How Do Cavities Form?

Dr. Matthew Hannan | My Dental Advocate
Author: Matt Hannan, DDS
Updated: August 1, 2023
Molar teeth damaged by cavities | Medically accurate illustration | My Dental Advocate

Teeth are the hardest substances in the human body. The enamel covering your teeth is even harder than bone, but like kryptonite and Superman, cavities are bad news for your teeth. Cavities, or tooth decay, occur when acid produced in the mouth attacks the tooth causing holes or cavitations.

Bacteria is always present in the mouth, and when proper oral hygiene is not maintained, bacterial flora will assemble into a thin, sticky substance known as plaque or biofilm. Bacteria will then consume sugars from foods and beverages, leading to acid formation and cavities. If left untreated, cavities can lead to toothache, infection, and tooth loss.

A tooth has three distinct layers that each serve a unique purpose:


  • Outer shell layer
  • Calcium and phosphorus-rich
  • Hardest tissue in body


  • Middle layer
  • Porous and permeable
  • Able to regenerate


  • Innermost layer
  • Contains nerves and blood vessels
  • Most sensitive area of tooth

The acid formation attacks the enamel first. Therefore, pain may not be elicited when cavities are contained in the enamel. The dentist may use a medicated fluoride paste to remineralize the decay if the cavity is discovered before bacteria creates a hole in the enamel.

Recommended Reading: Should You Use Prescription Fluoride Toothpaste? (Dentist’s Thoughts)

Unfortunately, if left untreated, it will progress into the dentin leading to pain and irreversible damage. Cavities can form on all surfaces of the teeth; however, the most common area is between the teeth. Let’s look at the most common factors that contribute to tooth decay.


  • Salivary flow
  • Tooth anatomy
  • Age
  • Fluoride
  • Oral hygiene
  • Immune system
  • Genetics


  • Bacterial load
  • Biofilm pH


  • Nutrition
  • Carbohydrate type
  • Frequency of eating/drinking

Each factor plays a key role! Healthy foods have fewer fermentable carbohydrates leading to less acid production. Sugar-rich foods are sticky and more difficult to clean, which leads to acid formation and attack on the teeth. Saliva, however, will aid in removing acid if the salivary flow is sufficient.

Many medications will cause dry mouth leading to low salivary flow and decreased oral pH. Chewing sugar-free gum, using salivary stimulants (Biotene), or sipping water throughout the day will combat this process. Lastly, some people are predisposed to cavities based on their genetic makeup and immune system response.

Ways to limit cavities

Diligent hygiene care and regular dental visits will aid in the prevention of cavities. Be sure to brush at least twice a day using an electric toothbrush and fluoride toothpaste. Fluoride combines with calcium and phosphate to repair and restore weakened enamel. Floss regularly to clean away bacteria between your teeth.

This area is best cleaned with dental floss using a “c-shaped motion” around adjacent teeth. If you have more significant gaps between your teeth, a Waterpik is better. Many people neglect this step, so “only floss the teeth you want to keep.” Also, rinse with an ADA-approved antiseptic mouth rinse to disrupt the congregation of bacteria biofilm.

Recommended Reading: What is the ADA Seal of Acceptance?

Cavity removing process | Medically accurate illustration | My Dental Advocate

How are cavities managed?

To formulate a preventive and restorative treatment plan, dentists utilize the patient’s medical history, x-rays, intra-oral photos, oral exam and oral hygiene habits. Sealants may be applied to prevent decay in the pits and fissures of permanent molars.

The stages of decay are classified into five stages: E1, E2, D1, D2, and D3. For example, an E1 or E2 incipient cavity is located in the outer enamel layer.

Often, these cavities can be repaired using a prescription fluoride toothpaste such as Clinpro or Prevident 5000 ppm. If you are prone to cavities, you would be considered “high cavity risk.”

The dentist may suggest nightly fluoride trays to allow the fluoride to penetrate the enamel over an extended period.

High cavity risk factors

  • Poor oral hygiene
  • Poor nutrition/diet
  • Low salivary flow
  • Multiple cavities
  • Poor-fitting restorations
  • Infrequent dental visits
  • Weakened immune response
  • Genetic predisposition

If the cavity has progressed into the dentin, the cavity will need to be removed and restored. If the tooth is still restorable, the tooth will require extensive treatment. If the tooth is deemed nonrestorable, an extraction is necessary to prevent the spread of infection. The most common tooth replacement options are implants, bridges, and partials.

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Final thoughts

Cavities can be a real pain, especially when you think you are doing enough to keep your teeth clean. Have you recently visited the dentist to find yourself in this situation? Desire a second opinion?

My Dental Advocate’s team of board-certified dentists can provide a second opinion on your planned treatment. We look forward to bringing you peace of mind by verifying your treatment plan, suggesting an alternative, or answering your questions.

Knowledge is power when cultivating healthy dental habits. The more informed you are, the better positioned you’ll be to prevent avoidable and potentially costly dental procedures for you and your family. Watch for future blog posts, where we’ll continue sharing important information, product reviews and practical advice!