Is it a Crack or a Craze Line? How Can I Distinguish Them?

This article is a part of our Q&A series in which we give detailed answers to our readers' questions. Have a question? Don't hesitate and send it to us to get a detailed answer!

Teeth are remarkably strong, but they can still crack, chip, or fracture. Cracks and craze lines are both types of fractures, but they differ in their severity and the dental approaches required for treatment. In the world of dentistry, the terms crack and craze line are often used to describe different types of fractures in the teeth. Although they might seem similar, it’s important to understand the differences between the two.

What are Craze Lines?

Craze lines are tiny, shallow lines or cracks that only affect the outer enamel of the tooth. They are usually harmless and often occur as a natural result of the aging process.

Craze lines characteristics:

• Superficial, shallow (limited to enamel, do not extend into dentin)
• Tip of a dental explorer usually would not penetrate into a craze (might be felt, but it would not stick in it)
• Do not usually weaken the tooth do not necessarily lead to fractures
• Do not usually get worse with time
• Usually does not stop transilluminated light from shining all the way through the tooth
• Are found in most adult teeth, long vertical craze lines are common on anterior teeth
• Not visible on x-rays
• Can cross marginal ridges, can extend along buccal and lingual surfaces
• Do not cause pain
• Can be considered inconsequential, do not need to be restored except for possibly cosmetic purposes

Causes of Craze Lines

• Chewing hard foods
• Teeth grinding (bruxism)
• Temperature changes in the mouth (such as eating something hot followed by drinking something cold)
• Minor trauma to the tooth
• Natural wear and tear over time

Appearance and Symptoms

Craze lines are typically very fine and may appear as vertical lines on the surface of the tooth. They usually don’t cause any pain or sensitivity, as they don’t extend beyond the enamel.

What are Cracks?

Unlike craze lines, cracks are deeper fractures that go beyond the enamel and can affect both the dentin (the layer underneath the enamel) and, in severe cases, the pulp of the tooth.

Cracks characteristics

• More than just a superficial craze line
• Can be felt with the dental explorer – tip can penetrate into a crack, it would stick in the crack
• Cracks are considered an incomplete fracture, can cause Cracked Tooth Syndrome (CTS)
• Might or might not extend into dentin
• Most commonly begin on the occlusal surface and extend apically
• If it reaches dentin, crack stops transilluminated light from shining all the way through the tooth
• Usually not visible on x-rays unless large
• More common in posterior teeth than anterior teeth
• Can range in size from very small to a large split tooth
• Treatment needs range from nothing to filling to crown

What is a Fracture?

• A portion of the tooth is displaced; tooth structure is actually gone
• Can range in size from small chips, to entire cusp missing
• Visibility on x-rays depends on size of missing piece, and presence of other restorations
• Treatment often requires crown or onlay

Causes of Cracks

• Severe teeth grinding
• Biting on hard objects or foods
• Large fillings that weaken the tooth structure
• Trauma or injury to the tooth
• Sudden temperature changes

Appearance and Symptoms

Cracks are usually more visible and may cause pain or sensitivity, especially when eating or drinking hot or cold substances. The pain might also occur when biting down and suddenly release when the pressure is removed.

How to Distinguish Between Craze Lines And Cracks

• Visibility: Craze lines are often hard to see without the help of a dentist and may require a dental light or magnifying glass. Cracks, however, are usually more visible to the naked eye.
• Sensitivity and Pain: Cracks in the teeth typically cause pain or sensitivity because they penetrate beyond the enamel. Craze lines usually don’t cause any discomfort.
• Location and Direction: Craze lines often appear as vertical lines that follow the natural contour of the tooth, whereas cracks may be more irregular and can be in any direction.
• Dentist’s Examination: A dentist will be able to help distinguish between a crack and a craze line through a thorough examination, possibly using special tools or dyes, and by asking about any symptoms.

Treatment Options and Recommendations

Craze Lines: Usually, no treatment is necessary for craze lines. For cosmetic reasons, some might choose to have them polished or covered with a composite material or veneer.
Cracks: Treatment for a crack depends on the depth and location but may include dental bonding, a crown, root canal therapy, or, in extreme cases, extraction of the tooth.

Prevention

• Avoid chewing hard foods or objects
• Wear a mouthguard during sports
• Use a nightguard if you grind your teeth
• Attend regular dental check-ups

Bottom Line

While craze lines are usually harmless and more of a cosmetic concern, cracks can be serious and require immediate dental attention. Knowing how to distinguish between them is valuable, but consulting a dentist is the most reliable way to determine the type of fracture and the appropriate course of action. Regular dental check-ups can help in early detection and prevention of further complications.

This Q&A series article is complete and was published on January 16, 2020, and last updated on July 29, 2023.