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Updated on September 30, 2022

Craze Lines in Teeth

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What are Craze Lines in Teeth?

Some people get worried when they notice small lines running through their front teeth. However, there is usually no reason to worry if you notice them, as they might only be craze lines (a harmless, cosmetic imperfection).

‘Craze line’ is a common term in dentistry. Craze lines are vertical lines that appear superficially on tooth surfaces. They can appear on front or back teeth. The appearance of craze lines usually comes as people age. They might be translucent or appear yellow, gray, or brown. 

The human enamel experiences reduction in permeability and discoloration as one ages. The visual appearance of vertical cracks and craze lines also increases with age. 

On the Importance of Aging to the Crack Growth Resistance of Human Ename

Craze lines appear as tiny cracks, also called 'hairline cracks.' They affect only the outer layer of the tooth (enamel) and don't extend into the dentin (the middle layer).

What Do Craze Lines Look Like?

Craze lines are vertical lines that look like tiny hairline cracks on the tooth enamel. They look like straight-line patterns, are shallow, and appear vertically on a tooth. 

Craze lines are easy to notice, especially if you flash a light on your teeth at a particular angle. The light will reflect off the surfaces of the hairline cracks. 

cracked tooth craze line

What Causes Craze Lines?

Craze lines can appear because teeth are exposed to stress every day. For example, years of chewing or bruxism (teeth grinding) put pressure on the teeth, potentially causing craze lines.

The following can cause the appearance of craze lines:

  • Clenching or grinding your teeth and jaw — When you clench your teeth, your lower teeth and upper teeth push together, causing pressure that can lead to craze lines.
  • Uneven bite — An unstable or uneven bite caused by misaligned teeth can cause craze lines as teeth might not be meeting where they should when your mouth is shut.
  • Eating frozen foods — Biting into frozen foods or chewing ice cubes instead of sucking the ice can cause craze lines.
  • Wear and tear Years of eating and chewing can induce stress on teeth, causing craze lines.
  • Temperature changes — Going from one extreme temperature to another can cause craze lines (e.g., eating a hot meal while drinking chilled water).
  • Nail-biting and other bad habits — Biting your nails and other bad habits, such as using your teeth to open bottles and other objects, can cause craze lines. Your teeth are meant for chewing, not for opening objects. 

How Common are Craze Lines?

Craze lines on tooth enamel are a common clinical finding. Even healthy teeth can develop craze lines. However, they appear more as one advances in age. Therefore, they are extremely common in adult teeth.

Craze Lines vs. Cracks

Craze lines and cracks are two terms that people usually confuse for each other in dentistry. However, they do not mean the same thing. 

In a post made on CDA Oasis (The Canadian Dental Association website), Dr. Mary Dabuleanu, in collaboration with Dr. Suham Alexander, gave an insight into the difference between craze lines and cracks.

According to the doctors, a craze line is a tiny crack that affects only the tooth enamel and usually doesn’t present with symptoms. Craze lines typically don't have a treatment need unless for an aesthetic purpose.

On the other hand, a crack affects not just the outer enamel but the dentin as well. At some point, the pulp gets affected as well due to the central location of the cracks.

Cracked teeth usually require treatment (such as root canal treatment). The decision to treat and restore teeth will depend on the diagnosis. About 20% of cracked teeth cases diagnosed as reversibly inflamed will need a dentist to perform root canal treatment within six months. 

Can Craze Lines Lead to Cracked Teeth?

Craze lines are typically not a sign of dental health issues like tooth decay or weak teeth. They also usually don’t predispose your teeth to cracks or cause or worsen cracked teeth. 

Do Craze Lines Weaken Teeth?

No, craze lines don’t weaken your teeth. They are just harmless, cosmetic issues that don’t impact your oral health standing. 

Craze lines also don’t indicate cracked teeth, nor do they lead to cracks. 

Tips for Preventing Craze Lines in Teeth

Here are things you can do to prevent craze lines and to reduce their visibility:

  • Stop bad habits like nail-biting and opening bottles with your teeth
  • Avoid chewing very cold or frozen foods like ice cubes
  • Use a night guard or mouthguard to protect against teeth grinding
  • Avoid eating staining foods or beverages like red wine and coffee as they can make craze lines more visible.
  • Avoid using tobacco products to reduce the visibility of craze lines

How to Fix Craze Lines in Teeth

If you have craze lines, your general dentist might recommend that you get porcelain veneers, as you might be unable to remove craze lines even after treatment. Porcelain veneers, also called dental veneers, are thin, custom-made shells of tooth-like materials made to cover the external surface of teeth so as to improve their appearance. 

Some other things that you can do to fix your teeth craze lines include:

Can You Whiten Teeth With Craze Lines?

Craze lines can cause tooth discoloration, which can affect people’s self-esteem. However, with certain dental care procedures, you can remove tooth stains. 

Some ways you can whiten teeth with craze lines include:

  • Use of mechanical stain remover
  • Use of chemical stain remover
  • Restoration with porcelain veneers
  • Opting for full coverage crowns
  • Bleaching with oxygenating chemicals such as hydrogen peroxide

Craze lines tend to cause tooth sensitivity after whitening using the oxygenating chemical- hydrogen peroxide.

Bleaching Induced Tooth Sensitivity: Do The Existing Enamel Craze Lines Increase Sensitivity? A Clinical Study
6 Sources Cited
Last updated on September 30, 2022
All NewMouth content is medically reviewed and fact-checked by a licensed dentist or orthodontist to ensure the information is factual, current, and relevant.

We have strict sourcing guidelines and only cite from current scientific research, such as scholarly articles, dentistry textbooks, government agencies, and medical journals. This also includes information provided by the American Dental Association (ADA), the American Association of Orthodontics (AAO), and the American Academy of Pediatrics (AAP).
  1. Dabuleanu, Mary, and Alexander Suham. “How Does One Decide Whether A Crack/Craze Line on An Asymptomatic Tooth Should Be Attempted To Be Removed, Either With A Restoration Or A Crown?” Canadian Dental Association,  5 June 2014, 
  2. Krell, Keith V, and Eric M Rivera. “A Six Year Evaluation of Cracked Teeth Diagnosed With Reversible Pulpitis: Treatment and Prognosis.” Journal of Endodontics, vol. 33, 12 : 1405-7. Doi: 10.1016/j.joen.007.08.015, 
  3. Mariona, Preethi, and Anthony Delphine. “Diagnostic Methods for Cracked Tooth by Two Endodontic Tools.” Drug Invention Today, vol 10, 2 : 0975-7619,
  4. Mutlu, Ozcan et al. “Bleaching Induced Tooth Sensitivity: Do the Existing Enamel Craze Lines Increase Sensitivity? A Clinical Study.” Odontology/ the Society of the Nippon Dental University, vol 102, 2 : 197-202.  
  5. “What are Craze Lines?” Dawson Dental. 
  6. Yahyazadefar, Mobin et al. “On the Importance of Aging to the Crack Growth Resistance of Human Enamel.” Acta Biomaterialia, vol. 32 : 264-274. Doi: 10.1016/j.actbio.2015.12.038,
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