What Does a Cavity Look Like?

We often hear statistics about the prevalence of tooth cavities from dentists. For example, the US Centers for Disease Control and Prevention 1 estimates that over 1 in every 4 US adults have untreated tooth decay. 

But what is a cavity and what does it look like? This blog article will review all of the signs and steps in the development of a cavity. The purpose of knowing the signs and steps of cavity development will help you to know when and understand when to see your professional dental provider.

What is a Dental Cavity, and How Does it Develop?

Dental cavities develop due to a slow-progressing process called tooth decay. Before we learn about dental cavities, it is important to know about the tooth decay process.  Our teeth are protected on the outside by a strong and highly mineralized layer called the dentinal  enamel. This layer protects the underlying layers called the dentin and the inner most layer called the pulp. 

Under healthy conditions, the enamel forms a robust barrier around the tooth. However, if this layer is damaged, either due to the action of disease-causing bacteria or because of dental trauma, the underlying, softer layers are exposed. Unfortunately, these layers are less mineralized and can get damaged very easily. Over time, the small pits develop on these softened layers and grow in size and can progress to different layers of the tooth. These growing pits are known as dental cavities.

What is the Difference Between Tooth Staining and Tooth Decay? 

Tooth staining is the build up of dark elements from dark liquids or food in the deep grooves and crevices of the teeth. Discoloration can also happen due to plaque and bacteria build up. Tooth decay can have a discolored appearance due to the breakdown of minerals in the teeth, but is not due to the build up of dark elements. Staining in deep grooves can be an early sign of bacteria build up and therefore can lead to decay if left untreated.

What Do Cavities Look Like?

So, now that we know how dental cavities develop, let us see what they look like. As discussed earlier, tooth decay and cavity formation are relatively slow processes. It begins with removing the minerals from the affected tooth, leaving it softened and unprotected. This so-called demineralized region of the tooth appears whiter than the rest. So, in the initial stages in the enamel layer, a cavity appears as “white spots.” These white spots simply mean that the tooth decay process has been initiated in the enamel. But the good news is that a tooth can be fully restored at this stage, because it has not progressed to the dentinal layer. Your dentist will simply use fluoride-containing varnish over the affected tooth, which will be remineralized once again. 

But what will happen if tooth decay continues unchecked beyond this stage? Cavities will start developing on the tooth surface. Initially, these cavities will appear tooth-colored or slightly bluish/ grayish. However, as the decay extends into dentine, the cavities appear yellowish or brownish. This is due to the different composition of the dentine compared to enamel. Unfortunately, once a cavity extends into the dentine and causes demineralization, it cannot be remineralized. At this stage, the only solution is to restore the damaged tooth structure with a suitable filling/restoration.

What Happens if a Cavity Becomes Too Deep?

If tooth decay remains untreated, the damage caused due to demineralization can eventually reach the pulpal tissue. When the pulpal tissue is infected by bacteria, an inflammation process will cause a painful throbbing sensation that will continue until the tooth is treated or the nerve dies.  At this stage, the only solution to save the damaged tooth is to perform a root canal procedure to remove the infected pulpal tissue.

What Does a Cavity Look Like on an X-ray?

Dentists have various tools to diagnose tooth decay. Many dental cavities are visible to dentists upon a physical examination, but some demineralized areas are only detectable by examination of dental X-rays. 

On an x-ray image a healthy tooth appears bright on an x-ray. Why? Because it contains the optimal amount of minerals. As a result, it reflects more light and appears brighter. But other things also appear bright on a tooth. For example, a silver amalgam filling or a metal crown will appear very bright on an x-ray. Similarly, a tooth affected with decay will appear dark due to the absence of the minerals that reinforce it. So, the darker an area of a tooth is, the more decay it has. 

Besides physical examination and x-rays, dentists also use disclosing agents that stain the area of a tooth that has tooth decay. Furthermore, handheld devices are also available that can differentiate between a healthy and a damaged tooth.

Why is it Important to Treat Cavities in Baby Teeth? 

Dental demineralization develops much faster in baby teeth due to thinner enamel. With faster progression of decay, the bacteria can spread to neighboring teeth causing rampant decay very quickly. If the decay progresses too quickly, baby teeth eventually will have to be extracted. If baby teeth are extracted before they are ready, permanent teeth will tend to erupt in the wrong area. Neighboring teeth will also want to drift and will block permanent teeth from erupting properly. If space needs to be maintained, a device called a space maintainer will have to be cemented into place to hold space for erupting teeth. This process of tooth decay, tooth extraction and possible space maintenance can become laborious and expensive very quickly.

How to Prevent and Treat Dental Cavities?

Dental cavities can cause various complications, such as pain, difficulty in eating, and even tooth loss. Not to mention the cost of filling the cavity. But the good news is that dental cavities can be prevented. How? By maintaining optimal oral hygiene through regular brushing and flossing. More importantly, one should visit their dentist regularly for checkups so that early demineralization can be diagnosed and treated timely. 

In case one has developed tooth decay, the solution is to remove the damaged tooth structure and replace it with a suitable filling/restoration. If there is extensive tooth damage, your dentist may consider placing a crown over the tooth after filling to reinforce it. Similarly, if there is an underlying infection, your dentist will perform a root canal procedure and restore the tooth. 

So, to summarize, dental cavities form mainly because of poor oral hygiene maintenance, and diet. If we can prevent plaque and tartar formation, we can prevent dental problems such as teeth cavities and gum disease. With a low sugar and simple carbohydrate diet, oral bacteria are not able to excrete demineralizing acid that can cause cavities. With the knowledge of the steps of dental demineralization and the signs of tooth decay, you are able to make informed decisions on when to reach out to your dental provider or ask for advice for treatment.


All Second Opinion Dentist content is medically reviewed and fact-checked by a licensed dentist to ensure the information is factual, current, and relevant.

  1. CDC. (2019). Adult Oral Health. Centers for Disease Control and Prevention. https://www.cdc.gov/oralhealth/basics/adult-oral-health/index.html
  2. WHO. (2022, November 18). Oral health. Who.int; World Health Organization: WHO. https://www.who.int/news-room/fact-sheets/detail/oral-health
  3. X-Rays Radiographs. (n.d.). Www.ada.org. https://www.ada.org/resources/research/science-and-research-institute/oral-health-topics/x-rays-radiographs

About the author

Dr. Latecia Miller is a board-certified dentist and graduate of The University of Utah School of Dentistry. She has several years of clinical practice experience across a wide variety of cases, treatment, and research. Dr. Miller's primary goal is to spread her love of dental health to her patients and the public.