically do not tolerate it because it makes the bite feel “high”.
  • Fluoride treatments. Those who are at high risk for cavities may benefit from professional fluoride treatment. These products are highly concentrated in fluoride.

Nutritional tips for prevention:

  • Drink water. About 73% of the public water system in the US is fluoridated. Simply drinking water throughout the day can wash away plaque and help remineralize teeth.
  • Minimize snacking. Whenever you eat or drink, the pH in the mouth drops and the bacteria become active. It only gets exacerbated if you’re having sweets.
  • Healthy diet. Consuming a diet that contains a lot of minerals and vitamins which can help repair and strengthen your teeth.
    • Minerals – Calcium, Phosphorus, Fluoride
    • Vitamins – Vitamins A, C D, K; Potassium


Can cavities be reversed?

Yes, they can but only in the demineralized stage or when they’re very shallow in the enamel. There are literally two products available which can aid in the remineralization and that is fluoride and hydroxyapatite. All other home remedies may potentially help but they won’t directly expedite the remineralization.

Can a cavity kill you?

Potentially yes but it would need to be really severe for that to occur. For most people, once the lesion reaches the pulp you’ll experience throbbing root canal pain that can’t be ignored. It usually gets treated at this point and does not progress further.

Nonetheless if you manage to ignore it, it can becoming life threatening and develop into a condition called ludwig’s angina. The facial swelling gets so severe that it can cut off your airway making it difficult for you to breathe. That is certainly life-threatening.


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A lot of nuances cannot be detected without an in-person clinical exam, which means it is near impossible to diagnose and treat virtually.

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